Ultrasound imaging catheter

Abstract

An ultrasound imaging catheter includes an ultrasound transducer array provided at a distal end of the ultrasound imaging catheter. The ultrasound transducer array includes a plurality of ultrasound transducers and is adapted to transmit and receive ultrasound signals. The ultrasound imaging catheter includes a local memory provided at the distal end of the ultrasound imaging catheter. The local memory is adapted to store a plurality of activation patterns, each activation pattern corresponding to a plurality of transducer elements of the plurality of transducer elements to be activated and a plurality of transducer elements of the plurality of transducer elements to be deactivated. The ultrasound imaging catheter includes a control unit provided at the distal end of the ultrasound imaging catheter, the control unit being adapted to: access the local memory; select any one of the plurality of activation patterns; and generate control signals to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of ultrasound imaging systems, and more specifically to an ultrasound imaging catheter. BACKGROUND

[0002] Intravenous ultrasound imaging catheters are widely used for many different clinical applications. Typically, the ultrasound imaging catheter is fully controlled by a back-end processing unit or console. For each ultrasound transducer element in the ultrasound imaging catheter, a decision needs to be made whether the transducer element is active during the transmission of an ultrasound pulse and whether the transducer element should be activated during the reception of an echo from the transmitted pulse.

[0003] In order to improve the imaging quality of the ultrasound imaging catheter, attempts have been made to increase the number of transducer elements that can be located at the catheter tip.

[0004] By increasing the number of transducer elements and increasing the number of return channels for echoes, the full control of the console over the transducer element array at the catheter tip poses significant challenges (e.g. steep signal slopes and high bandwidth requirements), resulting in increased communication pressure between the console and the catheter.

[0005] Typically, due to mechanical requirements, the communication channel in the ultrasound imaging catheter system comprises wires with relatively high resistance and capacitance, resulting in disturbances in the communication signal and reducing the accuracy of the images produced by the ultrasound imaging catheter.

[0006] Therefore, there is a need for improved means to handle the communication between the ultrasound imaging catheter and the console. SUMMARY

[0007] The invention is defined by the claims.

[0008] According to an example in accordance with an aspect of the invention, there is provided an ultrasound imaging catheter, the ultrasound imaging catheter comprising:

[0009] an ultrasound transducer array provided at a distal end of the ultrasound imaging catheter and adapted to transmit and receive ultrasound signals, wherein the ultrasound transducer array comprises a plurality of ultrasound transducers;

[0010] a local memory provided at the distal end of the ultrasound imaging catheter and adapted to store a plurality of activation patterns, wherein each activation pattern corresponds to a plurality of transducer elements to be activated and a plurality of transducer elements to be deactivated among the plurality of transducer elements; and

[0011] a control unit provided at the distal end of the ultrasound imaging catheter and adapted to:

[0012] access the local memory;

[0013] selecting any one of the plurality of activation patterns; and

[0014] generating control signals to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter, the imaging phase comprising a transmit period and a receive period.

[0015] In this way, the functionality of the front-end of the ultrasound imaging catheter can be improved, thereby reducing the amount of communication required between the front-end processing unit and the back-end processing unit, which in turn provides means to achieve higher frame rates, a larger number of transducer elements in the transducer array, and a larger number of echo return channels.

[0016] In embodiments, the ultrasound imaging catheter further comprises:

[0017] a plurality of registers, each register comprising a plurality of bits, wherein each bit is associated with one of the plurality of ultrasound transducers; and

[0018] a local oscillator in communication with the plurality of registers and adapted to receive the control signals generated by the control unit and to manipulate the plurality of bits in the plurality of registers to activate and / or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern.

[0019] In this way, an asynchronous communication scheme can be implemented in the ultrasound imaging catheter front-end, which would otherwise require a free-running clock signal in order to provide the surplus signal edges to initiate the operation of the registers.

[0020] In embodiments, the local oscillator is adapted to operate outside of the imaging phase of the ultrasound imaging catheter.

[0021] In this way, potential imaging artifacts due to signal feedthrough or crosstalk from the local oscillator can be avoided.

[0022] In embodiments, the local oscillator is adapted to operate at a frequency that is larger than the bandwidth of the plurality of ultrasound transducers.

[0023] In this way, imaging artifacts caused by the local oscillator can be reduced or eliminated.

[0024] In embodiments, the local oscillator is adapted to generate a square wave with a predetermined duty cycle. The duty cycle is such that a component of the frequency spectrum of the local oscillator is outside of the bandwidth of the plurality of ultrasound transducers.

[0025] In this way, the harmonics of the local oscillator are made outside the bandwidth of the ultrasound transducer, thereby reducing any imaging artifacts caused by the local oscillator.

[0026] In embodiments, the plurality of registers is arranged in a plurality of register groups, each register group comprising:

[0027] a first register comprising a first register bit;

[0028] a second register comprising a second register bit; and wherein,

[0029] a transducer element of the plurality of transducer elements is associated with the first register bit and the second register bit, the first register bit being adapted to control whether the transducer element is active or inactive during the transmit period, the second register bit being adapted to control whether the transducer element is active or inactive during the receive period.

[0030] By providing independent registers for each function, a greater flexibility of activation patterns and their application can be achieved.

[0031] In further embodiments, the ultrasound transducer array comprises a plurality of output channels, and wherein each register group further comprises a third register, the third register comprising a third register bit, and wherein the transducer element is further associated with the third register bit, the third register bit being adapted to control to which output channel of the plurality of output channels a signal received at the transducer element is outputted.

[0032] In embodiments, the plurality of register groups is connected in a daisy chain, wherein each register group is connected in series with an adjacent register group.

[0033] In this way, the number of connections required at the front end of the catheter can be reduced without negatively affecting the functionality of the ultrasound imaging catheter.

[0034] In embodiments, the ultrasound imaging catheter further comprises a signal conditioning unit, the signal conditioning unit being provided at the distal end of the ultrasound imaging catheter and being adapted to signal condition the received ultrasound signals.

[0035] In this way, signals can be conditioned before being transmitted to the back-end processing unit, thereby reducing imaging artifacts that can be exaggerated during transmission and thus improving the accuracy of the final ultrasound image.

[0036] In further embodiments, the signal conditioning unit comprises a low noise amplifier.

[0037] In embodiments, the signal conditioning unit comprises one or more time gain compensation units.

[0038] According to examples in accordance with an aspect of the application, there is provided an ultrasound imaging system, the system comprising:

[0039] an ultrasound imaging catheter as described above;

[0040] a processing unit in communication with the ultrasound imaging catheter and adapted to generate an ultrasound image based on the received ultrasound signals; and

[0041] a display adapted to display the ultrasound image.

[0042] According to examples in accordance with an aspect of the application, there is provided a method for controlling an ultrasound imaging catheter, the ultrasound imaging catheter comprising an ultrasound transducer array having a plurality of ultrasound transducers, the method comprising:

[0043] accessing a local memory provided at the distal end of the ultrasound imaging catheter;

[0044] selecting any one of a plurality of activation patterns stored on the local memory, wherein each activation pattern corresponds to a plurality of transducer elements of the plurality of transducer elements to be activated and a plurality of transducer elements of the plurality of transducer elements to be deactivated; and

[0045] generating a control signal to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter, the imaging phase comprising a transmit period and a receive period.

[0046] In embodiments, the method further comprises:

[0047] providing the control signal to a local oscillator; and

[0048] manipulating a plurality of bits of a plurality of registers, wherein each bit is associated with one of the plurality of ultrasound transducers to activate and / or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern.

[0049] According to examples in accordance with an aspect of the application, there is provided a computer program comprising computer program code means which is adapted, when said computer program is run on a computer, to implement the above-described method.

[0050] These and other aspects of the application will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0051] For a better understanding of the present application, and to show more clearly how it can be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

[0052] Figure 1 An ultrasound diagnostic imaging system is shown to explain general operation;

[0053] Figure 2 A schematic diagram of an ultrasound imaging catheter is shown;

[0054] Figure 3 A schematic diagram of an ultrasound imaging catheter is shown in more detail; Figure 2

[0055] Figure 4 An example implementation of a portion of an ultrasound imaging catheter is shown;

[0056] Figure 5 An example register connection scheme is shown;

[0057] Figure 6 A schematic diagram of a register relative to a catheter is shown; and

[0058] Figure 7 A method of the present application is shown. DETAILED DESCRIPTION

[0059] The present application will be described with reference to the accompanying drawings.

[0060] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of apparatuses, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the present application. These and other features, aspects, and advantages of the apparatuses, systems and methods of the present application will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings for like or similar items.

[0061] ​An ultrasound imaging catheter is provided, comprising an ultrasound transducer array provided at a distal end of the ultrasound imaging catheter and adapted to transmit and receive ultrasound signals, wherein the ultrasound transducer array comprises a plurality of ultrasound transducers. The ultrasound imaging catheter further comprises a local memory provided at the distal end of the ultrasound imaging catheter and adapted to store a plurality of activation patterns, wherein each activation pattern corresponds to a plurality of transducer elements of the plurality of transducer elements to be activated and a plurality of transducer elements of the plurality of transducer elements to be deactivated. In addition, the ultrasound imaging catheter further comprises a control unit provided at the distal end of the ultrasound imaging catheter and adapted to: access the local memory; select any one of the plurality of activation patterns; and generate a control signal to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter, the imaging phase comprising a transmit period and a receive period.

[0062] Reference will now be made to Figure 1 The general operation of an exemplary ultrasound system will first be described.

[0063] The system includes an array transducer probe 4 having a transducer array 6 for transmitting ultrasound waves and receiving echo information. The transducer array 6 can include CMUT transducers; piezoelectric transducers formed from a material such as PZT or PVDF; polymer-based transducers; or any other suitable transducer technology. In this example, the transducer array 6 is a two-dimensional array of transducers 8 capable of scanning a region of interest in a two-dimensional plane or a three-dimensional volume. In another example, the transducer array can be a one-dimensional array.

[0064] The transducer array 6 is coupled to a microbeamformer 12 that controls signal reception by the transducer elements. The microbeamformer is capable of at least partially beamforming signals received by sub-arrays (often referred to as “groups” or “tiles”) of transducers, as described in U.S. Patents US 5997479 (Savord et al.), US 6013032 (Savord), and US 6623432 (Powers et al.).

[0065] It should be noted that the microwave beamformer is entirely optional. In addition, the system includes a transmit / receive (T / R) switch 16 that can be coupled to the microwave beamformer 12 and switches the array between transmit and receive modes and protects the main beamformer 20 from high energy transmit signals in the case where the microwave beamformer is not used and the main system beamformer operates the transducer array directly. Transmission of ultrasound beams from the transducer array 6 is directed by a transducer controller 18 that is coupled to the microwave beamformer through the T / R switch 16 and to the main transmit beamformer (not shown) that can receive input from user operation from a user interface or control panel 38. The controller 18 can include transmit circuitry arranged to drive the transducer elements of the array 6 (directly or via the microwave beamformer) during transmit mode.

[0066] In a typical line-by-line imaging sequence, the beamforming system within the probe can operate as follows. During transmission, the beamformer (which can be the microwave beamformer or the main system beamformer, depending on the implementation) activates a transducer array or a sub-aperture of the transducer array. The sub-aperture can be a one-dimensional line of transducers or a two-dimensional patch of transducers within a larger array. In transmit mode, the focusing and steering of the ultrasound beams generated by the array or sub-aperture of the array is controlled as described below.

[0067] Upon receiving the backscattered echo signals from the object, the received signals are subjected to receive beamforming (as described below) to align the received signals and, in the case of using a sub-aperture, the sub-aperture is then shifted, for example, by one transducer element. The shifted sub-aperture is then activated and the process is repeated until all of the transducer elements of the transducer array have been activated.

[0068] For each line (or sub-aperture), the total received signal for the associated line that is used to form the final ultrasound image will be the sum of the voltage signals measured by the transducer elements of the given sub-aperture during the receive period. Following the beamforming process below, the resulting line signal is often referred to as the radio frequency (RF) data. Each line signal (RF data set) generated by the individual sub-apertures is then subjected to additional processing to generate a line of the final ultrasound image. The amplitude of the line signal as a function of time will contribute to the brightness of the ultrasound image as a function of depth, where high amplitude peaks will correspond to bright pixels (or collections of pixels) in the final image. Peaks that occur near the beginning of the line signal will represent echoes from shallow structures, while peaks that occur progressively later in the line signal will represent echoes from structures within the object that are increasing in depth.

[0069] One of the functions controlled by the transducer controller 18 is the direction of beam steering and focusing. The beam can be steered straight ahead (perpendicular to the transducer array), or steered at different angles to obtain a wider field of view. The steering and focusing of the transmitted beam can be controlled according to the transducer element actuation times.

[0070] In general ultrasound data acquisition, two methods can be distinguished: plane wave imaging and "beam steering" imaging. The difference between these two methods is the presence of beam shaping in the transmit mode ("beam steering" imaging) and / or in the receive mode (plane wave imaging and "beam steering" imaging).

[0071] Looking first at the focusing function, the transducer array generates a plane wave by activating all transducer elements simultaneously, which diverges as it travels through the subject. In this case, the beam of ultrasound waves remains unfocused. By introducing a position-dependent time delay to the activation of the transducers, it is possible to make the wavefront of the beam converge at a desired point, which is referred to as the focal zone. The focal zone is defined as the point where the lateral beam width is less than half the transmitted beam width. In this way, the lateral resolution of the final ultrasound image is improved.

[0072] For example, if the time delay causes the transducer elements to be activated serially starting from the outermost elements and ending at the central element(s) of the transducer array, a focal zone will be formed at a given distance from the probe, which is in line with the central element(s). The distance of the focal zone from the probe will vary according to the time delay between each subsequent round of transducer element activation. After the beam passes through the focal zone, it will start to diverge, thereby forming a far-field imaging region. It should be noted that for focal zones located close to the transducer array, the ultrasound beam will diverge rapidly in the far field, resulting in beam width artifacts in the final image. Generally, the near field, which is located between the transducer array and the focal zone, shows little detail due to the large amount of overlap in the ultrasound beam. Thus, changing the position of the focal zone can cause a significant change in the quality of the final image.

[0073] It should be noted that in the transmit mode, only one focal point can be defined unless the ultrasound image is divided into multiple focal zones (each of the multiple focal zones can have a different transmit focal point).

[0074] Additionally, upon receiving echo signals from inside the subject, the inverse of the above process can be performed in order to perform receive focusing. In other words, the incoming signals can be received by the transducer elements and subjected to electronic time delays before being passed into the system for signal processing. The simplest example of this case is known as delay-and-sum beamforming. The receive focusing of the transducer array can be dynamically adjusted according to time.

[0075] Now turning to the function of beam steering, by applying the correct time delay to the transducer elements, it is possible to impart a desired angle to the ultrasound beam as it leaves the transducer array. For example, by activating the transducers on the first side of the transducer array and then ending the sequence with the remaining transducers at the opposite side of the array, the wavefront of the beam will be angled toward the second side. The size of the steering angle relative to the normal of the transducer array depends on the size of the time delay between the activation of the subsequent transducer elements.

[0076] Additionally, it is possible to focus the steered beam, where the total time delay applied to each transducer element is the sum of both the focusing time delay and the steering time delay. In this case, the transducer array is referred to as a phased array.

[0077] In the case of CMUT transducers that require a DC bias voltage for their activation, the transducer controller 18 can be coupled to control the DC bias control 45 for the transducer array. The DC bias control 45 sets the DC bias voltage(s) applied to the CMUT transducer elements.

[0078] For each transducer element of the transducer array, the analog ultrasound signal, often referred to as channel data, enters the system through the receive channel. In the receive channel, the microbeamformer 12 produces a partially beamformed signal from the channel data, which is then passed to the main receive beamformer 20, where the partially beamformed signals from the individual tiles of transducers are combined into a fully beamformed signal (which is referred to as radio frequency (RF) data). The beamforming performed at each stage can be performed as described above, or can include additional functionality. For example, the main beamformer 20 can have 128 channels, each of which receives a partially beamformed signal from a tile of tens or hundreds of transducer elements. In this way, the signals received by thousands of transducers of the transducer array can effectively contribute to a single beamformed signal.

[0079] The beamformed receive signal is coupled to the signal processor 22. The signal processor 22 can process the received echo signal in various ways, such as bandpass filtering; decimation; I and Q component separation; and harmonic signal separation, which is used to separate linear signals from nonlinear signals, so that nonlinear (higher harmonics of the fundamental frequency) echo signals returned from tissue and microbubbles can be identified. The signal processor can also perform additional signal enhancements, such as speckle reduction, signal compounding, and noise cancellation. The bandpass filter in the signal processor can be a tracking filter, which slides its passband from higher to lower frequency bands as the echo signal is received from increasingly deeper depths, so as to reject higher frequency noise from greater depths, which typically has no anatomic information.

[0080] The beamformer used for transmission and the beamformer used for reception are implemented in different hardware and are capable of different functions. Of course, the design of the receiver beamformer must take into account the characteristics of the transmission beamformer. For simplicity, in... Figure 1 Only receiver beamformers 12 and 20 are shown in the diagram. Throughout the system, there will also be a transmit chain, which includes a transmit microwave beamformer and a main transmit beamformer.

[0081] The function of microwave beamformer 12 is to provide an initial combination of signals in order to reduce the number of analog signal paths. This is typically performed in the analog domain.

[0082] The final beamforming is performed in the main beamformer 20, and is typically done after digitization.

[0083] The transmit and receive channels use the same transducer array 6 with a fixed frequency band. However, the bandwidth occupied by the transmit pulse can vary depending on the transmit beamforming used. The receive channel can capture the entire transducer bandwidth (this is the classic approach), or it can use bandpass processing so that it only extracts the bandwidth containing the desired information (e.g., harmonics of the main harmonic).

[0084] The RF signal can then be coupled to a B-mode (i.e., luminance mode or 2D imaging mode) processor 26 and a Doppler processor 28. The B-mode processor 26 performs amplitude detection on the received ultrasound signal to image structures in the body, such as organs, tissues, and blood vessels. In the case of line-by-line imaging, each line (beam) is represented by an associated RF signal whose amplitude is used to generate a luminance value to be assigned to a pixel in the B-mode image. The exact location of a pixel within the image is determined by measuring its position along the associated amplitude of the RF signal and the number of lines (beams) of the RF signal. As described in U.S. Patent US 6283919 (Roundhill et al.) and U.S. Patent US 6458083 (Jago et al.), B-mode images of such structures can be formed in a harmonic imaging mode or a fundamental imaging mode, or a combination of both. The Doppler processor 28 processes signals that differ temporally due to tissue movement and blood flow for the detection of moving material (e.g., blood cell flow in the image field). Doppler processor 28 typically includes a wall filter whose parameters are set to allow or reject echoes returning from a selected type of material in the body.

[0085] The structural and motion signals produced by the B-mode and Doppler processors are coupled to a scan converter 32 and a multiple planar reformatter 44. The scan converter 32 places the echo signals in the desired image format in terms of the spatial relationships in which the echo signals were received. In other words, the scan converter functions to convert the RF data from a cylindrical coordinate system to a Cartesian coordinate system appropriate for displaying ultrasound images on the image display 40. In the case of B-mode imaging, the brightness of a pixel at a given location is proportional to the magnitude of the RF signal received from that location. The scan converter can place the echo signals into a two-dimensional (2D) sector format or a pyramidal three-dimensional (3D) image, for example. The scan converter can overlay a B-mode structural image with colors corresponding to motion at various points in the image field, the Doppler estimated velocities at which give a given color. The combined B-mode structural image with color Doppler image depicts tissue motion and blood flow within the structural image field. The multiple planar reformatter converts echoes received from points in a common plane in a volumetric region of the body into an ultrasound image of that plane, as described in U.S. Patent 6,443,896 (Detmer). The volume renderer 42 converts echo signals of a 3D data set into a projected 3D image as viewed from a given reference point, as described in U.S. Patent 6,653,0885 (Entrekin et al.).

[0086] The 2D or 3D images are coupled from the scan converter 32, the multiple planar reformatter 44, and the volume renderer 42 to the image processor 30 for further enhancement, buffering, and temporary storage for display on the image display 40. The imaging processor can be adapted to remove some imaging artifacts from the final ultrasound image, such as: acoustic shadows caused by strong attenuators or refractions; post- enhancement caused by weak attenuators; reverberation artifacts at locations immediately adjacent to highly reflective tissue interfaces; etc. In addition, the image processor can be adapted to process certain speckle reduction functions in order to improve the contrast of the final ultrasound image.

[0087] In addition to being used for imaging, the blood flow values produced by the Doppler processor 28 and the tissue structure information produced by the B-mode processor 26 can be coupled to a quantification processor 34. In addition to structural measurements (e.g., organ size and gestational age), the quantification processor produces measures of different flow conditions (e.g., volume rate of blood flow). The quantification processor can receive inputs from the user control panel 38 (e.g., points in the anatomy of the image at which measurements are to be made).

[0088] The output data from the quantification processor is coupled to a graphics processor 36 for rendering images on a display 40 together with measurement graphics and measurement values and for audio output integrated into the display device 40. The graphics processor 36 is also capable of generating graphic overlays for display with the ultrasound images. These graphic overlays can contain standard identification information (e.g. patient name), date and time of the image, imaging parameters, etc. To this end, the graphics processor receives input from the user interface 38 (e.g. patient name). The user interface is also coupled to the transmit controller 18 to control the ultrasound signal generation from the transducer array 6 and thus the images produced by the transducer array and the ultrasound system. The transmit control function of the controller 18 is only one of the functions performed. The controller 18 also takes into account the operating mode (given by the user) and the corresponding required transmitter configuration and bandpass configuration in the receiver analog-to-digital converter. The controller 18 can be a state machine with fixed states.

[0089] The user interface is also coupled to a multiplanar reformatter 44 for selecting and controlling the planes of a multi-slice multiplanar reformatted (MPR) image which can be used to perform the quantified measurements in the image field of the MPR image.

[0090] Figure 2 A schematic diagram 100 of an ultrasound imaging catheter 110 is shown.

[0091] The ultrasound imaging catheter 110 comprises an ultrasound transducer array 120 provided at a distal end of the ultrasound imaging catheter, said ultrasound imaging catheter comprising a plurality of ultrasound transducers 125.

[0092] The ultrasound imaging catheter 110 further comprises a local memory (LM) 130 provided at the distal end of the ultrasound imaging catheter and adapted to store a plurality of activation patterns. Each of the plurality of activation patterns corresponds to a plurality of ultrasound transducers 125a of the plurality of transducer elements to be activated and a plurality of ultrasound transducers 125b of the plurality of transducer elements to be deactivated during an imaging phase of the ultrasound imaging catheter.

[0093] The imaging phase can be seen as two different time periods: a transmit time period and a receive time period. In the transmit time period, the ultrasound transducers generate ultrasound signals and the ultrasound signals are transmitted into the object. In the receive time period, echoes from the transmitted ultrasound transducers are received at the ultrasound transducers.

[0094] In addition, the ultrasound imaging catheter 110 comprises a control unit (CU) 140 provided at the distal end of the ultrasound imaging catheter and adapted to access the local memory and to select any one of the plurality of activation patterns stored in the local memory.

[0095] The control unit then generates control signals 150 to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern. In Figure 2 The example shown, the CU 140 manipulates the LM 130 in order to pass control signals 150 to the transducers, controlling the activity of the transducers. The CU 140 also acts as a communication link between the circuitry at the distal end of the ultrasound imaging catheter 110 and the rest of the ultrasound system.

[0096] By having the local memory 130 and control unit 140 located at the catheter rather than at the back-end processing unit, the required communication between the back-end console and the catheter is reduced.

[0097] In other words, operational control features are added to the catheter, such that it can independently perform at least part of the manipulation of the transmit element selection, receive element selection and / or return channel selection. This results in a significant reduction of the communication needs between the console and the catheter, allowing for a higher frame rate, a larger number of ultrasound transducer elements and a larger number of echo return channels to be employed in the system.

[0098] The ultrasound imaging catheter can act as the ultrasound probe 4 described above with reference to Figure 1 The ultrasound imaging catheter 110 is shown in more detail in a schematic diagram 200.

[0099] Figure 3 The ultrasound imaging catheter 110 is shown in more detail in a schematic diagram 200. Figure 2 In the example shown, the ultrasound imaging catheter 110 is shown as having two component groups: a digital part 210 and an analog part 220.

[0100] Figure 3 In the digital part 210, there is a two-wire serial interface (SI) 230, which can for example communicate with a console or any other suitable back-end processing unit for controlling the ultrasound imaging catheter 110. Signals can be provided to a parameter control unit (P) 240 through the serial interface, which is adapted to set and read back parameters for controlling the operation of the analog part 220 and the digital part 210 of the ultrasound imaging catheter.

[0101] The digital part 210 further comprises a transducer selection unit (TSU) 250, which can comprise the local memory 130 and the control unit 140 described above with reference to The ultrasound imaging catheter 110 is shown in more detail in a schematic diagram 200.

[0102] Figure 2 The ultrasound imaging catheter 110 is shown in more detail in a schematic diagram 200.

[0103] ​The transducer selection unit determines which transducer elements of the transducer array 120 should be active during the transmit phase and which transducer elements will be used during the receive phase. This is accomplished by the control unit accessing local memory to retrieve an activation mode from a variety of activation modes.

[0104] exist Figure 3 In the example shown, the transducer selection unit generates a control signal 255, which is provided to the driver unit (D) 260 and the receiver unit (R) 270. The driver unit activates the ultrasonic transducers of the transducer array during the transmission period based on the control signal received from the transducer selection unit. Similarly, the receiver unit activates the ultrasonic transducers of the transducer array during the reception period based on the control signal received from the transducer selection unit.

[0105] In other words, during the transmission and reception phases of the imaging stage, the transducers of the ultrasonic transducer array are activated according to the activation mode-based control signal generated by the transducer selection unit.

[0106] In other words, based on the activation mode stored in the local memory located at the distal end of the ultrasound imaging catheter, the transducer elements of the transducer array, which is also located at the distal end, are activated.

[0107] During the transmission phase, for example when the ultrasound imaging catheter is inside the object (e.g., inside a blood vessel of the object), the operation is selected according to the activation mode to activate the ultrasound transducer to generate ultrasound pulses.

[0108] During the receiving phase, the ultrasonic transducer receives echo signals 290 from the object's body. The received echo signals may undergo signal conditioning before being sent to the appropriate back-end processing system.

[0109] exist Figure 3 In the example shown, the analog section 220 of the ultrasound imaging catheter 110 includes a low-noise amplifier 300 to condition the incoming received echo signal; however, any other signal conditioning unit, such as a time gain compensation unit, may also be implemented in the analog section.

[0110] The conditioned signal is then passed to a signal selector (SS) 310, which applies selection criteria to the conditioned signal to determine which signals can be sent to the backend for processing to generate an ultrasound image. For example, the selection criteria may include a given signal quality metric, such as signal-to-noise ratio. The selection criteria can be adjusted according to the application of the ultrasound imaging catheter, for example, by means of user input.

[0111] When the transducer selection unit receives signal 320 to initiate a "give next acquisition" instruction (i.e., an instruction to begin the subsequent imaging phase), the transducer selection unit determines the transducer that will be used as both a transmitting and receiving element for the next imaging operation. More specifically, this instruction can cause the control unit to access local memory to select an activation mode corresponding to the transducer to be activated or deactivated.

[0112] Figure 4 It shows Figure 3 Example implementation 400 of the digital portion 210 of the ultrasound imaging catheter.

[0113] exist Figure 4 In the example shown, the intelligence level of the transducer selection unit is relative to the reference. Figure 3 The described example is slightly reduced. As a result, the communication requirements between the back-end processing unit or console and the ultrasound imaging catheter may be slightly increased, but they are still significantly reduced compared to a standard ultrasound imaging catheter. However, this example offers greater flexibility in determining which ultrasound elements to activate or deactivate during the transmit and receive phases. Additionally, this example provides greater flexibility in selecting the return channel for sending the received echo signals to the back-end processing system.

[0114] Figure 4 The example shown uses two communication mechanisms for operation. The first communication interface 410 is used for setting and reading back as referenced above. Figure 3 The serial interface describes the parameters of the analog and digital components of the described ultrasound imaging catheter. The serial interface can be connected to I... 2 C interface 420, I 2 The C interface 420 operates based on two signals: the serial clock (SCL) signal and the serial data (SDA) signal.

[0115] The second communication interface 430 may include a high-speed serial (HS) interface 440, which is the one referenced above. Figure 3 The one-way equivalent of the described instruction to "give the next acquisition".

[0116] Figure 4 Several cores located in an ultrasound imaging catheter are shown: a main core 450 and multiple secondary cores 460. This can be implemented and may include I... 2 The first communication interface 410 of the C interface 420 is made identical for all dies. 2The three address pins on the C interface unit determine the die type (master die 450 or slave die 460). If the address pin reads "000", the die is considered a master die 450. Conversely, if the address pin reads between "001" and "111", the die is considered a slave die 460. In this example, the maximum allowed number of slave dies 460 is 7; however, the number of slave dies can be increased or decreased depending on the application.

[0117] From die 460 I 2 The C interface unit 420 can be connected to an analog circuit, which may include circuits such as those referenced above. Figure 3 The description includes components such as low-noise amplifiers (LNAs) and / or time-gain compensation (TGCs), as well as slave units 470 connected in each die 460. Slave units 470 are components in the circuit that provide the following indications for each ultrasonic transducer 480: whether each ultrasonic transducer 480 will be active or deactivated during transmission, during reception, and on which output channel the received echo signal should be placed.

[0118] exist Figure 4 In the example shown, each slave die 260 can address up to 24 independent transducers 280. This information includes: which transducer elements are active during the transmit phase; which transducer elements are active during the receive phase; and which output channel the received echo signal is provided to for storage in three 24-bit registers. Therefore, with a maximum of seven slave dies, a conduit with up to one hundred and sixty-eight transducer elements can be constructed according to this embodiment.

[0119] The first communication interface 410 and the second communication interface 430 are completely asynchronous, meaning that the clock edges in the communication protocol itself are used to register data. In other words, there is no free-running clock in the conduit that can be used to sample the communication interfaces. For several reasons (e.g., electromagnetic compatibility (EMC) and potential image artifacts), it can be advantageous to have no free-running clock in the conduit during the imaging phase. Since the number of clock edges in the two communication interfaces matches the amount of data being transmitted, there are no extra edges available for the HS interface 440 to manipulate the information in the slave unit's registers, and therefore the information to be included in the application mode is applied to the ultrasonic transducer 480.

[0120] Therefore, the ultrasound imaging catheter may also include a local oscillator (LO) 490, which communicates with multiple registers and is adapted to receive control signals generated by the control unit and manipulate multiple bits in the multiple registers to activate and / or deactivate multiple transducer elements of the transducer array according to a selected activation mode.

[0121] The local oscillator 490 can be located on the master die 450, which can be enabled by the HS unit 440 in order to perform the required manipulation of the registers. The manipulation of the registers by the HS unit and thereby the running of the local oscillator only takes place outside the imaging phase, preventing potential image artifacts due to e.g. feedthrough or crosstalk of the local oscillator. Another mechanism for preventing image artifacts caused by the local oscillator is to ensure that the lowest frequency of the local oscillator is higher than the bandwidth of the ultrasound transducers 480. The local oscillator can be adapted to generate a square wave with a given duty cycle in order to bring the harmonics of the local oscillator outside the bandwidth of the ultrasound transducers. For example, the duty cycle can be 50% or 60%, or indeed any suitable duty cycle that ensures that the spectral components of the oscillator are outside the bandwidth of the multiple ultrasound transducers.

[0122] Figure 5 An example 500 of interconnections between registers 510 from different slave units 470 on the die 460 is shown. Each register comprises a number of bits, where each bit is associated with one of a number of ultrasound transducers in a transducer array of the ultrasound imaging catheter.

[0123] In Figure 5 In the shown example, each slave unit 470 comprises three registers 510, including a transmit register Tx adapted to control which of the associated transducer elements are activated or deactivated during a transmit period, a receive register Rx adapted to control which of the associated transducer elements are activated or deactivated during a receive period, and an output channel register Rxmap adapted to control which of a number of output channels the signals received at the transducer elements are output to. In this case, a given transducer element will be associated with one bit from each of the three registers of a given slave unit.

[0124] In order to limit the number of connections required between the slave dies, the registers for transmission (Tx), the registers for reception (Rx), and the registers for mapping to output channels (Rxmap) can be connected to the next die via a single connection.

[0125] The single connection between the dies, also referred to as a daisy chain connection, means that the manipulation of the transmit registers, the receive registers, and the output channel registers must be performed sequentially.

[0126] In order to select an appropriate number of transducer elements, two methods are available: selecting the number of slave dies in the catheter, up to 7; and selecting the number of elements controlled by each die, up to 24.

[0127] In the above embodiment, the slave die can control 24 transducer elements. Fewer transducer elements can also be connected to the slave die. (The last part, "connected to, is incomplete and likely refers to a different implementation, possibly related to transducer control.") Figure 5 The number of transducer elements in the register daisy chain shown can be determined by... Figure 4 I described in 2 The parameters in the C interface unit 420 are used for setting. The HS unit 440 does not need to know the exact number of transducer elements in the register daisy chain because the register units are daisy chained and no data is lost due to shift operations. For example, if a conduit with 114 elements is required, five slave dies should be used, four of which will control 24 elements and one of which will control 18 elements.

[0128] Figure 6 A conceptual representation 600 is shown of the circumference of the circular conduit, the transmit Tx register, the receive Rx register, and the output channel Rxmap register associated with the boundary of the die 460 and the transducer element 480. Figure 6 Some example data and their meanings for the three register chains are shown.

[0129] Note transducer element 0, as indicated by the arrow. The register indicates that this element is used to transmit ultrasonic pulses (as shown by 1 in the transmit Tx register), to receive echoes (as shown by 1 in the receive Rx register), and to transmit the received echoes via channel 1 (as shown by 1 in the output channel Rxmap register). A 0 in the transmit or receive register indicates that the element will be deactivated during the transmit or receive period, respectively. A 0 in the channel output register indicates that the received echoes should be output on channel 0.

[0130] It should be noted that, as mentioned above Figure 5 and Figure 6 As shown, the transmit Tx register, receive Rx register, and output channel Rxmap register, along with the Tx, Rx, and Rxmap bits together, can be combined as shown in the reference. Figure 2 The portion of the local memory (LM) 130 described.

[0131] Figure 7 A method 700 for controlling an ultrasound imaging catheter is shown, the ultrasound imaging catheter including an ultrasound transducer array having a plurality of ultrasound transducers.

[0132] The method begins at step 710: accessing local memory provided at the distal end of the ultrasound imaging catheter;

[0133] In step 720, any one of a plurality of activation patterns stored on the local memory is selected, wherein each activation pattern corresponds to a plurality of transducer elements of the plurality of transducer elements to be activated and a plurality of transducer elements of the plurality of transducer elements to be deactivated.

[0134] In step 730, a control signal is generated to activate or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern during an imaging phase of the ultrasonic imaging catheter, the imaging phase comprising a transmit period and a receive period.

[0135] In step 740, the control signal is provided to the local oscillator.

[0136] In step 750, a plurality of bits of a plurality of registers are manipulated to activate and / or deactivate the plurality of transducer elements of the transducer array according to the selected activation pattern, wherein each bit is associated with one of the plurality of ultrasonic transducers.

[0137] Variations of the disclosed embodiments can become apparent to those of ordinary skill in the art upon reading the foregoing disclosure and understanding the appended claims. In the claims, the term “comprising” does not exclude other elements or steps, and the words “a” or “an” do not exclude a plurality. A single processor or other unit can fulfill the functions of several items recited in the claims. Brackets in claims are not to be construed as limiting the scope of the claims. Steps of a method can be rearranged or re-ordered without affecting the outcome or the scope of the claims. If a computer program is discussed above, it can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but it can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. If the term “adapted to” is used in the claims or specification, it should be noted that the term “adapted to” is intended to be equivalent to the term “configured to.” Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. An ultrasound imaging catheter, the ultrasound imaging catheter comprising: an ultrasound transducer array provided at a distal end of the ultrasound imaging catheter and adapted to transmit and receive ultrasound signals, wherein the ultrasound transducer array comprises a plurality of ultrasound transducers; a local memory provided at the distal end of the ultrasound imaging catheter and adapted to store a plurality of activation patterns, wherein each activation pattern corresponds to a plurality of ultrasound transducer elements of the plurality of transducer elements to be activated and a plurality of ultrasound transducer elements of the plurality of transducer elements to be deactivated; a control unit provided at the distal end of the ultrasound imaging catheter and adapted to: access the local memory; select any one of the plurality of activation patterns; and generate control signals to activate or deactivate the plurality of transducer elements of the ultrasound transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter, the imaging phase comprising a transmit period and a receive period; a plurality of registers, each register comprising a plurality of bits, wherein each bit is associated with one of the plurality of ultrasound transducers; and a local oscillator in communication with the plurality of registers and adapted to receive the control signals generated by the control unit and manipulate the plurality of bits in the plurality of registers to activate and / or deactivate the plurality of transducer elements of the ultrasound transducer array according to the selected activation pattern.

2. The ultrasonic imaging catheter of claim 1, wherein, the local oscillator is adapted to operate outside the imaging phase of the ultrasound imaging catheter.

3. The ultrasonic imaging catheter of any of claims 1-2, wherein, the local oscillator is adapted to operate at a frequency that is greater than a bandwidth of the plurality of ultrasound transducers.

4. The ultrasonic imaging catheter of any of claims 1-2, wherein, the local oscillator is adapted to generate a square wave with a given duty cycle, wherein the given duty cycle is such that a component of a frequency spectrum of the local oscillator is outside the bandwidth of the plurality of ultrasound transducers.

5. The ultrasonic imaging catheter of any of claims 1-2, wherein, the plurality of registers are arranged in a plurality of register groups, each register group comprising: a first register comprising a first register bit; a second register comprising a second register bit; and wherein a transducer element of the plurality of transducer elements is associated with the first register bit and the second register bit, the first register bit being adapted to control whether the transducer element is activated or deactivated during the transmit period, the second register bit being adapted to control whether the transducer element is activated or deactivated during the receive period.

6. The ultrasonic imaging catheter of claim 5, wherein, the ultrasound transducer array comprises a plurality of output channels, and wherein each register group further comprises a third register comprising a third register bit, and wherein the transducer element is further associated with the third register bit, the third register bit being adapted to control into which of the plurality of output channels a signal received at the transducer element is outputted.

7. The ultrasonic imaging catheter of claim 5, wherein, the plurality of register groups are connected in a daisy chain, wherein each register group is connected in series with an adjacent register group.

8. The ultrasonic imaging catheter of any of claims 1, 2, 6, and 7, wherein, The ultrasound imaging catheter further comprises a signal conditioning unit provided at the distal end of the ultrasound imaging catheter and adapted to signal condition the received ultrasound signals.

9. The ultrasonic imaging catheter of claim 8, wherein, The signal conditioning unit comprises a low noise amplifier.

10. The ultrasonic imaging catheter of claim 8, wherein, The signal conditioning unit comprises one or more time gain compensation units.

11. An ultrasound imaging system, the system comprising: an ultrasound imaging catheter according to any one of claims 1 to 10; a processing unit in communication with the ultrasound imaging catheter and adapted to generate an ultrasound image based on the received ultrasound signals; and a display adapted to display the ultrasound image.

12. A method for controlling an ultrasound imaging catheter, the ultrasound imaging catheter comprising an ultrasound transducer array having a plurality of ultrasound transducers, the method comprising: accessing a local memory provided at a distal end of the ultrasound imaging catheter; selecting any one of a plurality of activation patterns stored on the local memory, wherein each activation pattern corresponds to a plurality of transducer elements of the plurality of transducer elements to be activated and a plurality of transducer elements of the plurality of transducer elements to be deactivated; generating a control signal to activate or deactivate the plurality of transducer elements of the ultrasound transducer array according to the selected activation pattern during an imaging phase of the ultrasound imaging catheter, the imaging phase comprising a transmit period and a receive period; providing the control signal to a local oscillator; and manipulating a plurality of bits of a plurality of registers, wherein each bit is associated with one of the plurality of ultrasound transducers to activate and / or deactivate the plurality of transducer elements of the ultrasound transducer array according to the selected activation pattern.

13. A computer program product comprising computer program code means which is adapted, when said computer program product is run on a computer, to implement the method according to claim 12.

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