JP6005956B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  Embodiments described herein relate generally to an ultrasonic diagnostic apparatus.

  A medical ultrasonic diagnostic apparatus transmits ultrasonic waves from an ultrasonic probe brought into contact with the body surface of a subject into the body, and transmits ultrasonic signals reflected at different parts of the body with different acoustic impedances. It is a device that receives and generates an ultrasound image showing information in the body based on the signal, and is used for various diagnoses because of its high safety.

  FIG. 7 shows a schematic configuration of a conventional ultrasonic diagnostic apparatus 200. The ultrasonic diagnostic apparatus 200 includes a transmission unit (pulse generation unit) 201, a transmission / reception switching switch unit (hereinafter referred to as “TRSW”) 202, an ultrasonic probe 203, an amplification unit 204, a processing unit 205, and a display unit. 206. When a pulse signal (hereinafter referred to as “transmission signal”) transmitted from the transmission unit 201 is input to the ultrasonic probe 203, an ultrasonic transducer (not shown) built in the ultrasonic probe 203 responds to the transmission signal. Generate ultrasonic waves. The ultrasonic wave reflected in the body is received by an ultrasonic transducer and converted into an electric signal, and the electric signal (hereinafter referred to as “echo signal”) is input to the amplifying unit 204 via the TRSW 202 as a received signal. After being amplified at a predetermined amplification factor, the processing unit 205 performs signal processing and the like, and an ultrasonic image generated thereby is displayed on the display unit 206.

  The TRSW 202 is configured by combining a diode bridge circuit 210 and a clamp circuit 220 as shown in FIG. The diode bridge circuit 210 includes bias power sources V10 and V11, bias resistors R10 and R11 connected to the bias power sources V10 and V11, respectively, and diodes D10 to D13. The clamp circuit 220 is configured to include diodes D14 and D15 that are grounded and have different polarities.

  In the diode bridge circuit 210, when a pulse signal is transmitted from the transmission unit 201, the amplitude of the transmission signal is large (for example, several tens of Vpp or more). Therefore, when the high-voltage pulse is a positive pulse, the diodes D10 and D13 are When the high voltage pulse is a negative pulse, the diodes D11 and D12 are turned off with the reverse bias. For this reason, the high voltage pulse is limited to the amplitude determined by the diode bridge circuit 210 and the clamp circuit 220, and does not pass through as it is. That is, at the time of transmission, the input of the amplification unit 204 is protected from the high-voltage pulse of the transmission signal by the amplitude limiting function combining the diode bridge circuit 210 and the clamp circuit 220.

  On the other hand, when the amplitude of the input signal is small (for example, less than several hundred mVpp), such as an echo signal received via the ultrasonic probe 203, the input signal is the resistor R10 and the diode D10 of the diode bridge circuit 210. Since it is weaker than the bias current flowing through D13 and resistor R11, the diodes D10 to D13 are not turned off, and the input signal passes through as it is.

  Here, when the echo signal is a short-distance reflection echo near the body surface, for example, the amplitude of the echo signal is so large that it exceeds the saturation level of the input amplitude of the amplifying unit 204. The clamp circuit 220 saturates the amplification unit 204 when the amplitude of the transmission signal or the echo signal is, for example, an excessive amplitude exceeding the saturation level of the subsequent amplifier, and correctly displays an image near the body surface. become unable. In addition to the above, the TRSW can be configured by a semiconductor switch such as an FET.

JP 2006-68090 A

  In the above-described prior art, when the echo signal is reflected near the body surface, the signal portion of the input echo signal that exceeds the predetermined voltage is cut, so the output signal waveform of the amplifier is distorted. End up. Since the ultrasonic diagnostic image displayed on the display unit based on such a distorted signal waveform includes unnecessary artifacts, the echo signal reflected near the body surface cannot be accurately reproduced (drawn).

  The embodiment has been made to solve the above-described problems, and amplifies the echo signal without degrading the ultrasonic image even when the echo signal is reflected near the body surface. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of preventing amplifier saturation.

Ultrasonic diagnostic apparatus according to the embodiment, the transmission signal is a transmission unit for transmitting an ultrasound signal into the object via the ultrasonic probe, reception obtained are reflected in the object in the receiving period immediately after the transmission An ultrasonic diagnostic apparatus having an amplifying unit for amplifying a signal, the ultrasonic diagnostic apparatus being disposed between the output unit of the ultrasonic probe and the amplifying unit and receiving a reception signal from the output unit A first series circuit and a second series circuit having the same configuration including a diode and a resistor, wherein the first series circuit has one end on the cathode side of the diode, The second series circuit is provided with one end on the anode side of the diode connected to the connection point, and applies a positive voltage to the other end of the first series circuit. The opposite polarity with the same magnitude as the positive voltage at the end A damping unit having a voltage generator to provide a negative voltage, the relative voltage generating unit, the magnitude of the positive voltage and the negative voltage, immediately after the transmission, the first series circuit of a diode Is a voltage that conducts at the positive voltage of the reception signal immediately after the transmission, and the voltage at which the diode of the second series circuit is conductive at the negative voltage of the reception signal, and then, according to the passage of time, A bias control unit that reduces the magnitude of the voltage and sets the voltage to zero after a predetermined period of time shorter than the reception period of the received signal.

1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment. It is a figure which shows the structure of a receiving part. It is a figure which shows the signal waveform of TRSW pre-stage and the signal waveform in the pre-attenuator section when the attenuator is operating. It is a figure which shows the signal waveform of TRSW front | former stage when the attenuation | damping part is not operate | moving, and the signal waveform in the front part of damped part. It is a figure which shows the structure of a bias control part. It is a figure which shows an example of the control data used for controlling supply of the variable bias power supply in the positive electrode side. It is a figure which shows an example of the control data used for controlling supply of the variable bias power supply in the negative electrode side. It is a block diagram of the conventional ultrasonic diagnostic apparatus. It is a figure which shows the structure of an input protection circuit.

  With reference to FIGS. 1-5, the ultrasonic diagnosing device 1 which concerns on embodiment is demonstrated. FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment. FIG. 2 is a diagram illustrating a configuration of the receiving unit. FIG. 3 is a diagram illustrating a signal waveform in the previous stage of TRSW and a signal waveform in the previous stage of the attenuation section when the attenuation section is operating. FIG. 4 is a diagram illustrating a signal waveform in the previous stage of TRSW and a signal waveform in the previous stage of the attenuation section when the attenuation section is not operating. FIG. 5A is a diagram illustrating an example of control data used to control the supply of the variable bias power supply on the positive electrode side, and is a diagram illustrating a time change of the bias voltage supplied to the diode of the attenuation unit. FIG. 5B is a diagram illustrating an example of control data used to control the supply of the variable bias power supply on the negative electrode side, and is a diagram illustrating a time change of the bias voltage supplied to the diode of the attenuation unit.

<Overall configuration of ultrasonic diagnostic apparatus>
As shown in FIG. 1, the ultrasonic diagnostic apparatus 1 includes an ultrasonic probe 15, a transmission unit (pulse generation unit) 11, a reception unit 12, a processing unit 21, a bias control unit 23, and an operation unit 25. The display unit 27 is provided. The reception unit 12 is provided for each reception channel, and includes a TRSW 13, an attenuation unit 17, and an amplification unit 19. The number of reception units 12 is the same as the number of reception channels, but for the sake of convenience of explanation, only one reception unit 12 is shown in FIG. Further, the number of reception channels is the same as the number of ultrasonic transducers described later. As an application example, the number of transmission / reception channels is set to be smaller than the number of ultrasonic transducers, combined with an analog switch, and can be connected to all ultrasonic transducers by switching the transmission / reception channels. There may be.

  The ultrasonic probe 15 is configured to include an array-shaped ultrasonic transducer including a plurality of vibration elements that transmit and receive ultrasonic waves to and from a living body. R1 is the signal source impedance (internal impedance) when the ultrasonic probe 15 is equivalently regarded as the signal source Vs.

  The transmitter 11 supplies a transmission signal (high-pressure pulse) to an ultrasonic transducer (not shown) built in the ultrasonic probe 15. At the time of reception, the reception signal output from the ultrasonic transducer is input to the attenuation unit 17 via the TRSW 13.

  When the transmission signal from the transmission unit 11 is input to the ultrasonic probe 15, the ultrasonic transducer of the ultrasonic probe 15 generates an ultrasonic wave corresponding to the transmission signal. The ultrasonic wave reflected in the body is converted into an electric signal by the ultrasonic transducer. This electrical signal (hereinafter referred to as “echo signal”) is input to the TRSW 13 as a received signal. The echo signal input to the TRSW 13 is input to the amplification unit 19 via the attenuation unit 17. The echo signal amplified by the amplifying unit 19 is sent to the processing unit 21, where an ultrasonic image is constructed by performing predetermined signal processing and the like.

  The acquired ultrasonic image data is input to a display control unit (not shown) and converted into a format that can be displayed on the screen of the display unit 27. An ultrasonic image is displayed on the display unit 27. The bias control unit 23 controls supply of a bias voltage by a variable bias power source (described later) provided in the attenuation unit 17 (details will be described later).

  The TRSW 13 is configured by combining a diode bridge circuit (high voltage cutoff switching circuit) 31 and a clamp circuit (amplitude limiting circuit) 34 as shown in FIG. The diode bridge circuit 31 connects in parallel a combination of diodes D1 and D3 connected in series with the same polarity and a combination of diodes D2 and D4 connected in series with the same polarity. Connected).

  A bias resistor R3 connected to the bias power source V1 is connected to the anode side of the diodes D1 and D2. A bias resistor R4 connected to the bias power source V2 is connected to the cathode side of the diodes D3 and D4. The clamp circuit 34 is configured to include diodes D5 and D6 that are grounded and have different polarities.

  The attenuating unit 17 includes a first circuit 17a including a resistor R5, a diode D7, and a variable bias power source V3 connected to the signal line L1, and a resistor R6, a diode D8, and a variable bias power source V4 connected to the signal line L1. The second circuit 17b is connected in parallel. The attenuator 17 is connected to a bias controller 23 that controls the bias voltage at the variable bias power sources V3 and V4. The control of the bias control unit 23 is performed based on control data (described later) set in advance by a selection instruction from the operation unit 25. Details of this will be described later.

  A variable bias power source V3 is connected to the anode side of the diode D7, and a resistor R5 is connected to the cathode side. A variable bias power source V4 is connected to the cathode side of the diode D8, and a resistor R6 is connected to the anode side.

  The amplifying unit 19 includes an amplifier (preamplifier) 40, and amplifies the input echo signal with a predetermined amplification factor. R2 is an equivalent input impedance (resistance) of the amplifying unit 19.

  The processing unit 21 performs known signal processing (for example, A / D conversion processing, delay addition processing, etc.) on the amplified echo signal, and an ultrasonic image generated thereby is displayed on the display unit 27.

<Operation of TRSW 13>
Next, the operation of TRSW 13 will be described along the respective flows of the transmission signal and the reception signal.

  The transmission unit 11 outputs a high-pressure pulse wave (hereinafter referred to as “transmission signal”) in response to a predetermined transmission timing signal input from a transmission control unit (not shown). This transmission signal usually has a large amplitude of about 100 Vpp for driving the ultrasonic transducer of the ultrasonic probe 15 and is sent to the ultrasonic probe 15 via the input of the TRSW 13. This large amplitude transmission signal is applied to the ultrasonic transducer. The ultrasonic transducer is excited by applying a transmission signal, and the ultrasonic probe 15 emits an ultrasonic signal.

  Note that the amplitude of the transmission signal described above is limited in the TRSW 13, so the transmission signal is not directly applied to the amplifying unit 19 side. Since this principle has already been described above in the description of the conventional example, the description thereof is omitted here.

  Next, the ultrasonic signal emitted from the ultrasonic probe 15 is reflected by the living tissue inside the subject, and the reflected echo signal (reception signal) is received by the ultrasonic probe 15 again.

  Since the signal level of this echo signal is usually several tens of mVpp or less, which is much smaller than about ± 0.7 V limited by the forward voltage of the diodes D5 and D6 of the TRSW, the echo signal passes through the TRSW as it is. The echo signal that has passed is input to the attenuation unit 17.

<Operation of the attenuation unit 17>
The forward voltage of the diode D7 is Vf, the anode side voltage of the diode D7 (the bias voltage of the variable bias power supply V3) is v3, and the input voltage of the receiving unit 2 (the input voltage of the TRSW 13 (at the node P1) at the time of echo signal reception) Voltage) When E is ± Vin, the diode D7 becomes conductive when E = −Vin arrives and satisfies the relationship of the following formula (1).
-E + v3 = Vin + v3> Vf (1)
However, Vf> v3

When the forward voltage of the diode D8 is Vf and the voltage on the cathode side of the diode D8 (the bias voltage of the variable bias power supply V4) is −v4 , the diode D8 has the following formula (when the input voltage E = + Vin arrives) Conduction when the relationship of 2) is satisfied. -V4 usually - number by having a 100 m V voltage of approximately diodes D5, D6 operating voltage can be turned on D8 a smaller voltage than the.
E + v4 = Vin + v4> Vf (2)
However, Vf> v4

  By the way, the echo signal is affected by attenuation when propagating through the specimen. That is, the signal level attenuation increases as the depth from the subject surface increases. Therefore, when the echo signal reflected near the subject surface is compared with the echo signal reflected at a depth of about a few tens of centimeters from the subject surface, the echo signal reflected near the subject surface is more The signal amplitude (signal level) is much larger than the echo signal reflected when it is carried out to a depth of about several tens of centimeters from the subject surface.

  In the present invention, when an echo signal reflected near the surface of the subject is received, the attenuating unit 17 is operated to change the voltage division ratio in the previous stage of the amplifying unit 19 so as to decrease the input voltage of the amplifying unit 19. To do. On the other hand, when a reflected signal is received from the subject surface to a predetermined depth, the operation of the attenuation unit 17 is stopped and the echo signal input to the TRSW 13 is input to the amplification unit 19 as it is. To do.

First, the operation of the attenuator 17 when a signal reflected near the subject surface is received will be described. Hereinafter, the forward voltage Vf of the diodes D7 and D8 is 0.7V , for example, and the input voltage E = ± Vin at the node P1 of the echo signal S1 (see FIG. 3) reflected near the subject surface is, for example, ± 1V. The bias voltage v3 immediately after receiving the echo signal S1 of the variable bias power supply V3 is assumed to be 0.4V, for example, and the bias voltage −v4 immediately after reception of the echo signal S1 of the variable bias power supply V4 is assumed to be −0.4V , for example.

When the receiving unit 2 receives the echo signal S1 reflected near the surface of the subject, when the input voltage E = −Vin arrives, the voltage −Vin (= −1V) and the bias voltage v3 (= 0.4V). When a forward voltage Vf (= 0.7 V) condition of the diode D7 is substituted into the equation (1), 1 + 0.4> 0.7, and the so satisfies the relationship of equation (1) described above, the diode D7 Turns on. Similarly, when the input voltage E = + Vin arrives, the voltage Vin (= + 1 V), the bias voltage −v4 (= −0.4 V, that is, v4 = 0.4 V) , the forward voltage Vf of the diode D8 ( = 0.0). If the condition of 7V) is substituted into the above equation (2), 1 + 0.4> 0.7 is satisfied, and the relationship of the above equation (2) is satisfied, so that the diode D8 is turned on.

When the diodes D7 and D8 are turned on, the voltage Vout of the echo signal S2 (see FIG. 3) at the node P2 on the input side of the attenuation unit 17 is obtained by the following equation (3).
Vout = Rx · Vin / (R1 + Rx) (3)
The diodes D7 and D8 are assumed to be ideal switches. Actually, the on-resistances of the diodes D7 and D8 are taken into account, but if the resistance values of the resistors R5 and R6 are sufficiently larger than the on-resistances of the diodes D7 and D8, the above equation (3) is generally satisfied.

Here, Rx is obtained by the following mathematical formula (4). Note that the resistors R5 and R6 act on the voltage Vin by half a wave, so that the resistors R5 and R6 function for one wavelength (both positive and negative waves). Therefore, the symmetry of the waveform can be ensured by setting R5 = R6.
Rx = R2 / R5 / (R2 + R5) (4)

  Here, assuming that the resistors R1 and R2 are 200Ω and the resistors R5 and R6 are 50Ω, respectively, the voltage Vout is Vout = 0.167Vin.

  Therefore, immediately after receiving the echo signal S1 reflected in the vicinity of the body surface, the amplitude (signal voltage level) of the echo signal input to the amplifying unit 19 can be reduced. This is shown in FIG. For the echo signals S1 and S2 shown in FIG. 3, for the sake of convenience of explanation, when the resistance values of the resistors R1 to R4 constituting the receiving unit 12 are different from the above values, the amplification unit 19 It is a signal that flows to the previous stage.

  In the example of FIG. 3, the amplitude of the echo signal S1 at the node P1 is ± 1.0 V, the amplitude of the echo signal S2 at the node P2 is as small as about ± 0.4 V, and the large amplitude echo signal It can be seen that when S1 is input to the receiving unit 2, the amplitude (signal voltage level) is reduced before the amplifying unit 19. In the example of FIG. 3, Vout = 0.4Vin.

  Thereafter, echo signals reflected from the vicinity of the body surface to a deeper position as time elapses are received one after another. Here, when the amplitude of the echo signal is reduced to such an extent that the amplifier 40 constituting the amplifier 19 is not saturated, the supply of the bias voltages v3 and v4 is stopped, and the diodes D7 and D8 are turned off.

When the diodes D7 and D8 are turned off, the voltage Vout at the node P2 on the input side of the attenuating unit 17 is obtained by the following equation (5).
Vout = R1 · Vin / (R1 + R2) (5)

  Therefore, regarding the voltage Vout, Vout = 0.5 Vin when the resistors R1 and R2 are 200Ω. For this reason, after the attenuating unit 17 stops operating, the echo signal output from the ultrasonic probe 15 is input to the amplifying unit 19 while maintaining almost the same state. This is shown in FIG. The signal S3 is a signal whose amplitude (for example, voltage 40 mVpp) is reduced to such an extent that the amplifier 40 is not saturated, and the signal S4 is an echo signal at the node P2. As shown in FIG. 4, it can be seen that the echo signal S3 having a small amplitude is input to the amplifying unit 19 through the TRSW 13 and the attenuating unit 17 as it is. That is, in the case of a small signal amplitude, the attenuation unit 17 does not affect the echo signal so as to deteriorate the characteristics.

  Here, the attenuating unit 17 is associated with the amplitude level of the echo signal S1 (S3) reflected from the vicinity of the subject surface, and is based on a plurality of voltage waveform information that changes with the lapse of time immediately after the transmission signal is transmitted. The operation is performed until a predetermined time elapses immediately after the end of transmission, and the operation is stopped after the predetermined time elapses. Here, the predetermined time is a time shorter than the reception continuation time of the echo signal immediately after the end of transmission, and a time during which a short-distance echo signal near the body surface is received immediately after the transmission. The transmission time of the transmission unit 11 and the reception time of the reception unit 12 are combined to form one cycle.

  Specifically, the variable bias power source V3 supplies a bias voltage from the positive potential to the zero potential until a predetermined time elapses immediately after the end of transmission, and supplies the voltage to the diode D7 after the predetermined time elapses. To stop. The variable bias power supply V4 supplies a bias voltage from the negative potential toward the zero potential until the predetermined time elapses immediately after the end of transmission, and stops the voltage supply to the diode D8 after the predetermined time elapses.

<Bias voltage control>
The bias voltage supply control is performed by the bias controller 23. As shown in FIG. 5, the bias control unit 23 includes a control unit 23A and a storage unit 23B. For example, a bias voltage waveform as shown in FIGS. 6A and 6B is stored in the storage unit 23B.

  The control unit 23A reads out a control mode based on the bias control mode instruction set from the operation unit 25 from the storage unit 23B, and inputs a control signal based on the control mode to the attenuation unit 17.

  Here, the control unit 23A may be, for example, a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Omitted Integrated ROM). (Random Access Memory) or HDD (Hard Disc Drive). Examples of the storage unit 23B include a ROM, a RAM, and an HDD.

  The storage unit 23B stores in advance a plurality of bias voltage waveform information (control data) that is associated with the amplitude level of the echo signal S1 reflected from the vicinity of the subject surface and that changes with the lapse of time immediately after the transmission signal is transmitted. Has been. An optimum waveform is selected by the user from the plurality of bias voltage waveform information stored in the storage unit via the operation unit 25. The bias control unit 23 determines a bias voltage waveform selected by the user, and executes bias control for the attenuation unit 17 based on the determined bias voltage waveform. Examples of the operation unit 25 include a keyboard, various operation buttons, and a trackball. Each of the variable bias power supplies V3 and V4 supplies a bias voltage to the diodes D7 and D8 according to the determined voltage waveform information.

  The bias control unit 23 is supplied for a predetermined time immediately after the end of transmission of ultrasonic waves in a cycle synchronized with the transmission / reception cycle of ultrasonic waves, and calculates a bias voltage based on a bias voltage waveform selected and determined via the operation unit 25. The variable bias power sources V3 and V4 are controlled so as to be changed.

  For the variable bias power source V3, the value of the bias voltage (positive voltage) immediately after the end of transmission is set to the maximum (400 mV), and the supply amount of the bias voltage gradually decreases with time. Thereafter, when a predetermined time elapses immediately after the supply of the transmission signal to the ultrasonic probe 15 is stopped, the supply of the bias voltage is stopped. The bias controller 23 changes the supply amount of the bias voltage in accordance with the level of the echo signal (reception signal). For example, when the voltage Vout at the node P2 gradually decreases, the supply amount of the bias voltage is changed according to the decrease rate. Then, when the voltage Vout at the node P2 is reduced to a level that does not saturate the amplifier 40 of the amplifier 19, supply of the bias voltage is stopped.

  Here, the predetermined time is the time required from immediately after the end of transmission until the amplitude level of the echo signal is reduced to a level at which the amplifier 40 is not saturated. This time varies depending on, for example, the body type of the subject and the examination environment (type of ultrasonic probe, operation mode, etc.). Therefore, it is desirable to secure a plurality of bias voltage waveforms in advance under various body shapes and examination environments of the subject. The “maximum bias voltage (positive voltage) value (400 mV)” described here is an example, and is determined as appropriate depending on conditions such as the saturation level of the amplifier 19 and the input signal level.

  For the variable bias power source V4, the value of the bias voltage (negative voltage) immediately after the end of transmission is set to the maximum (−400 mV), and the supply amount of the bias voltage gradually increases with time. Thereafter, supply of the bias voltage is stopped when a predetermined time elapses immediately after the supply of the transmission signal to the ultrasonic probe 15 is stopped. The bias controller 23 changes the supply amount of the bias voltage in accordance with the level of the echo signal (reception signal).

  The bias controller 23 sets the maximum value of the bias voltage generated by the variable bias power supply V3 to be less than the forward voltage Vf of the diode D7, and sets the maximum value of the bias voltage generated by the variable bias power supply V4 to the diode. It is desirable to set it to be less than the forward voltage of D8.

  With this setting, for example, even when an echo signal (small amplitude echo signal) reflected from the subject surface at a predetermined depth is received, the diodes D7 and D8 of the attenuation unit 17 are not turned on. Therefore, attenuation of the small amplitude echo signal can be reliably stopped.

  By changing the bias voltage as described above, an echo signal from the vicinity of the subject surface having a high amplitude level (signal level) is greatly attenuated when passing through the attenuating unit 17, and the echo signal from a deep region having a low signal level is detected. The echo signal can pass through the attenuating unit 17 while maintaining the signal strength.

  Control data for changing the bias voltage as shown in FIGS. 6A and 6B can be created by the following method, for example.

  The control data is obtained by varying the gain of the amplifier 19 or adjusting the gain of the digital signal after AD conversion according to the signal level of the echo signal reflected from the subject (depth from the subject surface). Created. The control data is configured to attenuate a received signal that is greater than the saturation level converted to the input of the amplifier 19. Control data is usually switched according to the type of ultrasonic probe and the operation mode (B mode for displaying a tomographic image, Doppler mode for displaying a blood flow Doppler signal, etc.).

  In the above-described embodiment, the TGC function for adjusting the reception gain (reception gain) according to the return time (depth from the subject surface) from transmission to reception is controlled in conjunction with the control data generation method described above. Data may be created.

  Here, in order to exert the TGC function, a time gain control (hereinafter referred to as “TGC”) processing unit (not shown) and a setting unit (not shown) for setting TGC data related to TGC processing are attenuated. 17 is provided in the subsequent stage. By linking the reception gain adjustment by TGC, the contents of the control data to be created can be set more finely, and as a result, the types of control data to be created can be increased.

  In this way, the value of the bias voltage corresponding to the elapsed time immediately after the end of transmission is determined. The storage unit in the bias control unit 23 stores a predetermined number of bias voltage waveforms obtained as described above. Before starting transmission, a desired bias voltage waveform is selected from a plurality of bias voltage waveforms stored in the storage unit via the operation unit 25, and the bias control unit 23 selects a variable bias power source based on the selected bias voltage waveform. V3 and V4 are controlled.

  An example of the bias voltage waveform described above is shown in FIGS. 6A and 6B. The bias voltage waveform shown in FIG. 6A shows that the bias voltage v3 of 400 mV is supplied to the diode D7 immediately after the end of transmission (T = 0), and the bias voltage v3 supplied to the diode D7 reaches 200 mV when 5.0 μsec has elapsed. The waveform is such that the supply of the bias voltage to the diode D7 is stopped when 10.0 μsec elapses (corresponding to the predetermined time described above).

  The bias voltage waveform shown in FIG. 6B shows that the bias voltage v4 of −400 mV is supplied to the diode D8 immediately after the end of transmission (T = 0), and the bias voltage v4 supplied to the diode D8 is −200 mV when 5.0 μsec elapses. The waveform is such that the supply of the bias voltage to the diode D8 is stopped when 10.0 μsec has elapsed (corresponding to the predetermined time described above).

  In FIG. 6A and FIG. 6B, in the period of 0.0 μsec to 10 μsec, the diodes D7 and D8 conceptually operate from on to off for each half wave of the signal, so Will be in series with R5 and R6.

  When a semiconductor switch using a FET or the like, a diode switch, a mechanical switch, or the like is used, switching noise due to the crosstalk of the control signal to the echo signal when the switch is switched is added to the echo signal. Therefore, when the switch control of the attenuation unit 17 is controlled only by the reception time, if the signal amplitude is a minute timing, switching noise is displayed on the image. On the other hand, in the present embodiment, since the switch control of the attenuation unit 17 is performed without using a semiconductor switch using an FET or the like, the above-described problem does not occur.

  In the present invention in which on / off is controlled for each half wave of the signal, the switch for turning on / off the attenuating unit 17 always operates only when the amplitude of the echo signal is large, and the switching noise is the signal amplitude. Will not appear in the image.

<Effect>
The ultrasonic diagnostic apparatus 1 according to the present embodiment includes a receiving unit 2 that processes a reception signal obtained by reflecting a transmission signal having both positive and negative polarities within a subject via an ultrasonic probe 15. The reception unit 2 includes a TRSW 13 that prevents the transmission signal from entering the reception unit 2, an amplification unit 19 that amplifies the reception signal, and an attenuation unit 17 that is disposed between the TRSW 13 and the amplification unit 19 and attenuates the reception signal. Is provided. The attenuation unit 17 changes the attenuation amount from large to small immediately after the end of transmission until a predetermined time shorter than the reception time elapses.

  Specifically, the attenuating unit 17 includes a first circuit 17a and a second circuit 17b. The first circuit 17a includes a diode D7 and a resistor R5 connected in series, and includes a variable bias power supply V3 that generates a bias voltage v3 that changes from a positive potential toward a zero potential. The second circuit 17b includes a diode D8 and a resistor R6 connected in series, and includes a variable bias power supply V4 that generates a bias voltage v4 that changes from a negative potential toward a zero potential.

  The variable bias power supply V3 supplies a bias voltage from the positive potential to the zero potential until the predetermined time elapses immediately after the end of transmission, and stops supplying the bias voltage to the diode D7 after the predetermined time elapses. The variable bias power supply V4 supplies a bias voltage from the negative potential toward the zero potential until the predetermined time elapses immediately after the end of transmission, and stops the voltage supply to the diode D8 after the predetermined time elapses.

  Thus, when an echo signal with a small amplitude reflected at a position deeper than the vicinity of the subject surface is received, the echo signal is input to the amplification unit 19 as it is without operating the attenuation unit 17. On the other hand, when an echo signal having a large amplitude reflected near the surface of the subject is received, the attenuating unit 17 is operated to reduce the resistance voltage division ratio in the previous stage of the amplifying unit 19, thereby attenuating the amplitude of the echo signal. Let

  Therefore, even when an echo signal having a large amplitude reflected in the vicinity of the subject surface is received, the signal amplitude is attenuated before reaching the preceding stage of the amplification unit, and as a result, waveform distortion can be suppressed. That is, according to this embodiment, it is possible to prevent saturation of the amplifier that amplifies the echo signal reflected near the subject surface and to improve the image quality of the ultrasonic image displayed on the display unit.

  In addition, the ultrasonic diagnostic apparatus 1 of the present embodiment is selected from a storage unit that stores a plurality of voltage waveform information that is associated with the level of the received signal and changes with the lapse of time immediately after the end of transmission, and the storage unit And a bias controller 23 that generates a bias voltage for a predetermined time with respect to the variable bias power sources V3 and V4 based on the voltage waveform information. The bias control unit 23 determines voltage waveform information to be generated by the variable bias power supplies V3 and V4 from the association information stored in advance according to the selection from the operation unit 25.

  Thus, since the bias voltage waveform pattern can be selected and determined as appropriate from the association information, an optimum bias voltage waveform pattern can be selected according to, for example, the body shape of the subject. Therefore, it is possible to always display an accurate ultrasonic image regardless of the body shape of the subject.

  Further, since the attenuation ratio when the attenuating unit 17 operates is known, the original signal can be reproduced more accurately by correcting the attenuation ratio according to the amplitude after AD conversion, for example.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment is included in the invention described in the scope of claims and its equivalent scope as well as included in the scope and spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 11 Transmission part 12 Reception part 13 Transmission / reception switching switch part (TRSW)
DESCRIPTION OF SYMBOLS 15 Ultrasonic probe 17 Attenuation part 19 Amplification part 21 Processing part 23 Bias control part 23A Control part 23B Storage part 25 Operation part 27 Display part

Claims (2)

A reception unit including a transmission unit that transmits an ultrasonic signal into the subject via the ultrasonic probe, and an amplification unit that amplifies the reception signal obtained by being reflected in the subject within a reception period immediately after transmission. An ultrasonic diagnostic apparatus comprising:
The ultrasonic probe has a connection point that is disposed between the output unit of the ultrasonic probe and the amplification unit, receives a reception signal from the output unit and sends the reception signal to the amplification unit, and includes a diode and a resistor. One series circuit and a second series circuit, wherein the first series circuit has one end on the cathode side of the diode, and the second series circuit has one end on the anode side of the diode connected to the connection point. And a voltage generator that applies a positive voltage to the other end of the first series circuit and applies a negative voltage having the same magnitude and the opposite polarity as the positive voltage to the other end of the second series circuit. An attenuation part having
With respect to the voltage generator, the positive voltage and the negative voltage are set so that immediately after the transmission, the diode of the first series circuit becomes conductive with the positive voltage of the received signal immediately after the transmission. The voltage of the second series circuit is made conductive at the negative voltage of the reception signal, and then the voltage is reduced with time, and the reception signal is received from the reception period. An ultrasonic diagnostic apparatus comprising: a bias control unit that reduces the voltage to zero after a short predetermined period of time . The bias control unit sets the positive voltage to v and the negative voltage −v, the diode forward voltage to Vf, the voltage of the received signal immediately after the transmission to E, and the positive voltage to E = When + Vin and the negative side voltage is E = −Vin,
When E = −Vin, Equation (1) is established in the first series circuit, and when E = Vin, the positive voltage v having such a magnitude that Equation (2) is established in the second series circuit. And generating the negative voltage -v,
-E + v> Vf Formula (1)
E + v > Vf Equation (2)
However, Vf> v
The ultrasonic diagnostic apparatus according to claim 1.

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