JP3396518B2 - Ultrasound diagnostic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to continuous wave Doppler (CW
The present invention relates to an ultrasonic diagnostic apparatus capable of performing diagnosis by the D) method and the pulse Doppler (PWD) method, and particularly to improvement of a reception delay adder circuit thereof.

[0002]

2. Description of the Related Art As one of scanning methods for ultrasonic diagnostic equipment,
The electronic scanning method is used. When scanning by this electronic scanning method, usually, an electronic focus method is used in which the timing of driving and receiving for each transducer is electronically controlled by a delay line, and the transmitted and received ultrasonic signals are converged. This improves the resolution in the scanning direction.

As a specific example of the reception delay adder circuit for performing this electronic focusing, there is known a configuration disclosed in, for example, Japanese Patent Laid-Open No. 2-26548 (the name of the invention is "ultrasound diagnostic apparatus"). According to one aspect of the configuration described in this publication, ultrasonic waves are transmitted / received to / from a subject using an ultrasonic vibrator (arrangement group of transducers) composed of a plurality of elements (piezoelectric transducers). The reception delay adder circuit employs the digital delay method shown in FIG.
This will be described for any one channel. An echo signal obtained by transmitting and receiving an ultrasonic signal is amplified by the preamplifier 100, converted into a digital signal by the A / D converter 101, and temporarily stored in the memory 102. Stored in.
This echo signal is then sent to the digital delay lines 103a, 1
03b is branched and supplied, and is delayed. Then, in the multipliers 104a and 104b, the echo signals delayed by, for example, 50 nsec are multiplied by the phase control signal, and the phases are matched. The multiplication signals are added to the adders 105a and 105a, respectively.
After being combined with that of another channel at 105b, LPF
An image signal is obtained by passing through 106a and 106b. As a result, it is possible to apply a highly accurate reception delay.

[0004]

However, in the above-mentioned conventional reception delay adder circuit, only the digital type circuit is mounted alone, so continuous wave Doppler (CWD) and pulse Doppler (CWD) of the ultrasonic Doppler method are provided. When applied to an ultrasonic diagnostic apparatus that implements PWD), the reception delay adder circuit is shared by the continuous wave Doppler method and the pulse Doppler method, which leaves the following unsolved problems. It was

Since the dynamic range (D / R) of the echo signal by the continuous wave Doppler method is wider than that of the pulse Doppler method, the dynamic range of the reception delay adder circuit using both Doppler methods is the same as that of the continuous wave Doppler method. It is theoretically desirable to match. The dynamic range of the above-mentioned digital reception delay adder circuit is determined by the number of bits of the A / D converter, and in consideration of cost performance, usually about 8 bits are adopted.

However, this number of bits is not sufficient for the continuous wave Doppler method. In the continuous wave Doppler method, since there is crosstalk between transmission and reception in the ultrasonic probe,
The input amplitude to the delay addition circuit is 2 compared to the pulse Doppler method.
It is about 3 bits (10 to 20 dB) larger. For this reason,
I would like to have a more multi-bit A / D converter in accordance with the continuous wave Doppler method, but this A / D converter is required for each receiving channel, and the price per unit is very high for multi-bit devices. Since the cost is high, increasing the number of bits to about 8 bits or more significantly increases the manufacturing cost of the entire device and is not a practical measure.

On the other hand, as described above, when the number of bits of the A / D converter is adjusted to the dynamic range of the pulse Doppler method due to cost considerations, the number of bits is insufficient in the continuous wave Doppler method, which results in A / D conversion. Distortion may occur at the input stage of the instrument. When this amplitude distortion occurs,
Due to the sensitivity deterioration due to saturation, the image quality deteriorates,
There is also a problem that an artifact such as a mirror image occurs in the image due to the cross modulation.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to obtain an optimum dynamic range for an echo signal in both modes of the continuous wave Doppler method and the pulse Doppler method, and the echo signal. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of eliminating the increase in the circuit scale and the increase in the component cost of the reception delay addition circuit for processing the.

[0009]

In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention is provided with a plurality of transducers capable of electro-acoustic conversion and an ultrasonic pulse signal via the plurality of transducers. A first transmitting means for transmitting the
Wherein the first received signal processing means for delaying adding said ultrasonic sound waves pulse signal receiving signal corresponding to the input through the plurality of transducers and the received signal into a digital amount from a subject, wherein and second transmitting means for transmitting via a plurality of transducers ultrasound continuous signal into the subject, wherein through said ultrasonic continuous signal received signals of said plurality that corresponds to the vibrator from the subject input and Bei a second reception signal processing means for delaying adding the received signals in analog quantity of state
The second received signal processing means is configured to transmit the ultrasonic continuous signal.
For one cycle of each of the multiple carrier frequencies that can be used for
Delay time and predetermined amount for each of the plurality of delay times
A compound consisting of only taps with selectable delay time
A number of taps have been withdrawn and delivered to each tap
A delay line that adds an analog amount of current, and the plurality of vibrations.
Involved in the transmission / reception mode by the ultrasonic continuous signal in the child
To switch the received signals of multiple channels.
Be characterized in Tsu that a flop supplying a signal switching circuit
It In addition, the plurality of taps of the delay line are, for example, continuous.
Each one of multiple carrier frequencies used in wave Doppler mode
It is also possible to form a delay time of a period and a delay time of a predetermined quantization interval for each of the delay times from only selectable taps.

Further, the plurality of taps of the delay line are
If example, have been pulled out so that the delay time is at irregular intervals
It

According to the present invention, when the non-continuous wave Doppler mode such as pulse Doppler mode, the transducer group in the pulse signal by the first transmission means are driven, the echo signal (reception signal) is first The reception signal processing means digitally adds delays. As the A / D converter required for this digital delay addition, since the echo signal has a narrow dynamic range in the discontinuous wave Doppler mode, a normal number of bits, for example, about 8 bits, which is also cost-effective, is used. be able to.

On the other hand, in the continuous wave Doppler mode, the transducer group is driven by the continuous wave signal by the second transmitting means, and the echo signal (received signal) is received by the second received signal processing means. Delayed addition is performed with the analog amount. This delay addition is performed by, for example, an analog delay line in which a plurality of taps are drawn out at unequal intervals. As a result, delay addition can be performed without using an A / D converter.
It is possible to eliminate an increase in component cost such as when a D converter is required. Furthermore, since a wide dynamic range required in the continuous wave Doppler mode is secured at the same time, deterioration of reception sensitivity and occurrence of artifacts such as mirror images are prevented.

Further, the plurality of taps of the delay line are, for example,
Plurality of carrier frequencies husband for continuous wave Doppler mode s
And its delay that can select the delay time for one cycle of
Since it consists only of taps that can select a delay time of a predetermined quantization interval for each time , the number of taps to be pulled out can be kept to a necessary minimum compared to the case where a plurality of taps are pulled out at equal intervals, and a reception delay addition circuit Figure is compact
To be

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a transmission / reception unit for one channel of the ultrasonic diagnostic apparatus according to this embodiment. This transmission / reception unit has a plurality of channels (for example, 128 channels) for electro-acoustic conversion.
Transducer group TG composed of transducers 10 ...
Is equipped with.

Of the oscillators 10 ... 10 of the oscillator group TG, all channels are connected to a high voltage drive pulse generating circuit 11 by the pulse Doppler method. In addition, in this embodiment, the 64-channel oscillator 1 from the 1st to the 64th channels is used.
0 ... 10 are also connected to the CW drive transmission circuit 12 by the continuous wave Doppler method. The pulse generation circuit 11 is a "POWERONPW" supplied from a control circuit (not shown).
The CW drive transmission circuit 12 is driven when the signal is on, and is driven when the "POWERONCW" signal is on.

Thus, in the diagnostic mode by the pulse Doppler method (hereinafter referred to as pulse Doppler mode), the drive pulse signals from the high voltage drive pulse generation circuit 11 excite the transducers 10 ... The excited transducers 10 ... 10 send an ultrasonic signal toward the inside of the subject and receive the reflected echo signal. In the diagnostic mode by the continuous wave Doppler method (hereinafter, referred to as continuous wave Doppler mode), the continuous wave drive signal from the CW drive transmission circuit 12 instead of the high voltage drive pulse generation circuit 11 causes the 1st to 64th channels. The vibrators 10 ... 10 are excited. The reflected echo signal accompanying this excitation reaches the transducers 10 ... 10 of all channels. It is also possible to provide a drive circuit that also serves as the high-voltage drive pulse generation circuit 11 and the CW drive transmission circuit 12.

Of the vibrators 10 ... 10, the first to the 64th
The channel is connected to the preamplifier 14a for amplitude amplification via the electronic switch 13, and the 65th to 1st
The 28th channel is also connected to another preamplifier 14b. The electronic switch 13 is energized by turning on and off the "POWERONPW" signal to be conductive and non-conductive, and transmits the echo signal converted into an electric signal by the vibrators 10 to 10 to the preamplifier 14a in the pulse Doppler mode. Has become. As a result, in the pulse Doppler mold, the transducers 10 ... 10 of all channels are involved in the reception, and in the continuous wave Doppler mode, the transducers 10 ... 10 of only the 65th to 128th channels are involved in the reception.

A first reception phasing addition circuit 15 for pulse Doppler mode is connected to the output sides of the preamplifiers 14a and 14b. The reception phasing addition circuit 15 has a mixer 16 provided on the input side thereof and a reception delay circuit 17 which receives the output of the mixer 16. Reception delay circuit 17
Is provided with an A / D converter 18 provided on the input side thereof, and a digital beam former (DBF) 19 which receives a conversion signal of the A / D converter 18 and performs digital phasing addition. . The digital beam former 19 has the same structure as, for example, the one described in the above-mentioned conventional Japanese Patent Application Laid-Open No. 2-26548, and can perform delay addition with high accuracy.
Output of this digital beam former 19 (addition signal)
Is a digital scan converter (DS
C), it is sent to the spectrum Doppler signal processing circuit and the like. Desired signal processing is performed by these circuits, and spectrum Doppler information and two-dimensional color information of blood flow are displayed on a display device (not shown).

A second reception phasing addition circuit 18 dedicated to the continuous wave Doppler mode is provided in parallel with the first reception phasing addition circuit 15 on the output side of one of the preamplifiers 14a and 14b. It is provided.

The second reception phasing addition circuit 18 is shown in FIG.
As shown in FIG. 2 (only the main part is shown in FIG. 1), buffers 2065 to 20128 for channels 65 to 128 are provided on the input side. This buffer 2
The output side of 065 to 20128 is eight multiplexers 21a to 21i having 8 inputs and 16 outputs (multiplexer unit 2
8 channels are connected to each other). The 16 output terminals of each of the multiplexers 21a to 21i are connected to each other at the output terminals having the same numbers, and have 16 unequal-spaced taps TAP1 to 16 for analog addition of a current delay line 22 (coil). Connected to each tap.
The multiplexers 21a to 21i include the 65th to 128th
The 64 input signals of the channel are fed to the tap T of the delay line 22.
A switching control signal AYX that determines which of AP1 to 16 is supplied is supplied from a control circuit (not shown).

A concrete example of the delay line 22 is as shown in FIG. That is, the delay line 22 has three sub delay lines 22a to 22 having a maximum delay time of 200 [nsec].
16 of the sub delay lines 22a to 22c, and 16 taps TAP1 to 16 of unequal intervals are drawn from the sub delay lines 22a to 22c. The taps TAP1 to TAP16 have a smaller delay time interval as the density of the lead-out intervals is higher, and a larger delay time interval as the density is rougher.

Here, TAP 1 to 16 in this embodiment
Explain how to decide.

First, consider the maximum required delay time. As shown in FIG. 4, the delay amount (delay time) of the delay line 22 normally gives a time difference corresponding to each sound path length difference from the focus F to the receiving transducers 1065 ... 10128. For example, as shown in FIG. 4, assuming that the sound path lengths between the transducers 1065 ... 10n are L65 ... Ln, respectively, the sound path length difference ΔLn.
Is

## EQU1 ## ΔLn = Ln-L65 And the sound velocity is C, the delay time τn is

## EQU2 ## τn = ΔLn / C. Therefore, for example, L65 = 1000 mm, Ln
= 1006.1 mm and C = 1530 m / sec, the delay time τn = 4 μsec.

However, in the continuous wave Doppler mode, the same phase information is repeated for each waveform of the received ultrasonic wave (there is waveform periodicity) as shown in FIG. It is not necessary to give the time difference of. That is, the time difference corresponding to the maximum value of the sound path length difference is unnecessary, and one wavelength of the carrier frequency, τnCW, is sufficient.
On the other hand, in the pulse Doppler mode, since the echo signal is a pulse wave, the time difference τnPW corresponding to the sound path length difference ΔLn is required.

Table 1 shows each of the carrier frequencies f (1.
5 to 10 MHz), the time for one wavelength λ and the time for λ / 8 minutes are shown. From this, it can be seen that even if the lower limit of the carrier frequency f is set to 2 MHz, a delay amount of about 500 nsec is sufficient. Therefore, the maximum delay time is considerably smaller than that in the non-CW mode, and the number of lines is larger than that of the analog delay line for the receiving circuit in the non-CW mode (however, the digital signal is processed in this embodiment). Is less.

[0026]

[Table 1] Next, the delay time accuracy required for tap positioning will be considered. Even in the continuous wave Doppler mode, the reflected echo signal from the subject is electronically delayed so that the echo signal from the desired region of interest (ROI) becomes the strongest. At this time, the sound field at the focus (intensity distribution of the echo signal) is usually as shown in FIG. Especially, in the continuous wave Doppler mode, it is known that the contribution of the side lobe component is small and the extent of the main beam determines the reception sensitivity.

The accuracy of the delay quantization is "λ /" of the carrier signal.
When the roughness is 8 "or less, the spread of the main beam is 10% or less as compared with the case without delay quantization (continuous delay), and the sensitivity deterioration due to the beam spread is" -1 dB ".
It turns out that it can be suppressed within. For this reason, as can be seen from the above-mentioned Table 1 (refer to the item of “λ / 8”), for example, for carrier frequencies of 2 MHz to 6 MHz, it is sufficient to have a quantization accuracy of 60 nsec to 20 nsec.

The tap interval will be decided based on these conditions. Since it is necessary to set the delay accuracy for each carrier frequency to be equal to or less than “1/8” cycle, if the carrier frequency f = 7.5 MHz (wavelength λ = 133 nsec) is set as the upper limit, in this case, quantization of 16.7 nsec intervals is performed. And the maximum delay amount = 7λ / 8 = 1116 nsec. On the other hand, the lower limit carrier frequency f =
When set to 1.8 MHz (wavelength λ = 556 nsec), 6
Quantization at 9.4 nsec intervals and maximum delay amount = 7λ / 8
= 486 nsec is required. This carrier frequency f
Table 2 shows tap allocations that satisfy the quantization accuracy and the maximum delay amount for = 7.5 MHz and 1.8 MHz. As can be seen from the table, the delay time τ = 0 in order to obtain the quantization accuracy of “1/8” cycle or close to it.
It can be seen that the tap can be pulled out finely in the range of up to 133 nsec and rough in the range of 133 to 500 nsec.

[0029]

[Table 2] That is, conventionally, in the case of the above-described example, at least 29 (= 486 / 16.7) for the continuous wave Doppler mode.
Was pulling out the tap. In continuous wave Doppler mode,
Even if the detected Doppler echo band is large, ± 50 kHz is sufficient, and since the spread for each carrier frequency does not have to be taken into consideration, it is not necessary to use all 29 taps. This exemplary two carrier frequencies f =
Looking at 7.5 MHz and 1.8 MHz, the number of taps is almost 14, which is much smaller than 29.

The analog delay line 22 adopted in this embodiment
Then, based on the above idea, the carrier frequency f = 1.875MH
16 taps that are extended over a wide range from z to 6 MHz and satisfy both the quantization accuracy and the maximum delay amount are determined as shown in Table 3. That is, the required maximum delay time is within a short range (maximum delay time corresponding to f = 5 MHz =
In a range up to 180 nsec), taps TAP1 to TAP10 are drawn out at intervals of 20 nsec. Then, as the required maximum delay time becomes larger than this, 4
Taps TAP11 to 0nsec and 60nsec intervals
16 are extracted, and the total number of taps is 16 which is a very small number, but a wide range of carrier frequencies f =
It enables a highly accurate delay for 1.875 MHz to 6 MHz.

[0031]

[Table 3] 1 and 2, the output terminal of the delay line 22 is the amplifier 2
It is connected to one input end of a two-input electronic switch 24 via 3. A reception signal (pencil echo signal) from the pencil-type continuous wave probe is input to the other input terminal of the electronic switch 24. The output end of the electronic switch 24 is connected to a two-channel processing circuit on the sin side and the cos side. This processing circuit includes 2-channel mixers 25a and 25b, 2-channel detection signal processing (filter etc.) circuits 26a and 26b including a bandpass filter, and 16-bit 2-channel A / D converters 27a and 27b. , Digital output buffers 28a and 28b. As a result, the 16-bit digital addition signal is output from the digital output buffers 28a and 28b to the digital signal processing system (DSP).

Next, the overall operation of this embodiment will be described.

First, in the pulse Doppler mode, FIG.
As shown in, the “POWERONPW” signal = on and the “POWERONCW” signal = off are set.
As a result, the first reception phasing addition circuit 15 on the pulse Doppler side is activated, but the second reception phasing addition circuit 18 on the continuous wave Doppler side is deactivated. As a result, as described above, the 128-channel echo signals amplitude-amplified by both the preamplifiers 14a and 14b are input to the first digital reception phasing addition circuit 15 for signal processing, and a desired digital amount is obtained. Image data of is sent to the display side.

On the other hand, in the continuous wave (CW) Doppler mode, as shown in FIG. 8, "POWERONPW"
Signal = off and “POWERONCW” signal = on. Therefore, contrary to the above, only the second reception phasing addition circuit 18 on the continuous wave Doppler side is activated, and the amplitude required by one of the preamplifiers 14b (actually, the number of channels corresponding to 64 channels is provided). The received echo signal amplified up to is input to the second received phasing addition circuit 18.

The echo signals of the 65th to 128th channels input to the second reception phasing addition circuit 18 are stored in the buffer 2
It is input to the multiplexer unit 21 via 065 to 20128. The switching control signal AYX corresponding to the currently used carrier frequency f is given to the multiplexer unit 21. As a result, the echo signals for 64 channels are switched to 16 taps TAP1 to TAP16 for several channels in a manner satisfying the quantization accuracy and the maximum delay time.

For example, the used carrier frequency f = 2.5M
Hz, λ = 400 nsec, λ / 8 = 50 ns
ec. As a result, the allowable quantization precision = λ / 8
= 50 nsec, the required maximum delay time = 7λ / 8
= 350 nsec, the tap selected by the multiplexer unit 21 is

[Outer 1] Becomes In this case, for example, a delay tap (TAP4) of 60 nsec is selected for a delay time of 50 nsec, and although an error occurs, the quantization accuracy of λ / 8 or less is secured as a whole, so the influence of the error Can be ignored. Similarly for other carrier frequencies f,
The tap is selected in a state where the quantization accuracy and the required maximum delay time are compatible with each other.

Therefore, each of the 64-channel echo signals has taps TAP1 to TAP with an appropriate delay amount selected.
It is input to one of the APs 16, and the current delay addition is performed by the delay line 22 with the analog amount. This added output is then output to mixers 25a and 25b, detection signal processing (filters, etc.) circuits 26a and 26b, and A / D converters 27a and 27b.
After that, it is converted into digital image data and sent to the display side.

Since this embodiment functions as described above, compared with the conventional ultrasonic diagnostic apparatus having only the digital type reception delay addition circuit and sharing the circuit for the pulse Doppler mode and the continuous wave Doppler mode, There are advantages like. This advantage will be described again in detail with respect to the disadvantages of the conventional device.

Since it is necessary to provide as many reception delay circuits as the number of channels corresponding to the number of transducers, the component cost greatly affects the manufacturing cost of the entire apparatus. Therefore,
Consider the component cost when the A / D converter 101 is provided for each channel in the reception delay circuit as in the conventional apparatus of FIG.

It is sufficient for the A / D converter 101 bit number to cover the dynamic range of the output signal of the preamplifier 100 at the preceding stage. At present, the dynamic range is the A / D converter when transmitting and receiving a pulse wave (PW). Is about 6 to 7 bits. Therefore, it is sufficient that the number of bits of the A / D converter is 8 bits. This state is shown by a broken line Lpw in FIG.

On the other hand, when receiving a continuous wave (CW), the dynamic range of the output signal of the preamplifier 100 is 10 to 1 as shown by the solid line Lcw in FIG.
It becomes 1 bit. The reason for this is as follows.

FIG. 10 schematically shows how ultrasonic signals are transmitted and received in the continuous wave Doppler mode. In the figure, the two-division steering system is used, and among sector probes having 128 transducers (channels), channels 1 to 64 are used as transmission channels and channels 65 to 128 are used as reception channels. In this case, a continuous wave of about 10 Vpp is applied to the transducer of the transmission channel in a delayed state with a pattern for a predetermined time, and thereby a continuous wave signal of ultrasonic waves is sent toward the focus F (a plane wave may be used. ). The reflected echo signal accompanying the transmitted ultrasonic wave is received by each transducer of the reception channel and enters the reception delay addition circuit.

At this time, since transmission and reception are performed by continuous waves, crosstalk schematically shown in FIG. 10 occurs in the transmission circuit and the probe (transducer group), and a signal leaks from the transmission system to the reception system. Will end up. The amplitude of the reflected echo signal when there is no crosstalk is usually 1 to 10 mVpp or less. For example, when the transmission drive amplitude is 10 Vpp,
When the crosstalk from the transmission circuit is -60 dB, the leakage to the reception channel side reaches 10 mVpp, and the total amplitude of the input signal to the reception delay addition circuit becomes considerably large. In the pulse Doppler mode, since there is a time difference between the time of transmission and the time of reception, the above-mentioned crosstalk between transmission and reception does not pose a problem.

Further, in the continuous wave Doppler mode, "clutter", which is irrelevant to the detection of blood flow information, is included in the reflected echo signal.
Since the component from the in-vivo organ, which is referred to as, is included, the amplitude of the reflected echo signal also increases due to this component. That is, the dynamic range in the continuous wave Doppler mode is larger than that in the pulse Doppler mode due to the clutter.

As described above, the dynamic range of the output signal of the preamplifier 100 in the continuous wave Doppler mode in the conventional device is 10 to 11 bits in terms of the number of bits of the A / D converter mainly due to crosstalk and clutter. It will also be lost. Therefore, in order to maintain this dynamic range, multiple bits (for example, 12 bits)
When the A / D converter of is installed, the A / D converter requires a high-speed converter (for example, a sample rate of 20 MHz) that matches the received signal bandwidth (for example, 10 MHz),
The cost of parts per unit will be extremely high. Moreover, if the multi-bit A / D converters are provided for the number of reception channels, the entire apparatus becomes expensive. For this reason, a digital type reception delay adder circuit provided with a multi-bit A / D converter and used in both the pulse Doppler mode and the continuous wave Doppler mode has faced the reality of being practically difficult.

On the other hand, in the conventional device of FIG. 18, it is possible to use an A / D converter of about 8 bits in order to suppress the component cost. In that case, as described above, the dynamic range is small for the received echo signal in the continuous wave Doppler mode, so that there is a problem that the reception circuit is saturated.

A simulation example of this problem is shown in FIGS.
It will be described with reference to FIG. As shown in FIG. 11, a calculation model is introduced in which a part of the amplitude of the input signal is clipped in a rectangular shape by a saturated system (FIG. 12 shows the clipped output signal). As shown in FIG. 13, the clutter echo component of the living body is f0, the Doppler echo component is f1, and f0 = 30
Assuming dB × f1, the intermodulation mirror component f2 (= 2f0
-F1: See FIG. 14) was calculated, and the results shown in FIG. 15 were obtained. That is, the horizontal axis represents the clip ratio corresponding to the saturation of the echo signal, and the vertical axis represents the input signal component f.
The ratio of the mirror image f2 caused by the attenuation of 0 and f1 and the intermodulation is shown. From the figure, it was found that even if the saturation clip of 10% occurs, the intermodulation mirror component of about -10 dB (1/3 in voltage amplitude) is generated with respect to the Doppler signal component. This mirror component, as shown in FIG.
In the ultrasonic Doppler display, the Doppler blood flow image and the mirror image IM are displayed, which may lead to misdiagnosis. Note that FIG. 17 shows a normal Doppler blood flow image when there is no mirror image.

Further, when the reception delay adder circuit is saturated, there is a problem that the sensitivity of the Doppler signal deteriorates. In the simulation example described above, it was found that the sensitivity of the Doppler signal itself also deteriorates by about 2 to 3 dB when the saturation clip is 10%.

As described above, in the continuous wave Doppler mode, it is essential to secure a wide dynamic range, and a device having a narrow dynamic range cannot exhibit sufficient diagnostic ability. Further, if the dynamic range is to be widened, the conventional device has the above-mentioned problem of manufacturing cost.

In order to solve the above problems, this embodiment does not
As described above , the reception delay adder circuit for the pulse Doppler mode and the continuous wave Doppler mode are separated. In the pulse Doppler mode, in consideration of the narrow dynamic range, the first reception phasing addition circuit 15 using an A / D converter with a relatively low cost of about 8 bits is dedicated to the continuous wave Doppler mode. In the mode, the second reception phasing addition circuit 18 of the analog system is dedicated.

As described above, by providing an analog type reception phasing addition circuit exclusively for the continuous wave Doppler mode, the use of a multi-bit A / D converter for continuous wave reception can be eliminated, and the reception circuit It is possible to secure a sufficient dynamic range for both pulse and continuous wave Doppler modes while minimizing the circuit scale and component cost. Therefore, the manufacturing cost of the entire apparatus can be suppressed, the mirror image (artifact) in the continuous wave Doppler mode can be almost eliminated, and the deterioration of the reception sensitivity can be prevented.
It is possible to exert sufficient diagnostic ability such as an improvement in N ratio. Further, the configuration of the reception delay addition circuit is also simplified and becomes smaller. On the other hand, in the pulse Doppler mode, it is possible to maintain the superiority of the signal processing of digital delay addition.

Further, in the above-described embodiment, the first and second reception phasing addition circuits 15 and 18 are complementarily switched according to the diagnosis mode, and the power supply of the circuits not involved in the selected diagnosis mode is in the off state. Maintained at. As a result, an increase in power consumption due to the provision of the second reception phasing addition circuit 18 dedicated to the continuous wave Doppler mode is suppressed, and energy saving is achieved. Moreover, in the continuous wave Doppler mode, the "POWERONPW" signal and the "POWERO
Since the high voltage drive pulse generation circuit 11, the CW drive transmission circuit 12 and the electronic switch 13 are also turned on and off by being urged to turn on and off the "NCW" signal, the above power saving effect becomes more remarkable.

Further, the second reception delay adder circuit 18 dedicated to the continuous wave Doppler mode of the present embodiment switches between each reception channel and the delay tap by using the multiplexer IC, and the carrier frequency in each of the predetermined range is changed. On the other hand, the tap configuration has unequal intervals that can secure high quantization accuracy and the required maximum delay time. Therefore, it is not necessary to pull out taps at equal intervals, and the peripheral circuit configuration of the analog delay line 22 can be downsized, which leads to simplification and downsizing of the device. This advantage works synergistically with the advantage of miniaturization derived by not providing the second reception delay addition circuit 18 with an A / D converter for each channel.

Although the above embodiment does not mention saturation of the echo signal by the preamplifier,
Unlike the A / D converter, the preamplifier can easily increase the output amplitude by increasing the power supply voltage or the output current, and it is easy to avoid saturation.

Further, the tap interval of the analog delay line dedicated to the continuous wave Doppler mode according to the present invention does not necessarily have to be equal to or less than 1/8 cycle of each carrier signal as described above, and the quantization is roughened. Other than "1/8 period or less" may be used as long as the divergence of the main beam is within the allowable range.

[0056]

As described above, the ultrasonic diagnostic apparatus according to the present invention has a digital reception delay addition configuration for the discontinuous wave Doppler mode (pulse Doppler mode),
Since the analog delay line addition configuration based on the analog delay line for the continuous wave Doppler mode is provided side by side, and the two are selectively used according to the mode, the digital system,
The advantages of the analog system are that they complement each other, and the optimum dynamic range of the received signal can be obtained in both modes. In particular, deterioration of the receiving sensitivity in the continuous wave Doppler mode and the occurrence of mirror images, etc. are eliminated. hand,
It contributes to higher image quality and higher diagnostic capability, and is inexpensive and can be formed on a small scale.

In particular, the delay line used for analog-type reception delay addition can extract the required delay time range in a particularly fine manner by extracting a plurality of taps at equal intervals with the maximum delay time and quantization accuracy according to the carrier frequency. Therefore, the peripheral circuits of the delay line can be remarkably simplified as compared with the case where the taps are simply drawn out at equal intervals .

[Brief description of drawings]

[0058]

FIG. 1 is a partial block diagram in which a reception delay addition circuit of an ultrasonic diagnostic apparatus according to an embodiment of the present invention is a main part.

[0059]

FIG. 2 is a block diagram showing a second reception phasing addition circuit dedicated to the continuous wave Doppler mode.

[0060]

FIG. 3 is a circuit diagram showing a tap drawing state of an analog delay line.

[0061]

FIG. 4 is a diagram illustrating a difference in sound path length for different transducers.

[0062]

FIG. 5 is a diagram illustrating a required delay time for each mode.

[0063]

FIG. 6 is a waveform diagram of a sound field at a focus position in a continuous wave Doppler mode.

[0064]

FIG. 7 is a diagram for explaining an operation status of a phasing addition circuit in a pulse Doppler mode.

[0065]

FIG. 8 is a diagram for explaining an operation state of a phasing addition circuit in a continuous wave Doppler mode.

[0066]

FIG. 9 is a graph for explaining the dynamic range of the echo signal for each mode in terms of the number of bits of the A / D converter.

[0067]

FIG. 10 is a diagram schematically illustrating crosstalk between transmission and reception.

[0068]

FIG. 11 is a diagram of a model for calculating intermodulation mirror components.

[0069]

FIG. 12 is an explanatory diagram showing an example of a waveform clip.

[0070]

FIG. 13 is an explanatory diagram of a spectrum of a signal input to the calculation model.

[0071]

FIG. 14 is an explanatory diagram of a spectrum of a signal output from the calculation model.

[0072]

FIG. 15 is a graph showing an example of calculation results of intermodulation mirror components.

[0073]

FIG. 16 is a diagram of a Doppler image in which a mirror image appears.

[0074]

FIG. 17 is a diagram of a Doppler image when there is no mirror image.

[0075]

FIG. 18 is a partial block diagram of a digital reception delay addition circuit according to a conventional device.

[0076]

[Explanation of symbols]

10 Transducer 11 High-voltage drive pulse generation circuit (first transmission means) 12 CW drive transmission circuit (second transmission means) 15 First reception phasing addition circuit (first reception signal processing means) 18 Second Reception phasing addition circuit (second received signal processing means) 21 multiplexer unit (signal switching circuit) 22 analog delay line TG transducer group TAP1 to 16 taps at unequal intervals

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-58-212434 (JP, A) JP-A-4-250149 (JP, A) JP-A 52-106224 (JP, A) JP-A-2- 291845 (JP, A) JP-A-2-98344 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (2)

(57) [Claims] 1. A electro - acoustic convertible plurality of transducers, a first transmission means for transmitting ultrasonic pulse signals through the plurality of transducers into a subject, the greater from the subject via a first received signal processing means for delaying sum into digital quantity input and the received signal the received signal corresponding through the plurality of transducers in the sound pulse signal, said plurality of transducers analog and second transmitting means, the ultrasound reception signal corresponding to the continuous signal inputted through the plurality of transducers and the received signal from the subject that transmits an ultrasonic continuous signal into a subject Second reception signal processing means for delaying and adding in a quantity state , wherein the second reception signal processing means comprises a plurality of carrier frequencies usable for the ultrasonic continuous signal.
Each one cycle of delay time and each of the plurality of delay times
, A delay time of a predetermined quantization interval for
A plurality of taps consisting of
Delay line that adds the analog amount of current supplied to the
And transmitting and receiving the ultrasonic continuous signal among the plurality of transducers.
Switching the reception signals of multiple channels involved in the reception mode
And a signal switching circuit for supplying to the plurality of taps.
An ultrasonic diagnostic apparatus characterized by the following. A plurality of taps according to claim 2, wherein the delay line, the claims and characterized in that the delay time is drawn at irregular intervals
The ultrasonic diagnostic apparatus according to 1.