JP2008183306A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus equivalently applying appropriate delay not only to a signal component near the center frequency but also to a signal component separate from the center frequency by applying the phase rotation with a multiplier to ultrasonic receiving signals. <P>SOLUTION: The ultrasonic diagnostic apparatus comprises an ultrasonic transmission/receiving means for transmitting/receiving ultrasonic pulses to/from a subject by using a plurality of ultrasonic vibrators; a delay addition circuit for adjusting the time and adding a plurality of receiving signals of a plurality receiving channels i received by the plurality of ultrasonic vibrators; and an image data-generating means for generating ultrasonic image data from the receiving signals generated by the delay addition circuit. The delay addition circuit is configured to perform the phase rotating process with at least two multipliers Mi1 and Mi2 using reference signals Ri1 and Ri2 with the same frequency and different phases for the receiving signal of a single receiving channel i. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus that scans an ultrasonic beam to obtain an image in a subject, and in particular, applies different time delays to ultrasonic echoes received by a multi-channel array ultrasonic transducer. The present invention relates to an electronic scan type ultrasonic diagnostic apparatus that performs focusing and steering of an ultrasonic reception beam by performing addition processing.

  An ultrasonic diagnostic apparatus is an apparatus that obtains an image in a subject by scanning an ultrasonic beam. Among ultrasonic diagnostic equipment, focusing and steering of the ultrasonic reception beam is performed by performing addition processing by applying different time delays to ultrasonic echo signals received using a multi-channel array ultrasonic transducer. The thing is called an electronic scan type (see, for example, Patent Document 1 and Patent Document 2).

  In this electronic scan type ultrasonic diagnostic apparatus, the reception signal is delayed in the reception delay adding circuit in order to adjust the timing of the reception signal obtained from the ultrasonic transducer and form an ultrasonic reception beam. As a delay method of the received signal in the reception delay adding circuit, a method of directly delaying the time of the received signal using a delay line, a method of delaying the received signal equivalently by giving a phase rotation by a multiplier, and multiplication with the delay line There is a way to combine it with a vessel.

  First, a reception delay method using a delay line will be described.

  FIG. 9 is a configuration diagram of a reception delay adding circuit using a delay line provided in a conventional ultrasonic diagnostic apparatus.

  The conventional reception delay adding circuit 1 shown in FIG. 9 includes a plurality of delay lines DLi corresponding to a plurality of reception channels i and a single adder S. Received signals from a plurality of ultrasonic transducers output from a preamplifier (not shown) are guided to corresponding delay lines DLi. As the delay line DLi, it is possible to use an LC delay line that directly delays the time of the received signal, a digital delay line composed of a shift register or a digital filter, or a delay line using a charge transfer device such as a CCD (Charge Coupled Device). it can. The LC delay line is an analog delay line composed of a coil and a capacitor. Each delay line DLi is controlled by a control signal from a control system (not shown), and delays the received signal. The output destination of each delay line DLi is a common adder S, and the adder S adds the reception signal delayed in each delay line DLi. The reception signal added by the adder S is output to a signal processing unit (not shown) in the subsequent stage.

Here, assuming that the envelope (envelope) of the received signal input to the delay line DLi corresponding to the received channel i is A (t), the center frequency is fc, and the phase is φ, the received signal is expressed by equation (1). expressed.
[Equation 1]
Ai (t) ・ sin (ωc t ＋ φi) (1)
However, ωc = 2πfc.

Also, assuming that the delay time in the delay line DLi is Tdi, the output of the delay line DLi is expressed as in equation (2).
[Equation 2]
Ai (t−Tdi) ・ sin {ωfc (t−Tdi) ＋ φi} (2)
That is, each delay line DLi can be delayed by the delay time Tdi without changing the waveform of the received signal.

  FIG. 10 is a diagram showing a waveform of a reception signal input to each delay line DLi of the conventional reception delay adding circuit 1 shown in FIG. 9, and FIG. 11 is a diagram showing each waveform of the conventional reception delay adding circuit 1 shown in FIG. It is a figure which shows the waveform of the received signal output from the delay line DLi.

  As shown in FIG. 10, it is assumed that the reception signal S2 of the envelope E2 having the same waveform delayed by Tdi with respect to the reception signal S1 of the envelope E1 and the reception signal S1 is input to the corresponding delay line DLi. . Since reception signal S1 is delayed by Tdi in delay line DLi, reception signal S1 and reception signal S2 output from delay line DLi match each other as shown in FIG. In other words, the waveforms of a plurality of received signals having a time difference of Tdi can be adjusted so as not to have a time difference by the action of each delay line DLi. Further, the envelope E1 of the received signal S1 and the envelope E2 of the received signal S2 can be matched.

  However, the number of reception channels in the real-time ultrasonic diagnostic apparatus is usually 100 or more, and a delay line is connected to each reception channel, so that there is a problem that the scale of the reception delay addition circuit becomes enormous. Furthermore, in recent years, real-time three-dimensional ultrasonic diagnostic apparatuses using a two-dimensional array ultrasonic transducer have been developed. The number of reception channels in the three-dimensional ultrasonic diagnostic apparatus is 1000 or more. Even in a three-dimensional ultrasonic diagnostic apparatus, in order to form a good ultrasonic reception beam, it is necessary to connect delay lines to all reception channels and adjust the time of a reception signal received by an ultrasonic transducer. However, there is a problem that the scale of the reception delay adding circuit becomes enormous and the number of cables connecting the ultrasonic probe to the ultrasonic diagnostic apparatus becomes very large, so that the feasibility is lacking.

  As a measure to reduce the number of cables, it is considered that a part of the reception delay adding circuit is built in the ultrasonic probe side and added by performing partial reception delay for each of several ultrasonic transducers (subarrays). It is done.

  However, in order to incorporate a part of the reception delay addition circuit on the ultrasonic probe side, the large scale of the reception delay addition circuit that performs time delay is an obstacle.

  From such a background, as a technique for reducing the scale of the reception delay addition circuit, a method using a reception delay addition circuit that performs an equivalent delay by phase rotation using a multiplier having a small circuit scale, or time delay by phase rotation and a delay line A method of reducing the circuit scale by combining the above has been devised.

  Therefore, a reception delay method using a multiplier will be described.

  FIG. 12 is a configuration diagram of a reception delay adding circuit using a multiplier provided in a conventional ultrasonic diagnostic apparatus.

  The conventional reception delay adding circuit 1A shown in FIG. 12 includes a plurality of first low pass filters (LPF) LPFi corresponding to a plurality of reception channels i, a plurality of first multipliers MPLi, Adder S, a single second low-pass filter LPF, and a single second multiplier MPL. Received signals from the plurality of ultrasonic transducers are guided to corresponding first low-pass filters LPFi. The received signal that has passed through the first low-pass filter LPFi is guided to the corresponding first multiplier MPLi. In the first multiplier MPLi, the received signal is phase-rotated by multiplying the received signal by the phase-controlled reference signal.

That is, the received signal having the envelope A (t), the center frequency fc, and the phase φ shown in Expression (1) is input to the first multiplier MPLi corresponding to the reception channel i. Then, as shown in Expression (3), the received signal is multiplied by a reference signal whose phase is controlled at a frequency fr and a phase φr.
[Equation 3]
sin (ωrt + φri) (3)
However, ωr = 2πfr.

Then, the output of the first multiplier MPLi is as shown in Equation (4).
[Equation 4]
Ai (t) ・ sin (ωct ＋ φi) ・ sin (ωrt ＋ φri)
= (Ai (t) / 2) · [−cos {(ωc + ωr) t + (φi + φri)} + cos {(ωc−ωr) t + (φi−φri)}]
(Four)

Here, when the component of ωc + ωr is extracted using a filter (not shown) and the amplitude of the received signal is adjusted, the output of the first multiplier MPLi shown in Equation (5) is obtained.
[Equation 5]
Ai (t) ・ cos {(ωc + ωr) t + (φi + φri)} (5)

  That is, the first multiplier MPLi converts the frequency of the received signal into an intermediate frequency that is a difference from the frequency of the reference signal. The output signals of the first multipliers MPLi are added in the adder S at the subsequent stage. The reception signal added in the adder S is guided to the second multiplier MPL via the second low-pass filter LPF.

  Then, in the second multiplier MPL, the reception signal added in the adder S is multiplied by a reference signal having the same frequency as the reference signal of the first multiplier MPLi. As a result, the frequency of the received signal after addition converted to the intermediate frequency by the first multiplier MPLi is returned to the original frequency. However, the received signal after the addition may be output to a signal processing unit (not shown) as an intermediate frequency to perform signal processing. Here, a case where the intermediate frequency of the received signal after addition is returned to the original frequency will be described.

That is, when the output signal of the first multiplier MPLi is multiplied by the reference signal sinωrt having the same frequency as the reference signal used in the first multiplier MPLi in the second multiplier MPL, Equation (6) is obtained.
[Equation 6]
Ai (t) ・ cos {(ωc + ωr) t + (φi + φri)} ・ sinωrt
= (Ai (t) / 2) ・ [sin {(ωc + 2ωr) t + (φi + φri)}-sin {ωct + (φi + φri)}] (6)

Therefore, when the component of ωc is extracted using a filter (not shown) and the signal amplitude is adjusted, the received signal output from the second multiplier MPL is expressed by Equation (7).
[Equation 7]
Ai (t) · sin {ωct + (φi + φri)} = Ai (t) · sin {(ωct + φri) + φi} (7)
Here, when the reception delay is performed using the delay line DLi, the equation (2) and the equation (7) are compared, and if the equation (8) is set, the delay with respect to the carrier component of the center frequency fc A delay equivalent to the time Tdi can be given.
[Equation 8]
φri ＝ −ωc ・ Tdi = -2πfc ・ Tdi (8)

  FIG. 13 is a diagram showing a waveform of a reception signal output from the first multiplier MPLi of the conventional reception delay adding circuit 1A shown in FIG.

  As shown in FIG. 10, it is assumed that reception signal S1 and reception signal S2 having the same waveform delayed by Tdi with respect to reception signal S1 are input to corresponding first multipliers MPLi. Then, as shown in FIG. 13, the carrier component of frequency fc coincides with the waveform of reception signal S2 due to the phase rotation of reception signal S1. The envelope Ai (t) is not delayed because it is not affected by the phase rotation. Therefore, the envelope E1 of the received signal S1 and the envelope E2 of the received signal S1 do not coincide with each other, and a slight error occurs.

  In this way, similarly to the case of using the delay line DLi, the waveform of the received signal having a time difference of the delay time Td can be adjusted so as not to have a time difference by phase rotation using the multiplier MPLi.

  In addition, in the time delay using the multiplier MPLi as described above, since the sum and difference of the center frequency fc and the reference frequency fr appear in the output, a filter (not shown) for selecting which one is used for signal processing. )is required. Furthermore, since unnecessary band noise appears after frequency conversion at the respective outputs of the first multiplier MPLi and the second multiplier MPL, the first multiplier MPLi and the second multiplier MPL are used to prevent the noise from increasing. A first low-pass filter LPFi and a second low-pass filter LPF are provided in front of the multiplier MPL. Then, the influence of unnecessary bands is suppressed by the first low-pass filter LPFi and the second low-pass filter LPF.

  However, the multiplier is usually a small device, and can be configured on a small scale even if the filter described above is included. For this reason, when there are many reception channels, an increase in the scale of the reception delay addition circuit can be suppressed.

  FIG. 14 is a configuration diagram of a reception delay adding circuit using a combination of a delay line and a multiplier provided in a conventional ultrasonic diagnostic apparatus.

The reception delay adding circuit 1B shown in FIG. 14 is provided with both a plurality of multipliers MPLi and a plurality of delay lines DLi respectively corresponding to the plurality of reception channels i. The received signal can be delayed by combining the delay line DLi that directly delays the received signal and the phase rotation by the multiplier MPLi. In this case, since the delay processing is shared by the multiplier MPLi and the delay line DLi, the scale of the delay line DLi can be slightly reduced as compared with the case where the delay processing is performed only by the delay line DLi shown in FIG.
Japanese Patent No. 5,676,147 Japanese Patent No. 5,573,001

  However, in the case of a reception delay adding circuit using a delay line, the same time delay can be performed for the waveform of any frequency component within the frequency band of the delay line, whereas the reception delay due to phase rotation is possible. In the case of an adder circuit, an accurate delay is possible at the center frequency of the received signal, but there is a problem that an error occurs in the delay time for a signal component far from the center frequency. For this reason, in the case of a reception delay adding circuit based on phase rotation, the received sound field may be deteriorated and the image quality may be lowered. That is, when the phase of the received signal is rotated using a multiplier, the circuit scale can be reduced, but an error in the delay time occurs for the signal component away from the center frequency.

  FIG. 15 is a diagram illustrating a signal generated in a conventional reception delay adding circuit using phase rotation.

  In each of FIGS. 15A, 15B, and 15C, the horizontal axis indicates time, and the vertical axis indicates the intensity of the received signal. FIG. 15A shows an example of a reception signal having two bands input to a conventional reception delay addition circuit using phase rotation. That is, the reception signal S2 of the reception channel 2 has a time delay Tdi with respect to the reception signal S1 of the reception channel 1.

For example, consider a case where the center frequency of the received signal S1 is fc = 2.5 MHz and has a band of ± 1 MHz. When a delay of time delay Tdi = 50 nsec is given to the received signal S1, Equation (8) becomes Equation (9).
[Equation 9]
φri = -2πfc ・ Tdi = -2π ・ 2.5 × 10 ⁶・ 50 × 10 ^-9 = -π / 4 (9)

The phase rotation of -π / 4 is performed from equation (9), but the phase rotation of -π / 4 is equivalent to a delay of the delay time shown in equation (10) for the 2MHz component. .
[Equation 10]
Tdi = -φri / ω = (π / 4) / (2π ・ 2 × 10 ⁶ ) = 62.5nsec (10)

Further, the phase rotation of −π / 4 is equivalent to a delay of the delay time shown in Expression (11) with respect to the 3 MHz component.
[Equation 11]
Tdi = −φri / ω = (π / 4) / (2π ・ 3 × 10 ⁶ ) ≒ 41.7nsec (11)

  That is, as shown in Equation (10) and Equation (11), even if the target delay is given at the center frequency of the band of the received signal S1 by phase rotation, the delay time for the frequency component away from the center frequency Cause an error.

  FIG. 15B is a diagram illustrating the waveform of the reception signal S1 and the waveform of the reception signal S2 that are time-adjusted after the phase rotation process. As shown in FIG. 15 (b), in the vicinity of the center frequency of the band of the received signal S1, the time can be matched with the received signal S2, but a time lag occurs in the frequency component away from the center frequency. When the received signal S1 and the received signal S2 after the phase rotation processing as shown in FIG. 15B are added for beam forming, the received signal S1 and the received signal S2 are not properly added, and the received signal after the addition is added. The waveform of is significantly different from the waveforms of the received signals S1 and S2 in the receiving channel.

  FIG. 15 (c) is a diagram showing an output waveform S3 of the reception delay adding circuit obtained by adding the reception signal S1 and the reception signal S2 after the phase rotation post-processing shown in FIG. 15 (b). As shown in FIG. 15C, the waveform S3 of the received signal after the addition is significantly different from the waveforms of the received signals S1 and S2 in the receiving channel shown in FIG. As a result, there is a problem that the shape of the ultrasonic reception beam is deteriorated and the image quality is lowered.

  The present invention has been made in order to cope with such a conventional situation, and by performing phase rotation using a multiplier on an ultrasonic wave reception signal, signal components separated from the center frequency as well as near the center frequency. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of equivalently performing an appropriate delay.

  In order to achieve the above-described object, an ultrasonic diagnostic apparatus according to the present invention provides ultrasonic transmission / reception means for transmitting / receiving ultrasonic pulses to / from a subject using a plurality of ultrasonic transducers. A delay addition circuit that adjusts and adds time of a plurality of reception signals of a plurality of reception channels received by the plurality of ultrasonic transducers, and ultrasonic image data from the reception signal generated by the delay addition circuit The delay addition circuit is configured to perform phase rotation by at least two multipliers using reference signals having the same frequency and different phases with respect to the reception signals of a single reception channel. It is characterized by being configured to perform processing.

  In the ultrasonic diagnostic apparatus according to the present invention, by performing phase rotation using a multiplier on the ultrasonic reception signal, an appropriate delay is applied not only to the vicinity of the center frequency but also to a signal component away from the center frequency. Can be done equivalently.

  Embodiments of an ultrasonic diagnostic apparatus according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

  The ultrasonic diagnostic apparatus 10 includes an ultrasonic probe 11, a transmission / reception circuit 12, a signal processing unit 13, an image processing unit 14, a display unit 15, a control circuit 16, and an operation panel 17. In the ultrasonic probe 11, a plurality of ultrasonic transducers 18 are arranged in an array of one row. Each ultrasonic transducer 18 of the ultrasonic probe 11 is electrically connected to the transmission / reception circuit 12 and converts the transmission signal applied as an electric pulse signal from the transmission / reception circuit 12 into an ultrasonic pulse to convert the heart of the subject O. The ultrasonic echo generated under the influence of the observation part in the subject O is received, converted into a reception signal which is an electric signal, and given to the transmission / reception circuit 12.

  The transmission / reception circuit 12 generates transmission signals to be applied to the ultrasonic transducers 18 of the ultrasonic probe 11 and applies the generated transmission signals to the ultrasonic transducers 18. It has a function of generating a reception signal having directivity by performing predetermined preprocessing such as amplification processing and reception delay addition processing on the received reception signal and supplying the generated reception signal to the signal processing unit 13. For this purpose, the transmission / reception circuit 12 is provided with a transmission delay circuit 19, a reception delay addition circuit 20, a plurality of pulsers 21, and a plurality of preamplifiers 22.

  The transmission delay circuit 19 is connected to each pulsar 21. The transmission delay circuit 19 sets the timing of the transmission signal applied to each ultrasonic transducer 18 so that an ultrasonic transmission beam having directivity is formed by the ultrasonic transmission signal transmitted from each ultrasonic transducer 18. The function of determining and providing a delay time from the determined reference timing to the corresponding pulser 21 is provided. The delay time is determined to be different from each other according to the transmission direction of the ultrasonic beam.

  Each pulser 21 is connected to a corresponding ultrasonic transducer 18. Each pulser 21 has a function of generating an electric pulse of a predetermined voltage level and applying the generated electric pulse to the corresponding ultrasonic transducer 18 according to the delay time received from the transmission delay circuit 19.

  Each preamplifier 22 is connected to a corresponding ultrasonic transducer 18. Each preamplifier 22 has a function of amplifying a weak received signal from the corresponding ultrasonic transducer 18 to a level at which signal processing is possible and outputting the amplified received signal to the reception delay adding circuit 20.

  The reception delay adding circuit 20 has a function of performing delay processing on the reception signals of the respective reception channels input from the respective preamplifiers 22 using different delay times, and adding the reception signals after the delay processing. Thereby, an ultrasonic reception beam is formed. The formed ultrasonic reception beam is output from the reception delay adding circuit 20 to the signal processing unit 13.

  The signal processing unit 13 performs signal processing on the ultrasonic reception beam acquired from the reception delay adding circuit 20, thereby information on a structure such as a heart in the observation site in the subject O and a blood flow velocity in the observation site. It has a function to detect information. Information on the detected structure and blood flow velocity information is given from the signal processing unit 13 to the image processing unit 14.

  The image processing unit 14 performs image processing for displaying the structure information and blood flow velocity information received from the signal processing unit 13 as an image, generates image data, and gives the generated image data to the display unit 15. It has a function.

  The display unit 15 includes a display device such as a cathode ray tube (CRT) or a liquid crystal display (LCD), and has a function of displaying image data received from the image processing unit 14.

  The control circuit 16 has a function of controlling the transmission delay circuit 19, each preamplifier 22, the reception delay addition circuit 20, the signal processing unit 13, the image processing unit 14, and the display unit 15.

  The operation panel 17 is an input device such as a mouse or a key for inputting operation information to the control circuit 16.

  Next, the operation and action of the ultrasonic diagnostic apparatus 10 will be described.

  When a control signal is given from the control circuit 16 to the transmission delay circuit 19, the transmission delay circuit 19 causes each ultrasonic wave so that an ultrasonic transmission beam having a predetermined directivity is formed from the ultrasonic probe 11 toward the subject O. Transmission delay time information of ultrasonic pulses transmitted from the acoustic transducer 18 at different timings is generated. The generated transmission delay time information is given from the transmission delay circuit 19 to the corresponding pulser 21. Each pulser 21 generates an electrical pulse of a predetermined voltage level, and applies the generated electrical pulse to the corresponding ultrasonic transducer 18 according to the delay time received from the transmission delay circuit 19. Thereby, an ultrasonic pulse with a predetermined time delay is transmitted from each ultrasonic transducer 18 toward the subject O, and an ultrasonic transmission beam having a predetermined directivity is formed.

  The ultrasonic transmission beam is reflected by an interface having different acoustic impedance such as a boundary of a structure in the subject O, and is received by each ultrasonic transducer 18 as an ultrasonic echo. The ultrasonic echoes received by the ultrasonic transducers 18 are converted into reception signals, which are electrical signals, and output to the preamplifiers 22. Each preamplifier 22 amplifies a weak reception signal from the corresponding ultrasonic transducer 18 to a level at which signal processing is possible, and outputs the amplified reception signal to the reception delay addition circuit 20.

  The reception delay adding circuit 20 adjusts the timing of the reception signal by performing time delay processing on the reception signal given from the ultrasonic transducer 18 via each preamplifier 22. The reception delay adding circuit 20 adds the reception signals after the time delay processing and outputs the result to the signal processing unit 13. The signal processing unit 13 detects the reception signal after addition acquired from the reception delay adding circuit 20 and detects an envelope as reception data. The detected reception data indicates information on structures such as the heart at the observation site in the subject O and blood flow velocity information at the observation site, and is provided from the signal processing unit 13 to the image processing unit 14.

  The image processing unit 14 converts the received data received from the signal processing unit 13 according to the imaging section in the subject O, and generates image data by performing image processing such as gradation processing suitable for image display. To do. The generated image data is given from the image processing unit 14 to the display unit 15. Thereby, the form in the observation region in the subject O is displayed on the display unit 15 in real time.

  The reception delay adding circuit 20 of such an ultrasonic diagnostic apparatus 10 has a high-density circuit configuration so as to cope with the increase in the number of reception signals.

  FIG. 2 is a circuit diagram showing a configuration of reception delay adding circuit 20 shown in FIG.

  The reception delay adding circuit 20 includes a plurality of third low-pass filters 30 (LPFi), a plurality of analog third multipliers 31 (Mi1, Mi2), a plurality of filters 32 (Fi1, Fi2), and an adder 33 (S ), A fourth low-pass filter 34 (LPF), and an analog fourth multiplier 35 (M).

  The third low-pass filter 30 (LPFi) corresponds to each of a plurality of reception channels i (i is a natural number) of the reception signal output from each preamplifier 22. That is, the third low-pass filter 30 (LPFi) is connected to the output side of the corresponding preamplifier 22. The third low-pass filter 30 (LPFi) removes unnecessary band signal components from the received signal and outputs them to the corresponding third multipliers 31 (Mi1, Mi2). That is, a plurality of third multipliers 31 (Mi1, Mi2) are provided for each reception channel i, and the output side of each third low-pass filter 30 (LPFi) has a plurality of third multipliers 31 respectively. Connected with (Mi1, Mi2). FIG. 2 shows an example in which two third multipliers 31 (Mi1, Mi2) are provided in parallel for each reception channel i.

  In each third multiplier 31 (Mi1, Mi2), the time delay process of the received signal is equivalently performed by changing the phase of the received signal. For this purpose, of the two third multipliers 31 (Mi1, Mi2), one third multiplier 31 (Mi1) receives the reference signal Ri1 having the frequency fr + φi1 and the other third multiplier 31 (Mi2). Is supplied with a reference signal Ri2 of frequency fr + φi2. That is, in the plurality of third multipliers 31 connected in parallel to each reception channel i, the phase rotation process of the reception signal is performed using the reference signals Ri1 and Ri2 having the same frequency and different phases.

Further, time delay processing is performed for two or more different frequency components of the received signal for each third multiplier 31. Therefore, the phases of the reference signals Ri1 and Ri2 are set so that the equivalent delay time is the same for each frequency component. For example, in the case where a delay of Td is given to the reception signal using two third multipliers 31 (Mi1, Mi2), the one third multiplier 31 (Mi1) is within the band of the reception signal. The signal component of the frequency f1 is subjected to delay processing. Then, in one third multiplier 31 (Mi1), the phase rotation shown in Expression (12) is given to the received signal.
[Equation 12]
φi1 = −ω1 ・ Td = −2πf1 ・ Td = −2π ・ Td / T 1 (12)
However, T1 = 1 / f1.

Similarly, in the other third multiplier 31 (Mi2), the signal component of the frequency f2 within the band of the received signal is subjected to delay processing. That is, the phase rotation shown in Expression (13) is given to the received signal.
[Equation 13]
φi2 = −ω2 ・ Td = −2πf2 ・ Td = −2π ・ Td / T2 (13)
However, T2 = 1 / f2.

For example, when a received signal having a center frequency of 2.5 MHz and a band of ± 1 MHz is delayed by approximately 50 nsec within the band of the received signal, two third multipliers 31 (Mi1, Mi2) are used, respectively, and f1 = 2 MHz. And a phase rotation φ1 and a phase rotation φ2 corresponding to 50 nsec are given to a signal component having a frequency of f2 = 3 MHz. The phase rotation φ1 and the phase rotation φ2 are obtained from the equations (12) and (13) as shown in the equations (14-1) and (14-2), respectively.
[Formula 14]
φ1 = −ω1 ・ Td = −2πf1 ・ Td = −2π ・ 2 × 10 ⁶・ 50 × 10 ^-9 = −π / 5 (14-1)
φ2 = −ω2 ・ Td = −2πf2 ・ Td = −2π ・ 3 × 10 ⁶・ 50 × 10 ^-9 ≒ −π / 6.67 (14-2)

Accordingly, the waveforms of the reference signals Ri1 and Ri2 of the two third multipliers 31 (Mi1 and Mi2) have the frequency fr (= ωr / 2π) as shown in the equations (15-1) and (15-2). And the phases φi1 and φi2 have waveforms of −π / 5 and −π / 6.67, respectively.
[Equation 15]
Ri1 = sin (ωr t + φi1) = sin {(2πfr t− (π / 5)} (15-1)
Ri2 ＝ sin (ωr t ＋ φi2) ＝ sin {(2πfr t− (π / 6.67)} (15-2)

  Then, by inputting the reference signals Ri1 and Ri2 having the waveforms shown in the equations (15-1) and (15-2) to the corresponding third multipliers 31 (Mi1, Mi2), the center frequency becomes 2.5 MHz. Thus, a delay of 50 nsec can be equivalently given to a signal component of 2 MHz and a signal component of 3 MHz among received signals having a band of ± 1 MHz.

  That is, the output of one third multiplier 31 (Mi1) is set to an equivalent delay time of 50 nsec with respect to the frequency f1 at the frequency f1 + fr, and the output of the other third multiplier 31 (Mi2) is the frequency f2 + fr. Is set to an equivalent delay time of 50 nsec for the frequency f2. Since the outputs of the two third multipliers 31 (Mi1, Mi2) are different in frequency from each other in this way, if they are added as they are, distortion occurs in the signal waveform due to interference.

  Therefore, the corresponding filters 32 (Fi1, Fi2) are connected to the output sides of the third multipliers 31 (Mi1, Mi2), respectively. In each filter 32 (Fi1, Fi2), filtering is performed to reduce interference caused by different frequency bands for the output signals of the third multipliers 31 (Mi1, Mi2). Then, the interference between the output signals of the third multiplier 31 (Mi1, Mi2) is mitigated by these filters 32 (Fi1, Fi2). The characteristic of the filter 32 (Fi1, Fi2) is a bandpass characteristic that allows a necessary band to pass.

  FIG. 3 is a diagram showing the characteristics of the filter 32 shown in FIG.

  In FIG. 3, the horizontal axis indicates the frequency. As shown in FIG. 3, for example, a received signal having a frequency spectrum SP1 with a center frequency of fc = 2.5 MHz is input to two third multipliers 31 (Mi1, Mi2). On the other hand, in the third multiplier 31 (Mi1), the phase rotation process is performed on the signal component having the frequency f1 = 2 MHz by using the reference signal having the frequency fr = 5 MHz. In the other third multiplier 31 (Mi2), the phase rotation process is performed on the signal component having the frequency f2 = 3 MHz by using the reference signal having the frequency fr = 5 MHz.

  The frequency f1 that is the target of phase rotation in one third multiplier 31 (Mi1) is smaller than the frequency f2 that is the target of phase rotation in the other third multiplier 31 (Mi1) (f1 <f2). Then, the characteristic of the filter 32 (Fi1) connected to the third multiplier 31 (Mi1) targeting the small frequency f1 is a signal on the lower frequency side than the center frequency fc + fr of the received signal after phase rotation. The band-pass characteristics that pass through On the contrary, the characteristic of the filter 32 (Fi2) connected to the third multiplier 31 (Mi2) targeting the large frequency f2 is a signal on the higher frequency side than the center frequency fc + fr of the received signal after phase rotation. The band-pass characteristics that pass through As a result, an output signal having a frequency spectrum SP2 similar to the frequency spectrum SP1 of the received signal is obtained.

  That is, the filter 32 (Fi1) is basically a low-pass type and the filter 32 (Fi2) is a high-pass type, but each filter 32 (Fi1, Fi2) is a third multiplier 31 (Mi1, Fi2). Among the output signals of Mi2), a band-pass type that removes unused high-frequency and low-frequency signals in order to suppress sidebands and noise. The sideband to be removed is a difference frequency component when the sum frequency component of the output signal of the third multiplier 31 (Mi1, Mi2) is used, and the difference frequency component is used. In this case, it is the sum frequency component.

  The output side of each filter 32 (Fi1, Fi2) is connected to a common adder 33 (S). Then, in the adder 33 (S), the output signals of the filters 32 (Fi1, Fi2) are added. Therefore, the signals divided by the filters 32 (Fi1, Fi2) are added in the adder 33 (S). Here, it is important to set the cutoff characteristic of each filter 32 (Fi1, Fi2) so that the signal after addition is not disturbed around the edge of the divided frequency band.

  FIG. 4 is a diagram showing a method for setting the characteristics of the filter 32 shown in FIG.

  As shown in FIG. 4, the filter characteristics of the signal passing region superimposed by superimposing the frequency bands divided by the filters 32 (Fi1, Fi2) are formed by the filters 32 (Fi1, Fi2). It is important to set the cutoff characteristic of each filter 32 (Fi1, Fi2) so as to have a flatness equivalent to the filter characteristic of the signal passing region. Even when three or more (n) third multipliers 31 are provided, it is important to set the cutoff characteristics of the corresponding filters 32 in the same manner.

  Since the output signals of the respective filters 32 (Fi1, Fi2) having such characteristics have similar waveforms in time with each other due to time delay, one waveform having a large amplitude by addition in the adder 33 (S). Is obtained. The center frequency of the signal obtained in the adder 33 (S) is fc + fr.

  A fourth low-pass filter 34 (LPF) is connected to the output side of the adder 33 (S). The signal obtained in the adder 33 (S) is output to the fourth low-pass filter 34 (LPF), and unnecessary sidebands are removed in the fourth low-pass filter 34 (LPF).

  A fourth multiplier 35 (M) is connected to the output side of the fourth low-pass filter 34 (LPF). The signal obtained in the fourth low-pass filter 34 (LPF) is output to the fourth multiplier 35 (M), and the phase multiplication processing of the signal is performed in the fourth multiplier 35 (M). That is, the fourth multiplier 35 (M) multiplies the output signal of the fourth low-pass filter 34 (LPF) by the reference signal having the same frequency fr as the reference signal of the third multiplier 31, thereby The center frequency of the output signal of the fourth low-pass filter 34 (LPF) is returned to the center frequency fc before the phase rotation processing in the third multiplier 31. Then, the output signal of the fourth multiplier 35 (M) is the reception signal after the delay addition process output from the reception delay addition circuit 20.

  That is, in the reception delay adding circuit 20, a time delay of the reception signal is performed for each reception channel in order to match the timing of the reception signals received by the plurality of reception channels, and the timing-matched reception signal is added to the adder 33 ( It is added by S) to become one system of received signals. Such a signal processing process in the reception delay adding circuit 20 is called reception beam forming, and is an operation of focusing the reception beam on a region to be imaged. In other words, the waveforms of the reception signals received by the respective reception channels by reception beam forming are added after matching the timing, and a signal having a large amplitude similar to the reception signals received by the respective reception channels is extracted.

  In particular, in the reception delay adding circuit 20 shown in FIG. 2, the band of the received signal is divided, and a multiplier is assigned to each band. The reference signal of each multiplier has the same frequency, and a phase equivalent to the delay time at each center frequency of the divided band of the received signal is set for the reference signal. Further, the reception delay adding circuit 20 is provided with a filter 32 having a characteristic corresponding to the band of the received signal on the output side of each multiplier, and corresponds to the division of the band of the received signal and eliminates unnecessary sidebands generated by the multiplication process. After the removal, the addition is performed. Further, when returning to the original frequency after phase rotation of the received signal, a reference signal having the same frequency as the reference signal used for phase rotation is multiplied using another multiplier.

  According to the reception delay adding circuit 20 having such a circuit configuration, it is possible to accurately perform an equivalent time delay due to phase rotation at a plurality of frequencies in at least two places of the band of the reception signal. For this reason, compared with the conventional equivalent time delay by the phase rotation in the frequency of one place, the delay precision in the whole received signal improves. Further, the circuit configuration of the reception delay adding circuit 20 using the multiplier can be made extremely small by the integrated circuit technology even if the existence of the filter is taken into consideration. Therefore, even if two multipliers are provided in the reception delay addition circuit 20, the circuit scale of the reception delay addition circuit 20 is only slightly increased.

  FIG. 5 is a diagram showing a signal generated with phase rotation in the reception delay adding circuit 20 shown in FIG.

  5A, 5B, and 5C, the horizontal axis indicates time, and the vertical axis indicates the strength of the received signal. FIG. 5A shows an example of a received signal having two bands input to the reception delay adding circuit 20. That is, the reception signal S2 of the reception channel 2 has a time delay Tdi with respect to the reception signal S1 of the reception channel 1. For example, the center frequency of the received signal S1 is fc = 2.5 MHz, and has a band of ± 1 MHz. The time delay is about Tdi = 50 nsec.

  FIG. 5B shows a waveform of the reception signal S1 and a waveform of the reception signal S2 that are time-adjusted by dividing the reception signal into a plurality of bands and performing phase rotation processing for each band using a plurality of multipliers. FIG. As shown in FIG. 5 (b), the time can be matched with the received signal S2 not only in the vicinity of the center frequency of the band of the received signal S1, but also in the frequency component away from the center frequency.

  FIG. 5C is a diagram showing an output waveform S3 of the reception delay adding circuit 20 obtained by adding the reception signal S1 and the reception signal S2 after the phase rotation processing shown in FIG. 5B. As shown in FIG. 5C, a delay time of approximately 50 nsec can be given to the received signal within the band of the received signal. As a result, it is possible to obtain a signal having a waveform obtained by adding a substantially similar waveform to the waveform of the reception signal in each reception channel.

  That is, according to the reception delay adding circuit 20, an appropriate delay can be performed even for a signal component away from the center frequency of the reception signal, and the reception sound field and image quality can be improved. Further, since the multiplier can be configured with a small circuit, the circuit scale of the reception delay adding circuit 20 can be reduced even in the ultrasonic diagnostic apparatus 10 having a large number of reception channels.

  In order to improve the uniformity of the delay time within the band of the received signal, the number of multipliers per receiving channel may be increased.

  Next, an example in which the reception delay adding circuit 20 having a plurality of multipliers for each band of the divided reception signals is applied to a three-dimensional ultrasonic diagnostic apparatus will be described.

  FIG. 6 is a configuration diagram showing an embodiment of a three-dimensional ultrasonic diagnostic apparatus according to the present invention.

  The three-dimensional ultrasonic diagnostic apparatus 40 shown in FIG. 6 is configured by connecting a two-dimensional array probe 41 and an apparatus main body 42 with a probe cable 43. The apparatus main body 42 is provided with a main body side transmitting / receiving unit 44, an image processing unit 45, and a display unit 46. The two-dimensional array probe 41 is provided with a probe built-in transmission / reception unit 47 and a two-dimensional array transducer 48.

  FIG. 7 is a block diagram of the two-dimensional array transducer 48 shown in FIG.

  As shown in FIG. 7, the two-dimensional array transducer 48 is configured by arranging two-dimensionally arrayed micro ultrasonic transducers 48A of, for example, 64 elements × 64 elements = 4096 elements.

  The three-dimensional ultrasonic diagnostic apparatus 40 can perform three-dimensional imaging in real time by delay-controlling the micro ultrasonic transducer 48A to form an ultrasonic beam. However, the number of reception channels in the three-dimensional ultrasonic diagnostic apparatus 40 including the two-dimensional array transducer 48 is 1000 or more. For this reason, if the delay control of the reception signal from each micro ultrasonic transducer 48A is to be performed on the apparatus main body 42 side, the apparatus main body 42 needs to have a number of reception delay circuits corresponding to the number of micro ultrasonic transducers 48A. There is. In the example shown in FIG. 7, 4096 sets of reception delay circuits are required.

  If a large number of reception delay circuits are provided in this way, the circuit scale becomes enormous, and the number of signal lines accommodated in the probe cable 43 is about the same as the number of micro ultrasonic transducers 48A, for example, 4096 in the example of FIG. Necessary. Therefore, the configuration in which the delay control of the reception signal from each micro ultrasonic transducer 48A is performed on the apparatus main body 42 side lacks feasibility and practicality.

  Therefore, as shown in FIG. 7, the two-dimensional array transducer 48 is divided into subarrays 48B having several to dozens of micro ultrasonic transducers 48A. FIG. 7 shows an example in which 4 × 4 = 16 micro ultrasonic transducers 48A form one subarray 48B. In the two-dimensional array probe 41, delay addition processing of reception signals from the micro ultrasonic transducers 48A in the subarray 48B is performed, while delay addition processing of reception signals from each subarray 48B is performed on the apparatus main body 42 side. Is called. For this purpose, the probe built-in transmission / reception unit 47 in the two-dimensional array probe 41 is provided with a plurality of subarray reception delay addition circuits 49, while the main body side transmission / reception unit 44 is a main delay addition circuit on the apparatus main body 42 side. A beam former 50 is provided.

  FIG. 8 is a circuit diagram showing a configuration of the probe built-in transmission / reception unit 47 shown in FIG.

  As shown in FIG. 8, the probe built-in transmission / reception unit 47 is provided with a plurality of intra-probe preamplifiers 60, a plurality of intra-probe pulsers 61, and a plurality of subarray reception delay adding circuits 49. The intra-probe preamplifier 60 and the intra-probe pulser 61 are each connected to each micro ultrasonic transducer 48A. The subarray reception delay adding circuit 49 is provided for each subarray 48B, and is connected to a plurality of in-probe preamplifiers 60 corresponding to the single subarray 48B.

  Each intra-probe pulser 61 has a function of applying a transmission signal to a corresponding micro ultrasonic transducer 48A with a delay time received from a transmission delay circuit (not shown). The intra-probe preamplifier 60 has a function of amplifying the reception signal received from the micro ultrasonic transducer 48A to a level at which signal processing is possible and outputting the amplified signal to the sub-array reception delay adding circuit 49.

  The subarray reception delay adding circuit 49 has a function of performing delay addition processing of reception signals obtained from the micro ultrasonic transducer 48A in the subarray 48B via the in-probe preamplifier 60. Further, each subarray reception delay adding circuit 49 has a circuit configuration as shown in FIG. That is, the time delay processing is equivalently performed by dividing the band of the reception signal from one micro ultrasonic transducer 48A and performing phase rotation processing on the divided signals using corresponding multipliers.

  Thus, by making the circuit configuration of each sub-array reception delay adding circuit 49 using a multiplier for each band of the received signal, while maintaining the time delay accuracy of the frequency component away from the center frequency of the received signal, The circuit scale of each subarray reception delay adding circuit 49 can be reduced. As a result, each subarray reception delay adding circuit 49 can be accommodated in the two-dimensional array probe 41.

  The delay-added reception signal output from the sub-array reception delay adding circuit 49 is given to the main beam former 50 on the apparatus main body 42 side through a corresponding signal line in the probe cable 43. The main beamformer 50 has a function of performing delay addition processing of received signals corresponding to each sub-array 48B.

  That is, by dividing the delay addition processing for forming the three-dimensional ultrasonic reception beam B into two stages, the scale of the delay addition circuit and the number of signal lines in the probe cable 43 are reduced. Since the signal lines in the probe cable 43 need only be provided by the number of subarrays 48B, the number of signal lines is reduced to 4096/16 = 256 in the example of FIG.

  In addition, the number of subarray reception delay addition circuits 49 is 256, and the main beamformer 50 may have a circuit scale necessary for performing delay addition processing for 256 reception signals.

  An image processing unit 45 is connected to the subsequent stage of the main beam former 50, and a display unit 46 is connected to the output side of the image processing unit 45. The image processing unit 45 generates a 3D image data by performing signal processing and image processing on the received signal delayed and added in the main beamformer 50, and the generated 3D image data to the display unit 46. It has the function to give. The display unit 46 includes a display device such as a CRT or LCD, and has a function of displaying the 3D image data received from the image processing unit 45.

  In the three-dimensional ultrasonic diagnostic apparatus 40 configured as described above, a transmission signal with a time delay for forming the ultrasonic transmission beam B from the main body side transmission / reception unit 44 is transmitted via each signal line in the probe cable 43. This is given to a transmission delay circuit (not shown) in the dimension array probe 41. The transmission signal is given to each intra-probe pulser 61 from the transmission delay circuit in the two-dimensional array probe 41.

  Then, each intra-probe pulser 61 applies the transmission signal to the corresponding micro ultrasonic transducer 48A with a delay time. Thereby, an ultrasonic pulse is transmitted from each micro ultrasonic transducer 48A, and an ultrasonic echo is received. The ultrasonic echoes received by each micro ultrasonic transducer 48A are given to the corresponding pre-amplifier 60 in the probe from each micro ultrasonic transducer 48A as a reception signal with a time delay. Each intra-probe preamplifier 60 amplifies the reception signal received from the corresponding micro ultrasonic transducer 48 </ b> A to a level at which signal processing is possible and outputs the amplified signal to the subarray reception delay addition circuit 49.

  In each subarray reception delay addition circuit 49, delay addition processing is performed on the reception signal from each micro ultrasonic transducer 48A belonging to the corresponding subarray 48B. In the example shown in FIG. 7, in one subarray reception delay addition circuit 49, delay addition processing is performed on the reception signals from the 16 micro ultrasonic transducers 48A. The reception signal after the delay addition in the sub-array reception delay addition circuit 49 is given to the main beam former 50 of the main body side transmission / reception unit 44 via the signal line in the probe cable 43.

  In the main beamformer 50, delay addition processing is performed on the reception signals after the delay addition in each subarray reception delay addition circuit 49. The one-system received signal after delay addition generated in this way is supplied from the main beamformer 50 to the image processing unit 45. In the image processing unit 45, signal processing and image processing are performed on the reception signal delayed and added in the main beamformer 50, and three-dimensional image data is generated. The generated three-dimensional image data is given from the image processing unit 45 to the display unit 46. As a result, a three-dimensional image is displayed on the display unit 46.

  In this way, the circuit configuration of the reception delay circuit of the three-dimensional ultrasonic diagnostic apparatus 40 is configured to include a plurality of multipliers for each reception channel, so that the reception signal equivalent to the phase rotation within the band of the reception signal can be obtained. An error in the time delay process can be reduced. A good ultrasonic reception beam B can be formed.

  The ultrasonic diagnostic apparatus 10 having the ultrasonic probe 11 having the one-dimensional array of ultrasonic transducers 18 and the three-dimensional ultrasonic diagnosis having the two-dimensional array probe 41 having the two-dimensional array of ultrasonic transducers 18. Although the application example of the present invention to the delay signal addition circuit of the reception signal provided in the apparatus 40 has been described, the delay addition of the reception signal provided in the ultrasonic diagnostic apparatus 10 having an ultrasonic probe in the form of another array that can be realized. The present invention can also be applied to circuits.

  Further, a delay line and a multiplier can be combined as in the conventional reception delay adding circuit shown in FIG. That is, the present invention is such that a plurality of multipliers connected in parallel and a delay line are connected in series, and both the equivalent time delay by phase rotation and the direct time delay are performed to perform the delay processing of the received signal. It is also possible to configure a reception delay adding circuit. In this case, since the direct time delay by the delay line is used together, the accuracy of the time delay process can be improved.

1 is a configuration diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. FIG. 2 is a circuit diagram showing a configuration of a reception delay adding circuit shown in FIG. 1. The figure which shows the characteristic of the filter shown in FIG. The figure which shows the setting method of the characteristic of the filter shown in FIG. The figure which shows the signal produced | generated with a phase rotation in the reception delay addition circuit shown in FIG. 1 is a configuration diagram showing an embodiment of a three-dimensional ultrasonic diagnostic apparatus according to the present invention. The block diagram of the two-dimensional array transducer shown in FIG. FIG. 7 is a circuit diagram showing a configuration of a probe built-in transmitting / receiving unit 47 shown in FIG. The block diagram of the reception delay addition circuit using the delay line with which the conventional ultrasonic diagnosing device is equipped. The figure which shows the waveform of the received signal input into each delay line of the conventional receiving delay addition circuit shown in FIG. The figure which shows the waveform of the received signal output from each delay line of the conventional receiving delay addition circuit shown in FIG. The block diagram of the reception delay addition circuit using the multiplier with which the conventional ultrasonic diagnosing device is equipped. The figure which shows the waveform of the received signal output from the 1st multiplier of the conventional receiving delay addition circuit shown in FIG. The block diagram of the reception delay addition circuit by the combination of the delay line with which the conventional ultrasonic diagnosing device is equipped, and a multiplier. The figure which shows the signal produced | generated in the reception delay addition circuit by the conventional phase rotation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic diagnostic apparatus 11 Ultrasonic probe 12 Transmission / reception circuit 13 Signal processing part 14 Image processing part 15 Display part 16 Control circuit 17 Operation panel 18 Ultrasonic transducer 19 Transmission delay circuit 20 Reception delay addition circuit 21 Pulser 22 Preamplifier 30 3rd Low-pass filter 31 third multiplier 32 filter 33 adder 34 fourth low-pass filter 35 fourth multiplier 40 three-dimensional ultrasonic diagnostic device 41 two-dimensional array probe 42 device main body 43 probe cable 44 main body side transmitting / receiving unit 45 Image processing unit 46 Display unit 47 Transmitter / receiver with built-in probe 48 Two-dimensional array transducer 48A Micro ultrasonic transducer 48B Subarray 49 Subarray reception delay addition circuit 50 Main beam former 60 In-probe preamplifier 61 In-probe pulser O Subject

Claims (6)

Ultrasonic transmission / reception means for transmitting / receiving ultrasonic pulses to / from a subject using a plurality of ultrasonic transducers;
A delay addition circuit that adjusts and adds times of a plurality of reception signals of a plurality of reception channels received by the plurality of ultrasonic transducers;
Image data generating means for generating ultrasonic image data from the reception signal generated by the delay addition circuit;
The delay addition circuit is configured to perform a phase rotation process by at least two multipliers using reference signals having the same frequency and different phases with respect to a reception signal of a single reception channel. Ultrasound diagnostic device. The delay addition circuit uses the reference signal having a phase set so that equivalent delay times by the phase rotation processing are the same for at least two frequencies within a band of a reception signal of the single reception channel. 2. The ultrasonic wave according to claim 1, further comprising a filter configured to perform the phase rotation processing and to suppress interference between the at least two frequencies on an output side of the at least two multipliers. Diagnostic device. The ultrasonic diagnostic apparatus according to claim 2, wherein the filter is a band-pass type or a combination of a low-pass type and a high-pass type. 3. The cutoff characteristic of the filter is determined so that a characteristic of a pass region of the filter obtained by superimposing the filters has a flatness equivalent to that of each pass region of the filter. Ultrasound diagnostic equipment. The super delay circuit according to claim 1, further comprising a delay line that performs time delay processing on at least one of the reception signal of the single reception channel and the reception signal after the phase rotation processing. Ultrasonic diagnostic equipment. The ultrasonic diagnostic apparatus according to claim 1, wherein the delay addition circuit is built in an ultrasonic probe that houses the plurality of ultrasonic transducers.

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