JP3030993B2 - Ultrasonic diagnostic equipment beamformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beamformer of an ultrasonic diagnostic apparatus used for detecting in-vivo information in the medical field.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus, a beamformer that delays echo signals obtained from a plurality of elements in consideration of the distance from each element and additionally improves the S / N ratio is used in many ultrasonic diagnostic apparatuses. It is used in an ultrasonic diagnostic apparatus, and the technique is known.

As a delay means in a beamformer, an analog delay line using LC is often used.
However, analog delay lines have limited frequency characteristics,
This is a problem particularly when a large delay time is required at a high frequency. In addition, there is a problem that there is a variation in delay time between individual delay lines and taps, and when performing dynamic focusing, switching by a switch is required, and noise occurs at the time of switching.

Therefore, what has been considered is a digital delay line using an A / D converter and a memory. FIG. 2 shows a conventional example of a beamformer using a digital delay line.
In FIG. 2, 101a, 101b, 101c,.
1n is an element, 102a, 102b, 102c,...
102n is a variable gain amplifier, 103a, 103b, 10
.. 103n are A / D converters, 104a, 104
b, 104c,... 104n are memories (hereinafter, referred to as memories) that can simultaneously execute writing and reading asynchronously,
105n are D / A converters, 106 is a timing control circuit, 107 is an analog adder, and 108 is a low-pass filter. Hereinafter, the operation of this device will be described.

An electric pulse generated by a pulse generation circuit (not shown) is applied to elements 101a, 101b, 1
.. 101n are converted into ultrasonic waves and radiated into the body, and the radiated signals are reflected by portions having different acoustic impedances, and the elements 101a, 101n.
b, 101c,... 101n, and are converted into electric signals. Elements 101a, 101b, 101c,..., 10
1n are received by the variable gain amplifier 102
a, 102b, 102c,... 102n, after being amplified to an appropriate size, A / D converters 103a, 103b, 10
103n are converted into digital signals. The digitized echo signals are stored in memories 104a, 104
b, 104c,... 104n,
.. 104n are read /
Since the writing can be executed simultaneously and at asynchronous timing, the already written data is read out while writing the data, and the D / A converters 105a, 105b, 105
c,... 105n to output analog signals. Therefore, when the conversion timing and the memory write / read timing of the A / D converter and the D / A converter are controlled by the timing control circuit 106, the delay time can be freely controlled. Thus, the elements 101a, 101b, 101c,.
101n is delayed by the analog adder 1
Add at 07. The output of the analog adder 107 is
A low-pass filter 1 is used to cut harmonic components generated by converting the digital signal once.
08.

[0006] As another system, FIG.
There is a method shown in In FIG. 3, 111a, 111
b, 111c,... 111n are elements of the probe, 11
.. 112n are variable gain amplifiers, 130a, 130b, 130c,... 130n are delay circuit blocks, 131 is an analog adder, and 132 is a low-pass filter. Delay circuit blocks 130a, 13
.. 130n are the same, and regarding the delay circuit block 130a, 113a is a sample and hold circuit, 114a and 115a are A / D converters,
116a and 117a are memories, 118a and 119a are D
The / A converter 120a is an analog subtractor.

The echo signal obtained by the element 111a is amplified by the variable gain amplifier 112a with a gain in consideration of the dynamic range of the A / D converter at the subsequent stage and the luminance of image display. The amplified signal is sampled by a sample-and-hold circuit 113a, and the analog subtracter 120a and A
/ D converter 114a. A / D converter 114
The subsequent stage of a is composed of a memory 116a and a D / A converter 118a, and the amount of digital delay in this portion is an integral multiple of the interval between transmission pulses. D / A converter 118
The output of a is subtracted from the output of the sample-and-hold circuit 113a in the analog subtractor 120a. However, when the transmission pulse is continuously transmitted in the same direction as in a Doppler blood flow meter, the output of the sample-and-hold circuit 113a and D / D are output. The output of the A converter 118a is an echo of the same part in the living body due to different transmission pulses. Therefore, an echo that has no or little motion at that part is attenuated because both signals are subtracted by the analog subtractor 120a,
If there is a movement, it is output without being attenuated. Therefore, the echo of the blood vessel wall with almost no movement is greatly reduced, and the echo of the blood flow has a large change, and thus the degree of the reduction is small. Thereby, the echo of the blood vessel wall having a large amplitude is attenuated in the output of the analog subtractor 120a, and the echo of the blood flow having a small amplitude can be extracted. The output of the analog subtractor 120a is digitally delayed by an A / D converter 115a, a memory 117a, and a D / A converter 119a, and then added to a signal from another element by an analog adder 131a to obtain a harmonic component. To the low-pass filter 12
Cut with a.

[0008] In addition to the problem of refinement of the delay time of the delay line and the improvement of the frequency characteristics, there is a problem of increasing the frame rate. This is because, when observing a fast-moving part such as the heart, if the frame rate is low, problems such as the inability to correctly recognize the shape of the valve occur.

As a method for solving this problem, a dual beam receiving method has been proposed. In this method, 1
Two sets of beamformers are prepared for the set of elements, and the delay time of the two beamformers is set so that the position of the sound axis is slightly different for one transmission. This is a method of increasing the frame rate by a factor of two.

[0010]

The echoes from the body include echoes from various tissues. While there are strong echoes from the diaphragm and the like, there are weak echoes from the blood flow. Therefore, for example, in a Doppler blood flow meter, it is necessary to secure a dynamic range capable of receiving a weak echo of a blood flow without saturating such a strong echo.In a digital beamformer,
A with a large number of bits to secure the dynamic range
/ D converter is required. However, A /
There is a problem that the D converter is expensive. Further, in a digital beamformer, two systems of delay parts are required to realize dual beamforming. However, when a high frame rate is not required, this configuration has a problem that there is much waste.

The present invention solves these problems, and uses a low-cost low-bit A / D converter to secure a wide dynamic range and realize dual beam forming. The purpose is to provide a beamformer.

[0012]

According to the present invention, in order to achieve the above object, two systems of a sample hold circuit, an A / D converter, a memory, and a D / A converter are provided in an angular delay circuit block. The difference between the output of the sample and hold circuit of the first system and the output of the D / A converter of the first system is taken, and the A / A of the second system is calculated.
It has a configuration including an analog switch to be input to the D converter and a subtractor for calculating a difference.

[0013]

According to the present invention, two low-bit A's having a lower cost than one A / D converter having a large number of bits are constructed by the above-described configuration.
With the / D converter, a digital beamformer capable of receiving a blood flow signal can be realized, and a high frame rate by dual beamforming can be realized by switching a switch.

[0014]

FIG. 1 is a block diagram of a beamformer of an ultrasonic diagnostic apparatus according to one embodiment of the present invention. In FIG. 1, 1a, 1b, 1c,...
2n are variable gain amplifiers, 20a, 2a, 2b, 2c,.
, 20n are delay circuit blocks, 11
A and 11B are analog adders, and 12A and 12B are low-pass filters. Delay blocks 20a, 20b, 20
20n are the same, and for the delay circuit block 20a, 3aa, 3ab are sample hold circuits, 4a, 5a are A / D converters, 6a, 7a are memories, and 8a, 9a are D / A conversions. And 10a are analog subtractors, and 14a and 15a are analog switches.

First, the operation of the dual beam former will be described. At the time of the dual beam former, the analog switches 14a and 15a are respectively connected to the b side. Therefore, the sample and hold circuits 3aa,
The portion after 3ab is completely independent of two systems, and each is controlled by the timing control circuit 13.

Next, the operation of Doppler blood flow measurement will be described. Analog switches 14a and 15 for Doppler blood flow measurement
a is connected to the a side. A / D converter 4
a, the memory 6a, and the delay time of the delay circuit by the D / A converter 8a are set to the period of the transmission pulse or an integral multiple thereof. This makes it possible to detect a weak blood flow echo among strong echoes as described with reference to FIG.

As described above, according to the beamformer of the ultrasonic diagnostic apparatus according to the embodiment of the present invention, the data is encoded by the A / D converter 4, converted into an analog quantity by the D / A converter 8, and converted to an analog subtractor 10. , The difference from the input amount is obtained, and the difference output is quantized by the A / D converter 5.
By using the D converter, a dynamic range equivalent to a high bit A / D converter can be obtained, and an analog switch can be provided to operate as a dual beam former.

In this embodiment, the extraction of the blood flow echo in the ultrasonic pulse Doppler blood flow meter has been described. However, the present invention is effective even in an ultrasonic blood flow imaging apparatus based on the same principle. Needless to say.

[0019]

As is apparent from the embodiments described above, according to the present invention, by using a plurality of A / D converters having a low bit number, a blood flow signal can be obtained without the influence of strong echo on the blood vessel wall. Thus, an inexpensive ultrasonic diagnostic apparatus can be realized, and a beamformer of an ultrasonic diagnostic apparatus capable of realizing a dual beamformer with almost no change in circuit configuration by switching with an analog switch can be provided.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a beam former of a conventional ultrasonic diagnostic apparatus.

FIG. 3 is a block diagram showing a configuration of another example of a beamformer of a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 2a, 2b, 2c,... 2n Variable gain amplifiers 3aa, 3ab Sample and hold circuits 4a, 5a A / D converters 6a, 7a Memory 8a, 9a D / A converters 10a Analog subtractors 14a, 15a Analog switches

Continuation of the front page (56) References JP-A-5-137720 (JP, A) JP-A-5-137718 (JP, A) JP-A-5-137717 (JP, A) JP-A-58-146338 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) A61B 8/00-8/14 G01N 29/00-29/28

Claims (1)

(57) [Claims] A variable gain amplifier for amplifying an echo signal from a body obtained by a plurality of elements of an ultrasonic probe from a body to a predetermined magnitude; a sample and hold circuit for sampling an output of the variable gain amplifier; An A / D converter for analog-to-digital conversion of the output of the sample-and-hold circuit, a memory capable of storing the output of the A / D converter and simultaneously asynchronously reading the signal, and a digital signal for reading the signal read from the memory; In a beamformer of an ultrasonic diagnostic apparatus including a D / A converter for performing analog conversion and an analog adder for adding an analog output of the D / A converter, the sample hold is configured to obtain two delayed addition outputs. The circuit after the circuit is provided with two systems, and the output of the sample and hold circuit of the first system and the D / D of the first system are provided.
A beamformer for an ultrasonic diagnostic apparatus, comprising: a switch for taking a difference from an output of an A converter and inputting the difference to an A / D converter of a second system; and a subtractor for taking the difference.