JPH07111992A - Ultrasonic diagnostic equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce image noise as much as possible. [Structure] An ultrasonic diagnostic apparatus transmits an ultrasonic signal to a living body and, when displaying tomographic image data obtained from an ultrasonic reflected signal from the living body, correlates transmission waveform information and reception waveform information by FFT. The tomographic image data is generated by the arithmetic processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus for transmitting ultrasonic transmission signals to a living body and displaying tomographic image data obtained from ultrasonic reflected signals from the living body.

[0002]

2. Description of the Related Art Ultrasonic diagnostic apparatuses used in the medical field generally display real-time tomographic data on a monitor in real time. This type of ultrasonic diagnostic apparatus includes a probe that transmits and receives ultrasonic waves, a transmission circuit that gives a drive pulse to the probe, and a reception circuit that receives and processes ultrasonic reflection signals from the living body received by the probe to obtain tomographic data. , A DSC (digital scan converter) for outputting the obtained tomographic data in synchronization with the TV synchronizing signal, and a monitor.

In this ultrasonic diagnostic apparatus, a drive circuit applies a drive pulse to a probe, and the probe emits an ultrasonic wave transmission signal for scanning the inside of a living body. Then, an ultrasonic wave reflected signal from the living body is received by the probe, and predetermined reception processing is applied to the probe to obtain tomographic data. The obtained fault data is D
It is written in the frame memory in the SC and is output to the monitor for display in synchronization with the TV sync signal.

[0004]

In such a conventional ultrasonic diagnostic apparatus, it is necessary to reduce image noise as much as possible. When noise is mixed in the image, the image becomes difficult to see. For this reason, the receiving circuit is provided with a logarithmic compression processing circuit and noise removing means such as a low-pass filter. However, even if these noise removing means are used,
Not enough noise can be removed.

An object of the present invention is to enable noise to be removed as much as possible.

[0006]

An ultrasonic diagnostic apparatus according to the present invention is an apparatus for transmitting an ultrasonic wave transmission signal to a living body and displaying tomographic image data obtained from an ultrasonic wave reflection signal from the living body. , A transmission means, a reception means, a storage means, a correlation calculation means, a tomographic image data generation means, and a display means.

The transmitting means transmits the ultrasonic transmission signal to the living body. The receiving means receives the ultrasonic reflection signal from the living body. The storage means stores the transmission waveform information of the ultrasonic transmission signal. The correlation calculation means performs a correlation calculation between the transmission waveform information stored in the storage means and the reception waveform information of the ultrasonic reflection signal received by the reception means. The tomographic image data generating means generates tomographic image data based on the calculation result of the correlation calculating means. The display means displays the tomographic image data generated by the tomographic image data generating means.

[0008]

In the ultrasonic diagnostic apparatus according to the present invention, the transmitting means transmits the ultrasonic transmission signal to the living body. Then, the receiving means receives the ultrasonic wave reflected signal from the living body. In addition, the transmission waveform information of the ultrasonic transmission signal is stored in advance in the storage means. Then, the reception waveform information of the ultrasonic reflected signal received by the reception means and the transmission waveform information stored in the storage means are subjected to correlation calculation by the correlation calculation means. By this correlation calculation processing, only the received waveform information related to the transmitted waveform information is extracted. Then, based on the calculation result of the correlation calculating means, the tomographic image data generating means generates tomographic image data, which is displayed on the display means.

Here, since the correlation calculation means performs the correlation calculation processing of the transmission waveform information and the reception waveform information, information which is not related to the transmission waveform information such as noise contained in the reception waveform information is removed. Therefore, noise and the like can be removed as much as possible.

[0010]

Embodiment 1 FIG. 1 shows a schematic configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In the figure, a probe 1 is composed of a plurality of micro-vibrators, and is connected to a transmission circuit 2 and a selector 3. The transmission circuit 2 has a high frequency pulse oscillator for transmitting an ultrasonic beam. The reception circuit 4 and the transmission waveform processing unit 5 are connected to the selector 3. The selector 3 selectively outputs the ultrasonic reflection signal received by the probe 1 to the reception circuit 4 and the transmission waveform processing unit 5, and normally outputs the ultrasonic reflection signal to the reception circuit 4 side.

The receiving circuit 4 includes a receiver for receiving and processing reflected echoes, a delay circuit for performing electronic scanning, a logarithmic compression circuit for obtaining tomographic information, and a waveform shaping circuit including a low-pass filter. An A / D conversion circuit 6 is connected to the reception circuit 4. The A / D conversion circuit 6 converts the tomographic data obtained by waveform shaping into digital tomographic data. A DSC 7 is connected to the A / D conversion circuit 6. A monitor 8 is connected to the DSC 7.

The DSC 7 has a line buffer 9, a frame memory 10 and a read circuit 11. In the DSC 7, tomographic data is written in the line buffer 9 for each scanning line, and the obtained tomographic data is arranged in the frame memory 10 in the display form of the monitor 8. The readout circuit 11 is a TV
The tomographic data stored in the frame memory 10 is read in synchronization with the synchronization signal and output to the monitor 8.

The transmission waveform processing section 5 is for generating transmission waveform information. In the transmission waveform processing unit 5, a special ultrasonic transmission signal, which will be described later, selected by the selector 3 is subjected to waveform processing to generate a transmission waveform g (t), which is subjected to fast Fourier transform (hereinafter referred to as FFT) processing. , The conjugate complex number data G ^* (ω) of the FFT result is obtained. This data G ^* (ω) is the transmission waveform information.

The transmission waveform processing unit 5 includes a transmission waveform memory 12
Are connected. The transmission waveform memory 12 stores the transmission waveform information G ^* (ω) generated by the transmission waveform processing unit 5. An arithmetic circuit 13 is connected to the transmission waveform memory 12. The arithmetic circuit 13 reads the transmission waveform information G ^* (ω) from the transmission waveform memory 12, and the reception waveform information F (ω) obtained from the reception waveform f (t) of the tomographic data stored in the line buffer 9. Perform correlation calculation with. The result of the correlation calculation is stored in the frame memory 10 in the DSC 7 in a display form.

As shown in FIG. 2, the arithmetic circuit 13 has an FF.
It has a T circuit 14 and a multiplication circuit 15. The FFT circuit 14 performs FFT processing on the received waveform for one line stored in the line buffer 9, and the conversion result F (ω)
And the FFT of the transmission waveform stored in the transmission waveform memory 12
The resulting common benefit complex number data G ^* (ω) is multiplied. The multiplication result H (ω) is given again to the FFT circuit 14 and inverse Fourier transformed to the frame memory 1 of the DSC 7.
It is output to 0. That is, in the arithmetic circuit 13, the FFT
After performing, the calculation of H (ω) = F (ω) × G ^* (ω) is performed, and the calculation result of the inverse Fourier transform is also performed.

H (t) = F ^-1 {H (ω)} = F ^-1 {F
(Ω) × G ^* (ω)} Next, the operation of the above-described embodiment will be described. In this ultrasonic diagnostic apparatus, the transmission waveform information is stored in the transmission waveform memory 12 before the diagnosis. When storing the transmission waveform information, the selector 3 is switched to the lower side (transmission waveform processing unit 5 side). In this state, for example, the probe 1 is placed on a standard specimen filled with water, a predetermined drive pulse is oscillated from the transmission circuit 2, and an ultrasonic wave is oscillated from the probe 1 toward the standard specimen. Then, the ultrasonic reflected signal is sent to the selector 3
Is given to the transmission waveform processing unit 5 via. Transmission waveform processing unit 5
Then, the transmission waveform g (t) shown in FIG. 3B is extracted therefrom, and FFT processing is further performed to obtain the transmission waveform information G ^* of the conjugate complex number data. Then, the obtained transmission waveform information is stored in the transmission waveform memory 12.

In ultrasonic diagnosis, when the apparatus is activated, a drive pulse is applied from the transmission circuit 2 to the probe 1. The probe 1 irradiates the living body with ultrasonic waves by the drive pulse. Then, the ultrasonic reflection signal from the living body is generated by the probe 1.
The signal is received by and is given to the receiving circuit 4 via the selector 3. The ultrasonic reflection signal is subjected to reception shaping processing by the reception circuit 4 to obtain tomographic data. The obtained fault data is A /
The data is converted into digital data by the D conversion circuit 6 and then converted into DSC.
7 to the line buffer 9. Then, the reception waveform f (t) on which the noise shown in FIG. 3A is superimposed is given to the arithmetic circuit 13 from the line buffer 9.

In the arithmetic circuit 13, the transmission waveform information G ^* stored in the transmission waveform memory 12 is calculated by the above-mentioned arithmetic expression ^.
(Ω) and the correlation calculation (H (ω)) between the received waveform information F (ω) obtained from the tomographic data stored in the line buffer 9.
= F (ω) × G ^* (ω)) is performed. And FIG.
As shown in (c), tomographic data h (t) obtained by inverse Fourier transforming the calculation result is stored in the frame memory 10. In the frame memory 10, the obtained tomographic data is stored in a display form according to the display mode. At this time, if the stored tomographic data is insufficient, the tomographic data is created by interpolation processing or the like. And read circuit 1
The tomographic data stored in the frame memory 10 in synchronization with the TV sync signal from 1 is read out and displayed on the monitor 8.

Since the correlation calculation processing is performed here, noise information unrelated to the transmission waveform information included in the reception waveform information is removed and the S / N ratio is improved. Also, FF
Since the correlation calculation process is performed by the T process, the correlation calculation process can be performed by the dedicated hardware, and the processing speed is increased. Second Embodiment In the first embodiment, the probe 1 emits an ultrasonic wave transmission signal having a constant cycle to the living body, but here, the probe 1 uses an ultrasonic wave whose cycle changes with time like a chirp signal. Send a send signal. In this case, the correlation calculation process can improve not only noise but also resolution. That is, when the chirp signal is used, the signal is efficiently compressed by performing the correlation calculation, and the resolution in the depth direction is improved even with the ultrasonic transmission signal having a relatively low frequency.

FIG. 4 shows a schematic configuration of the ultrasonic diagnostic apparatus according to the second embodiment. In the figure, reference numeral 1 to reference numeral 1
Up to 3 are common to the first embodiment, and the description is omitted. The transmission waveform memory 12 has two types of storage areas.
One is an area for storing the transmission waveform information generated by the transmission waveform processing unit 5. The other one is an area for storing a processing result in a winner filter processing unit described later.

A Wiener filter processing section 16 is connected to the transmission waveform memory 12. The winner filter processing unit 16 performs the following winner filter processing.

[0022]

[Equation 1] In this Wiener filter processing unit 16, the coefficient α is “1”.
When it is, it operates as a matched filter, and when the coefficient α is "0", it operates as an inverse filter. When the coefficient α is between “0” and “1”, it operates as an approximate Wiener filter. Where the coefficient α is
It is appropriately input from the outside, for example, by an operator.
In the matched filter when the coefficient α is “1”,
The resolution is not improved so much, but the noise removal performance is improved. Further, when the coefficient α is “0”, the filter becomes an inverse filter and high resolution can be obtained, but it is weak against noise. The operator can obtain an image with high resolution and reduced noise by adjusting the coefficient α while observing the displayed image.

In the transmission waveform memory 12, G ^* (ω) as the transmission waveform information and G '(W') which is the result of the Wiener processing thereof.
(Ω) and are stored. Then, the output G ′ (ω) of the Wiener filter processing unit 16 is given to the arithmetic circuit 13 and is multiplied by the Fourier transform result F (ω) of the received waveform f (t) stored in the line buffer 9, and vice versa. The conversion result h (t) is stored in the frame memory 10.

The operation here is only that the processing by the winner processing unit 16 is added to the first embodiment, and the detailed description is omitted. When storing this transmission waveform information, FIG.
When the transmission waveform h (t) whose frequency fluctuates is given, the FFT processing result is subjected to the Wiener filter processing, but G ′ (ω) is stored in the transmission waveform memory 12 as the transmission waveform information.

At the time of ultrasonic diagnosis, the arithmetic circuit 13 stores the transmission waveform information G '(ω) stored in the transmission waveform memory 12 and the line buffer 9 shown in FIG. Received waveform f of the acquired tomographic data
A correlation calculation (H (ω) = F (ω) × G ′ (ω)) with the received waveform information F (ω) obtained from (t) is performed. Then, as shown in FIG. 5C, tomographic data h (t) obtained by inverse Fourier transforming the calculation result is stored in the frame memory 10. Here, by setting the coefficient α to an appropriate value, the compression process can be performed more efficiently, and a higher resolution image can be obtained.

Other Embodiments (a) Instead of the Wiener filter treatment, other filter treatment may be performed. (B) Instead of the chirp signal, left-right asymmetric ultrasonic waves may be emitted from the probe 1. (C) In the first embodiment, the chirp signal may be transmitted. In this case, high resolution can be achieved in addition to noise reduction.

[0027]

In the ultrasonic diagnostic apparatus according to the present invention, since the correlation processing between the transmission waveform information and the reception waveform information is performed, noise can be reduced and the S / N ratio can be improved.

[Brief description of drawings]

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

FIG. 2 is a schematic block diagram of an arithmetic circuit.

FIG. 3 is a diagram showing a signal waveform.

FIG. 4 is a schematic block diagram of an ultrasonic diagnostic apparatus according to another embodiment.

FIG. 5 is a diagram showing a signal waveform when a chirp signal is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 probe 2 transmission circuit 4 reception circuit 7 DSC 8 monitor 12 transmission waveform memory 13 arithmetic circuit 14 fast Fourier transform circuit 15 multiplication circuit 16 Wiener filter processing unit

Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus for transmitting an ultrasonic wave transmission signal to a living body and displaying tomographic image data obtained from an ultrasonic wave reflection signal from the living body, wherein the ultrasonic wave transmission signal is transmitted to the living body. Transmitting means, receiving means for receiving the ultrasonic reflection signal from the living body, storage means for storing transmission waveform information of the ultrasonic transmission signal, transmission waveform information stored in the storage means and the reception Correlation calculation means for performing a correlation calculation with the received waveform information of the ultrasonic reflection signal received by the means, tomographic image data generation means for generating tomographic image data based on the calculation result of the correlation calculation means, and the tomographic image data generation means And a display unit that displays the tomographic image data generated in step 1.