JPS6264341A - How to display echo signals in ultrasound diagnostic equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method for displaying echo signals in an ultrasonic diagnostic apparatus that can diagnose tissue properties by measuring the attenuation rate of ultrasonic waves in real time. Regarding.

(B) Conventional technology and its problems Ultrasonic waves emitted into the subject are reflected and absorbed according to the acoustic impedance of tissues within the subject, so the echo signal intensity that appears as shading in the tomographic image is It reflects the internal tissue properties to some extent. However, diagnosing tissue properties based on the shading of tomographic images not only requires advanced specialized knowledge and extensive experience, but also makes it impossible to obtain quantitative information. For this reason, attempts have recently been made to measure the attenuation rate of ultrasound waves to diagnose tissue properties.

However, all conventional methods are performed in vitro or offline, and lack real-time performance. This is because the frequency of the transmitted and received ultrasonic waves is as high as about 3 MHz, and the echo signals cannot be sufficiently sampled. That is, 3.5MHz
If you use a transducer that can emit ultrasonic waves,
Since the frequency band extends to at least about 5 MHz, the sampling frequency needs to be at least 10 MHz. Therefore, in order to sample at any frequency, the entire circuitry of the device, including the A and /D converters, must be very expensive to put it into practical use.

The present invention was made in view of the second situation, and it is an object of the present invention to make it possible to diagnose tissue properties in vivo by making it possible to understand the state of attenuation of ultrasound waves inside a subject in real time. purpose.

(・＼) Means for Solving the Problems In order to achieve the above object, the present invention performs orthogonal detection on one echo signal obtained by emitting ultrasonic waves, and then performs orthogonal detection on this signal. The real part signal and imaginary part signal obtained by detection are sequentially digitized for each predetermined sample data length, and then the digitized real part signal and imaginary part signal are Fourier-transformed to obtain each sample data length. The frequency spectrum of the echo signal is calculated for each time, and the frequency change of the echo signal is displayed in correspondence with the depth within the subject based on each calculated frequency spectrum.

(d) Embodiment FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus applied to carry out the method of the present invention. In the figure, reference numeral 1 indicates the entire ultrasonic diagnostic apparatus, 2 is a transducer that transmits and receives ultrasonic waves, and 4 is a pulser that provides pulses to excite and drive the transducer 2. 6 is an amplifier that amplifies the echo signal obtained by receiving the ultrasonic echo from the transducer; 8 is a correction circuit that temporally controls the gain of the echo signal that has passed through amplifier 6; and 10 is a circuit that is 90' out of phase with each other. A reference signal generation circuit 12 generates a sine wave signal and a COS wave signal, and 12 converts the echo signal that has passed through the correction circuit 8 into a sine signal that is given from the reference signal generation circuit 10.
A first phase detection circuit 14 detects the phase of the wave signal and outputs it as a real part signal, and 14 detects the phase of the echo signal that has passed through the correction circuit 8 using the COS wave signal given from the reference signal generation circuit 10 and outputs it as an imaginary part signal. This is a second phase detection circuit that outputs.

16.18 is an A/D converter that digitizes the real part signal and imaginary part signal output from the first and second phase detection circuits 12.14, respectively, for each predetermined sample data length; 20 is each A/D converter; A Fourier transform circuit 22 that performs fast Fourier transform on the real part signal and imaginary part signal digitized by the converter 16 and 18 for each predetermined sample data length.
The Fourier transform circuit 20 calculates the absolute value from the real part data and the imaginary part data obtained by fast Fourier transform, and calculates the frequency spectrum for each sample data length of the echo signal. an arithmetic circuit that performs gamma correction, etc. to remove the influence of gain correction; 24;
26 is a monitor such as a CRT that displays the calculation results of the calculation circuit 22, a pulser 4, a correction circuit 8, and a reference signal generation circuit I.
This is a control circuit that controls each operation of the O1 arithmetic circuit 22.

Next, the method of the present invention will be explained by applying the above-mentioned ultrasonic diagnostic apparatus 1.

When transmitting and receiving ultrasonic waves, a control signal is given from the control circuit 26 to the pulser 4, the pulser 4 outputs a driving pulse, and this driving pulse is applied to the transducer 2.

As a result, the transducer 2 is excited and ultrasonic waves are emitted into the subject. This ultrasonic wave is reflected within the subject and is received by the transducer 2 again. Then,
The transducer 2 outputs an echo signal corresponding to the received ultrasonic echo as shown in FIG. and the second phase detection circuit 14 in common. At this time, a sine wave signal is sent from the reference signal generation circuit IO to the first phase detection circuit 12, and the second phase detection circuit 1
The phase of the echo signal is detected by applying a cosine wave signal to each of the echo signals.

In this way, if the echo signal is orthogonally detected, if a 3.5MHz ultrasonic wave is emitted from the transducer, 3
, an echo signal with a frequency band centered on 5 MHz and extending to about 3 MHz on both sides is converted to a signal with a frequency band of about 3 MHz on both sides centered on z, so the practical sampling frequency This makes it possible to digitize the echo signal.

Therefore, the real part signal obtained by phase detection of the echo signal in the first phase detection circuit 12 and the imaginary part signal obtained by phase detection of the echo signal in the second phase detection circuit 14 are used for each A/D.
Converters 16 and 18 sequentially digitize each predetermined sample data length T. For example, 256 points are sampled for each sample data length T. Then, the digitized real part signal and imaginary part signal are provided to the Fourier transform circuit 20, where both signals are subjected to fast Fourier transform. The output of the Fourier transform circuit 20 is the real part data and the imaginary part data of the complex signal, so its absolute value is calculated from the real part data and the imaginary part data, and then gain correction is performed in the correction circuit 8. In order to remove the influence of , gamma correction is performed to obtain the frequency spectrum. Furthermore, the peak value or average value of this frequency spectrum is determined.

The peak value or average value of the frequency spectrum thus determined corresponds to the frequency of the echo signal at that time.

Therefore, as shown in FIG. 3, the sample data length T
If the peak value or average value of the frequency spectrum of the echo signal is displayed on the monitor 24 in correspondence with the depth d inside the subject, the degree of frequency attenuation in the depth direction of the echo signal can be easily determined. It turns out.

In the above embodiment, the echo signal is sampled serially for each sample data length T, but as shown in FIG.
．． As shown in 2.3, . . . , it is also possible to partially overlap. In this way, the display becomes smooth and the resolution in the distance direction improves.

(e) Effects As described above, according to the present invention, one echo signal obtained by emitting ultrasonic waves is orthogonally detected, and then Fourier transformed for each predetermined sample data length. The frequency spectrum of the echo signal is calculated, and based on this result, the frequency change of the echo signal is displayed according to the depth inside the subject, so the attenuation of ultrasound inside the subject can be seen in real time. I understand. Therefore, tissue properties can be diagnosed in vivo.
Excellent effects such as

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an ultrasonic diagnostic apparatus applied to carry out the method of the present invention, and Fig. 2 is a waveform of an echo signal obtained by emitting ultrasonic waves and a reference signal for orthogonal detection of the echo signal. FIG. 3 is an explanatory diagram showing an example of display according to the method of the present invention, and FIG. 4 is an explanatory diagram of another echo signal sampling method. l... Ultrasonic diagnostic device, 2... Transducer,
12.14...First and second phase detection circuits, 20...Fourier transform circuit, 22... Arithmetic circuit.

Claims (1)

[Claims] (1) Perform orthogonal detection on one echo signal obtained by emitting ultrasonic waves, and then use the real part signal and imaginary part signal obtained by orthogonal detection for each predetermined sample data length. After sequentially digitizing the digitized real part signal and imaginary part signal, the frequency spectrum of the echo signal is calculated for each sample data length by Fourier transform, and based on each calculated frequency spectrum, A method for displaying an echo signal in an ultrasonic diagnostic apparatus, characterized in that a frequency change of the echo signal is displayed in correspondence with a depth within a subject.