Method and system for reversing the depolarization effect exhibited by an ultrasonic transducer

Abstract

The present invention is entitled a method and system for reversing a depolarization effect exhibited by an ultrasonic transducer. The present invention provides an ultrasound system, probe, and method. The ultrasound system, probe, and method include a transducer having a piezoelectric transducer element (104, 1410) polarized in a polarization direction (1423). Over time, one or more of the transducer elements exhibit a depolarization effect. One or more drive circuits (1412, 1414, 1405) are configured to: i) generate a transmit signal (650) having at least a first polarity segment and a second polarity segment (652, 654), the first polarity segment and the second polarity segment (652, 654) having corresponding first peak amplitude and second peak amplitude (+V T, ‑V T ); and ii) generating a repolarization signal (1421) having a repolarization pattern configured to at least partially reverse the depolarization effect exhibited by the one or more transducer elements (104, 1410).

Description

[0001] Related patent applications

[0002] This patent application is a continuation-in-part of and claims priority to U.S. patent application No. 16 / 516,798, filed on July 19, 2019, entitled “METHOD AND SYSTEM TO PREVENTDEPOLING OF ULTRASOUND TRANSDUCER,” the entire subject matter of which is hereby incorporated by reference in its entirety. Technical Field

[0003] Aspects of the present disclosure relate to medical imaging. More specifically, certain embodiments relate to methods and systems for preventing depolarization of an ultrasound transducer and for reversing the effects of depolarization when experienced. Background Art

[0004] Single-crystal piezoelectric materials can be used to form acoustic stacks in ultrasound probes. The fabrication of acoustic stacks used within ultrasound probes involves stacking or sandwiching the piezoelectric material with other layers of material, such as graphite-based materials or heavy-duty epoxy materials that can be used to form matching layers, flexible materials embedded with copper traces, and / or other very stiff materials. During manufacturing, the ultrasonic transducer is "poled" to improve the piezoelectric effect. This poling process occurs by applying an electric field to the transducer in a predetermined direction relative to a reference axis of the piezoelectric material. The single-crystal material and other transducer layers are cut into subassemblies that define individual transducer elements. During the assembly process, the transducer elements are attached with electrodes. These electrodes are used to transmit transmitted signals to corresponding transducer elements within the piezoelectric material and to collect received signals from the corresponding transducer elements.

[0005] During operation, a transmitting voltage is applied between electrodes connected to the piezoelectric material to induce an electric field in the transducer. This electric field, due to the piezoelectric effect, produces a mechanical dimensional change in the transducer element. This mechanical dimensional change is used to form an acoustic wave emitted by the probe. This acoustic wave is partially reflected at different anatomical layers. During the receiving operation, the reflected wave causes mechanical deformation of the transducer element. The mechanical deformation during the receiving operation induces an electrical signal within the transducer due to the piezoelectric effect. These electrodes transmit the electrical signals to the ultrasound console, where they are used to form an ultrasound image. The transmitting and receiving operations are applied to a large number of electrodes and the associated large number of transducer elements.

[0006] If excessive voltage is applied in the direction opposite to the initial polarization, the piezoelectric effect can be degraded. This degradation results in a decrease in the sensitivity of the ultrasound probe (also known as the depolarization effect). The amount of degradation depends on many factors, such as transducer temperature, the mode of the applied voltage signal, the polarity of the cutoff voltage (positive or negative), the material composition of the transducer, the thickness of the transducer, and so on. The depolarization effect is a major challenge facing single-crystal ultrasound probes.

[0007] To date, methods have been proposed to try to reduce the depolarization effect. For example, U.S. Patent 6,497,660 to Dillman et al. proposes adding a large bias voltage to the transmit voltage signal. Dillman teaches biasing the bipolar voltage signal to maintain the same polarity as the polarization direction of the transducer throughout the transmit operation. During the transmit cycle, Dillman's bias generator offsets the bipolar voltage signal so that the bipolar voltage signal is not at 0 volts in the static state, but at at least -XV volts. Figure 4 In [1], Dillman shows a biased bipolar voltage signal with a quiescent state at -XV, a peak value of 0 volts, and a minimum value of -2XV, indicating that the biased bipolar voltage signal should preferably not exceed 0 volts. However, to maintain Dillman's large bias voltage, the system must include expensive and unreliable high-voltage bias circuitry. Additionally, applying a large bias voltage to the probe throughout the entire transmit cycle can shorten the probe's lifespan and introduce additional circuit complexity.

[0008] Additional limitations and disadvantages of conventional and traditional approaches will become apparent to those skilled in the art by comparing such systems with aspects of the present disclosure as described in the remainder of this application with reference to the accompanying figures. Summary of the Invention

[0009] According to embodiments herein, an ultrasound system is provided. The ultrasound system includes a transducer having a piezoelectric transducer element polarized in a polarization direction. A transmit circuit is configured to generate a transmit signal having a first polarity segment and a second polarity segment. The first polarity segment and the second polarity segment have corresponding first and second peak amplitude segments. A bias generator is configured to generate a bias signal in the direction of the polarization direction. The bias signal is combined with the transmit signal to form a biased transmit signal that is offset in the direction of the polarization direction and still includes both positive and negative voltages during a transmit cycle.

[0010] Optionally, the piezoelectric transducer element may be formed of a single crystal material polarized in a polarization direction. The single crystal material may be a binary single crystal material. The bias signal may be a DC voltage continuously applied to the probe connector. The bias generator may be configured to generate the bias signal to have a steady-state voltage between 2.5V and 10V. The bias generator may be configured to generate the bias signal to have a steady-state voltage between 4V and 6V. The bias generator may be configured to generate the bias signal to have a steady-state voltage up to 15% of at least one of the first peak amplitude or the second peak amplitude of the transmit signal.

[0011] Optionally, the transmit signal may include a repeating series of pulses. The pulses may have a predetermined pulse width to provide an active transmit signal for up to 5% of a transmit period. The bias generator may be configured to continuously apply the bias signal during 90% or more of the transmit period. The transmit signal may include a repeating series of pulses having a predetermined pulse width to provide an active transmit signal for up to 5% of a transmit period, the bias generator being configured to continuously apply the bias signal during the transmit period.

[0012] Optionally, the ultrasound system may include a probe coupled to a distal end of a probe cable. The probe cable may include a probe connector at a proximal end of the probe cable. The probe connector may be configured to connect to an ultrasound console. The bias generator may be located downstream of the transmit circuitry within the ultrasound console and before the probe connector. The ultrasound system may include a probe. The bias generator may be located within the probe.

[0013] According to embodiments herein, an ultrasound probe is provided. The ultrasound probe includes a transducer having a piezoelectric transducer element polarized in a polarization direction. A probe connector and a transmission line extend from the probe connector to the transducer. The transmission line is configured to transmit a transmit signal in different modes. The different mode segments have corresponding peak amplitudes. A bias generator is coupled to the transmission line. The bias generator is configured to generate a bias signal in the direction of the polarization direction. The bias signal is combined with the transmit signal to form a biased transmit signal that is offset in the direction of the polarization direction and still includes both positive and negative voltages during a transmit cycle. The bias signal may also be active during receive time.

[0014] Optionally, the piezoelectric transducer element may be formed of a single crystal material that is polarized in a polarization direction. The single crystal material may refer to a binary single crystal material or a ternary crystal material. The bias generator may be configured to generate the bias signal to have a steady-state voltage between 2.5V and 10V.

[0015] According to embodiments herein, a method is provided. The method utilizes a transducer to transmit an ultrasonic signal and receive an echoed ultrasonic signal from a region of interest. The transducer includes a piezoelectric transducer element polarized in a polarization direction. The method generates a transmit signal having a plurality of polarity segments. Different polarity segments have correspondingly different peak amplitudes. The method generates a bias signal in the direction of the polarization direction and combines the bias signal with the transmit signal to form a biased transmit signal that is offset in the direction of the polarization direction and still includes both positive and negative voltages during a transmit cycle. The bias signal may also be active during receive time.

[0016] Optionally, the method may include providing a piezoelectric transducer element formed from a single crystal material that is polarized in a polarization direction. The method may utilize binary or ternary single crystal materials to form the transducer element. The method may be capable of continuously applying a DC voltage as the bias signal. The method may include at least one of: generating the bias signal to have a steady-state voltage of up to 10V; generating the bias signal to have a steady-state voltage of up to 6V; generating the bias signal to have a steady-state voltage of up to 15% of at least one of the first peak amplitude or the second peak amplitude of the transmit signal; or continuously applying the bias signal during 90% or more of the transmit period.

[0017] According to an embodiment of the present invention, an ultrasound system is provided, comprising: a transducer having piezoelectric transducer elements polarized in a polarization direction, wherein over time, one or more of the transducer elements may exhibit a depolarization effect; and one or more drive circuits configured to: i) generate a transmit signal having at least first polarity segments, the first segments having corresponding first peak amplitudes; ii) generate a complex polarization signal having a complex polarization pattern, the complex polarization pattern being configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements; and iii) generate a bias signal in the polarization direction, the bias signal being combined with at least one of the transmit signal or the complex polarization signal to form a corresponding at least one of a biased transmit signal or a biased complex polarization signal shifted in the polarization direction.

[0018] Additionally or alternatively, the one or more driver circuits are further configured to generate a bias signal simultaneously with the transmit signal in time, the bias signal being combined with the transmit signal to form a biased transmit signal that is shifted in polarization direction. Additionally or alternatively, the one or more driver circuits are further configured to generate a bias signal simultaneously with the repolarization signal in time, the bias signal being combined with the repolarization signal to form a biased repolarization signal that is shifted in polarization direction. Additionally or alternatively, the one or more driver circuits include a transmit driver circuit configured to generate the transmit signal. Additionally or alternatively, the one or more driver circuits include a repolarization driver circuit configured to generate the repolarization signal. Additionally or alternatively, the one or more driver circuits include at least one common driver circuit configured to generate at least two of the transmit signal, the bias signal, and the repolarization signal. Additionally or alternatively, the one or more driver circuits are configured to generate a series of at least one positive pulse and / or at least one negative pulse as the repolarization signal. Additionally or alternatively, the one or more driving circuits are configured to generate the repolarization signal to have a voltage amplitude up to four times greater than a voltage amplitude of the transmit signal.

[0019] According to an embodiment of the present invention, an ultrasound probe is provided, comprising: a transducer having piezoelectric transducer elements polarized in a polarization direction, wherein over time, one or more of the transducer elements exhibit a depolarization effect; a probe connector and a transmit line extending from the probe connector to the transducer, the transmit line being configured to transmit a transmit signal having at least a first polarity segment having a corresponding first peak amplitude; the transmit line being further configured to transmit a complex polarization signal having a complex polarization pattern, the complex polarization pattern being configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements; and a bias generator configured to generate a bias signal in the direction of the polarization direction, the bias signal being combined with the transmit signal to form a biased transmit signal, the biased transmit signal being offset in the direction of the polarization direction and still including both positive and negative voltages during a transmit cycle.

[0020] Additionally or alternatively, the bias generator is further configured to generate a bias signal simultaneously with the repolarization signal in time, the bias signal being combined with the repolarization signal to form a biased repolarization signal that is shifted in polarization direction. Additionally or alternatively, a repolarization drive circuit is provided within the housing of the ultrasound probe, the repolarization drive circuit being configured to generate the repolarization signal. Additionally or alternatively, the repolarization signal includes a series of at least one positive pulse and at least one negative pulse. Additionally or alternatively, the voltage amplitude of the repolarization signal is up to four times the voltage amplitude of the transmit signal.

[0021] According to an embodiment of the present invention, a method is provided, which includes: utilizing a transducer to transmit an ultrasonic signal and receive an echo ultrasonic signal from a region of interest, the transducer including a piezoelectric transducer element polarized in a polarization direction, wherein over time, one or more of the transducer elements exhibit a depolarization effect; generating a transmit signal having at least a first polarity segment having a corresponding first peak amplitude; generating a complex polarization signal having a complex polarization pattern, the complex polarization pattern being configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements; and generating a bias signal in the polarization direction, the bias signal being combined with at least one of the transmit signal or the complex polarization signal to form a corresponding at least one of a biased transmit signal or a biased complex polarization signal shifted in the polarization direction.

[0022] Additionally or alternatively, generating the bias signal includes generating the bias signal simultaneously with the transmit signal in time, the bias signal being combined with the transmit signal to form a biased transmit signal that is offset in polarization. Additionally or alternatively, generating the bias signal further includes generating the bias signal simultaneously with the repolarization signal in time, and combining the bias signal with the repolarization signal to form a biased repolarization signal that is offset in polarization. Additionally or alternatively, the repolarization signal is generated after at least one of the acquisition of ultrasound data of an ultrasound image frame is completed or during a freeze mode. Additionally or alternatively, the repolarization signal includes a series of at least one positive pulse and at least one negative pulse. Additionally or alternatively, the voltage amplitude of the repolarization signal is up to 4 times the voltage amplitude of the transmit signal. Additionally or alternatively, the method continuously applies a DC voltage as the bias signal to both the transmit signal and the repolarization signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 An ultrasound system including a transmitter that drives an array of transducer elements within a probe to transmit pulsed ultrasound signals into a body is shown according to embodiments herein.

[0024] Figure 2 A 3D-capable miniaturized ultrasound system is shown having a probe that may include elements comprising single crystal material and / or single crystal composite materials according to embodiments herein.

[0025] Figure 3 A mobile ultrasound imaging system disposed on a movable base according to embodiments herein is shown.

[0026] Figure 4 A hand-carried or pocket-sized ultrasound imaging system according to embodiments herein is shown, wherein the display and user interface form a single unit.

[0027] Figure 5A method for manufacturing a transducer array according to embodiments herein is shown.

[0028] Figure 6A A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown.

[0029] Figure 6B An example of a transmit signal that may be transmitted during one transmit cycle according to embodiments herein is shown.

[0030] Figure 7 A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown.

[0031] Figure 8 A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown.

[0032] Figure 9 A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown.

[0033] Figure 10 Test results collected in conjunction with one type of transducer with an applied DC bias according to embodiments herein are shown.

[0034] Figure 11 Shown in accordance with the embodiment of the present invention as combined Figure 10 The tests were conducted in conjunction with test results collected with the same type of transducer without a DC bias.

[0035] Figure 12 Shown are test results collected without DC bias in conjunction with one type of transducer according to embodiments herein.

[0036] Figure 13 Shown in accordance with the present invention, the combination of Figure 12 The test results are the same type of transducer used in the test results collected with an applied DC bias.

[0037] Figure 14A A block diagram of an ultrasound system including an implemented DC bias circuit and a repolarization drive circuit according to embodiments herein is shown.

[0038] Figure 14B A block diagram of an ultrasound system including an implemented DC bias circuit and a repolarization drive circuit according to alternative embodiments herein is shown.

[0039] Figure 14C Examples of repolarization signals that may be transmitted during repolarization periods between consecutive transmit periods are shown.

[0040] Figure 14D Examples of biased repolarization signals that may be transmitted during repolarization periods between consecutive transmit periods according to embodiments herein are shown.

[0041] Figure 14E Examples of alternative repolarization patterns formed according to embodiments herein are shown.

[0042] Figure 15 An example of the timing relationship between the transmit period and the repolarization period according to embodiments herein is shown.

[0043] Figure 16 A process for achieving repolarization according to embodiments herein is shown.

[0044] Figure 17 A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown.

[0045] Figure 18 A block diagram of an ultrasound system including an implemented DC bias circuit according to embodiments herein is shown. DETAILED DESCRIPTION

[0046] When reading in conjunction with the accompanying drawings, the following specific embodiments of the foregoing invention summary and certain embodiments will be better understood. With regard to the scope of the figure of the functional block of various embodiments shown in the accompanying drawings, the functional block does not necessarily represent the division between the hardware circuit. Therefore, for example, one or more functional blocks (for example, processors or memories) can be realized in a single piece of hardware (for example, a general-purpose signal processor or random access memory block, a hard disk, etc.) or multiple pieces of hardware. Similarly, a program can be an independent program, can be included in an operating system as a subroutine, can be a function in an installed software package, etc. It should be understood that the various embodiments are not limited to the arrangement and the instrument shown in the accompanying drawings. It should also be understood that embodiments can be combined, or other embodiments can be utilized, and structural, logical and electrical changes can be made without departing from the scope of the various embodiments. Therefore, the following detailed description should not be considered as a restrictive meaning, and the scope of the present invention is limited by the appended claims and their equivalents.

[0047] As used herein, an element or step recited in the singular and beginning with the word "a" or "an" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to "an embodiment," "one embodiment," "a representative embodiment," "an example embodiment," "various embodiments," "certain embodiments," and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, unless explicitly stated to the contrary, embodiments that "comprise," "include," or "have" an element or elements having a particular property may include additional elements that do not have that property.

[0048] The term "sensitivity" shall mean the ratio of electrical output to signal input or signal output to electrical input.

[0049] The term "depolarization effect" shall mean the change between i) the current level or degree of polarization of a transducer element and ii) the previous level or degree of polarization of the transducer element. The previous level or degree of polarization may be defined as a baseline polarization level. For example, the depolarization effect may represent a decrease in the level or degree of polarization relative to the level of polarization exhibited when the ultrasound probe or transducer was manufactured, assembled, or refurbished. For the avoidance of doubt, it should be recognized that transducer elements may exhibit various levels of depolarization effect (e.g., small, moderate, or large amounts of depolarization). Additionally, for the avoidance of doubt, it should be recognized that new or initial transducer elements (e.g., recently manufactured, recently refurbished, unused) may not be fully polarized. Instead, the degree of initial polarization of the transducer element may be used as a baseline or base polarization level / degree.

[0050] The embodiments herein may be implemented in conjunction with the structures and functions described in one or more of the following published patent applications: U.S. Patent No. 9,966,578, entitled “SEAL RING AND ASSOCIATED METHOD,” published on May 8, 2018; U.S. Patent No. 8,978,216, entitled “METHOD FOR FORMING AN ACOUSTICAL STACK FOR AN ULTRASOUND PROBE,” published on March 17, 2015; U.S. Patent No. 7,621,028, entitled “METHOD FOR OPTIMIZED DEMATCHING LAYER ASSEMBLY IN AN ULTRASOUND TRANSDUCER,” published on November 24, 2009; U.S. Patent No. 7,621,028, entitled “METHOD FOR OPTIMIZED DEMATCHING LAYER ASSEMBLY IN AN ULTRASOUND TRANSDUCER,” published on June 9, 2009; and U.S. Patent No. 8,978,216, entitled “METHOD FOR FORMING AN ACOUSTICAL STACK FOR AN ULTRASOUND PROBE,” published on March 17, 2015. No. 7,545,012, entitled “Capacitive Micromachined Ultrasonic Transducer Fabricated with Epitaxial Silicon Membrane”; No. 7,289,336, entitled “ELECTRONIC PACKAGING AND METHOD OF MAKING THE SAME”, published on October 30, 2007; No. 7,094,444, entitled “METHOD FOR PREPARING COATED COMPONENTS USING NIAL BOND COATS”, published on August 22, 2006; No. 7,078,073, entitled “METHOD FOR REPAIRING COATED COMPONENTS”, published on July 18, 2006; No. 7,084,073, entitled “ULTRASOUND TRANSDUCER”, published on December 23, 2003 No. 6,6666,825 for "Ultrasound Transducer for Improving Resolution in Imaging System." The entire subject matter of the published patents, patent applications, and other publications cited above and below are expressly incorporated herein by reference in their entirety.

[0051] The embodiments herein can be implemented in conjunction with a variety of ultrasonic transducers, without limitation to the transducer geometry. However, the embodiments herein may be more suitable when used in conjunction with transducers made of materials susceptible to depolarization, including but not limited to single crystal materials, etc. In particular, the embodiments herein are well suited for limiting or eliminating depolarization effects in transducer elements that are substantially constructed of binary or ternary single crystal materials or have a substantially uniform composition of binary or ternary single crystal materials. In particular, the embodiments herein utilize a low voltage bias signal, as compared to the voltage level of the bias signal used with ternary single crystal materials, to stabilize the weaker binary single crystal material when utilizing a bias signal having a lower voltage.

[0052] Embodiments may be implemented in conjunction with ultrasound probes having various types and arrangements of transducers that are configured to collect any and all types of ultrasound data sets, including (but not limited to) B-mode data, power Doppler data, Doppler data, strain data, two-dimensional data, three-dimensional data, four-dimensional data, shear wave data, or other data, as described herein and in the patents, patent applications, and other publications referenced and incorporated herein.

[0053] While the primary embodiments are described in conjunction with ultrasound transducers utilized in conjunction with diagnostic imaging, it should be appreciated that the embodiments may be implemented in conjunction with ultrasound transducers for other applications. Non-limiting examples of other applications for ultrasound transducers include ultrasound therapy systems (e.g., ultrasound-based treatment of tumors, ultrasound-based removal of adipose tissue), photoacoustic ultrasound, sonar, ultrasound-based inspection of mechanical structures, ultrasound-based inspection of mechanical connections (e.g., welds and other bonded interfaces), and the like. Traditionally, transducers used for therapeutic, sonar, and inspection applications have utilized different crystal structures (e.g., non-single crystal materials) that are less susceptible to depolarization and, therefore, have not been able to utilize the other benefits provided by single crystal structures. For example, the higher voltages utilized in conjunction with therapeutic, sonar, and inspection applications can inherently accelerate the depolarization process and degradation of the transducer, rendering single crystal structures unsuitable for such applications. However, with the addition of the improvements described herein, depolarization can be avoided even at higher transmit voltages, allowing single crystal transducers to be used in higher voltage applications.

[0054] Figure 1An ultrasound system 100 is shown that includes a transmitter 102 that drives an array of transducer elements 104 (e.g., piezoelectric elements) within a probe 106 to transmit pulsed ultrasound signals into the body. The elements 104 may comprise single crystal materials as discussed herein. The elements 104 may be arranged, for example, in one or two dimensions. A variety of geometries may be used, and the probe 106 may be capable of acquiring one-, two-, three-, and / or four-dimensional image data. The system 100 may have a probe port 120 for connecting the probe 106, or the probe 106 may be hardwired to the system 100.

[0055] The transmitter and ultrasound probe may be implemented and / or configured for one-dimensional (1D), two-dimensional (2D), three-dimensional (3D), and / or four-dimensional (4D) ultrasound scanning. The ultrasound probe may include a one-dimensional (1D, 1.25D, 1.5D, or 1.75D) array or a two-dimensional (2D) array of piezoelectric elements. The ultrasound probe may include a set of transmit transducer elements and a set of receive transducer elements, which generally constitute identical elements. The transmitter may be driven by a transmit beamformer. The transmit beamformer may include suitable circuitry for controlling the transmitter, which drives the set of transmit transducer elements via a transmit subaperture beamformer to transmit an ultrasound transmit signal into a region of interest (e.g., a human, an animal, an underground cave, a physical structure, etc.). In this regard, a set of transmit transducer elements may be activated to transmit an ultrasound signal. The ultrasound signal may include, for example, a pulse sequence repeatedly triggered at a pulse repetition frequency (PRF), which may typically be in the kilohertz range. The pulse sequence may be focused at the same transmit focal position having identical transmit characteristics. A series of transmit triggers focused at the same transmit focal position may be referred to as a "packet."

[0056] Ultrasound signals are backscattered from structures within the body, such as fat tissue or muscle tissue, to produce echoes that return to element 104. The echoes are received by receiver 108. The received echoes pass through beamformer 110, which performs beamforming and outputs a radio frequency (RF) signal. The RF signal then passes through RF processor 112. Alternatively, RF processor 112 may include a complex demodulator (not shown) that demodulates the RF signal to form an in-phase and quadrature (IQ) data pair representing the echo signal. The RF or IQ signal data may then be routed directly to memory 114 for storage.

[0057] The ultrasound system 100 also includes a processor module 116 to process the acquired ultrasound information (e.g., RF signal data or IQ data pairs) and prepare frames of ultrasound information to be displayed on a display 118. The processor module 116 is adapted to perform one or more processing operations based on a plurality of selectable ultrasound modalities on the acquired ultrasound information. As echo signals are received, the acquired ultrasound information can be processed and displayed in real time during a scanning session. Additionally or alternatively, the ultrasound information can be temporarily stored in the memory 114 or the memory 122 during a scanning session and then processed and displayed in an offline operation.

[0058] The user interface 124 can be used to input data into the system 100, adjust settings, and control the operation of the processor module 116. The user interface 124 may have a keyboard, trackball and / or mouse, as well as a plurality of knobs, switches or other input devices such as a touch screen. The display 118 includes one or more monitors that present patient information including diagnostic ultrasound images to the user for diagnosis and analysis. One or both of the memory 114 and the memory 122 can store two-dimensional (2D) and / or three-dimensional (3D) data sets of ultrasound data, wherein such data sets are accessed to present 2D and / or 3D images. Multiple continuous 3D data sets can also be acquired and stored over time, such as to provide real-time 3D or four-dimensional (4D) displays. These images can be modified using the user interface 124 and the display settings of the display 118 can also be manually adjusted.

[0059] Figure 2 A miniature ultrasound system 130 with 3D capabilities is shown having a probe 132 that may include an element 104 having a single crystal material as discussed herein. The probe 132 may be configured to acquire 3D ultrasound data. For example, the probe 132 may have a 2D array of transducer elements 104. A user interface 134 (which may also include an integrated display 136) is provided to receive commands from an operator.

[0060] As used herein, "miniature" means that the ultrasound system 130 is a handheld or hand-portable device, or is configured to be carried in one's hand, pocket, briefcase-sized bag, or backpack. For example, the ultrasound system 130 can be a hand-portable device having the dimensions of a typical laptop computer (e.g., having dimensions of approximately 2.5 inches in depth, approximately 14 inches in width, and approximately 12 inches in height). The ultrasound system 130 can weigh approximately ten pounds and thus be convenient for an operator to carry. An integrated display 136 (e.g., an internal display) is also provided and is configured to display medical images.

[0061] The ultrasound data may be sent to an external device 138 via a wired or wireless network 140 (or a direct connection, such as via a serial or parallel cable or a USB port). In some embodiments, the external device 138 may be a computer or workstation with a display. Alternatively, the external device 138 may be a separate external display or printer capable of receiving image data from the hand-portable ultrasound system 130 and displaying or printing images that may have a greater resolution than the integrated display 136. It should be noted that various embodiments may be implemented in conjunction with miniaturized ultrasound systems having different sizes, weights, and power consumption.

[0062] Figure 3 A mobile ultrasound imaging system 144 is shown disposed on a movable base 146. The ultrasound imaging system 144 may also be referred to as a cart-based system. A display 142 and a user interface 148 are provided, and it should be understood that the display 142 may be independent of or separate from the user interface 148. The system 144 has at least one probe port 150 for receiving a probe (not shown), which may have an element 104 comprising a single crystal material as discussed herein.

[0063] The user interface 148 may optionally be a touch screen, allowing the operator to select options by touching displayed graphics, icons, and the like. The user interface 148 also includes control buttons 152 that can be used to control the system 144 as desired or needed and / or as typically provided. The user interface 148 provides a plurality of interface options that a user can physically manipulate to interact with displayed ultrasound and other data, as well as to input information and set and change scan parameters. The interface options may be used for specific input, programmable input, contextual input, and the like. For example, a keyboard 154 and a trackball 156 may be provided.

[0064] Figure 4A hand-held or pocket-sized ultrasound imaging system 170 is shown in which a display 172 and a user interface 174 form a single unit. By way of example, the pocket-sized ultrasound imaging system 170 may be approximately 2 inches wide, approximately 4 inches long, and approximately 0.5 inches deep and weigh less than 3 ounces. The display 172 may be, for example, a 320×320 pixel color LCD display on which a medical image 176 may be displayed. A typewriter-style keyboard 180 of buttons 182 may optionally be included in the user interface 174. The system 170 is connected to a probe 178 having a transducer element 104 comprising a single crystal material as discussed herein. Functions may be assigned to the multi-function controls 184 according to the system's operating mode. Thus, each of the multi-function controls 184 may be configured to provide multiple different actions. If desired, a label display area 186 associated with the multi-function control 184 may be included on the display 172. The system 170 may also have additional buttons and / or controls 188 for specialized functions, which may include, but are not limited to, "Freeze," "Depth Control," "Gain Control," "Color Mode," "Print," and "Store."

[0065] The term acoustic stack may be used herein to refer to several layers attached together in a stacked configuration. Figure 1 Each element in the acoustic stack (shown in FIG) includes an acoustic stack. In one embodiment, the acoustic stack includes a piezoelectric layer formed of a piezoelectric material, such as a single crystal piezoelectric material. The piezoelectric layer may have a thickness of approximately ½ or ¼ λ, where λ is the wavelength of sound in the piezoelectric material for the desired center frequency of the usable bandwidth. Electrodes may be formed using thin metal layers and deposited on at least the top and bottom sides of the piezoelectric material.

[0066] Figure 5A method for manufacturing a transducer array according to embodiments herein is shown. At 502, a thin sheet of piezoelectric material is provided. The thin sheet of piezoelectric material may also be referred to as a piezoelectric substrate, which may be formed from different types of piezoelectric compounds. Typically, the piezoelectric material is fully metallized on the outer surface. After the acoustic stack is cut into individual elements, this metallization forms the individual element electrodes. According to at least some embodiments, the substrate may be formed as a single crystal material. While the single crystal material may be binary or ternary, it is more preferably a binary single crystal material. Non-limiting examples of usable single crystal materials include binary composites such as lead zinc niobate-lead titanate (PZN-PT) and lead magnesium niobate-lead titanate (PMN-PT). PMN-PT has an internal structure that results in different but specific properties. PMN-PT exhibits piezoelectric properties and is composed of two different groups of atoms that behave as a unit, both of which are oxides, known as free radicals (e.g., Pb(Mg1 / 3Nb2 / 3)O3 and PbTiO3). PMN-PT is part of the relaxor ferroelectric material class and has a single-crystal structure, unlike common piezoelectric materials, which have a granular piezoelectric ceramic structure. This means that defects and grain boundaries are absent, allowing PMN-PT to be machined to a much higher degree of precision, achieving an optical-grade finish. Other properties that distinguish PMN-PT from granular piezoelectric materials, such as PZT, are also directly related to the single-crystal structure. These properties can be optical, mechanical, or electrical, and can be anisotropic (directly related). Another advantage of PMN-PT having a single-crystal structure is its uniformity, which ensures consistent piezoelectric coefficient values.

[0067] The piezoelectric substrate includes a proximal surface or front surface and a distal surface or back surface. Once the substrate is assembled into an ultrasound probe, the probe can be positioned proximal to the region of interest during operation of the probe, and ultrasound waves are transmitted into the ROI in a scanning direction. Structures within the ROI emit signals in response to the transmitted ultrasound waves. In medical imaging and therapeutic applications, the probe is held in close contact with the tissue of the ROI, with the front face of the probe oriented approximately perpendicular to the scanning direction. In non-destructive testing, the probe is held in close contact with the structure containing the ROI with the scanning direction extending into the ROI. In sonar applications, the probe is positioned within a fluid (e.g., the ocean). The proximal surface is the surface of the substrate that is closest to (or in close contact with) the tissue, structure, or fluid containing the ROI with the scanning direction extending into the ROI.

[0068] According to some probe designs, the proximal and distal surfaces of the substrate may extend along substantially parallel planes (e.g., for a linear transducer configuration). Optionally, the proximal and distal surfaces may extend along substantially concentric arcs (e.g., for a curved transducer configuration). Optionally, the proximal and / or distal surfaces may be configured to extend along non-planar and / or other paths that lack a constant curve. For example, at least the proximal surface may extend in a planar manner in a first direction (e.g., a longitudinal direction), but extend along a curved path in an orthogonal second direction (e.g., a transverse direction). The proximal and distal surfaces of the substrate are separated from each other by the depth or thickness of the substrate (as measured along the depth direction). Generally, the proximal and distal surfaces of the substrate may be oriented substantially parallel to each other, but in certain embodiments, the proximal and distal surfaces may be oriented at a non-parallel angle to each other.

[0069] At 504, the piezoelectric substrate is "poled" by applying an electric field to the piezoelectric substrate along a predetermined direction. Prior to the poling operation, the piezoelectric substrate exhibits an unpolarized state consisting of at least partially randomly oriented electric dipoles. In the unpolarized state, the substrate exhibits relatively weaker piezoelectric sensitivity than after poling. The poling operation orients the electric dipoles within the substrate in a common direction, referred to as the "polarization direction." The polarization of the piezoelectric material is along the transmission direction, i.e., perpendicular to the acoustic stack. The perpendicular direction extends in the radial direction for curved probes and in the longitudinal direction for linear or phased probes.

[0070] For example, one or an array of proximal electrodes may be connected at or near the proximal surface of the substrate, wherein the electrodes are arranged in a pattern corresponding to the pattern of transducer elements to be utilized by the probe. The distal surface of the substrate may be connected to a similar array of distal electrodes, fewer electrodes, and / or a common electrode. A voltage potential is applied across the proximal and distal electrodes to form an electric field. The electric field is applied with sufficient intensity to reorient the electric dipoles within the piezoelectric substrate so that they align along a common direction, i.e., along the scanning direction. For linear probes, the scanning direction extends generally parallel to the depth axis and perpendicular to the probe face. For curved probes, when operating in conjunction with a single transmit, the scanning direction extends parallel to the local depth axis (near the transmit axis) and perpendicular to the local region of the probe near the transmit axis.

[0071] The polarization direction (and the orientation of the dipole) extends generally in a direction between the electrodes coupled to the transducer elements. These electrodes may be positioned on the front / proximal surface and the rear / distal surface of the transducer element (or stack). Thus, the polarization direction extends parallel to the depth axis of the stack of transducer elements. As another example, the transducer elements are arranged in an array in a probe, wherein the probe has a front / proximal surface configured to be positioned proximal to the region of interest. The front surface of the probe extends along a plane. The polarization direction extends generally perpendicular to the plane of the front surface of the probe and the array of transducer elements.

[0072] At 506, the substrate of piezoelectric material is cut using cutting parameters or conditions. For example, the cutting operation can completely cut through all acoustic layers, such as cutting through all conductive layers, thereby separating all acoustic elements and allowing individual electrical connections. In addition, the elements can be cut in small pieces to achieve specific aspect ratios and preferred vibration modes. However, the small pieces still maintain the electrical connections of the element subcomponents. Optionally, the cutting operation can be limited to partially or partially cutting through half of the substrate material, so that the substrate material remains as a thin sheet rather than individual pieces. Optionally, the cutting parameters or conditions can be based on the mechanical properties and geometry of the single crystal. The cutting parameters may include, but are not limited to, blade material, spindle speed, feed rate, etc. Thus, the quality of the single crystal is maintained while avoiding the cracking and degradation experienced when using the cutting conditions required when cutting the entire acoustic stack. The processes used to manufacture the acoustic stack introduce stresses in both the ceramic and single crystal materials. Typically, an annealing step is performed to stress relieve these materials before polarizing the elements.

[0073] In another embodiment, laser cutting, ion milling, chemical etching, wire sawing, plasma cutting, and / or other processes or methods may be used and may be optimized based on single crystal materials. In one embodiment, the sheet of single crystal material may be a single piece of material, and in another embodiment, the sheet of single crystal material may be a stack of two or more sheets of single crystal material. Generally, the cutting operation may cut completely through the layers to separate the electrical connections. The cutting operation forms single crystal elements, each of which corresponds to a single element in the probe. The cuts may extend from the proximal surface or the front surface of the sheet through the single crystal material. In one embodiment, the cuts may be spacers, i.e., the cuts may completely separate the single crystal elements. The cuts have a width corresponding to the width of the first cut. The cuts are filled with a cut filling material. The cut filling material may be a silicon material, an organic polymer, an epoxy-based material, or other material suitable for both filling the cuts and for subsequent cutting operations that will cut the acoustic stack.

[0074] At 508, an electrode array is sputtered onto the piezoelectric material before the component is laminated into a stack. For example, at least the proximal and distal surfaces of the piezoelectric material may be coated with a layer of a conductive material, such as gold, nickel, a combination of conductive materials, or the like. Isolation lines may be made on the proximal and distal surfaces of the crystal to define signal and ground areas.

[0075] It should be understood that other methods can be used to form electrodes and / or define signal and ground areas. For example, high-frequency arrays can be formed using elements defined by preformed electrodes on piezoelectric material. In the aforementioned example, no cutting operation is performed. For example, cutting can be avoided in high-frequency arrays where a cutting kerf, for example, 30 μm wide, would occupy too much spacing in the material and would therefore be technically infeasible. Optionally, at least one matching layer can be affixed to the side of the crystal without the isolation scribe, such as by using an adhesive, glue, or other material. A flexible circuit is sandwiched or laminated within the acoustic stack to interconnect the stack with system 100. The flexible circuit has a flexible insulating layer that can be formed from a material such as Kapton (a polyimide film). Other materials can also be used. Upper traces are formed on one side of the flexible insulating layer, and lower traces are formed on the other side of the flexible insulating layer. In one embodiment, the upper and lower traces can be copper or another metallic material or combination of materials and can be printed on the flexible insulating layer using printing methods known in the art.

[0076] At 510, the transducer subassembly is assembled into the probe housing along with any other electrical or mechanical components suitable for fully assembling the ultrasound probe. Next, the discussion turns to methods and systems for managing the operation of an ultrasound probe to limit or eliminate depolarization of the piezoelectric material according to embodiments herein. During operation, a transmit voltage is applied to the probe, inducing an electric field in the transducer. This electric field, based on the piezoelectric effect, produces a mechanical dimensional change in the transducer elements. This mechanical dimensional change is used to form an acoustic wave emitted by the probe. This acoustic wave is partially reflected at different anatomical layers within the region of interest. The reflected wave impacts the transducer and causes mechanical deformation of the transducer elements. This mechanical deformation, again based on the piezoelectric effect, creates an electric field across the corresponding transducer elements. The electric field within the individual transducer elements creates a potential between electrodes connected to the corresponding transducer elements. This potential is sensed as a raw received ultrasound signal and processed to form ultrasound data and an ultrasound image.

[0077] If excessively high voltage is applied to a transducer element in a direction opposite to the polarization direction, the high voltage degrades the piezoelectric effect exhibited by the transducer element. For example, the high voltage reorients at least a portion of the electric dipoles within the components of the transducer element, thereby reintroducing at least a partially unpolarized state into the components of the transducer element. This degradation of the polarization of the transducer element reduces the piezoelectric effect exhibited by the transducer element, thereby reducing the sensitivity of the ultrasound probe. The amount of depolarization or piezoelectric effect degradation for a particular probe will depend on various factors, such as the voltage amplitude applied in conjunction with the transmit signal, transducer temperature, and / or signal pattern. Complex voltage signal patterns applied during the transmit signal can become more relevant to potential depolarization. For example, some voltage signal patterns may have segments where the amount of time and / or voltage level increases in a direction opposite to the polarization direction. As the number or length of segments increases in a direction opposite to the polarization direction, the likelihood of depolarization increases.

[0078] When using simpler transmit signals, the amount of depolarization and degradation may depend on the polarity of the cutoff voltage of each transmit signal relative to the polarization direction (e.g., positive or negative voltage). For example, a cutoff voltage polarity corresponding to the polarization direction will have little or no depolarization effect, while a cutoff voltage polarity opposite to the polarization direction may have a limited depolarization effect.

[0079] The negative effects associated with depolarization present a significant challenge when incorporating newer probe designs, particularly ultrasound probes that utilize single-crystal materials for their transducer arrays. During extensive analysis, the inventors of the present application observed that depolarization can be substantially eliminated in at least some crystalline materials when a "low" level DC bias voltage is applied to the transducer elements during at least transmit operation. The level of the DC bias voltage is defined as a ratio or relationship to the voltage applied during transmit operation. According to at least some embodiments, the low-level DC bias voltage is maintained at or below 15% of the peak voltage applied during transmit operation. For example, when the transmit voltage varies between + / - 60V, the DC bias voltage is maintained at or below + / - 9V. By maintaining the DC bias voltage as a small percentage of the transmit voltage, the embodiments herein stabilize the orientation of the constituent electric dipoles within the transducer elements and thereby avoid (or at least substantially mitigate) depolarization effects.

[0080] Furthermore, it has been discovered that if the DC bias voltage is present for a relatively long period of time during the transmit and receive cycles compared to the length of the transmit voltage pulses, the low-level DC bias voltage stabilizes the orientation of the constituent electric dipoles within the transducer elements. For example, the DC bias voltage may be maintained continuously throughout the transmit and receive cycles and / or maintained for a substantial portion (e.g., 90% or more) of the transmit and receive cycles. For example, the transmit signal may include a repeated series of pulses, wherein the pulses have a predetermined pulse width to provide an active transmit signal for up to 5% of the complete transmit and receive cycles. As another example, in conjunction with a B-mode imaging procedure, the imaging sequence (transmit and receive cycle) may include a series of transmit pulses that repeat every 200 μs, wherein each individual pulse width is between 200 and 500 ns, thereby providing an active transmit signal for approximately 5% of the time during the entire transmit operation. The DC bias voltage may be applied continuously throughout the transmit cycle and / or maintained for 90% or more of the transmit cycle.

[0081] Optionally, the duty cycle of the DC bias voltage can be varied based on the type of imaging operation and the corresponding type of transmit signal. For example, during pulsed wave Doppler imaging mode, the transmit signal will exhibit a different shape, pulse width, and duty cycle than the transmit signal associated with B-mode imaging. Similarly, the DC bias voltage applied during pulsed wave Doppler imaging can be varied. By utilizing a DC bias voltage set to a low percentage of the maximum transmit voltage and by maintaining the DC bias voltage for a substantially longer period of time relative to the pulse width of the transmit pulse, it has been found that embodiments herein can disproportionately increase the maximum transmit voltage for different transducer materials. The disproportionate increase in the maximum transmit voltage can be maintained without experiencing depolarization effect degradation or reduced sensitivity. The disproportionate increase in the maximum transmit voltage is relative to conventional methods that do not utilize a DC bias voltage and relative to conventional methods that utilize a significantly higher DC bias voltage substantially corresponding to the maximum transmit voltage (e.g., such as described by Dillman et al.). Thus, according to the embodiments herein, a voltage of only a few volts can result in a significant increase in the possible transmit voltage (tens of volts). At least one benefit of the embodiments herein is that the low voltage brings significant improvements when the voltage is applied for a long time compared to the transmit voltage signal length, while at the same time providing a much simpler and cost-effective solution by utilizing a low voltage DC bias circuit.

[0082] By substantially eliminating the depolarization effect, the embodiments herein provide a probe capable of operating the transducer at a higher voltage than conventional probes, thereby improving image quality. Additionally, by substantially eliminating the depolarization effect, the embodiments herein provide a probe capable of using transmission modes that provide better image quality, where such transmission modes were previously not possible due to the depolarization effect. Furthermore, the embodiments herein can be implemented as a retrofit solution for backward compatibility with existing probes, such as through design changes applied at the console of an ultrasound imaging system. By applying a retrofit solution, the embodiments improve the performance of existing products in the installed base.

[0083] Figure 6A FIG. 6 is a block diagram of an ultrasound system including a DC bias circuit implemented according to an embodiment of the present invention. The ultrasound system includes a console 600 connected to a probe connector 602. The console 600 may include a Figures 1 to 4 606 and 603. The probe connector 602 is provided on the proximal end of the probe cable 604. The distal end of the probe cable 604 is connected to the probe 606. Transmission lines 612 electrically connect the transducer elements 610 to corresponding contacts (not shown) in the probe connector 602. The probe connector 602 is configured to mate with a mating connector (not shown) provided on the console. The inductor 611 within the probe 606 and the inductor 603 within the probe connector 602 are provided along line 612. The probe cable 604 is connected to a transmit / receive (T / R) circuit 614 within the console 600 at the probe connector 602. Figure 6A In the example of FIG, the transmit line 612 can also be used as a receiver line to transmit the receive signal from the transducer element to the transceiver 614. Optionally, separate transmit and receive lines can be utilized. A capacitor is provided between the T / R circuit 614 and the node 622.

[0084] During transmit operation, the T / R circuit 614 delivers a transmit signal to cause the transducer element 610 to transmit an ultrasonic signal. During receive operation, the T / R circuit 614 records a return "echo" signal along line 612 corresponding to the ultrasonic echo sensed at the transducer element 610. A bias circuit 620 is connected within the console 600 at a node 622. The bias circuit 620 is configured to introduce a bias signal (such as a DC bias voltage) onto line 612. The bias signal is superimposed on the transmit signal generated by the transmit / receive circuit 614 at node 622.

[0085] Figure 6AA simplified schematic diagram associated with a single transducer element 610 is shown, but it should be understood that the probe 606 will include a transducer array having multiple transducer elements, multiple lines, and T / R circuits associated therewith. According to embodiments herein, a common bias circuit 620 can generate a common bias signal and apply it to each line 612 and the corresponding transducer element 610. Optionally, multiple bias circuits 620 can be used to generate corresponding bias signals and apply them to the lines 612 and the corresponding transducer elements 610. When multiple bias circuits 620 are used, the bias circuits 620 can individually generate bias signals having a common shape, amplitude, and duration. Optionally, when multiple bias circuits 620 are used, the bias circuits 620 can individually generate bias signals that differ from each other in one or more of shape, amplitude, and / or duration. Additionally or alternatively, it may be desirable to apply different bias signals to different sections of the transducer array, such as when different sections of the transducer array have different shapes and / or receive different transmit signals.

[0086] Figure 6A The configuration allows the combination of bias circuit 620 to be implemented within an ultrasound system without any modifications to existing ultrasound probes.

[0087] Figure 6B An example of a transmit signal 650 that may be transmitted during a transmit cycle is shown. Transmit signal 650 includes one or more mode segments, such as a first polarity segment 652 and a second polarity segment 654. First polarity segment 652 and second polarity segment 654 may include one or more pulses and / or may be interleaved with each other to collectively form a common mode segment or separate mode segments. For example, transmit signal 650 may include a complex combination of positive and negative voltage pulses and / or waveform steps having different amplitudes. First polarity segment 652 may be oriented in a polarization direction, while second polarity segment 654 may be oriented in an opposite or depolarization direction. Alternatively, first polarity segment 652 may be oriented in a depolarization direction, while second polarity segment 654 may be oriented in a polarization direction. The term polarity segment is generally used to collectively refer to any / all portions of transmit signal 650 having a common polarity during a transmit cycle. In this example, the first polarity segment 652 collectively refers to any and all portions of the transmit signal 650 having a positive polarity during a transmit cycle, while the second polarity segment 654 collectively refers to any / all portions of the transmit signal 650 having a negative voltage during a transmit cycle.

[0088] Figure 6B The transmit signal 650 in FIG. 1 represents a very simplified waveform comprising a single positive pulse in a first polarity segment 652 and a single negative pulse in a second polarity segment 654 with a peak voltage of + / - V T(e.g., + / - 60V). The transmit signal 650 has a peak-to-peak range corresponding to the sum of the positive peak voltage and the negative peak voltage. The transmit and receive length 656 is substantially longer than the duration of the positive pulse 652 and the negative pulse 654. For example, the transmit and receive time may have a time period of 200 μs in duration, while the positive and / or negative pulses have a pulse width between 200 ns and 500 ns. The receive time is the time between two transmit signals during which no voltage signal is sent to the probe. During the receive time, the ultrasound system collects receive data (echoes) from the probe.

[0089] According to embodiments herein, a bias signal 660 is generated (e.g., at bias circuit 620) having a polarity that is the same as and in the same direction as the polarization direction. For example, when the polarization direction is positive, the bias signal will have a positive amplitude. Alternatively, when the polarization direction is negative, the bias signal has a negative amplitude. The bias signal 660 has a constant bias amplitude V B , which is limited to a relatively small percentage of the peak positive pulse amplitude or peak negative pulse amplitude of the transmit signal. For example, the amplitude V of the bias signal 660 B The amplitude V of the bias signal 660 may be less than 15% of the positive peak amplitude of the transmit signal (eg, 1-9 V). Optionally, the amplitude V of the bias signal 660 may be limited based on the “peak-to-peak” voltage range exhibited by the transmit signal 650. B For example, transmit signal 650 may include a positive peak amplitude of +60 V and a negative peak amplitude of -60 V, thereby defining a peak-to-peak voltage range of 120 V. When the amplitude of bias signal 660 is defined in terms of peak-to-peak amplitude, the bias signal amplitude may be an even smaller percentage, such as less than or equal to 5% of the peak-to-peak amplitude of the transmit signal. Bias signal 660 remains at a "high" level for a substantial portion of the duration of the transmit signal (e.g., continuously for a duration of 200 μs or more than 90% of the 200 μs duration).

[0090] Bias signal 660 is combined with transmit signal 650 to form biased transmit signal 670, which includes a first bias polarity segment 672 and a second bias polarity segment 674. Biased transmit signal 670 is offset to have a quiescent level 676 that is offset in the same direction as the polarization direction by an amount corresponding to the amplitude of bias signal 660. Biased transmit signal 670 is offset in the direction of the polarization direction, but still includes both positive and negative voltages during a transmit cycle. In this example, first bias polarity segment 672 may extend in the polarization direction, while second bias polarity segment 674 may extend in the non-polarization direction. First bias polarity segment 672 has an amplitude corresponding to the sum of the amplitude of the peak positive transmit pulse and the amplitude of the bias signal (e.g., +V T +V B), and the second bias polarity segment 674 has a peak amplitude corresponding to the amplitude of the peak negative transmit pulse and the difference between the amplitude of the bias signal (eg, -V T +V B ) corresponding peak amplitude. In this example, the polarization direction is in the positive direction, so the first bias polarity segment 672 collectively refers to any / all portions of the biased transmit signal 670 having a positive voltage, while the second bias polarity segment 674 collectively refers to any / all portions of the transmit signal 650 having a negative voltage. Optionally, the first bias polarity segment 672 can extend in the non-polarized direction, while the second bias polarity segment 674 can extend in the polarized direction. The sequence of the first bias polarity segment 672 and the second bias polarity segment 674 is not significant. The bias signal 660 can be limited to the length of the transmit pulse 656, or the bias signal 660 can extend throughout the pulse repetition time. For example, the bias signal 660 can be active during the entire transmit / receive period, or the bias signal 660 can be any length in between.

[0091] The bias transmit signal 670 substantially eliminates depolarization in the transducer element by shifting the transmit signal in polarization by an amount corresponding to the level of the bias signal. The offset corresponding to the bias signal is defined as a ratio or relationship to the voltage applied during transmit operation. According to at least some embodiments, the offset corresponding to the bias signal is maintained in the range of 2.5V to 10V, and more preferably in the range of 4-9V, and even more preferably in the range of 5-6V. For transmit operation using a peak voltage of up to 30V, the bias signal can be up to 25% (and more preferably 15% or less, and even more preferably 10% or less) of the peak voltage of the transmit signal generated during the transmit cycle. For example, when the transmit voltage varies between + / - 60V, the DC bias voltage is maintained at + / - 9V or less, and more preferably + / - 6V or less. By maintaining the bias signal at a level between 2.5V and 10V, and more preferably between 4V and 9V, and even more preferably between 5V and 6V, embodiments herein form a biased transmit signal having a first bias polarity segment and a second bias polarity segment that substantially maintains the amplitude of the initial transmit signal extending in both the polarized and non-polarized directions, but with a small percentage shift in the polarized direction. The aforementioned biased transmit signal stabilizes the orientation of the constituent electric dipoles within the transducer element and thereby avoids (or at least substantially reduces) depolarization effects, while allowing implementations utilizing low-voltage bias circuitry.

[0092] Furthermore, the bias signal 662 is defined to have a relatively long pulse width compared to the length of the polarization segments (e.g., 652, 654) of the transmit signal, thereby further stabilizing the electric dipole orientation of the transducer material. For example, the DC bias signal may be maintained continuously throughout the transmit and receive cycles, and / or for a substantial portion (e.g., 90% or more) of the transmit and receive cycles.

[0093] Figure 7 FIG. 7 is a block diagram of an ultrasound system including an implemented DC bias circuit according to an embodiment of the present invention. The ultrasound system includes a console 700 connected to a probe connector 702. The console 700 may include a Figures 1 to 4 7. The probe connector 702 is provided at the proximal end of the probe cable 704. The distal end of the probe cable 704 is connected to the probe 706. Wires 712 electrically connect the transducer elements 710 to corresponding contacts (not shown) in the probe connector 702. Inductor assemblies 711, 713 are provided within the probe 706. Inductor 703 within the probe connector 702 is also provided along wires 712. The probe cable 704 is connected at the probe connector 702 to transmit / receive (T / R) circuitry 714 within the console 700.

[0094] During transmit operation, the T / R circuit 714 delivers a transmit signal to cause the transducer element 710 to transmit an ultrasonic signal. During receive operation, the T / R circuit 714 records a return "echo" signal along line 712 corresponding to the ultrasonic echo sensed at the transducer element 710. A bias circuit 720 is connected at a node 722 within the probe 706. The bias circuit 720 is configured to introduce a bias signal (such as a DC bias voltage) onto line 712. The bias signal is superimposed on the transmit signal generated by the transmit / receive circuit 714 at node 722. Figure 7 The configuration allows the bias circuit 720 to be implemented within each individual probe 706, thereby avoiding any need to modify the conventional console of the ultrasound system. In addition, if a parallel inductor between the transmit / receive line and ground is used in the probe handle or probe connector, then Figure 7 configurations are possible.

[0095] Optionally, Figure 7 The embodiments of (and other embodiments herein) may be implemented in conjunction with a wireless probe in which the bias circuitry is implemented within the probe handle.

[0096] Figure 8 FIG. 8 is a block diagram of an ultrasound system including a DC bias circuit implemented according to an embodiment of the present invention. The ultrasound system includes a console 800 connected to a probe connector 802. The console 800 may include a Figures 1 to 4806. A probe connector 802 is provided on the proximal end of a probe cable 804. The distal end of the probe cable 804 is connected to a probe 806. Wires 812 electrically connect the transducer elements 810 to corresponding contacts (not shown) in the probe connector 802. An inductor 811 is provided within the probe 806 along the wires 812, and an inductor 803 is provided within the probe connector 802. The probe cable 804 is connected to a transmit / receive (T / R) circuit 814 within the console 800 at the probe connector 802.

[0097] During transmit operation, the T / R circuit 814 delivers a transmit signal to cause the transducer element 810 to transmit an ultrasonic signal. During receive operation, the T / R circuit 814 records a return "echo" signal along line 812 corresponding to the ultrasonic echo sensed at the transducer element 810. A bias circuit 820 is connected at a node 822 within the probe connector 802. The bias circuit 820 is configured to introduce a bias signal (such as a DC bias voltage) onto line 812. The bias signal is superimposed on the transmit and receive lines at node 822. Figure 8 The configuration allows the bias circuit 820 to be implemented within the probe connector 802, thereby avoiding any need to modify existing designs of conventional consoles for ultrasound systems and potentially the internal components of the probe body.

[0098] Figure 9 FIG. 1 shows a block diagram of an ultrasound system including a DC bias circuit implemented according to an embodiment of the present invention. The ultrasound system includes a console 900 connected to a probe connector 902. The console 900 may include a Figures 1 to 4 906. The probe connector 902 is provided on the proximal end of the probe cable 904. The distal end of the probe cable 904 is connected to the probe 906. The transducer element 910 is electrically connected to the corresponding contact (not shown) in the probe connector 902. Inductor combinations 911 and 913 are provided in the probe 906, and inductor combinations 903 and 905 are provided in the probe connector 902. The inductor combination may include one or more parallel inductors and / or one or more series inductors. In at least one embodiment, the inductor combination may include two parallel inductors or two series inductors. The probe cable 904 is connected to the transmit / receive (T / R) circuit 914 in the console 900 at the probe connector 902.

[0099] During transmit operation, the T / R circuit 914 delivers a transmit signal to cause the transducer element 910 to transmit an ultrasonic signal. During receive operation, the T / R circuit 914 records a return "echo" signal along line 912 corresponding to the ultrasonic echo sensed at the transducer element 910. A bias circuit 920 is connected within the probe 906 at a node 922 between the transducer element 910 and ground. The bias circuit 920 is configured to introduce a bias signal, such as a DC bias voltage, onto line 912. The ground potential of the transducer is offset by the DC bias voltage. The bias signal is superimposed on the ground voltage level at node 922. Figure 9 The configuration allows the bias circuit 920 to be implemented within the probe connector 902, thereby avoiding any need to modify the conventional console of the ultrasound system. In addition, if a parallel inductor between the transmit / receive line and ground is used in the probe handle or probe connector, then Figure 9 Configurations are possible. The ground potential of the transducer is typically connected to many or all of the elements in parallel. Thus, Figure 9 The configuration does not require modification of each transmit / receive line and is easier to implement.

[0100] Optionally, Figure 9 The embodiments of (and other embodiments herein) may be implemented in conjunction with a wireless probe in which the bias circuitry is implemented within the probe handle.

[0101] from Figures 6A to 9 As can be seen in the previous examples in , bias voltages can be generated and introduced after the AC-coupled beamformer, at the probe connector, within the probe upstream of the transducer elements, within the probe downstream of the transducer elements, and elsewhere. Figure 7 and Figure 8 In an embodiment of the present invention, a bias signal is applied to each line carrying a corresponding transmit signal. Figure 9 In an embodiment, the ground connection can be DC decoupled at the transducer and the bias signal can be applied as a reverse voltage to the transducer ground terminal.

[0102] According to various aspects of the present invention, embodiments increase the stability of depolarization. According to various aspects of the present invention, embodiments enable relatively low bias voltages to be utilized (<10V, approximately <1 kV / cm) and do not necessarily result in a unipolar signal, but rather a biased bipolar signal. According to various aspects of the present invention, embodiments achieve a significant increase in depolarization stability when a bias voltage is applied to a binary SC material (e.g., PMN-PT). According to various aspects of the present invention, several unexpected results were discovered. First, it was unexpectedly discovered that a low DC bias achieved the same or better depolarization performance as a substantially higher voltage bias signal for a binary single crystal material (binary SC). Furthermore, it was unexpectedly discovered that a low voltage bias signal worked to some extent on a ternary single crystal (ternary SC), but not as well as the low voltage bias signal worked on a binary single crystal material. Furthermore, it was unexpectedly discovered that a low voltage bias signal stabilized the weaker binary SC material to a voltage that was equal to or exceeded the capabilities of the ternary SC material.

[0103] Testing was conducted to investigate the depolarization effects exhibited by piezoelectric substrates formed from certain types of single-crystal materials. Different transducers were analyzed. In conjunction with this testing, various transducers were excited with different transmission modes combined with bias signals having different voltage levels. Some of the test results are shown in the following figures.

[0104] Figure 10 Test results collected in conjunction with a type of transducer utilizing binary single crystal material are shown, with sensitivity indicated in decibels along the vertical axis and operating time indicated along the horizontal axis. In conjunction with the measurements, a transmit signal having a desired pattern and a bias signal having a 5V DC steady state amplitude were used to excite the transducer element. The transmit signal included one or more positive segments having a peak positive amplitude > 60V and one or more negative segments having a peak negative amplitude > -60V. When the bias signal was combined with the transmit signal, the resulting biased transmit signal was offset by a 5VDC steady state amplitude in the direction of the polarization direction of the transducer element. The biased transmit signal was applied to the transducer element for a total operating time of several hours. The sensitivity of the transducer element was measured periodically throughout operation to compare the ratio of the input power level to the output power level. As Figure 10 As shown, the sensitivity remains stable between 2dB and 3dB over hours of operation.

[0105] Figure 11 Shown as combined Figure 10 Test results collected in conjunction with the same type of transducer tested, with sensitivity indicated in decibels along the vertical axis and operating time indicated along the horizontal axis. Figure 10The transducer elements are excited by a transmit signal of the same transmit mode applied for the test, but no bias signal is added to the transmit signal (eg, the bias signal is set to 0 V). Figure 11 The test results in FIG indicate the sensitivity of the transducer during the test period of operation when the unbiased transmit signal alone is applied. The transmit signal is applied to the transducer element for a total operating time of several minutes. The sensitivity of the transducer element is measured periodically throughout the operating minutes to compare the ratio of the input power level to the output power level. Figure 11 As shown, the sensitivity drops at a relatively steep rate from an initial level of slightly less than 3 dB. Within the first 10 minutes, the sensitivity has dropped to -3 dB, at about 20 minutes, the sensitivity has dropped to -5 dB, and at 30 minutes, the sensitivity is close to -7 dB.

[0106] from Figure 10 and Figure 11 It is clear from the foregoing tests that applying a bias signal in the direction of the polarization direction of the transducer elements stabilizes the transducer over a period of several hours of operation.

[0107] Figure 12 Figure 1 shows test results collected in conjunction with a type of transducer utilizing binary single crystal material, with sensitivity indicated in decibels along the vertical axis and operating time indicated along the horizontal axis. During this test, a transmission signal utilizing harmonic pulse inversion was used to excite the transducer, but no bias signal (e.g., the bias signal was set to 0V) was added to the transmission signal. A series of horizontal measurement lines are shown, each corresponding to a measurement period of several minutes. During each measurement period, a specific voltage level was used for the transmission signal, with different voltage levels being applied during different measurement periods. For example, the transmission voltage started at approximately 25V and was gradually increased during each measurement period until it reached 120V. Sensitivity measurements remained relatively constant during the first 2-3 hours. However, after 3-4 hours of operation, sensitivity began to decline during the measurement period.

[0108] Figure 13 Shown in combination with Figure 12 The test results were collected using the same type of transducer used in the test results for , where sensitivity is indicated in decibels along the vertical axis and operating time is indicated along the horizontal axis. During this test, Figure 12 The transducer is excited using the same type of transmit signal and the same transmit voltage steps as used in Figure 1 , along with a bias signal having a steady-state amplitude of 10 V DC. A series of horizontal measurement lines are shown, each corresponding to a measurement period of several minutes. During each measurement period, a specific corresponding voltage level is used for the transmit signal, with different voltage levels applied during different measurement periods.

[0109] from Figures 12 to 13 As can be seen from the test results, applying a bias signal in the direction of the polarization direction of the transducer element stabilizes the transducer element at higher transmit voltages. For example, up to 6 dB higher transmit voltages can be used without the transducer element exhibiting depolarization effects.

[0110] Repolarization Implementation

[0111] As explained in accordance with the embodiments herein, by applying a low voltage bias signal during transmit operation, the methods and systems herein are able to stabilize the transducer to limit or avoid depolarization effects. However, in some cases, a certain amount of depolarization may still be experienced. For example, to achieve a certain level of image quality, a higher transmit voltage may be applied. Even at higher transmit voltages, a certain amount of depolarization may still occur. It should be appreciated that depolarization effects can occur due to a variety of factors, not simply through extended use over time or through the use of high transmit voltages. For example, depolarization effects may occur when the probe is stored at excessively high temperatures. In the past, when depolarization effects occurred, it was not possible to completely reverse the depolarization effects (repolarization) via the ultrasound imaging system console. Instead, conventional methods required the probe to undergo a refurbishment process, in which the probe was sent to a refurbishment facility and connected to a separate refurbishment machine (not the ultrasound console) specifically designed to deliver high voltage to the probe. The voltage delivered to the probe during the refurbishment process is substantially higher than the voltage level utilized during ultrasound imaging transmit operation. The ultrasound console of the ultrasound imaging system does not have the ability to operate at the high voltage levels utilized by the separate refurbishment machine. For example, a refurbishment machine may deliver 150V or higher voltage to repolarize the transducer elements during the refurbishment process. Alternatively, the probe can be disassembled during refurbishment to repolarize at a lower DC voltage. This is not possible with a fully assembled probe if a shunt inductor is used in the probe connector or probe handle.

[0112] According to the novel and unique aspects herein, it has been discovered that when an ultrasound system also combines a bias signal with a transmit signal to form a biased transmit signal that is offset in polarization, the transducer elements can be repolarized to reverse the effects of depolarization by applying a repolarization signal having a voltage lower than or similar to the voltage applied during transmit operation. The embodiments herein are capable of achieving repolarization even when the transducer elements exhibit substantially complete depolarization. According to the novel and unique aspects herein, the methods and systems described herein achieve good repolarization results in combination with binary single crystal materials and other transducer materials (e.g., ternary single crystals). For example, relatively long electrical pulses (e.g., up to several seconds) can be emitted from an ultrasound console and used to repolarize a transducer array, such as in conjunction with a configuration utilizing parallel inductors. The combination of a low-voltage DC bias signal and an active repolarization signal allows the use of higher transmit voltages (without concern for depolarization effects), which improves image quality. Since repolarization can be achieved within the ultrasound console and / or probe to allow for in-field probe repair, higher transmit voltages can now be used. Given that the repolarization signals and patterns described herein are capable of returning the state of the probe to an initial polarization level or near the initial polarization level, the embodiments herein allow the transducer array to be driven at a higher voltage during transmit operations, thereby increasing image quality, even though the higher voltage may cause the transducer elements to approach polarization limits.

[0113] The embodiments herein can implement repolarization methods and circuits in conjunction with a variety of ultrasonic transducers, without limitation to the transducer geometry. However, the repolarization embodiments herein may be more suitable when combined with transducers made of materials susceptible to depolarization, including but not limited to single crystal materials, etc. Specifically, the repolarization embodiments herein are well suited to at least partially (and preferably substantially) reversing the depolarization effect exhibited by one or more transducer elements that are substantially constructed of binary or ternary single crystal materials or have a substantially uniform composition of binary single crystal materials. Compared to traditional PZT, the lower coercive field strength of single crystal materials results in a higher risk of depolarization. The repolarization embodiments can be implemented in conjunction with ultrasonic probes having various types and arrangements of transducers, which are configured to collect any and all types of ultrasonic data sets, including but not limited to B-mode data, power Doppler data, Doppler data, strain data, two-dimensional data, three-dimensional data, four-dimensional data, shear wave data, or other data, as described herein and in the patents, patent applications, and other publications cited and incorporated herein.

[0114] Figure 14A FIG. 1 is a block diagram of an ultrasound system including a DC bias circuit and a repolarization drive circuit implemented according to an embodiment of the present invention. The ultrasound system includes a console 1400 connected to a probe connector 1402. The console 1400 may include a Figures 1 to 4 1406. The probe connector 1402 is disposed on a proximal end of the probe cable 1404. The distal end of the probe cable 1404 is connected to the probe 1406. Transmission lines 1412 electrically connect the transducer elements 1410 to corresponding contacts (not shown) in the probe connector 1402. The probe connector 1402 is configured to mate with a mating connector (not shown) disposed on a console. An inductor 1411 within the probe 1406 and an inductor 1403 within the probe connector 1402 are provided along lines 1412. The probe cable 1404 is connected at the probe connector 1402 to a transmit / receive (T / R) circuit 1414 within the console 1400. Figure 14A In the example of FIG, transmit line 1412 can also be used as a receiver line to transmit the receive signal from the transducer element to transceiver 1414. Optionally, separate transmit and receive lines can be utilized. A capacitor is provided between T / R circuit 1414 and node 1422.

[0115] During transmit operation, T / R circuit 1414 delivers a transmit signal to cause transducer element 1410 to transmit an ultrasonic signal. During receive operation, T / R circuit 1414 records a return "echo" signal along line 1412 corresponding to the ultrasonic echo sensed at transducer element 1410. Bias circuit 1420 is connected within console 1400 at node 1422. Bias circuit 1420 is configured to introduce a bias signal, such as a DC bias voltage, onto line 1412. The bias signal is superimposed on the transmit signal generated by transmit / receive circuit 1414 at node 1422.

[0116] According to new and unique aspects of the present invention, the ultrasound system further includes a repolarization signal. According to some embodiments of the present invention, the repolarization signal is generated by a repolarization drive circuit 1405. The repolarization drive circuit 1405 is connected to the transmission line 1412 at a node 1407. The repolarization drive circuit 1405 is configured to generate a repolarization signal having a repolarization pattern that is configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements 1410. Figure 14AIn the example of , the transmit / receive circuit 1414 is implemented as a separate and distinct driver circuit from the repolarization driver circuit 1405 and the bias circuit 1420 to provide different driver circuits. Alternatively, as explained herein, the common driver circuit may be configured to i) provide a transmit drive signal in conjunction with beamforming; ii) provide a repolarization signal and / or iii) provide a bias signal, or any combination thereof. For example, the T / R circuit 1414 may also generate a repolarization signal, while the bias circuit 1420 remains separate. Alternatively, the T / R circuit 1414 may also generate a bias signal, while the repolarization driver circuit remains separate. Alternatively, the T / R circuit 1414 may generate all three signals: a transmit signal, a repolarization signal, and a bias signal. The bias circuit 1420 generates the bias simultaneously in time with the transmit signal, so that the bias signal is combined with the transmit signal to form a biased transmit signal that is shifted in polarization direction. The bias circuit 1420 further generates a bias signal simultaneously in time with the repolarization signal, such that the bias signal is combined with the repolarization signal to form a biased repolarization signal that is also shifted in the polarization direction.

[0117] The repolarization signal can deliver an active repolarization pattern at various times, and as an example, can be used during a normal scanning sequence. For example, the repolarization signal can be applied at the end of a series of transmit / receive operations to collect ultrasound image frames. Additionally or alternatively, the repolarization signal can be applied at specific times during a scanning sequence, such as when an operator places the ultrasound system in freeze mode.

[0118] In this example, a common bias circuit 1420 is used in conjunction with the T / R circuit 1414 and the repolarization drive circuit 1405. The common bias circuit 1420 can add a common bias signal to both the transmit signal and the repolarization signal. Alternatively, the common bias circuit 1420 can add a first bias signal to the transmit signal and a different second bias signal to the repolarization signal. Alternatively, the first bias circuit 1420 can be used with the T / R circuit 1414, and a separate second bias circuit (not shown) can be used in conjunction with the repolarization drive circuit 1405. When separate first and second bias circuits 1420 are implemented with corresponding T / R circuits 1414 and repolarization drive circuits 1405, the first and second bias circuits 1420 can introduce a common bias signal into the transmit signal and the repolarization signal, or alternatively introduce different first and second bias signals into the respective transmit and repolarization signals.

[0119] Figure 14B FIG. 1 shows a block diagram of an ultrasound system including a DC bias circuit and a repolarization drive circuit implemented according to an alternative embodiment of the present invention. Figure 14BIn an embodiment of the present invention, the transmit / receive circuit 1413 is also configured to operate as a repolarization drive circuit, thereby providing a common drive circuit to generate both the transmit signal and the repolarization signal. Figure 14B Other components within the ultrasound system Figure 14A , so the description will not be repeated below.

[0120] Figure 14A and Figure 14B A simplified schematic diagram associated with a single transducer element 1410 is shown, but it should be understood that the probe 1406 will include a transducer array having multiple transducer elements 1410, multiple lines 1412, and multiple T / R circuits 1414, 1413. In some configurations, a separate T / R circuit 1414, 1413 may be provided for each line 1412 and each transducer element 1410. Alternatively, a subset Y of the transducer elements 1410 may be coupled to a common line 1412 and a common T / R circuit 1414 (e.g., in conjunction with a two-dimensional transducer array having a relatively large number of transducer elements). Figure 14B In the configuration of FIG, a common drive circuit 1414 is implemented for the T / R function and the repolarization function for a single line 1412, all lines 1412, and / or a subset of lines 1412.

[0121] Combine Figure 14A In a configuration such as that shown in FIG. 1 , a separate repolarization drive circuit 1405 may be provided for each line 1412. Alternatively, a common repolarization drive circuit 1405 may be coupled to all lines 1412 and all transducer elements 1410, where the lines 1412 and elements 1410 are selected individually or in groups. Alternatively, a subset of transducer elements 1410 may be coupled to a common line 1412 and a corresponding repolarization drive circuit 1405. For example, a number N of repolarization drive circuits 1405 may be provided, where each repolarization drive circuit is coupled to a subset of M transducer elements, thereby allowing a smaller group of N repolarization drive circuits 1405 to reverse the depolarization effects of a larger number N×M transducer elements.

[0122] According to embodiments herein, a common bias circuit 1420 can generate a common bias signal and apply it to each line 1412 and corresponding transducer element 1410. The common bias circuit 1420 can also be used in conjunction with transmit signals from multiple T / R circuits 1414 and / or one or more repolarization drive circuits 1405. Optionally, multiple bias circuits 1420 can be used to generate corresponding bias signals and apply them to the lines 1412 and corresponding transducer elements 1410. When multiple bias circuits 1420 are used, the bias circuits 1420 can individually generate bias signals having a common shape, amplitude, and duration. Optionally, when multiple bias circuits 1420 are used, the bias circuits 1420 can individually generate bias signals that differ from one another in one or more of shape, amplitude, and / or duration. Additionally or alternatively, it may be desirable to apply different bias signals to different sections of the transducer array, such as when different sections of the transducer array have different shapes and / or receive different transmit signals.

[0123] Figure 14A and Figure 14B The configuration allows one or more bias circuits 1420 and / or repolarization circuits 1405 to be implemented within an ultrasound system without any modifications to existing ultrasound probes. Figure 14B The configuration also allows reconfiguration of the T / R circuit 1413 within the ultrasound system to deliver a repolarization signal between transmit signals without any modification to the existing ultrasound probe.

[0124] Figure 14C An example of a repolarization signal 1421 that may be transmitted during a repolarization period between consecutive transmit cycles is shown. Repolarization signal 1421 includes a series of pulses having a first polarity segment 1422 and a series of pulses having a second polarity segment 1424, representing a mode segment. First polarity segment 1422 and second polarity segment 1424 may be part of a common mode segment or represent separate mode segments. First polarity segment 1422 and second polarity segment 1424 may include one or more pulses and / or may be interleaved with one another. For example, repolarization signal 1421 may include a complex combination of positive and negative voltage pulses having different amplitudes and / or waveform steps. First polarity segment 1422 may be along a polarization direction 1423, while second polarity segment 1424 may be along an opposite or depolarization direction 1425. In this example, first polarity segment 1422 includes more pulses than second polarity segment 1424, such that the repolarization signal begins and ends with a pulse in polarization direction 1423. Alternatively, the first pulse in repolarization signal 1421 may begin in depolarization direction 1425, while the last pulse in repolarization signal 1421 extends in polarization direction 1423.

[0125] Alternatively, the first polarity segment 1452 may extend in the depolarization direction while the second polarity segment 1454 extends in the polarization direction.

[0126] The term "polarity segment" is generally used to collectively refer to any / all portions of the repolarization signal 1421 having a common polarity during a repolarization cycle. In this example, the first polarity segment 1422 collectively refers to any and all pulses of the repolarization signal 1421 having a positive polarity during a repolarization cycle, while the second polarity segment 1424 collectively refers to any / all pulses of the repolarization signal 1421 having a negative voltage during a repolarization cycle. Figure 14C The repolarization signal 1421 in FIG. 1 represents a simplified waveform comprising a series of three positive pulses in a first polarity segment 1422 and a series of two negative pulses in a second polarity segment 1424 with a peak voltage of + / - V R The repolarization signal 1421 has a peak-to-peak range corresponding to the sum of the positive peak voltage and the negative peak voltage.

[0127] According to embodiments herein, a bias signal 1415 is generated (e.g., at bias circuit 620, 820, 1420) having a polarity that is the same as and in a common direction with the polarization direction 1423. The bias signal 1415 can be the same bias signal as the combined 660 of the transmit signal 650, or a different bias signal. For example, when the polarization direction is positive, the bias signal will have a positive amplitude. Alternatively, when the polarization direction is negative, the bias signal has a negative amplitude. The bias signal 1415 has a bias amplitude V defined based on one or both of the transmit signal and / or the complex polarization signal. B . For example, the amplitude of the bias signal 1415 can be defined as a percentage of the amplitude of the transmit signal. Additionally or alternatively, the amplitude of the bias signal 1415 can be defined as a percentage of the amplitude of the repolarization signal. Additionally or alternatively, the amplitude of the bias signal 1415 can be defined by subtracting a predetermined offset (e.g., transmit voltage -X volts) from the amplitude of the transmit signal. Additionally or alternatively, the amplitude of the bias signal 1415 can be defined by subtracting a predetermined offset (e.g., repolarization voltage -X volts) from the amplitude of the repolarization signal. Additionally or alternatively, the bias signal 1415 can be defined based on both the transmit signal and the repolarization signal. For example, the amplitude of the bias signal can be defined based on an average of the amplitudes of the transmit signal and the repolarization signal.

[0128] The bias signal 1415 is combined with the repolarization signal 1421 to form a biased repolarization signal 1416, which includes a first bias polarity segment 1418 and a second bias polarity segment 1419. The biased repolarization signal 1416 is offset to have a quiescent level 1417 that is offset in the same direction as the polarization direction by an amount corresponding to the amplitude of the bias signal 1415. The biased repolarization signal 1416 is offset in the direction of the polarization direction, but still includes both positive and negative voltages within the repolarization period. In this example, the first bias polarity segment 1418 may extend in the polarization direction, while the second bias polarity segment 1419 may extend in the non-polarization direction. The first bias polarity segment 1418 has an amplitude corresponding to the sum of the amplitude of the peak positive repolarization pulse and the amplitude of the bias signal (e.g., +V T +V B ), and the second bias polarity segment 1419 has a peak amplitude corresponding to the amplitude of the peak negative repolarization pulse and the difference between the amplitude of the bias signal (eg, -V T +V B ) corresponding peak amplitude. In this example, the polarization direction is in the positive direction, so the first bias polarity segment 1418 collectively refers to any / all portions of the bias repolarization signal 1416 having a positive voltage, while the second bias polarity segment 1419 collectively refers to any / all portions of the repolarization signal 1421 having a negative voltage. Optionally, the first bias polarity segment 1418 can extend in the depolarizing direction, while the second bias polarity segment 1419 can extend in the polarizing direction. The bias signal 1415 can extend throughout the entire pulse repetition time. For example, the bias signal 1415 can be active during the entire repolarization period or a desired portion of the repolarization period.

[0129] The bias signal may be applied i) continuously; ii) only during the delivery of the transmit signal; iii) only during the delivery of the repolarization signal and / or iv) during the delivery of both the transmit signal and the repolarization signal. Figure 14C In the aforementioned examples, the bias signal is shown as having a constant amplitude. Optionally, the bias signal may have a variable amplitude. For example, the bias signal may have a first component applied simultaneously with the transmit signal and a second component applied simultaneously with the repolarization signal. The first and second components may have constant but different voltages. Optionally, the first component may have a constant voltage while the second component has a variable voltage, or vice versa.

[0130] According to embodiments herein, the repolarization signal may have a peak-to-peak amplitude that is a function of the peak-to-peak amplitude of the transmit signal. According to some aspects herein, the amplitude of the repolarization signal may be up to 4 times the amplitude of the transmit voltage, and more preferably, according to other aspects herein, the amplitude of the repolarization signal may not exceed 2.5 times the amplitude of the transmit voltage, and even more preferably, not exceed 1.5 times the amplitude of the transmit voltage. According to other aspects herein, the amplitude of the repolarization signal may be limited to the original voltage. For example, the repolarization signal may have an amplitude between 40V and 150V, more preferably between 70V and 100V, and even more preferably between 80V and 90V.

[0131] In certain embodiments herein, the amplitude of the bias signal applied during the transmit signal is a smaller percentage of the amplitude of the transmit signal. Optionally, the bias signal applied during the repolarization signal may have an amplitude that is the same or a different percentage than the amplitude of the repolarization signal or the transmit signal. For example, the repolarization signal may have an amplitude between 40V and 150V, more preferably between 70V and 100V, and even more preferably between 80V and 90V. In conjunction with this, during the repolarization period, the bias signal may have an amplitude of up to 50V, more preferably between 2V and 25V, and even more preferably between 2V and 10V.

[0132] For probes with parallel inductors, the repolarization pattern can be defined by a series of positive and negative pulses having a predetermined frequency. The predetermined frequency can be defined based on the imaging type, transmit mode, receive mode, and the like. For example, the repolarization signal may utilize one repolarization frequency when performing repolarization in conjunction with a transmit cycle for B-mode imaging, a second repolarization frequency when performing repolarization in conjunction with a transmit cycle for color Doppler imaging, and a third repolarization frequency when performing repolarization in conjunction with a transmit cycle for pulsed-wave Doppler imaging. The repolarization frequency can be defined based on, but distinct from, the transmit frequency. For example, a transmit signal generated in conjunction with one type of ultrasound imaging may have a frequency between 1 MHz and 5 MHz, with a corresponding repolarization frequency between 0.5 MHz and 2 MHz, or more preferably between 1 MHz and 2 MHz. As another example, a transmit signal generated in conjunction with another type of ultrasound imaging may have a frequency between 10 MHz and 15 MHz, with a corresponding repolarization frequency between 8 MHz and 10 MHz. Probes without parallel inductors can use any frequency from DC to the probe's maximum transmit frequency.

[0133] Figure 14DAn example of a biased repolarization signal 1430 that can be transmitted during a repolarization period between consecutive transmit periods (or image frames) according to embodiments herein is shown. The repolarization signal 1430 includes a series of pulses having a first polarity segment 1431 (having a positive peak amplitude corresponding to the sum of the peak amplitude of the repolarization signal and the peak amplitude of the bias signal) and a series of pulses having a second polarity segment 1432 (having a negative peak amplitude corresponding to the difference between the peak amplitude of the repolarization signal and the peak amplitude of the bias signal). The first polarity segment 1431 includes a series of positive pulses 1433 having a first pulse width 1434. The second polarity segment 1432 includes a series of negative pulses 1435 having a second, different pulse width 1436. In this example, the positive pulses 1433 have a common pulse duration 1434 that is longer than the pulse duration 1436 of the negative pulses 1435, such as when the polarization direction is positive. Alternatively, when the polarization direction is negative, the duration of the negative pulse 1435 may be modified to be longer than the duration of the positive pulse 1433 .

[0134] Figure 14E An example of an alternative repolarization pattern according to an embodiment of the present invention is shown. The repolarization signal 1450 includes a series of positive multi-step pulses 1451-1452 and negative multi-step pulses 1453-1454. The first positive pulse 1451 includes a first amplitude V R1 and having a second amplitude V for a longer duration 1456 R2 At the end of the first pulse 1451, the repolarization signal 1450 transitions to a negative pulse 1453 at 1457, which has a first negative amplitude within a first duration 1458. - V R2 , then step down to a lower negative voltage amplitude for different durations - V R1 The negative pulse 1453 is followed by a short quiet period 1459 until the next positive pulse 1452 is initiated which comprises three segments. The first segment comprises a first positive voltage amplitude maintained for a first duration 1460. + V R1 , followed by a second segment that steps into a higher voltage maintained for a second duration 1461 + V R2 , until entering the third segment, which drops back to a lower positive voltage amplitude maintained for a third duration 1462 + V R1 The positive pulse 1452 is followed by a negative pulse 1453 having a similar stepped shape but in the negative direction.

[0135] Figure 15An example of the timing relationship between a frame transmit cycle and a repolarization cycle according to an embodiment of the present invention is shown. During a first transmit cycle 1502, one or more transmit signals may be transmitted, followed by associated receive operations to collect ultrasound data for a partial or complete image frame or 3D data set. During the transmit cycle 1502, a bias signal 1504 is added to each transmit signal, as described in conjunction with various embodiments of the present invention. After the transmit cycle 1502 is completed, a repolarization cycle 1506 is applied, during which the same or different bias signal 1508 is added to the repolarization signal 1510. This process is repeated for subsequent transmit / receive cycles 1512 and repolarization cycles 1514. The repolarization cycle 1506 can be implemented at various times, such as at the end of image frame acquisition, during freeze mode, after collecting a 3D data set, etc. Figure 15 An example of a bias voltage is shown. The bias voltage level can be achieved in various ways, such as a constant bias voltage where BT is equal to BR.

[0136] According to various aspects of this article, in B T With B R During the intervals between the repolarization cycles 1506 and 1514, the voltage level will not be zero. Instead, the voltage used for the repolarization bias signal 1508 will remain at that level from the end of the repolarization cycles 1506 and 1514 until the beginning of the next T / R cycle 1512. Following the T / R cycle, the voltage used for the transmit bias signal 1504 will remain at that level from the end of the T / R cycles 1502 and 1512 until the beginning of the next repolarization cycle 1506 and 1514.

[0137] Figure 15 The example of shows one way in which repolarization can be performed in real time during a single ultrasound scan. Figure 15 In the process of, the repolarization operation is intermittently performed between transmit / receive scanning operations. In addition or alternatively, the repolarization process can be achieved by an ultrasound system that is separate and isolated from any individual ultrasound imaging operation (and at a completely different time point).

[0138] Figure 16 A process for achieving repolarization according to an embodiment of the present invention is shown. At 1602, one or more ultrasound imaging operations are performed using an ultrasound system. The operation at 1602 may include the collection of a single ultrasound image (two-dimensional or three-dimensional), or the collection of multiple ultrasound images (e.g., in conjunction with a complete ultrasound examination performed during a clinical visit). In addition or alternatively, multiple ultrasound examinations may be performed at 1602 over an extended period of time. For example, the operation at 1602 may correspond to multiple days, weeks, months, or other time periods. The operation at 1602 may correspond to multiple hours of operating the ultrasound system. Operation 1602 may correspond to multiple hours of using an ultrasound probe, such as when tracking the operating time of a separate transducer array.

[0139] At 1604, one or more processors of the ultrasound system may perform a test to measure the depolarization level exhibited by one or more transducers of the transducer array. For example, the ultrasound system may implement a probe diagnostic analysis that includes, among other things, measurement of the sensitivity level of one or more transducers within the array. For example, the probe diagnostic analysis may be performed periodically by a technician while the probe is secured to a phantom or other probe diagnostic tool. Additionally or alternatively, the ultrasound system may automatically perform the probe diagnostic analysis, such as when the system is booting up, at the beginning or end of a patient exam, and the like.

[0140] The probe diagnostics analysis can measure and record the sensitivity levels of corresponding transducer elements over time. At the time of manufacture or refurbishment, a baseline sensitivity level can be recorded in the memory of the probe and / or ultrasound system, where the baseline sensitivity level indicates the degree of sensitivity associated with one or more transducer elements having no or minimal depolarization. After a period of use, at 1604, the current sensitivity level is measured.

[0141] At 1606, the one or more processors determine whether one or more transducers of the probe exhibit a depolarization level that exceeds a threshold. For example, the one or more processors may determine that the current sensitivity level has fallen below a predetermined sensitivity level. Additionally or alternatively, the one or more processors may determine that the current sensitivity level has fallen below a baseline sensitivity level by more than a threshold amount (e.g., baseline minus X) and / or by more than a threshold percentage (e.g., the current level is at least 30% below the baseline). When the depolarization level does not exceed the threshold, the process returns to 1602, where additional ultrasound imaging operations are performed. Alternatively, when the depolarization level exceeds the threshold, the process moves to 1608.

[0142] At 1608, one or more processors implement a repolarization operation by applying a repolarization signal (and optionally a bias signal) to the transducer array and / or selected transducer elements. By way of example, the processor may generate the repolarization signal after completing at least one of the acquisition of ultrasound data for an ultrasound image frame or during a freeze mode. Once the repolarization operation is complete, the process returns to 1602 for additional ultrasound imaging operations.

[0143] Figure 17 FIG. 1 shows a block diagram of an ultrasound system including an implemented DC bias circuit according to an embodiment of the present invention. The ultrasound system includes a console 1700 connected to a probe connector 1702. The console 1700 may include a Figures 1 to 417. A probe connector 1702 is provided at the proximal end of a probe cable 1704. The distal end of the probe cable 1704 is connected to a probe 1706. Wires 1712 electrically connect the transducer elements 1710 to corresponding contacts (not shown) in the probe connector 1702. Sensor assemblies 1711 and 1713 are provided within the probe 1706. Sensor assemblies 1703 and 1717 are also provided within the probe connector 1702 along wires 1712. The probe cable 1704 is connected to a transmit / receive (T / R) circuit 1714 within the console 1700 at the probe connector 1702.

[0144] During transmit operation, the T / R circuit 1714 delivers a transmit signal to cause the transducer element 1710 to transmit an ultrasonic signal. During receive operation, the T / R circuit 1714 records a return "echo" signal along line 1712 corresponding to the ultrasonic echo sensed at the transducer element 1710. A bias circuit 1720 is connected within the probe 1706 at a node 1722. The bias circuit 1720 is configured to introduce a bias signal (such as a DC bias voltage) onto line 1712. The bias signal is superimposed on the transmit signal generated by the transmit / receive circuit 1714 at node 1722.

[0145] In accordance with the novel and unique aspects of the present disclosure, the ultrasound system further includes a repolarization drive circuit 1705 disposed in a probe handle 1706. The repolarization drive circuit 1705 is connected to a transmit line 1712 at a node 1707. A single common repolarization drive circuit 1705 can be used to deliver a repolarization signal to all transducer elements 1710 within the transducer array. Alternatively, a separate repolarization drive circuit 1705 can be coupled to each individual transducer element 1710. Alternatively, a group of repolarization drive circuits 1705 can be used with a larger group of transducer elements, wherein each repolarization drive circuit 1705 applies a repolarization signal to a corresponding subset of the transducer elements 1710. The repolarization drive circuit 1705 is configured to generate a repolarization signal having a repolarization pattern that is configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements. Figure 17 The configuration allows the bias circuit 1720 and the repolarization circuit 1705 to be implemented within each individual probe 1706, thereby avoiding any need to modify the conventional console of the ultrasound system.

[0146] exist Figure 17In one embodiment, inductors 1713 and 1717 are provided in parallel with the repolarization drive circuit 1705 and can be configured to apply a voltage "overboost" operation. During a voltage overboost, when a pulse of the repolarization signal is initially applied, the pulse charges the inductor. During the next pulse of the repolarization signal, the charge stored in the inductor is applied to one side of the transducer element, while the repolarization drive circuit 1705 delivers the next pulse to the opposite side of the transducer element, thereby increasing the voltage potential seen by the transducer element based on the combination of the charge stored in the inductor and the charge delivered by the repolarization drive circuit. By utilizing the inductor to form an overboost circuit, embodiments herein reduce the maximum voltage required to be delivered by the repolarization drive circuit. For example, if the repolarization drive circuit is designed to deliver a maximum voltage of + / -40V, and inductors 1713 and 1717 are designed to produce a 20V voltage overboost, the resulting potential applied to the transducer element will shift between a maximum positive and negative voltage of +60V and -40V.

[0147] Optionally, Figure 17 The embodiments of (and other embodiments herein) may be implemented in conjunction with a wireless probe in which the bias circuitry and repolarization circuitry are implemented within the probe handle.

[0148] Figure 18 FIG. 1 shows a block diagram of an ultrasound system including an implemented DC bias circuit according to an embodiment of the present invention. The ultrasound system includes a console 1800 connected to a probe connector 1802. The console 1800 may include a Figures 1 to 4 1804. A probe connector 1802 is provided on the proximal end of a probe cable 1804. The distal end of the probe cable 1804 is connected to a probe 1806. Wires 1812 electrically connect the transducer elements 1810 to corresponding contacts (not shown) in the probe connector 1802. An inductor 1811 is provided within the probe 1806 along the wires 1812, and an inductor 1803 is provided within the probe connector 1802. The probe cable 1804 is connected to a transmit / receive (T / R) circuit 1814 within the console 1800 at the probe connector 1802. Inductors 1803 and 1811 are optional, and connection points 1807 and 1822 may be on either side of the inductor.

[0149] During transmit operation, T / R circuit 1814 delivers a transmit signal to cause transducer element 1810 to transmit an ultrasonic signal. During receive operation, T / R circuit 1814 records a return "echo" signal along line 1812 corresponding to the ultrasonic echo sensed at transducer element 1810. Bias circuit 1820 is connected at node 1822 within probe connector 1802. Bias circuit 1820 is configured to introduce a bias signal (such as a DC bias voltage) onto line 1812. The bias signal is superimposed on the transmit and receive lines at node 1822. In accordance with the novel and unique aspects herein, the ultrasound system further includes a repolarization drive circuit 1805 disposed within probe connector 1802. Repolarization drive circuit 1805 is connected to transmit line 1812 at node 1807. It should be understood that a single, common repolarization drive circuit 1805 can be used to deliver a repolarization signal to all transducer elements 1810 within the transducer array. Alternatively, a separate repolarization drive circuit 1805 may be coupled to each individual transducer element 1810. Alternatively, a set of repolarization drive circuits 1805 may be used with a larger set of transducer elements, with each repolarization drive circuit 1805 applying a repolarization signal to a corresponding subset of the transducer elements 1810. The repolarization drive circuit 1805 is configured to generate a repolarization signal having a repolarization pattern that is configured to at least partially reverse the depolarization effect exhibited by one or more transducer elements. Figure 18 The configuration allows the bias circuit 1820 and the repolarization circuit 1805 to be implemented within the probe connector 1802, thereby avoiding any need to modify existing designs of conventional consoles for ultrasound systems and potentially the internal components of the probe body.

[0150] Conclusion Statement

[0151] It should be clearly understood that the various arrangements and processes generally described and illustrated with respect to the accompanying drawings, and / or one or more individual components or elements of such arrangements and / or one or more process operations associated with such processes, may be used independently of or in conjunction with one or more other components, elements, and / or process operations described and illustrated herein. Thus, while various arrangements and processes are broadly contemplated, described, and illustrated herein, it should be understood that they are provided in an illustrative and non-limiting manner only and, furthermore, may be considered merely as examples of possible operating environments in which one or more devices or processes may function or operate.

[0152] Various aspects are described herein with reference to the accompanying drawings, which illustrate example methods, devices, and program products according to various example embodiments. These program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device or information processing device to generate a machine so that the instructions executed by the processor of the device implement the specified function / action. The program instructions may also be stored in a device-readable medium that can guide the device to operate in a particular manner so that the instructions stored in the device-readable medium produce a manufactured product including instructions for implementing the specified function / action. The program instructions may also be loaded onto a device, causing a series of operating steps to be performed on the device to generate a process for implementing the device, so that the instructions executed on the device provide a process for implementing the specified function / action.

[0153] It should be understood that the subject matter described herein is not limited in its application to the construction details and component arrangements set forth in the specific embodiments herein or shown in the drawings herein. The subject matter described herein may have other embodiments and can be practiced or executed in various ways. In addition, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered restrictive. The words "include," "comprise," or "have" and variations thereof used herein are intended to cover the items listed thereafter and their equivalents as well as additional items.

[0154] It should be understood that the above description is intended to be illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) can be used in combination with each other. In addition, without departing from the scope of the present invention, many modifications can be made to adapt specific situations or materials to the teachings of the present invention. Although the sizes and types of the materials and coatings described herein are intended to limit various parameters, they are by no means restrictive and are illustrative in nature. After reviewing the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the embodiments should be determined with reference to the appended claims and the full scope of equivalents to which these claims are given. In the appended claims, the terms "including" and "in..." are used as the colloquial Chinese equivalents of the corresponding terms "comprising" and "wherein". In addition, in the following claims, the terms "first", "second" and "third" etc. are used only as marks and are not intended to impose numerical requirements on their objects or impose an execution order on their actions.

Claims

1. An ultrasound system, comprising: A transducer having piezoelectric transducer elements (104, 1410) polarized in a polarization direction (1423), wherein one or more of the transducer elements exhibit a depolarization effect over time; as well as One or more driver circuits (1413, 1414, 1405), the one or more driver circuits (1413, 1414, 1405) being configured to: i) generating a transmit signal (650) having at least a first polarity segment and a second polarity segment (652, 654), the first polarity segment and the second polarity segment (652, 654) having corresponding first and second peak amplitudes (+V T ,-V T ); ii. generating a repolarization signal (1421) having a repolarization pattern configured to at least partially reverse the depolarization effect exhibited by the one or more transducer elements (104, 1410); as well as iii. generating a bias signal in the polarization direction, wherein the bias signal is combined with the complex polarization signal (1421) to form a complex polarization signal (1423) in the polarization direction. The biased repolarization signal (1416) shifted upward, The bias signal can be different depending on the period, and the repolarization signal (1421) can be formed in a multi-step form.

2. The ultrasound system of claim 1, the bias signal being combined with the transmit signal (650) to form a biased transmit signal (670) shifted in the polarization direction.

3. The ultrasound system of claim 2, wherein the bias generator (1420) is further configured to generate the bias signal simultaneously in time with the repolarization signal (1421).

4. The ultrasound system of claim 1, wherein the one or more drive circuits include a transmit drive circuit (1414) configured to generate the transmit signal (650).

5. The ultrasound system of claim 4, wherein the one or more drive circuits include a repolarization drive circuit (1405) configured to generate the repolarization signal (1421).

6. The ultrasound system of claim 1, wherein the one or more drive circuits include at least one common drive circuit (1413) configured to generate both the transmit signal and the repolarization signal.

7. The ultrasound system according to claim 1, wherein the one or more driving circuits are configured to generate a series of at least one positive pulse (1433, 1441-1443) and / or at least one negative pulse (1435, 1444-1445) as the repolarization signal. 8 . The ultrasound system of claim 1 , wherein the one or more drive circuits are configured to generate the repolarization signal to have a voltage amplitude between 70 V and 100 V.

9. An ultrasound probe, comprising: A transducer having piezoelectric transducer elements polarized in a polarization direction (1423), wherein one or more of the transducer elements exhibit a depolarization effect over time; a probe connector (1402) and a transmission line (1412) extending from the probe connector (1402) to the transducer, the transmission line (1412) being configured to transmit a transmission signal (650) having at least a first polarity segment and a second polarity segment (652, 654), the first polarity segment and the second polarity segment (652, 654) having corresponding first peak amplitudes and second peak amplitudes; The transmit line (1412) is further configured to transmit a repolarization signal (1421) having a repolarization pattern configured to at least partially reverse a depolarization effect exhibited by the one or more transducer elements; as well as a bias generator (1420) configured to generate a bias signal in the direction of the polarization direction, the bias signal being combined with the transmit signal to form a biased transmit signal (670), the biased transmit signal (670) being offset in the direction of the polarization direction and also including both a positive voltage and a negative voltage during a transmit cycle, the bias signal being combined with the repolarization signal (1421) to form a biased repolarization signal (1416) offset in the polarization direction, The bias signal can be different depending on the period, and the repolarization signal (1421) can be formed in a multi-step form.

10. The ultrasound probe according to claim 9, wherein the bias generator (1420) is further configured to generate the bias signal simultaneously in time with the repolarization signal (1421).

11. The ultrasound probe according to claim 9, further comprising a repolarization drive circuit (1705) within a housing of the ultrasound probe (1706), the repolarization drive circuit (1705) being configured to generate the repolarization signal (1421).

12. The ultrasound probe according to claim 9, wherein the repolarization signal (1421) includes a series of at least one positive pulse (1433) and at least one negative pulse (1435).

13. The ultrasound probe according to claim 9, wherein the repolarization signal (1421) has a voltage amplitude between 70V and 100V.

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