JP2009050414A - Ultrasonic imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an ultrasonic imaging system, where feedback only occurs with necessary timings for synchronization with signal transmission from and reception to an ultrasonic imaging system in order to stabilize a drive pulse at a target voltage level and securely prevent oscillation. <P>SOLUTION: The controller section 108 generates the sampling pulse with the timing of transmission of drive pulse, and a feedback section 40 makes it a rule to enforce the feedback of the output voltage of an amplifier 29 to its input section only with the timing of the sampling pulse generation. Consequently it can be realized that this prevents oscillations caused by the feedback and stabilizes the output voltage of the amplifier 29 at its target voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a probe unit that transmits an ultrasonic pulse to a subject, a transmission / reception unit that forms a drive pulse that causes the transmission, and a controller that controls the formation of the drive pulse. ) Unit.

  In the ultrasonic imaging apparatus, a driving pulse for driving a piezoelectric element of a probe unit is generated by an amplifier of a transmission / reception unit. In this amplifier, negative feedback is applied to stabilize the drive pulse applied to the piezoelectric element at a target voltage. As a result, the drive pulse matches the target voltage, and the output with stable image quality of the ultrasonic imaging apparatus is maintained.

  On the other hand, the ultrasonic imaging apparatus brings a probe unit into close contact with a subject and transmits / receives ultrasonic pulses. Here, the piezoelectric element of the probe section and the amplifier of the transmission / reception section for forming the drive pulse are connected by a coaxial cable (cable) of about 1 m. This coaxial cable causes an impedance change due to bending or the like, and causes a load characteristic applied to the output portion of the amplifier to fluctuate.

  In addition, in an ultrasonic imaging apparatus, in order to achieve high resolution, piezoelectric elements and amplifiers are being multi-channeled. In this multi-channel configuration, piezoelectric elements of about several tens to one hundred channels are transmitted and received almost simultaneously. Accordingly, the transmission / reception unit requires a large space and high-density mounting is essential. However, in high-density mounting, effects such as mutual stray capacitance between channels and stray inductance increase, and the oscillation phenomenon of the amplifier tends to occur in combination with the load fluctuation described above.

In order to prevent this oscillation phenomenon, for example, instead of continuous negative feedback of feedback information, feedback information is sampled intermittently to form intermittent negative feedback (for example, patents). Reference 1).
JP-A-2004-89466, (first page, FIG. 1)

  However, according to the above background art, although oscillation is suppressed, it is not easy to perform appropriate feedback in response to various imaging modes such as a B mode (moder) or a Doppler mode. That is, the timing (timing) of the driving pulse is different for each imaging mode, and it is necessary to perform feedback at an optimal timing for each driving pulse.

  In the ultrasonic imaging apparatus, drive pulses are repeatedly transmitted to a subject, and image information is collected during a reception period existing between these drive pulses. Considering these transmission / reception periods, performing intermittent feedback as described above can prevent oscillation more reliably and acquire stable image quality.

  Therefore, how to realize an ultrasonic imaging device that performs feedback only at the necessary timing synchronized with the transmission and reception of the ultrasonic imaging device, stabilizes the drive pulse to the target voltage, and reliably prevents oscillation. Is important.

  The present invention has been made to solve the above-described problems of the background art, and performs feedback only at a necessary timing synchronized with transmission / reception of the ultrasonic imaging apparatus to stabilize the drive pulse to a target voltage. Another object of the present invention is to provide an ultrasonic imaging apparatus that reliably prevents oscillation.

  In order to solve the above-described problems and achieve the object, an ultrasonic imaging apparatus according to the first aspect of the invention includes a probe unit in which piezoelectric elements that transmit ultrasonic pulses to a subject are arranged; An ultrasonic imaging apparatus comprising: a transmission / reception unit that forms a drive pulse for causing the piezoelectric element to perform the transmission; and a controller unit that controls the formation of the drive pulse, wherein the transmission / reception unit outputs the drive pulse. An amplifier, a feedback unit that feeds back an electric signal of an output unit of the amplifier at an input unit of the amplifier, and a switch unit that turns on and off the feedback, and the controller unit transmits transmission control information that controls formation of the drive pulse. On the basis of this, on / off of the switch unit is controlled.

  In the invention according to the first aspect, the transmission / reception unit includes an amplifier that outputs a drive pulse, a feedback unit that feeds back an electric signal of the output unit of the amplifier at an input unit of the amplifier, and a switch unit that turns on and off the feedback. The unit controls on / off of the switch unit based on transmission control information for controlling the formation of the drive pulse.

  An ultrasonic imaging apparatus according to the invention of the second aspect is the ultrasonic imaging apparatus according to the first aspect, wherein the transmission control information includes timing information indicating a timing for forming the drive pulse. It is characterized by that.

  The ultrasonic imaging apparatus according to the invention of the third aspect is the ultrasonic imaging apparatus according to the second aspect, wherein the controller unit turns on the switch unit in synchronization with the timing. Features.

  In the invention of the third aspect, the switch unit is turned on in synchronization with the formation of the drive pulse, and the output voltage is fed back.

  An ultrasonic imaging apparatus according to a fourth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to third aspects, wherein the transmission control information includes a maximum voltage of the drive pulse. It includes maximum voltage position information indicating the position.

  The ultrasonic imaging apparatus according to the fifth aspect of the invention is the ultrasonic imaging apparatus according to the fourth aspect, wherein the controller unit is configured to switch the switch unit at a maximum voltage position indicated by the maximum voltage position information. It is characterized by being turned on.

  In the fifth aspect of the invention, feedback is performed at the maximum voltage position.

  An ultrasonic imaging apparatus according to a sixth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to fifth aspects, wherein the drive pulse is transmitted from the subject after the transmission. It is a dummy pulse that does not receive a reflected ultrasonic pulse train that is reflected.

  In the invention of the sixth aspect, the drive pulse is adjusted to the target voltage by the dummy pulse before imaging.

  An ultrasonic imaging apparatus according to a seventh aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to sixth aspects, wherein the feedback unit outputs an electrical signal from the output unit of the amplifier. An A / D converter for digitizing, a feedback calculation unit for calculating a correction amount of the electric signal based on the digitized electric signal, and obtaining input information of the amplifier based on the correction amount, and the input information A D / A converter that outputs the signal in an analog form is provided.

  In the invention of the seventh aspect, feedback is performed by converting it into a digital signal.

  An ultrasonic imaging apparatus according to an eighth aspect of the invention is the ultrasonic imaging apparatus according to the seventh aspect, wherein the feedback unit includes a gain adjusting means for adjusting a feedback gain of the feedback. And

  In the eighth aspect of the invention, the feedback gain is adjusted so that the oscillation is efficient and does not occur.

  The ultrasonic imaging apparatus according to the ninth aspect of the invention is the ultrasonic imaging apparatus according to the seventh or eighth aspect, wherein the switch unit receives the digitized electrical signal of the A / D conversion unit. The output unit for outputting includes a sampling unit for sampling the electrical signal.

  An ultrasonic imaging apparatus according to a tenth aspect of the invention is the ultrasonic imaging apparatus according to the ninth aspect, wherein the controller unit sets the sampling unit in a sampling state when the feedback is turned on. It is characterized by.

  In the tenth aspect of the invention, the sampling unit is caused to turn on and off the feedback.

  An ultrasonic imaging apparatus according to an eleventh aspect of the invention is the ultrasonic imaging apparatus according to any of the seventh to tenth aspects, wherein the switch unit connects the output unit and the A / D conversion unit. Are provided with an analog switch.

  An ultrasonic imaging apparatus according to a twelfth aspect of the invention is the ultrasonic imaging apparatus according to the eleventh aspect, in which the controller unit electrically connects the analog switch when the feedback is turned on. It is characterized by making it a proper connection state.

  In the twelfth aspect of the invention, feedback is turned on and off by an analog switch.

  An ultrasonic imaging apparatus according to a thirteenth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to twelfth aspects, in which the amplifier generates the drive pulse and the transistor And a driver circuit for generating the drive pulse.

  In the thirteenth aspect of the invention, the amplifier is connected in two stages, and the operation of high output is stably performed.

  An ultrasonic imaging apparatus according to the fourteenth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to thirteenth aspects, wherein the amplifier detects an electrical signal of the output unit. A resistor is provided.

  In the fourteenth aspect, a voltage proportional to the output voltage of the drive pulse is detected.

  An ultrasonic imaging apparatus according to a fifteenth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to thirteenth aspects, wherein the feedback unit divides the voltage of the electrical signal. A pressure device is provided.

  In the fifteenth aspect of the invention, the detection resistor is eliminated, and the load of the amplifier driver is reduced.

  An ultrasonic imaging apparatus according to a sixteenth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to fifteenth aspects, wherein the transmitting / receiving unit includes an output unit of the amplifier and the piezoelectric element. A circuit is provided for electrically connecting the transformers.

  In the sixteenth aspect of the invention, the piezoelectric element and the amplifier are AC coupled.

  An ultrasonic imaging apparatus according to an invention of a seventeenth aspect is the ultrasonic imaging apparatus according to any one of the first to sixteenth aspects, in which the transmission / reception unit includes a positive voltage portion and a negative voltage of the drive pulse. When the waveform of the voltage portion has a point-symmetric structure, the amplifier includes two systems of the amplifier, the feedback portion, and the switch portion that separately form the positive voltage portion and the negative voltage portion.

  In the seventeenth aspect, bipolar drive pulses having positive and negative voltages are generated.

  An ultrasonic imaging apparatus according to an eighteenth aspect of the invention is the ultrasonic imaging apparatus according to the seventeenth aspect, in which the transmission / reception unit electrically connects the output unit of the two systems of amplifiers and the piezoelectric element. The circuit to be connected has a transformer, and two coils having different coil winding directions are provided on the primary side of the transformer to which the amplifier is connected.

  In the eighteenth aspect of the invention, bipolar drive pulses are generated using a positive or negative voltage power supply.

  According to the present invention, since feedback is performed at an optimal timing synchronized with transmission / reception in the imaging mode, oscillation caused by the feedback unit of the amplifier can be stably and reliably prevented regardless of the imaging mode. it can.

The best mode for carrying out an ultrasonic imaging apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited thereby.
(Embodiment 1)

  First, the overall configuration of the ultrasonic imaging apparatus 100 according to the first embodiment will be described. FIG. 1 is a block diagram showing the overall configuration of the ultrasonic imaging apparatus 100. The ultrasonic imaging apparatus 100 includes a probe unit 101, a transmission / reception unit 102, a B-mode processing unit 103, a Doppler processing unit 109, a cine memory unit 104, an image display control unit 105, a display unit 106, an input unit 107, and A controller unit 108 is provided.

  The probe unit 101 irradiates ultrasonic waves in a specific direction of the subject for transmitting / receiving ultrasonic waves, that is, a subject, and receives a reflected ultrasonic pulse train reflected from the inside of the subject as a time-series sound ray. To do. The probe unit 101 is also a part for performing electronic scanning that sequentially switches the irradiation position of ultrasonic waves. Inside the probe unit 101, piezoelectric elements are arranged in an array.

  The transmission / reception unit 102 is connected to the probe unit 101 by a coaxial cable, and generates a driving pulse for driving the piezoelectric element of the probe unit 101. The transmission / reception unit 102 also performs first-stage amplification of the electrical signal of the received reflected ultrasonic pulse train.

  The B mode processing unit 103 generates a B mode image in real time from the signal of the reflected ultrasonic pulse train amplified by the transmission / reception unit 102. The specific processing contents include a delay addition process of an electrical signal of a received reflected ultrasonic pulse train, an A / D (analog / digital) conversion process, and a cine memory described later as digital information after conversion as B-mode image information. For example, a process of writing in the unit 104.

  The Doppler processing unit 109 extracts phase change information from the electrical signal of the reflected ultrasonic pulse train amplified in the first stage by the transmission / reception unit 102, and in real time, such as the average blood flow velocity, power value, and dispersion inside the subject. Blood flow information at each imaging position included in the Doppler imaging region is calculated.

  The cine memory unit 104 is an image memory, and stores the B-mode image information generated by the B-mode processing unit 103 and the blood flow information generated by the Doppler processing unit 109.

  The image display control unit 105 performs display frame rate conversion of the B-mode image information generated by the B-mode processing unit 103 or the blood flow information generated by the Doppler processing unit 109, and further displays the shape of the image display And position control.

  The display unit 106 includes a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), or the like, and displays a B-mode image, a Doppler image, or the like.

  The input unit 107 includes a keyboard and the like, and an operation input signal is input by an operator. For example, information such as an operation input for selecting display in the B mode or display of Doppler processing or an operation input for inputting settings of a Doppler imaging region for performing Doppler processing is given to the controller unit 108.

  The controller unit 108 controls the operation of each unit of the ultrasonic imaging apparatus described above based on the operation input signal input from the input unit 107 and a program (program) or data (data) stored in advance. In particular, the controller unit 108 inputs transmission control information for controlling transmission of drive pulses for driving the piezoelectric element to the transmission / reception unit 102.

  FIG. 2 is a block diagram illustrating details of the probe unit 101, the transmission / reception unit 102, and the B-mode processing unit 103. The probe unit 101 includes an array-shaped piezoelectric element 10 and an analog multiplexer 11, and the B-mode processing unit 103 includes a reception beamformer 21 and a transmission beamformer 22. The arrayed piezoelectric element 10 is a one-dimensional array of piezoelectric elements.

  The analog multiplexer 11 is a high withstand voltage analog electronic switch (switch), and has an input / output terminal connected to the piezoelectric element of the piezoelectric element 10 on a one-to-one basis and an input / output terminal connected to the transmission / reception unit 102 on a one-to-one basis. For example, in the case of the piezoelectric element 10 having 256 channels and the transmission / reception unit 102 having 64 transmission / reception circuits, the analog multiplexer 11 is connected to the probe array. It has 256 channel connection terminals, and has 64 channel connection terminals on the side connected to the transmission / reception circuit.

  The transmission / reception unit 102 is a part that forms drive pulses for driving the piezoelectric elements and performs first-stage amplification of the reflected ultrasonic pulse train received by the piezoelectric elements. The transmission / reception unit 102 includes a similar transmission circuit 23 and reception circuit 24 arranged, for example, independently for 64 channels. The transmission beamformer 22 generates a delayed trigger signal for performing electronic focus based on the depth of focus information from the controller unit 108. The transmission circuit 23 of the transmission / reception unit 102 generates a predetermined drive pulse in synchronization with the input trigger signal. The reception beamformer 21 adds a delay for each channel to the reflected ultrasonic pulse train reflected from the inside of the subject, and outputs the result to the image display control unit 105 as sound ray information after addition.

  FIG. 3 is a block diagram illustrating a configuration of the transmission circuit 23. The transmission circuit 23 includes a transformer 27, an amplifier 29, and a feedback unit 40. The amplifier 29 includes a transistor 30 and a driver 31, and a feedback unit 40 includes a detection resistor 36, an A / D converter 35, a sampling circuit 34, a gain adjustment unit 37, a feedback calculation unit 38, and A waveform memory 39 is included.

  The transformer 27 has a primary side connected to the output of the transistor 30 and a secondary side connected to the piezoelectric element 10, and applies a drive pulse formed by the transistor 30 to the piezoelectric element 10.

  The transistor 30 is configured by an FET (Field Effect Transistor) having a high withstand voltage of about 100 V, for example, a drain terminal is connected to the primary side of the transformer 27, and a source terminal is connected via the detection resistor 36. Grounded. The output of the driver 31 is input to the gate terminal of the transistor 30 so that the transistor 30 performs stable switching. The driver 31 is a transistor having a smaller current capacity and withstand voltage than the transistor 30.

  The detection resistor 36 is connected between the source terminal and the ground terminal of the transistor 30 and detects a voltage proportional to the current flowing between the drain terminal and the source terminal of the transistor 30.

  The A / D converter 35 converts the voltage detected by the detection resistor 36 from an analog signal to a digital signal. The A / D converter 35 sequentially performs A / D conversion at a predetermined time interval, for example, at a time interval sufficiently shorter than the pulse width of the drive pulse.

  The sampling circuit 34 is a latch circuit that samples the digital signal output from the A / D converter 35 in synchronization with the transmission control information from the controller unit 108.

  The gain adjusting means 37 adjusts the gain of the digital signal sampled by the sampling circuit 34 and outputs it to the feedback calculation unit 38. The feedback calculation unit 38 compares the gain-adjusted digital signal with target reference voltage information, and calculates correction voltage information. Here, assuming that the correction voltage as a correction amount is ΔV, the gain is k, the target voltage is Vr, and the detection voltage is Vd,

ΔV = k (Vd−Vr) ――――――― (1)
Using the equation (1) having the relationship, correction voltage information is obtained. The target voltage Vr and the gain k are set from the controller unit 108 for each imaging mode. The target voltage Vr is calculated from the value of the detection resistor 36 and the target current flowing between the drain and source of the transistor 30, and if the gain k is increased, the correction effect due to feedback increases, but oscillation tends to occur. The value is determined so as not to cause oscillation and to have a correction effect.

  The waveform memory 39 is a memory in which the waveform of the drive pulse is stored. The drive pulses stored in the waveform memory 39 are sequentially read out by a counter (not shown) or the like in synchronization with the trigger signal from the transmission beamformer 22 and transmitted to the D / A converter 32. FIG. 4 is an explanatory diagram schematically showing an example of a burst waveform stored in the waveform memory 39. The horizontal axis represents the time to be read, and the vertical axis represents the amplitude Vo of the drive pulse. The pulse width T and the number of pulses of the burst waveform vary depending on the resonance frequency of the piezoelectric element 10 and the imaging mode used, and the waveform memory 39 is based on the imaging mode information from the controller unit 108 or the resonance frequency information of the piezoelectric element 10. The optimum burst waveform is selected from among the plurality of waveforms existing in.

  The feedback calculation unit 38 corrects the amplitude of the drive pulse information stored in the waveform memory 39 using the correction voltage information ΔV described above. For example, when the amplitude of the drive pulse information stored in the waveform memory 39 is Vo,

Vo = Vo−ΔV
The information in the waveform memory 39 is changed to drive pulse information having a new amplitude Vo.

  The D / A converter 32 converts digital information related to the drive pulse of the waveform memory 39 into analog information and inputs the analog information to the driver 31 of the amplifier 29.

  Next, operations of the controller unit 108 and the feedback unit 40 will be described. FIG. 5 is a flowchart illustrating the operation of the controller unit 108 and the feedback unit 40. First, the operator selects an imaging mode such as B mode or Doppler mode from the input unit 107 (step S501). As a result, transmission / reception control information including transmission control information according to the imaging mode and the attached probe unit 101 is formed in the controller unit 108.

  The controller unit 108 transmits this transmission control information to the transmission / reception unit 102, the B-mode processing unit 103, and the like. The transmission control information transmitted to the transmission / reception unit 102 includes drive pulse selection information stored in the waveform memory 39. For example, a drive pulse as shown in FIG. 4 is selected.

  The controller unit 108 receives depth of focus position information for electronic focusing from the input unit 107, and calculates delay time information for each channel of the drive pulse based on the depth of focus position information.

  The delay time information is included in the transmission control information, and is input to the transmission beam former 22 of the B mode processing unit 103. The transmission beamformer 22 generates a trigger signal for activating each channel of the transmission / reception unit 102 in synchronization with the transmission activation pulse 61 repeatedly generated from the controller unit 108 based on this delay time information and driven channel information. appear.

  Thereafter, the controller unit 108 generates a transmission activation pulse 61 that instructs transmission / reception of an ultrasonic pulse (step S502). This transmission start pulse generates a trigger signal after being transmitted to the transmission beamformer 22, and this trigger signal is further transmitted to the transmission circuit 23 to generate a drive pulse of the same type as the waveform memory 39 at the output of the amplifier 29. .

  FIG. 6A is an explanatory diagram showing the transmission activation pulse 61 generated from the controller unit 108 with the horizontal axis as a time axis. FIG. 6B shows a drive pulse 62 output to the drain terminal of the transistor 30 in synchronization with the transmission start pulse 61, with the vertical axis representing voltage and the horizontal axis representing the time axis common to FIG. 6A. It is explanatory drawing. The driving pulse 62 is generated in synchronization with a trigger signal generated by the transmission beam former 22 and delayed from the transmission activation pulse 61 by a delay time τ. The drive pulse 62 has a waveform as shown in FIG. 4 stored in the waveform memory 39.

  Thereafter, the sampling circuit 34 samples the voltage information of the source terminal of the transistor 30 which is an electric signal of the output part of the amplifier 29 in synchronization with the sampling pulse 63 input from the controller part 108 (step S503). FIG. 6C is an explanatory diagram showing the sampling pulse 63 input from the controller unit 108 to the sampling circuit 34 with the horizontal axis as the time axis common to FIGS. 6A and 6B.

  The sampling pulse 63 is sampled at a position corresponding to the maximum output voltage of the drive pulse 62 in consideration of the delay time τ for each channel set in the transmission beamformer 22 and the pulse width T of the drive pulse 62 which is maximum voltage position information. I do.

  That is, the controller unit 108 sets the time d such that T> d using the information on the delay time τ and the pulse width T, and outputs the sampling pulse 63 at a time delayed by τ + d with respect to the transmission activation pulse 61. The digital output of the A / D converter 35 is sampled. The time d is set to a time for accurately detecting the maximum output voltage of the drive pulse 62. For example, when waveform ringing or the like exists in the rising portion of the transmission start pulse 61, the time d is lengthened and sampling is performed at a position where no ringing exists.

  Thereafter, the feedback unit 40 feeds back the digital information acquired by the sampling circuit 34 to the input unit of the amplifier 29 (step S504). In this feedback, the gain k set in the gain adjusting unit 37 and the correction amount using the equation (1) of the feedback calculation unit 38 are calculated, and the amplitude information of the drive pulse stored in the waveform memory 39 is changed. Specifically, a correction voltage ΔV that is a correction amount proportional to the difference between the sampled detection voltage Vd and the target voltage Vr is calculated, and the amplitude information of the drive pulse stored in the waveform memory 39 is changed. The changed drive pulse information of the waveform memory 39 is output to the driver 31 of the amplifier 29 in synchronization with the next transmission start pulse 61. As a result, a drive pulse 62 having a new amplitude is output to the output unit of the amplifier 29.

  Note that the feedback only needs to correct the electric signal input to the amplifier 29, so that the drive pulse information written in the waveform memory 39 is not changed, and the reference voltage of the D / A converter 32 is increased or decreased. It can also be done.

  Thereafter, the controller unit 108 determines whether or not to continue the transmission (step S505). When the transmission is continued (Yes at step S505), the controller unit 108 proceeds to step S502 and generates the transmission start pulse 61 again. Note that the sampling pulse 63 is not generated until the transmission start pulse 61 is transmitted again, and therefore the feedback of the maximum voltage output of the drive pulse 62 is not performed. In this way, the feedback is not performed continuously, so oscillation is prevented. Further, when the transmission is not continued (No at Step S505), the controller unit 108 ends this process.

  As described above, in the first embodiment, the sampling pulse 63 is generated at the timing at which the drive pulse 62 is transmitted from the controller unit 108, and the feedback unit 40 is only at the timing at which the sampling pulse 63 is generated. Since the output voltage of the amplifier 29 is fed back to the input section of the amplifier 29, oscillation caused by this feedback can be prevented and the output voltage of the amplifier 29 can be set to a target voltage.

  In the first embodiment, after the transmission activation pulse 61, a reflected ultrasonic pulse train reflected from the subject is received and displayed as a B-mode image. However, before performing B-mode imaging, a dummy is received. It is also possible to transmit only the transmission start pulse 61 as a pulse (dummy pulse), adjust the output voltage of the amplifier 29 to a target voltage by feedback, and then perform B-mode imaging.

  In the first embodiment, an example in which B-mode imaging is performed is shown. However, in the imaging mode such as Doppler mode or B-flow mode, feedback timing is controlled in the same manner, and there is no oscillation. A stable image can be acquired.

  In the first embodiment, the feedback voltage is detected from the source terminal of the transistor 30 connected to the detection resistor 36. However, the detection resistor 36 is deleted and the feedback voltage is detected from the drain terminal of the transistor 30. You can also

  FIG. 7 is a block diagram illustrating an example of the transmission circuit 73 that detects the feedback voltage from the drain terminal of the transistor 30. The transmission circuit 73 includes a transformer 27, an amplifier 29, and a feedback unit 70. The transmission circuit 73 corresponds to the transmission circuit 23 shown in FIG. 3, and the amplifier 29 and the transformer 27 are exactly the same as the transmission circuit 23. The feedback unit 70 includes a voltage divider 71 and a capacitor 72 instead of the detection resistor 36 of the feedback unit 40 included in the transmission circuit 23.

In the first embodiment, the voltage at the output section of the amplifier 29 is sampled only once for one transmission activation pulse 61, but a plurality of transmission activation pulses 61 are sampled for one transmission activation pulse 61. When the drive pulse 62 is output, a sampling pulse 63 is generated for each drive pulse 62 and sampling can be performed a plurality of times.
(Embodiment 2)

  In the first embodiment, the feedback is turned on by the sampling operation of the sampling circuit 34. However, a switch is inserted between the source terminal of the transistor 30 and the A / D converter 35. The feedback can be turned on / off by the on / off operation of the switch. Thereby, the insulation characteristic when the feedback loop (loop) is in the OFF state can be made high, and as a result, oscillation caused by the feedback loop can be more reliably prevented.

  FIG. 8 is a block diagram showing a configuration of the transmission circuit 83 according to the second embodiment. The transmission circuit 83 includes a transformer 27, an amplifier 29, and a feedback unit 80. The transmission circuit 83 corresponds to the transmission circuit 23 shown in FIG. 3, and the amplifier 29 and the transformer 27 are exactly the same as those of the transmission circuit 23. The feedback unit 80 is obtained by adding a new switch 81 between the detection resistor 36 of the feedback unit 40 and the A / D converter 35.

  The switch 81 is configured by an analog switch or the like, and turns on / off the electrical connection of the analog switch based on on / off information from the controller unit 108. The analog switch has an insulation resistance of several MΩ when the input / output terminals are in an off state. Therefore, when the switch 81 is in the OFF state, the feedback loop has high insulation, and transmission due to the feedback loop can be reliably prevented.

  The sampling circuit 34, the gain adjusting unit 37, and the feedback calculation unit 38 are wired with high density using a semiconductor circuit. Isolation of electrical signals existing between these elements and between channels is not sufficient as compared with the insulation resistance of the switch 81 described above, and leakage (leak) is caused by an instantaneous pulse such as the drive pulse 62. ) Voltage or leakage current is generated.

  The controller unit 108 turns on / off the switch 81 in synchronization with the driving pulse 62 shown in FIG. 6B, for example. Accordingly, the controller unit 108 turns on the switch 81 when the sampling circuit 34 performs sampling, and turns off the switch 81 when sampling is not performed, and the output voltage of the amplifier 29 leaks to the feedback loop. To prevent this.

As described above, in the second embodiment, since the feedback loop is reliably turned on and off by the switch 81, the oscillation caused by the feedback loop is surely prevented and the output of the amplifier 29 is instantaneously generated. Therefore, it is possible to prevent a change or an external electrical noise from leaking to the feedback loop, and to perform a stable operation.
(Embodiment 3)

  In the first embodiment, one amplifier 29 is provided to generate a unipolar drive pulse 62 having an amplitude only in the positive voltage direction. However, two amplifiers 29 are provided to provide positive and negative voltages. Bipolar drive pulses with amplitudes in both directions of the voltage can also be generated.

  FIG. 9 is a block diagram showing a configuration of the transmission circuit 93 according to the third embodiment. The transmission circuit 93 includes two amplifiers 29 of two systems, a feedback unit 40, a delay unit 94, and a transformer 97. The amplifier 29 and the feedback unit 40 are exactly the same as those shown in FIG. The transformer 93 corresponds to the transformer 27 and is different from the transformer 27 in the internal coil configuration and wiring.

  The transformer 97 has two coils 90 and 91 on the primary side, in which the winding direction of the coils is different by 180 degrees. These two coils have one terminal connected to a common voltage power supply VDD and the other two terminals electrically connected to output terminals of different amplifiers 29. The primary side coils 90 and 91 are magnetically coupled to the secondary side coil 92. As a result, when a current in the same direction flows through the primary side coil 90 or 91, a current flowing in the reverse direction is induced in the secondary side coil 92, and a drive pulse having a reverse polarity is generated.

  The delay unit 94 generates a trigger signal having a time difference corresponding to a half of the period of the drive pulse 62 with respect to the trigger signal input from the transmission beamformer 22 by a pulse width T that is 180 degrees out of phase.

  FIG. 10A is an explanatory diagram showing a trigger signal 41 that is directly input from the transmission beamformer 22 to the feedback unit 40. FIG. 10B is an explanatory diagram showing the trigger signal 42 generated by the delay unit 94. The trigger signal 42 is delayed by the delay unit 94 by a time T corresponding to the half wavelength of the drive pulse 62 with respect to the trigger signal 41.

  FIG. 10C is an explanatory diagram showing bipolar drive pulses 43 generated by the transmission circuit 93. The positive voltage portion of the drive pulse 43 is formed by the trigger signal 41, and the negative voltage portion of the drive pulse 43 is formed by the trigger signal 42.

  As described above, in the third embodiment, two coils 90 and 91 having different winding methods are provided on the primary side of the transformer 97, and these two coils are activated by the two feedback units 40 and the amplifier 29. Therefore, the drive pulse 43 having both positive and negative voltages can be generated.

  In the third embodiment, the two feedback units 40 are provided in the transmission circuit 93. However, these two feedback units 40 that perform feedback are provided by the A / D converter 35 and the D / A. Since it is composed of a digital circuit such as the sampling circuit 34, the gain adjusting unit 37, the feedback calculation unit 38, and the waveform memory 39, except for the converter 32, it can be integrated into one circuit including the memory and the calculation processing unit.

  In the first to third embodiments, an FET is used as the transistor 30. Instead, a bipolar transistor, a CMOS FET, an IGBT in which a bipolar transistor and an FET coexist, and a thyristor. Etc. can also be used.

It is a block diagram which shows the whole structure of an ultrasonic imaging device. It is a block diagram which shows the structure of the probe part of a ultrasonic imaging device, a transmission / reception part, and a B mode process part. 1 is a block diagram showing a transmission circuit according to a first exemplary embodiment; 4 is an explanatory diagram illustrating an example of a drive pulse stored in a waveform memory according to the first embodiment; FIG. 3 is a flowchart showing an operation of the transmission circuit according to the first exemplary embodiment; 4 is an explanatory diagram showing sampling timing of a feedback unit according to the first embodiment; FIG. It is explanatory drawing which shows another form which detects the electric signal of an output part by the feedback concerning Embodiment 1. FIG. FIG. 3 is a block diagram showing a transmission circuit according to a second exemplary embodiment; FIG. 6 is a block diagram illustrating a transmission circuit according to a third embodiment; FIG. 9 is an explanatory diagram illustrating drive pulses generated by the transmission circuit according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric element 11 Analog multiplexer 21 Reception beam former 22 Transmission beam former 23, 73, 83, 93 Transmission circuit 24 Reception circuit 27, 93, 97 Transformer 29 Amplifier 30 Transistor 31 Driver 32, 35 A / D converter 34 Sampling circuit 36 Detection resistor 37 Gain adjustment means 38 Feedback calculation unit 39 Waveform memory 40, 70, 80 Feedback unit 41, 42 Trigger signal 43 Drive pulse 61 Transmission start pulse 62 Drive pulse 63 Sampling pulse 71 Voltage divider 72 Capacitor 81 Switch 90, 91, 92 Coil 94 Delay unit 100 Ultrasound imaging device 101 Probe unit 102 Transmission / reception unit 103 B mode processing unit 104 Cine memory unit 105 Image display control unit 106 Display unit 107 Input unit 108 Controller unit 109 Doppler processing unit

Claims (18)

A probe unit in which piezoelectric elements that transmit ultrasonic pulses to the subject are arranged; and
A transmission / reception unit for forming a drive pulse for causing the piezoelectric element to perform the transmission;
A controller unit for controlling the formation of the drive pulse;
An ultrasonic imaging apparatus comprising:
The transmission / reception unit includes an amplifier that outputs the drive pulse, a feedback unit that feeds back an electric signal of the output unit of the amplifier to an input unit of the amplifier, and a switch unit that turns on and off the feedback.
The ultrasonic imaging apparatus, wherein the controller unit controls on / off of the switch unit based on transmission control information for controlling formation of the drive pulse.   The ultrasonic imaging apparatus according to claim 1, wherein the transmission control information includes timing information indicating a timing for forming the drive pulse.   The ultrasonic imaging apparatus according to claim 2, wherein the controller unit turns on the switch unit in synchronization with the timing.   The ultrasonic imaging apparatus according to claim 1, wherein the transmission control information includes maximum voltage position information indicating a position of a maximum voltage included in the drive pulse.   The ultrasonic imaging apparatus according to claim 4, wherein the controller unit turns on the switch unit at a maximum voltage position indicated by the maximum voltage position information.   6. The ultrasonic wave according to claim 1, wherein the drive pulse is a dummy pulse that does not receive a reflected ultrasonic pulse train reflected from the subject after the transmission. Imaging device.   The feedback unit is an A / D conversion unit that digitizes an electrical signal at the output of the amplifier, calculates a correction amount of the electrical signal based on the digitized electrical signal, and based on the correction amount, The ultrasonic imaging apparatus according to claim 1, further comprising: a feedback calculation unit that obtains input information of an amplifier; and a D / A conversion unit that converts the input information into an analog output.   The ultrasonic imaging apparatus according to claim 7, wherein the feedback unit includes a gain adjusting unit that adjusts a feedback gain of the feedback.   The ultrasonic wave according to claim 7 or 8, wherein the switch unit includes a sampling unit that samples the electric signal at an output unit that outputs the digitized electric signal of the A / D conversion unit. Imaging device.   The ultrasonic imaging apparatus according to claim 9, wherein the controller unit sets the sampling unit to a sampling state when the feedback is turned on.   The ultrasonic imaging apparatus according to claim 7, wherein the switch unit includes an analog switch in a connection connecting the output unit and the A / D conversion unit.   The ultrasonic imaging apparatus according to claim 11, wherein the controller unit electrically connects the analog switch when the feedback is turned on.   The ultrasonic imaging apparatus according to claim 1, wherein the amplifier includes a transistor that generates the drive pulse and a driver circuit that causes the transistor to generate the drive pulse.   The ultrasonic imaging apparatus according to claim 1, wherein the amplifier includes a detection resistor that detects an electrical signal of the output unit.   The ultrasonic imaging apparatus according to claim 1, wherein the feedback unit includes a voltage divider that divides the voltage of the electrical signal.   16. The ultrasonic imaging apparatus according to claim 1, wherein the transmission / reception unit includes a transformer in a circuit that electrically connects the output unit of the amplifier and the piezoelectric element.   The transmitter / receiver has two systems of the amplifier and the feedback that separately form the positive voltage portion and the negative voltage portion when the waveforms of the positive voltage portion and the negative voltage portion of the drive pulse have a point-symmetric structure. The ultrasonic imaging apparatus according to claim 1, further comprising a switching unit and the switch unit. The transmission / reception unit includes a transformer in a circuit that electrically connects the output unit of the two amplifiers and the piezoelectric element, and the winding direction of the coil is different on the primary side of the transformer to which the amplifier is connected. The ultrasonic imaging apparatus according to claim 17, comprising one coil.

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