JPH05137718A - Beam former of ultrasontic diagnostic device - Google Patents

Abstract

PURPOSE:To provide the beam former of an ultrasonic diagnostic device which can obtain a satisfactory blood flow signal by using an A/D converter of a low bit. CONSTITUTION:The beam former is constituted by providing a circuit for delaying an output of an A/D converter 6a by a transmitting pulse interval portion by a memory 8a, returning it to an analog signal by a D/A converter 10a, and feeding it back to an output of a sample holding circuit 3a in an analog adder 4a provided between the sample holding circuit 3a and the A/D converter 6a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam former for 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 for improving the S / N ratio by adding echo signals obtained from a plurality of elements after delaying the distance from each element is used in many ultrasonic diagnostic apparatuses. It is used in a device and its method is well known.

An analog delay line using LC is often used as a delay means in a beam former.
However, analog delay lines have limited frequency characteristics,
This is a problem when a large delay time is required, especially at high frequencies. Further, there is a problem that there is variation in delay time between individual delay lines and taps, and switching is required by a switch when performing dynamic focusing, and noise is generated at the time of switching.

Then, what was conceived is a digital delay line including an A / D converter and a memory. FIG. 2 shows a conventional example of a beam former using a digital delay line.
In FIG. 2, 101a, 101b, 101c, ... 101
n is an element, 102a, 102b, 102c, ... 1
02n is a variable gain amplifier, 103a, 103b, 103
103n are A / D converters, 104a, 104b,
104n are memories (hereinafter, referred to as memories) in which writing and reading can be executed asynchronously at the same time.
105n is a D / A converter, 106 is a timing control circuit, 107 is an analog adder, and 108 is a low-pass filter. The operation of this device will be described below.

Electrical pulses generated by a pulse generator circuit (not shown) are elements 101a, 101b, 1
01c, ..., 101n, which are converted into ultrasonic waves and radiated into the body, the radiated signals are reflected by portions having different acoustic impedances, and the elements 101a, 101
b, 101c, ... 101n, and converted into an electric signal. Elements 101a, 101b, 101c ... 101
The echo signal received at n is the variable gain amplifier 102.
a, 102b, 102c, ... 102n, after being amplified to an appropriate size, A / D converters 103a, 103b, 10
Converted into digital signals at 3c, ... 103n. The digitized echo signal is stored in the memories 104a and 104.
b, 104c, ... 104n, but memory 1
04a, 104b, 104c, ... 104n read /
Since the writing can be executed at the same time and at an asynchronous timing, the already written data is read out while the data is being written, and the D / A converters 105a, 105b, 105
, 105n can be output as an analog signal. Therefore, if the timing control circuit 106 controls the conversion timing of the A / D converter and the D / A converter and the memory write / read timing, the delay time can be freely controlled. In this way, the elements 101a, 101b, 101
The echoes obtained at c, ..., 101n are delayed and added by the analog adder 107. The output of the analog adder 107 cuts the harmonic component generated by the conversion to the digital signal in the preceding stage,
It passes through the low-pass filter 108.

FIG. 3 shows another conventional example of a beamformer using a digital delay line. In FIG. 3, 101
a, 101b, 101c, ... 101n are elements, 1
02a, 102b, 102c, ... 102n are variable gain amplifiers, 103a, 103b, 103c, ... 103n are A /
104n are memories for which writing and reading can be simultaneously and asynchronously executed, 115a, 115b, 115c, ... 115p are digital adders, and 106 is a timing control circuit. The adders 115a, 115b, 115c ... 115p are arranged in a so-called "tournament" form. In this example, compared to the above-mentioned example, a digital adder is used as it is without using a D / A converter, and addition is performed using a digital adder.

[0007]

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 bloodstream. Therefore, for example, in a Doppler blood flow meter, it is necessary to secure a dynamic range capable of receiving a weak echo of blood flow without saturating such a strong echo, but in a digital beam former,
An A / D converter having a large number of bits is required to secure the dynamic range. However, A with many bits
There is a problem that the / D converter is expensive.

The present invention solves this problem, and an object of the present invention is to provide a beam former for a low-cost ultrasonic diagnostic apparatus using an A / D converter with a low number of bits.

[0009]

In order to achieve the above object, the present invention has a structure in which a second memory and a second D / A converter are used to feed back to the output of the sample hold circuit.

[0010]

According to the present invention, the low bit number A
A wide dynamic range can be secured by using the / D converter.

[0011]

1 is a block diagram of a beam former of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In FIG. 1, 1a, 1b, 1c ... 1n are elements of a probe, 2
a, 2b, 2c, ... 2n are variable gain amplifiers, and 20a, 2
20n are delay circuit blocks, 11 is an analog adder, 12 is a low-pass filter, and 13 is a timing control circuit. Delay circuit blocks 20a, 20
The contents of b, 20c, ..., 20n are all the same. Regarding the delay circuit block 20a, 3a is a sample hold circuit, 4a is an analog adder, 5a is an amplifier for satisfying the system stability condition, and 6a is A / D conversion. , 7a and 8a are memories, and 9a and 10a are D / A converters.

The delay circuit block 2 different from the conventional example will be described below.
The operation within 0a will be described. A feedback circuit for returning to the analog adder 4a via the output memory 8a of the A / D converter 6a and the D / A converter 10a is included. First, the operation excluding this feedback portion will be described.

The echo signal obtained by the element 1a is
The sample hold circuit 3a is passed through the variable gain amplifier 2a.
Sampled at. The output of the sample hold circuit 3a is input to the analog adder 4a.
Since it is assumed that the converter 10a is not operating, the input from the D / A converter 10a is 0, and the output of the adder 4a is equal to the input from the sample hold circuit 3a. This output is multiplied by k in the amplifier 5a and converted into a digital signal in the A / D converter 6a. The digitized signal is input to the memory 7a, read according to the necessary delay time, and converted into an analog signal by the D / A converter 9a. This operation is the same as the first conventional example shown in FIG.

Next, a state in which the feedback portion operates will be described. The output of the A / D converter 6a is input to the memory 7a and also to the memory 8a. Memory 8a
Is used to delay the signal, and the delay amount is equal to the interval between one transmission pulse and the next transmission pulse, or an integral multiple thereof. After undergoing such a delay, the signal becomes D /
It is converted into an analog signal by the A converter 10a and input to the adder 4a. In the Doppler blood flow meter, since the position of the beam is not changed unlike the B mode scan,
The two inputs of the adder 4a are echo signals of the same site in the living body for different transmission pulses. That is, due to this feedback, a signal having a small change such as a blood vessel wall has a large attenuation, and a signal having a large change such as a blood flow has a small attenuation. Thus, the echo of the blood vessel wall having a large amplitude is attenuated in the output of the A / D converter 6a, and the echo of the blood flow having a small amplitude can be extracted. As described above, according to the beam former of the ultrasonic diagnostic apparatus of the embodiment of the present invention, since the memory 8 and the D / A converter 10a are used to feed back to the input, the low bit A / D converter is used. High bit A / D
Similar to the use of the transducer, the dynamic range can be expanded, the echo of the blood vessel wall with large amplitude can be attenuated, and the echo of blood flow with small amplitude can be extracted.

In this embodiment, the extraction of the blood flow echo in the ultrasonic pulse Doppler blood flow meter has been described, but the present invention is also effective in an ultrasonic blood flow imaging apparatus based on the same principle. Needless to say.
Further, in this embodiment, the method of adding delayed signals by analog is described, but it is obvious that the method of digitally adding can also be realized.

[0016]

As is apparent from the embodiments described above, according to the present invention, the use of the low bit number A / D converter can
It is possible to obtain a blood flow signal without the influence of a strong echo of the blood vessel wall, and it is possible to provide a low-cost beamformer for an ultrasonic diagnostic apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram of a beam former 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 the configuration of another example of the beam former of the conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 4a Analog adder 5a Amplifier 8a Memory 10a D / A converter

Claims (2)

[Claims] 1. A sample hold circuit for sampling echo signals from the body obtained by a plurality of elements of an ultrasonic probe, and an analog output of the sample hold circuit.
An A / D converter for digital conversion, a first memory that can asynchronously read at the same time while storing the output of the A / D converter, and digital-analog conversion of a signal read from the second memory In a beamform of an ultrasonic diagnostic apparatus including a first D / A converter and an analog adder that adds analog outputs of the first D / A converter, the output of the A / D converter is stored. A second memory and a second D / A converter are included to form a delay circuit that is an integral multiple of the transmission pulse interval, and the output of the second D / A converter is subtracted from the output of the sample hold circuit. A beamformer for an ultrasonic diagnostic apparatus, comprising: a subtracter for adjusting the gain and an amplifier for adjusting a gain between the subtractor and the A / D converter. 2. A sample and hold circuit for sampling echo signals from the body obtained by a plurality of elements of an ultrasonic probe, and an analog output for the sample and hold circuit.
An A / D converter for digital conversion, a first memory that can simultaneously and asynchronously read while storing the output of the A / D converter, and a digital that adds signals read from the first memory In a beamform of an ultrasonic diagnostic apparatus including an adder, a second memory that stores the output of the A / D converter and a delay circuit that includes the second D / A converter and is an integral multiple of a transmission pulse interval are provided. A subtractor for subtracting the output of the second D / A converter from the output of the sample and hold circuit, the subtractor and the A / D
A beamformer for an ultrasonic diagnostic apparatus having an amplifier for adjusting a gain between transducers.