System and method for generating high-precision ultrasonic impulses for high-resolution ultrasound imaging catheters

Abstract

Systems, methods, and circuits for generating high-voltage wavelets to drive imaging transducers such as IVUS systems are disclosed. The disclosed embodiments are configured to generate clean, discrete sinusoidal pulses (which may be single pulses, double pulses, or "n" pulses) that are free from, at least substantially free from, or completely free from ringing or continuous oscillations.

Description

Technical Field

[0001] Related Application Data: This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 457,876, filed Apr. 7, 2023, "Systems and Methods for Generating High-Precision Ultrasonic Pulses for High-Resolution Ultrasonic Imaging Devices," which is hereby incorporated by reference in its entirety.

[0002] This disclosure relates to the control of ultrasonic transducers, and more particularly, to systems and methods for generating high-precision ultrasonic pulses for high-resolution ultrasonic imaging catheters.

Background Art

[0003] An ultrasonic transducer used in an intravascular ultrasound (IVUS) system typically consists of an ultrasonic impulse wave generator and a transducer for transmitting and capturing reflected waves. Predetermined impulse parameters are important for generating high-quality images, which affect the final resolution. For example, the impulse should have sufficient intensity, have a known waveform, and be in a clean state with little or no ringing at the start or end.

[0004] An example of an IVUS system is shown in U.S. Patent No. 8,864,674. As described in this patent, such a device generally includes a catheter consisting of an outer sheath and an inner imaging core, and an ultrasonic transducer is disposed at the distal end of the core. The imaging core is rotationally driven at the proximal end, and a pulse circuit is installed to cause the transducer to emit high-frequency ultrasonic pulses. A volumetric ultrasonic image of the blood vessel section is generated using the reflected signals received by the transducer when the imaging core is rotated and pulled out along a part of the blood vessel.

[0005] Transducers for IVUS applications are available in the ultrasonic range from 20 MHz to 80 MHz. A typical range is 40 MHz to 60 MHz. For example, a 50 MHz waveform has a duty cycle of only 20 nS (nanoseconds). A 20 nS single-period wavelet has a 10 nS portion in either the positive or negative direction, followed by a 10 nS portion in the opposite direction.

[0006] For good results, the waveform applied to the transducer should be a waveform with a single complete period (cycle) of sinusoidal voltage. In a given scenario, several complete sinusoidal cycles may be used to generate a "chirp". In either case, the sinusoidal wavelets (tiny waveforms) must start cleanly and end at the end of the "complete" cycle. If they start or end abruptly around the time the waveform period reaches zero, the quality of the wavelets will degrade, and consequently, the image quality. Unwanted ringing at the start or end of the wavelets can also lead to a decrease in image quality.

[0007] Because the timing of a single-period ultrasonic wave is extremely precise, it can be difficult for typical logic gates used in ASICs (Application-Specific Integrated Circuits) to determine the start and end of the waveform. For example, the aforementioned typical 50 MHz single waveform consists of two 10 nanosecond periods. Typical logic circuits experience fluctuations (jitter) of several nanoseconds. For example, if the start / end of the waveform is misdetected by 2 nanoseconds, this corresponds to 20% of a half-period, which is a significant error. Such timing errors can generate out-of-band carrier frequencies and harmonics, potentially interfering with (adversely affecting) image processing algorithms.

[0008] Typical PMUTs (piezoelectric micromachine ultrasonic transducers) used in IVUS applications have a capacitance of only a few pF (picofarads) and require high-voltage waveforms. Their impedance is high and varies with frequency. The peak-to-peak voltage applied to the PMUT can reach tens of volts. Output power increases exponentially with increasing voltage. For example, doubling the output voltage increases output power by 6 dB. These operating parameters present significant challenges in waveform transmission through an ultrasonic catheter. Conventional transmission lines are typically designed assuming only known resistive loads (e.g., a 50-ohm resistive load). The ideal voltage required to drive a PMUT requires a peak-to-peak voltage exceeding 50V, which is difficult to transmit through a small catheter lumen.

[0009] Embodiments disclosed herein improve prior art systems, enhance signal clarity, and reduce manufacturing costs by addressing these and other challenges with less complex electronic packaging. [Overview of the project] [Problems that the invention aims to solve]

[0010] Embodiments of the present disclosure include a pulse control system for an ultrasound imaging catheter, comprising a transducer tank circuit configured to generate ultrasound imaging pulses, and a switch circuit for driving the transducer tank circuit between an ON state and an OFF state. Here, the OFF state generates imaging pulses, and the ON state stops pulse generation. The transducer tank circuit and the switch circuit may be configured to be located together within the imaging core in the distal end region of the imaging core of the ultrasound imaging catheter.

[0011] In yet another embodiment, the disclosed pulse control system may further include a control logic circuit configured to control the on / off timing of a switch circuit and / or a current sensing circuit configured to detect current in a transducer tank circuit. The control logic circuit and the current sensing circuit may further be configured to be located within the distal end of the imaging core together with the transducer tank circuit and the switch circuit.

[0012] The disclosed embodiments also include pulse circuits for intravascular ultrasound imaging systems. The disclosed circuits include an inductor, a diode connected in series with the inductor, a current supply conductor (current source conductor) connected to the inductor on the opposite side of the diode, and a junction between the inductor and the diode. The junction is electrically connectable to an ultrasonic transducer to configure it to be connected in series or parallel with the inductor. The circuit also includes a controllable on / off switch connected to a diode located on the opposite side of the junction and communicating electrically with a ground conductor on the opposite side of the diode. In some embodiments, the controllable on / off switch is configured as a MOSFET, and the control logic circuit may also be realized as part of the MOSFET. Embodiments of such disclosed circuits are configured and dimensioned to be located within the distal end of the imaging core of an intravascular ultrasound imaging system.

[0013] Embodiments disclosed herein further include an imaging core for an intravascular ultrasound imaging catheter, comprising an ultrasound transducer positioned in the distal end region of a core housing and a pulse circuit disclosed herein. The disclosed imaging core may include a two-conductor cable extending within the core housing from the distal end to a pulse control system or pulse circuit, and a fixation material filling at least the distal end of the core housing surrounding the pulse control system or pulse circuit. The disclosed ultrasound transducers include PMUTs and other types of transducers. The disclosed imaging core may be combined with an outer catheter sheath to form an imaging catheter system.

[0014] The disclosed embodiment further includes an ultrasound imaging catheter comprising an imaging core having a distal end configured to be positioned within a patient's blood vessel, an ultrasound transducer positioned at the distal end of the imaging core, and a pulse control device positioned at the distal end of the imaging core and configured to control pulse generation by the ultrasound transducer. The disclosed pulse control device may comprise a transducer tank circuit including the ultrasound transducer and a switch circuit that drives the transducer tank circuit between an ON state and an OFF state, where the OFF state causes the generation of imaging pulses, and the ON state stops the generation of pulses. The disclosed imaging catheter also comprises a two-conductor cable connected to the pulse control device and extending through the imaging core to its proximal end.

[0015] Embodiments disclosed herein also include a method for controlling an ultrasonic transducer in an intravascular ultrasound imaging catheter, comprising the step of interrupting the current supplied to a resonant circuit including the ultrasonic transducer during the initial time when the ultrasonic transducer generates pulses, the pulses having a first positive half-period and a second negative half-period, and turning on the current to the resonant circuit at any point within an interval (period) corresponding to the entire duration of the second negative half-period, thereby stopping the pulse generation by the ultrasonic transducer. The resonant circuit may include a current-cutting inductor connected in series or parallel with the ultrasonic transducer, and therefore, interrupting this current includes a switch circuit connected to the junction between the ultrasonic transducer and the inductor and set to the off position during the initial time. Turning on the current (applying current) may include setting the switch circuit to the on position during the time interval (interval).

[0016] The disclosed method may be used to generate a series of clean n pulses by repeating an off-on step, starting from a first initial time, and maintaining a current supply to the resonant circuit until the next initial time, through a first time interval synchronized with a second negative half-period of the generated n pulses. These steps may be repeated as needed for multiple n pulse periods. Alternatively, the value of n may be changed between pulse periods. [Brief explanation of the drawing]

[0017] To illustrate this disclosure, the drawings illustrate aspects of one or more embodiments of this disclosure. However, it should be understood that this disclosure is not limited to the exact configurations or means shown in the drawings. [Figure 1] Figure 1 is a schematic cross-sectional view of the distal end of an imaging core according to an embodiment of this disclosure. [Figure 2] Figure 2 is a block diagram showing the main functional components of the pulse circuit according to this disclosure. [Figure 3]Figure 3 is a schematic diagram showing an example of a pulse circuit according to the embodiment of this disclosure. [Figure 3A] Figure 3A is a schematic diagram showing another example of a pulse circuit according to another embodiment of the present disclosure. [Figure 4] Figure 4 is a circuit board / block diagram of the embodiment of the pulse circuit shown in Figure 3. [Figure 5] Figure 5 is a graph of a single-period (single-cycle) impulse generated by the pulse circuit according to this disclosure, showing magnified details along with the timing reference. [Figure 6] Figure 6 is a graph of a two-cycle impulse generated by the pulse circuit according to this disclosure. [Figure 7] Figure 7 is a schematic cross-sectional view of the distal end of an imaging core and sheath according to another embodiment of the present disclosure. [Figure 8] Figure 8 is a schematic cross-sectional view of the distal end of an imaging core and sheath according to yet another embodiment of the present disclosure. [Modes for carrying out the invention]

[0018] This disclosure describes a system, method, and apparatus for generating high-voltage wavelets to drive transducers in an IVUS system, while addressing the technical challenges described above. The disclosed method and apparatus include transducer driving circuits that enable "measured" full-cycle wavelets at extremely high voltages. Generally, the disclosed circuits are divided into a proximal (patient-side) circuit and a distal (transducer-side) circuit. The proximal circuit typically includes control circuits such as current control circuits and optional pulse-synchronization logic and is often housed in a patient interface module (PIM). An example of a proximal circuit is disclosed in U.S. Patent No. 10,555,720, which is incorporated herein by reference. The distal circuit typically comprises components that generate one or more full-cycle sinusoidal wavelets. This disclosure focuses primarily on the distal circuit.

[0019] Embodiments according to the present disclosure include, as an example, an imaging core 10 configured as a rotatable guide wire type structure, the imaging core 10 having a housing portion 12 and terminated at a distal end 13. Adjacent to the distal end 13 are arranged a distal control module 14 and an ultrasonic transducer 16, which in the exemplary embodiment are connected by a current conducting connector 18. The ultrasonic transducer 16 may comprise a PMUT. Alternatively, as will be described later, the distal control module 14 and the transducer 16 may be integrated into a single electronic package and other forms of transducers replacing the PMUT shown in FIG. 1 may be employed. An electrical cable 20 extending from a proximal circuit (not shown) to the distal control module 14 comprises at least two conductors 20A, 20B (FIG. 3). When the transducer 16 is configured as a PMUT, the transducer 16 comprises a transducer portion 22, and the transducer portion 22 is disposed in an opening window within an epoxy resin 24 (or similar filler / fixing material) provided within the distal end of the housing portion 12 surrounding at least the distal control module 14 and the transducer 16. In use, as is well known in the prior art, the imaging core 10 is deployed within a catheter sheath 26. Further aspects of the imaging core 10 not separately described below may be adapted by one skilled in the art based on a conventional imaging system (imaging system) such as that disclosed in U.S. Patent No. 6,450,964, which is incorporated herein by reference.

[0020] The systems and circuits disclosed herein are configured to generate clean and discrete sine wave pulses in certain embodiments. The pulse may be a single pulse, a double pulse, or "n" pulses. A clean sine wave pulse refers to one or more discrete sine wave pulses in which ringing or continuous oscillation beyond the zero crossing point at the end of a predetermined n sine wave pulses is completely removed, at least substantially removed, or eliminated. For example, a series of clean single-shot (n = 1) sine wave pulses is shown in FIG. 5. As another example, a series of sine wave impulses for two cycles (n = 2) is shown in FIG. 6. As yet another example, the n value may be changed between pulse periods to generate a series of pulses for different periods. For example, by alternately switching between n = 1 and n = 2, a series in which clean single periods and double periods appear alternately may be generated.

[0021] FIG. 2 shows a pulse system according to the present disclosure in which the control logic circuit 36 drives the switch circuit 32 on / off for the transducer tank circuit 30, thereby driving the optional current sensing circuit 34. As will be described later, the transducer tank circuit 30 may include an ultrasonic transducer such as a PMUT and provides a capacitor (C) connected in series with an inductor (L). The control logic circuit 36 and the current sensing circuit 34 may be optionally implemented in a single ASIC configuration. With such a configuration, the switch circuit 32 has the ability to prevent the generation of resonant oscillations by the transducer and removes energy from the transducer tank circuit 30. Instead, when the switch circuit is turned back on at the negative portion of the generated signal pulse, the stored energy is bypassed (shunted) to the current feedback path, preventing ringing of the signal, as will be further described below.

[0022] During operation, the switch circuit 32 is in an off state during the initial sinusoidal positive pulse, re-inducing (redirecting) the current flow from the switch circuit to the transducer tank circuit 30. During the negative portion of the pulse, this prevents current from "reverse-flowing" through the switch circuit. The switch circuit 32 can be turned on by the control logic circuit 36 ​​at any timing during the negative portion of the pulse. This is an advantage because precise timing is not required. The timing of the switch circuit 32 is shown in detail in Figure 5, where time reference A (sign A) indicates the "off" time for the switch circuit to generate pulses in the transducer tank circuit 30. Time reference B (sign B) indicates the time interval during which the switch circuit 32 can be set "on" to suppress ring-down and generate a clean single-pulse signal. The switch circuit 32 then remains "on" until the next pulse is required at time reference A. Therefore, the switch circuit 32 can be on for a longer time at time interval B of the sinusoidal signal, which is particularly advantageous at high frequencies.

[0023] In some embodiments, the current sensing circuit 34 is configured to verify that a pulse is being generated and to provide feedback to the system. For example, the sensing circuit 34 (or 62, described later) may be used to determine whether the transducer 16 is within an appropriate range and whether the transducer is being overdriven by the pulse circuit. This functional verification may be controlled by an ASIC incorporating the current sensing circuit.

[0024] Figure 3 shows an embodiment of the pulse circuit 40 according to the present disclosure. The pulse circuit 40 can be distributed across multiple physical electronic components or integrated into a single electronic package. In the example of Figure 3, the pulse circuit 40 includes an inductor 42 for storing energy, and two switches: a controllable switch 46, which is a MOSFET including a parasitic diode as an example, and a one-way switch 44 (e.g., a diode). Control logic 50 drives the controllable switch 46. The inductor 42, diode 44, and controllable switch 46 are configured in series. A transducer 16 (which may be a PMUT in some embodiments) is connected to the junction (junction point) 48 between the inductor 42 and the diode 44. In this example, the transducer 16 and the inductor 42 constitute a transducer tank circuit 30, the controllable switch 46 and the diode 44 constitute a switch circuit 32, and the control logic 50 constitutes a logic circuit 36.

[0025] When the controllable switch 46 is ON, the one-way (diode) switch 44 is set to conduction mode. This keeps the voltage between the inductor 42 and the transducer junction 48 close to zero. To generate a pulse, the controllable switch 46 is turned OFF. This sends the energy stored in the inductor 42 to the transducer 16, which has a known capacitance.

[0026] During operation, the controllable switch 46 is in the off state for half a cycle of the first pulse, and only the capacitance of the inductor 42 and transducer 16 are connected in series. The energy stored in the inductor generates a variable current and voltage at the junction 48 according to the following formula.

number

[0027] A sinusoidal current flows through inductor 42, generating a sinusoidal voltage across transducer 16 only while inductor 42 is connected in series with the capacitance of transducer 16. The energy stored in the capacitor follows the equation 0.5*V^2*C, where "C" is the capacitance and "V" is the voltage across the capacitor. In the absence of a parallel auxiliary circuit, all energy from inductor 42 is transferred to the capacitance of transducer 16, thereby converting the energy stored inside inductor 42 into a voltage across transducer 16. A constant current "I" is set in the conductor 20A of cable 20 inside the device. This is used to set the impulse power. At the distal end 13 of the device, this current passes through inductor 42. The inductor stores energy equivalent to 0.5*I^2*L (where I is the set current and L is the inductance). A current sensing circuit 62 can optionally be used to determine the current to transducer 16.

[0028] As one example, if the controllable switch 46 is configured as a MOSFET, the inductor current is periodically interrupted. The MOSFET can be a silicon-based or GaN MOSFET with a control logic circuit 50, as shown in Figure 3. In this example, the second switch is a high-voltage diode that functions as a one-way switch 44. These two switches are connected in series with the inductor 42. The polarity of the diode is set to normally be in conduction mode. The junction 48 between the inductor 42 and the diode 44 is connected to the transducer 16. The capacitance of the transducer and this inductor resonate at a desired ultrasonic frequency (forming a tank circuit).

[0029] To further illustrate this example, the ASIC may be configured as a MOSFET control logic circuit 50. In such an embodiment, the main ASIC power rail 58 drives and powers the MOSFET logic circuit 50. The ground path 56 is the ground for the control logic.

[0030] The control gate output 60 is used to drive the MOSFET logic circuit. When it is low, the MOSFET does not conduct; when it is high, the MOSFET conducts. Gate control 1(52) is used for output protection. Gate control 1(52) is normally held at a low level, but if the current sensing circuit 62 detects an overcurrent in the transducer, this pin is pulled up to a high level. This keeps the control gate output 60 permanently high, preventing the MOSFET from turning off. As a result, new pulse generation will not begin until the overcurrent condition is resolved. Gate control 2(54) is the gate control for the main MOSFET. When gate control 2(54) goes low (pulled down) and no overcurrent is detected, output 60 also follows suit and goes low. This turns off MOSFET 46 and pulse generation begins.

[0031] The control logic circuit 50 normally keeps the MOSFET ON. In this configuration, current "I" flows through inductor 42, diode 44, MOSFET 46, and transducer 16, keeping the voltage close to zero. The capacitance of transducer 16 and inductor 42 form a tank circuit. When an impulse is needed, the ASIC turns off MOSFET 46. When the conduction of the MOSFET is interrupted, current "I" flows into the capacitance of transducer 16 (which is the only option when the MOSFET is OFF), and this initiates the formation of a sine wave. After half a cycle, when the voltage turns negative, MOSFET 46 turns ON. Diode 44 becomes reverse-biased, isolating the L / C circuit from the MOSFET parasitic diode, and the sine wave continues in the reverse direction regardless of the state of the MOSFET.

[0032] Figure 3A shows an alternative pulse circuit 40A comprising an inductor 42 and a transducer 16 arranged in parallel rather than in series, as in the embodiment shown in Figure 3. In the alternative pulse circuit 40A, the conductor 20A supplies current to a parallel subcircuit consisting of the inductor 42 and the transducer 16 which provides capacitance (C). An optional current sensor 62 may be provided at a branch of the transducer in the parallel subcircuit and connected at a junction 48 to a switch circuit consisting of a one-way switch (diode) 44 and a controllable on / off switch 46. The controllable switch 46 may be configured as described herein, or it may be connected to a control logic circuit via a control gate output 60 as described above.

[0033] As will be understood by those skilled in the art based on the teachings described herein, the advantages of the described circuit lies in the ability of the transistor and diode to remove energy from the LC resonant pair provided by the transducer element through capacitance (C). The ability to prevent the occurrence of LC resonant oscillations is achieved by preventing current from flowing back into the inductor. When the transistor is turned on again during the negative portion of the signal, the stored energy is bypassed to ground. This prevents signal ringing. Finally, as the signal returns to positive polarity, the diode clamps the voltage at the end of the sinusoidal pulse. This generates a single waveform.

[0034] The control ASIC configured as described above can be turned on during the second part of the wavelet without affecting the wavelet shape. At this point, diode 44 is in reverse polarity, keeping the transducer / inductor isolated from MOSFET 46. For example, in the case of a 50MHz wave, the second part of the wavelet is 10nS. The control logic circuit 50 can close (make non-conductive) MOSFET 46 at any time during the second part of the wavelet. In this example, the MOSFET can be turned on 15nS ± 5nS from the initial off state without affecting the wavelet shape. In other words, the timing circuit can close the switch at any time during the second part of the wavelet. This configuration provides flexibility to the timing logic and eliminates the need for stringent timing requirements.

[0035] When the voltage across transducer 16 crosses zero, MOSFET 46 is already turned on, and diode 44 begins to conduct. Inductor 42, MOSFET 46, and diode 44 become conductive again, and the set current "I" flows through this path. The current "I" begins to store energy in inductor 42 in preparation for the next impulse request (begins to charge). See Figure 5 for a single-period sinusoidal impulse generated by the exemplary pulse generation circuit shown in Figure 3.

[0036] An advantage of the disclosed embodiment is the “stacked” voltage tolerance of switches 44 and 46. In the circuit embodiment shown in Figure 3, N-channel MOSFETs are used, where the MOSFETs recognize only the positive voltage of the transducer and the diodes recognize only the negative voltage of the transducer. The sum of the maximum peak-to-peak voltages applied to the transducer can be as high as the combined maximum breakdown voltage of the MOSFETs and diodes. For example, if the maximum allowable drain-source voltage of the MOSFET is 100 volts and the maximum allowable reverse voltage of the diode is 100 volts, the maximum peak-to-peak voltage applied to the transducer can reach 200 volts.

[0037] As an example, when using a PMUT, the transducer voltage can reach up to 200 volts. As mentioned earlier, as the voltage applied to the PMUT increases, the output power increases exponentially. MOSFETs with the desired parameters and drain-source breakdown voltages of several hundred volts are available in sub-millimeter size products. The same applies to diodes. As yet another example, using a 200-volt multilayer MOSFET and diode voltage results in a 12 dB improvement compared to a 50-volt peak-to-peak drive. This directly corresponds to a 12 dB improvement in the signal-to-noise ratio of the processed image signal.

[0038] As mentioned above, the inductor current can be adjusted with a simple circuit located proximal to the system. This eliminates the influence of transmission line losses on the pulse wavelet shape. The lumen of the IVUS catheter is very narrow, and the wires or microcoaxial cables used for power transmission may exhibit significant resistance and loss. The embodiments described reduce or eliminate the influence of transmission losses on impulse energy and wavelet shape. Regardless of line resistance, the energy of the inductor depends only on the set current and is expressed by the formula 0.5*I^2*L. Both the current "I" and the inductance "L" are independent of transmission line losses.

[0039] In a typical IVUS catheter, the wire must pass through a rotating junction (rotating joint). This increases signal loss and noise sources. Here again, the aforementioned method of adjusting the line current eliminates the influence of the rotating junction (rotating joint) on the wavelet shape. Impedance fluctuations at the junction are compensated for by a set current control circuit. The power and shape of the wavelets are unaffected by the rotating junction, and there is no image degradation due to the movement of the junction.

[0040] If multiple cycles of a wavelet are required to generate a chirp, the control circuit or ASIC can initiate the cycles in a similar manner and turn off the controllable switch 46 (e.g., a MOSFET). The switch to the ON state occurs at any timing in the negative portion of the ending cycle. For example, if two cycles of a 50MHz wavelet are used, the controllable switch 46 can be turned on again in 35nS ± 5nS. If three cycles of a sine wave are used, the switch to the ON state occurs in 55nS ± 5nS, and so on. See Figure 6 for the two-cycle impulse generated by the circuit example in Figure 3.

[0041] Alternatively, the MOSFET can be replaced with a bipolar junction transistor as the controllable switch 46. In this alternative configuration, instead of the gate control voltage of the MOSFET, a small current is applied between the base and emitter of the bipolar junction transistor to keep it in the ON state. When this current is reduced to zero, the transistor turns off, producing the same effect as turning off the MOSFET.

[0042] In a typical IVUS catheter, pulses are synchronized with a motor that drives a torque cable. The torque cable, which extends along the entire length of the catheter to the distal end (transducer side), may not be perfectly synchronized with the motor. This can result in image artifacts (image side effects). A further feature of the embodiments disclosed herein is that pulses are generated distally and accessible to a distal control module or ASIC located there, so that the interruption of the current for generating impulses can be synchronized with the mechanical characteristics of the distal portion of the catheter (transducer side). For example, as shown in Figure 7, in one embodiment, a small magnet 70 attached to the catheter sheath 26 can be detected as the starting zero angle using a Hall effect sensor 72 located in the control module 14 or part of the transducer 16 at the distal end 13 of the imaging core 10. Alternatively, as shown in Figure 8, a marking 74 on the catheter sheath 26 can also be detected by a photocoupler or microswitch 76 located in the control module 14 or part of the transducer 16 at the distal end 13 of the imaging core 10. In this way, the image can be synchronized with the catheter sheath using pulses, eliminating image distortion and artifacts caused by vibrations in the torque cable.

[0043] Figure 4 shows one configuration of a circuit board / block diagram for embedding the distal control module 14 according to the present disclosure. In this example, a transducer 16 configured as a PMUT is connected to the distal control module 14 via a castellar conductor 18 (castle-shaped conductor 18). In addition to the components described above in relation to Figure 3, as shown in Figure 4, the control module 14 includes conductive pads 64 for connecting conductors 20A and 20B of the cable 20. In this case, the current sensing circuit 62 is implemented using two clipping diodes (D2, D3). In further alternative embodiments, the distal control module 14 may include one or more of a pressure sensor, a flow sensor, or a temperature sensor. The distal control module 14 also includes an appropriate ultrasonic signal amplification circuit depending on the type and power level of the transducer. Such an amplification circuit can be incorporated into the ASIC along with other control functions, as described above.

[0044] Those skilled in the art will understand that the teachings of this disclosure are not limited to the use of PMUT type transducers. Those skilled in the art may, guided by the teachings of this disclosure, use other types of transducers, including but not limited to CMUT type or conventional piezoelectric ultrasonic transducers, as alternatives.

[0045] The above is a detailed description of embodiments as specific examples of the present disclosure. In this specification and the appended claims, connecting expressions such as “at least one of X, Y, and Z” and “one or more of X, Y, and Z” shall be interpreted, unless otherwise stated or indicated, as meaning that each item in the connecting list may exist in any number, excluding all other items in the list. It also means that each item may exist in any number in any combination with any other item(s) in the connecting list. Each item may also exist in any number. Applying this general rule, the connecting phrases in the above examples (where the connecting list consists of X, Y, and Z) each include: one or more X; one or more Y; one or more Z; one or more X and one or more Z; and one or more X, one or more Y, and one or more Z.

[0046] Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Each feature of the various embodiments described above may be combined, where appropriate, with features of other described embodiments to provide combinations of multiple features in newer embodiments relating to the disclosure. Furthermore, although the foregoing describes several distinct embodiments, the content described herein is merely an example of the application of the principles of this disclosure. Moreover, even where certain methods are illustrated and / or described herein in a particular order, the order can be significantly altered to achieve the content of this disclosure within the scope of the art. Therefore, the descriptions herein should be understood as illustrative only and do not otherwise limit the scope of the inventions described herein or in the following claims.

Claims

1. A pulse control system for ultrasound imaging catheters, A transducer tank circuit configured to generate ultrasonic imaging pulses, A switch circuit that drives the transducer tank circuit between an ON state and an OFF state, wherein the OFF state causes the generation of the imaging pulse, and the ON state stops the generation of the pulse. Equipped with, The transducer tank circuit and the switch circuit are configured to be located together within the imaging core in the distal end region of the imaging core of the ultrasound imaging catheter. Pulse control system.

2. The system further comprises a control logic circuit configured to control the on / off timing of the switch circuit, The control logic circuit is further configured to be located within the distal end of the imaging core, together with the transducer tank circuit and the switch circuit. The pulse control system according to claim 1.

3. The circuit further comprises a current sensing circuit configured to detect the current in the transducer tank circuit, The current sensing circuit is further configured to be located within the distal end of the imaging core, together with the transducer tank circuit and the switch circuit. The pulse control system according to claim 1 or 2.

4. The transducer tank circuit comprises an inductor connected in series or parallel with the ultrasonic transducer. A pulse control system according to any one of claims 1 to 3.

5. The ultrasonic transducer is a micromachined ultrasonic transducer. The pulse control system according to claim 4.

6. The aforementioned micromachined ultrasonic transducer is a PMUT. The pulse control system according to claim 5.

7. The switch circuit comprises a controllable on / off switch and a one-way switch connected in series. A pulse control system according to any one of claims 1 to 6.

8. The one-way switch includes a diode positioned between the controllable on / off switch and the transducer tank circuit. The pulse control system according to claim 7.

9. The controllable on / off switch comprises a MOSFET including a parasitic diode. The pulse control system according to claim 8.

10. The control logic circuit is configured as part of a controllable on / off switch. A pulse control system according to any one of claims 2 to 9.

11. A pulse circuit for an intravascular ultrasound imaging system, Inductor and A diode connected in series with the aforementioned inductor, A current supply conductor connected to the inductor on the opposite side of the diode, The junction between the inductor and the diode is electrically connectable to an ultrasonic transducer, and the junction allows the ultrasonic transducer to be connected in series or in parallel with the inductor, A controllable on / off switch connected to the diode on the opposite side of the junction and electrically connected to a ground conductor on the opposite side of the diode, A pulse circuit equipped with the following features.

12. The controllable on / off switch includes a parasitic diode. The pulse circuit according to claim 11.

13. The controllable on / off switch is configured as a MOSFET. The pulse circuit according to claim 12.

14. The control logic circuit, which is configured as part of the MOSFET, further comprises The pulse circuit according to claim 13.

15. The pulse circuit is configured and sized to be positioned within the distal end of the imaging core of the intravascular ultrasound imaging system. A pulse circuit according to any one of claims 11 to 14.

16. An imaging core for an intravascular ultrasound imaging catheter, A core housing disposed in the distal end region of a pulse control system according to any one of claims 1 to 10, or a pulse circuit according to any one of claims 11 to 15 combined with an ultrasonic transducer, A two-conductor cable extending from the distal end through the core housing to the pulse control system or the pulse circuit, A fixing material that fills at least the distal end of the core housing portion surrounding the pulse control system or the pulse circuit, An imaging core equipped with [this feature].

17. The transducer is a PMUT. The imaging core according to claim 16.

18. An intravascular ultrasound imaging catheter comprising an imaging core according to claim 16, combined with an external catheter sheath.

19. An imaging core having a distal end configured to be positioned within the patient's blood vessels, An ultrasonic transducer located at the distal end of the imaging core, A pulse control unit is located at the distal end of the imaging core and is configured to control pulse generation by the ultrasonic transducer. Equipped with, The pulse control unit, A transducer tank circuit including the ultrasonic transducer, A switch circuit that drives the transducer tank circuit between an ON state and an OFF state, wherein the OFF state causes the generation of an imaging pulse, and the ON state stops the generation of the pulse. A two-conductor cable connected to the pulse control unit and extending through the imaging core to its proximal end, Equipped with, Ultrasound imaging catheter.

20. The transducer tank circuit comprises an inductor connected in series or parallel with the ultrasonic transducer. The imaging catheter according to claim 19.

21. The switch circuit comprises a controllable on / off switch and a one-way switch connected in series. The imaging catheter according to claim 19 or 20.

22. The one-way switch includes a diode positioned between the controllable on / off switch and the transducer tank circuit. The imaging catheter according to claim 21.

23. The controllable on / off switch comprises a MOSFET including a parasitic diode. The imaging catheter according to claim 22.

24. The pulse control unit further comprises a control logic circuit configured to control the on / off timing of the switch circuit. An imaging catheter according to any one of claims 19 to 23.

25. The control logic circuit is configured as part of a MOSFET including the controllable on / off switch. The imaging catheter according to claim 24.

26. The pulse control unit, Inductor and A diode connected in series with the aforementioned inductor, A current supply conductor connected to the inductor on the opposite side of the diode, The junction between the inductor and the diode is electrically connectable to an ultrasonic transducer, and the junction allows the ultrasonic transducer to be connected in series or in parallel with the inductor, A controllable on / off switch connected to the diode on the opposite side of the junction and electrically connected to a ground conductor on the opposite side of the diode, Equipped with, The inductor and the ultrasonic transducer constitute the transducer tank circuit, and the diode and the controllable on / off switch constitute the switch circuit. One of the conductors of the two-conductor cable is connected to the inductor on the opposite side of the joint and supplies current to the pulse control unit. The imaging catheter according to claim 19.

27. The ultrasonic transducer is a PMUT. An imaging catheter according to any one of claims 19 to 26.

28. The pulse control unit and the PMUT are integrated into a common electronic component. The imaging catheter according to claim 27.

29. With an additional outer sheath, The imaging core is slidably and rotatably disposed within the outer sheath. An imaging catheter according to any one of claims 19 to 28.

30. A marking element is positioned at the distal end of the catheter sheath, and a detector is positioned at the distal end of the imaging core. The marking element and the detector cooperate to provide a signal indicating the angular position of the imaging core relative to the outer sheath. The imaging catheter according to claim 18 or 29.

31. The marking element is a magnet, and the detector is a Hall effect sensor. The imaging catheter according to claim 30.

32. The marking element is an optically detectable surface marking, and the detector is a photocoupler or a microswitch. The imaging catheter according to claim 30.

33. A method for controlling the ultrasound transducer of an intravascular ultrasound imaging catheter, By turning off the current supplied to the resonant circuit including the ultrasonic transducer at an initial time, the ultrasonic transducer is made to generate pulses having a first positive half-period and a second negative half-period. The current supplied to the resonant circuit is turned on at any point in the time interval corresponding to the total time of the second negative half-period, thereby stopping pulse generation by the ultrasonic transducer. method.

34. The resonant circuit includes a current-blocking inductor connected in series or parallel with the ultrasonic transducer, and the off operation includes a switch circuit connected to the junction of the ultrasonic transducer and the inductor, which is set to off at an initial time. The method according to claim 33.

35. The aforementioned current-on operation includes setting the switch circuit to the ON position during the aforementioned time interval. The method according to claim 34.

36. The switch circuit comprises a one-way diode switch connected in series with a controllable on / off switch, the diode switch being positioned between the controllable on / off switch and the junction between the current interruption inductor and the ultrasonic transducer, Setting the switch circuit to the OFF state includes setting the controllable on / off switch to the OFF state via control logic, Turning on the switch circuit includes turning on the controllable on / off switch via the control logic. The method according to claim 35.

37. A series of clean single pulses are generated by repeating the off-state and on-state steps, starting from a first initial time and followed by a first time interval that coincides with the second negative half-period of the generated first pulse. Maintain the current supply to the resonant circuit until the next initial time, The generation step and the maintenance step are repeated over a plurality of single pulse periods, including, The method according to any one of claims 33 to 36.

38. A series of clean dual pulses are generated by repeating the off-state and on-state steps, starting from a first initial time and followed by a first time interval that coincides with the second negative half-period of the generated second pulse. Maintain the current supply to the resonant circuit until the next initial time, The generation step and the maintenance step are repeated over a plurality of double pulse periods, including, The method according to any one of claims 33 to 36.

39. A series of clean n pulses is generated by repeating the off-state and on-state steps, starting from a first initial time and followed by a first time interval that coincides with the second negative half-period of the n pulses generated. Maintain the current supply to the aforementioned resonant circuit until the next initial time, The generation step and the maintenance step are repeated over a plurality of n pulse periods, including, The method according to any one of claims 33 to 36.

40. Furthermore, this includes changing the n value between pulse periods. The method according to claim 39.

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