JPH04276243A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To display a smooth spectral pattern by effectively performing average processing with simple apparatus configuration and by removing influence of speckle. CONSTITUTION:An ultrasonic diagnostic apparatus is provided with a Doppler detecting circuit 3, multipliers 5, 6, a window data output circuit 7, an FFT 8, and an average circuit 10. The multipliers 5, 6, and the window data output circuit 7 apply a plurality of different weighting processing to digital processing against one diagnostic site successively generated from the Doppler detecting circuit 3. The average circuit 10 performs average processing to a plurality of power spectral data generated from the FFT 8.

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 that obtains the power spectrum of a Doppler signal using a reflected echo signal obtained from within a living body.

0002

[Prior Art] Generally, an ultrasonic diagnostic device transmits ultrasonic waves from an ultrasonic transducer called a probe into a living body such as a human body, and analyzes reflected echo signals from within the living body. Information on internal tissue structure and blood flow is obtained.

In this type of ultrasonic diagnostic apparatus, a Doppler signal obtained by orthogonal detection of a reflected echo signal is subjected to fast Fourier transform (FFT) to obtain its power spectrum, which is displayed as blood flow information.

On the other hand, echo signals reflected from blood are mainly reflected from red blood cells. It is known that the distribution of red blood cells spreads both in time and space, and that the spread is Gaussian random. As a result, the power spectrum of the Doppler signal obtained from the reflected echo signal has
Statistical fluctuations called speckles occur.

In order to suppress this statistical fluctuation, conventionally, while creating a Doppler signal for one-line display,
Several obtained power spectra are averaged to obtain the next 1-line Doppler signal. For example, the time it takes to create a Doppler signal for one line display is 5 ms, and F
If 1 ms is required for FT calculation (128 points), 1
Five FFT calculations can be performed while creating a line Doppler signal, and conventionally, the power spectra of the results of the five FFT calculations are averaged.

[0006]

By the way, the repetition rate of the ultrasonic beam in the pulsed Doppler method is, for example, about 4 kHz, and in this case, the data input to the FFT is updated every 250 microseconds.

[0007] Therefore, only four pieces of data (1 msec ÷ 250 μsec = 4) are updated during 1 msec, which is the time required for FFT calculation. Therefore, the data for each of the five FFT operations is 4 out of 128, that is, the data update rate is approximately 3% (4÷128).
Even when averaging was performed, the results were almost the same, and we could not expect much of an effect from averaging. Therefore, it was not sufficient to remove frequency speckles, and the displayed power spectrum pattern was not smooth and difficult to see. In particular, when a unimodal Hamming window with a large weighting coefficient in the center is applied to the data, the data in the updated part will not be affected much, and the effect of averaging processing cannot be expected. In order to make this power spectrum pattern smooth, it is necessary to perform smoothing processing using a complex spatial averaging circuit on the subsequent image memory, which requires a major modification of the hardware configuration.

An object of the present invention is to provide an ultrasonic diagnostic apparatus that can effectively perform averaging processing with a simple apparatus configuration, remove the influence of speckles, and display a smooth spectral pattern.

[0009]

[Means for Solving the Problems] The ultrasonic diagnostic apparatus according to the present invention obtains blood flow information from reflected echo signals obtained from within a living body, and includes an A/D conversion means, a weighting means, and a high-speed It is equipped with a Fourier transform means and an average calculation means. The A/D conversion means sequentially converts the received analog signals obtained from the reflected echo signals into digital signals. The weighting means applies a plurality of different weighting processes to the digital signal for one diagnostic site sequentially output from the A/D conversion means. The fast Fourier transform means performs fast Fourier transform on the weighted digital signal to generate a plurality of types of power spectrum data for the diagnostic site. The average calculation means performs average processing on the plurality of generated power spectrum data.

0010

In the present invention, received analog signals obtained from reflected echo signals from inside the living body are sequentially converted into digital signals by the A/D conversion means. The weighting means then applies a plurality of different weighting processes to the digital signal for one diagnostic site that is sequentially output from the A/D conversion means. The weighted digital signal is subjected to fast Fourier transform by fast Fourier transform means. Then, a plurality of different types of power spectrum data are generated for each of the plurality of weighting processes. The plurality of generated power spectrum data are averaged by an average calculation means.

[0011] Therefore, by adding a weighting means composed of a memory or the like, the weighting process increases the data update rate of the digital signal input to the fast Fourier transform means, improves the effect of the averaging process, and improves the spec. This makes it possible to reduce costs.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the general configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. probe 1
is composed of a plurality of micro oscillators and is connected to the wave transmitting/receiving circuit 2. The transmitting/receiving circuit 2 includes a high-frequency pulse oscillator for transmitting an ultrasound beam, a receiver for receiving reflected echoes, a delay circuit for performing electronic scanning, a delay amount selection circuit, and the like. The output of the wave transmitting/receiving circuit 2 is connected to a Doppler detection circuit 3.

The Doppler detection circuit 3 is composed of a 90° phase shifter, a mixer, an A/D conversion circuit, and the like. The Doppler detection circuit 3 performs orthogonal detection and A/D conversion on the reflected echo signal from within the living body received by the wave transmitting/receiving circuit 2, and generates digital Doppler data of real and imaginary parts. Doppler detection circuit 3 is connected to buffer memory 4 . Buffer memory 4 includes Doppler detection circuit 3
The Doppler data for one line display generated in is temporarily stored. The output of the buffer memory 4 is input to multipliers 5 and 6. The multipliers 5 and 6 also receive the output of a window data output circuit 7 using memories such as ROM and DRAM, and output Doppler data from the buffer memory 4 and window data WD from the window data output circuit 7.
1 to WD4 and converts the fast Fourier transform circuit (hereinafter F
(referred to as FT).

FIG. 2 is a graph showing an example of output data from the window data output circuit 7, in which the vertical axis represents the weighting coefficient, and the horizontal axis represents the number of input data points to the FFT 8, that is, the time axis. The window data output circuit 7 outputs four types of window data WD1 to WD4 as shown in FIGS. 2A to 2D. Here, in the window data WD1, more weighting is applied to the input data input in the first half, and less weighting is applied to the data input in the latter half. Further, in the window data WD2, weighting is applied to a slightly earlier half of the input data from the center, and input data before and after it is not weighted much. Further, the window data WD3 is the window data WD2.
There is a symmetrical relationship between the window data WD
4 has a shape that is laterally symmetrical to the window data WD1.

The FFT 8 performs fast Fourier transform processing on 128 points of input data and outputs the frequency distribution (power spectrum) of the Doppler signal. The output of the FFT 8 is input to a power conversion circuit 9.

The power conversion circuit 9 calculates the power of each frequency by squaring the real part power spectrum and the imaginary part power spectrum output from the FFT 8 and adding them. The output of the power conversion circuit 9 is connected to an averaging circuit 10. The averaging circuit 10 receives four types of window data WD1 to WD output from the window data output circuit 7.
FFT8 for 4 types of input data weighted by 4
The calculation results are stored, added together, and the average spectrum of the power spectra is output. The output of the averaging circuit 10 is input to the DSC 11. DSC11
converts the obtained power spectrum signal into a television signal and outputs it to the CRT 12.

On the other hand, these constituent blocks are each controlled by a control circuit 13 including a CPU. In particular, the control circuit 13 outputs a read signal S1 to the buffer memory 4, and outputs an output signal S2 to the averaging circuit 10.

Next, the general operation of the ultrasonic diagnostic apparatus configured as described above will be explained. First, the wave transmitting/receiving circuit 2
The probe 1 is driven, and an ultrasound beam is transmitted from the probe 1 into the living body. The reflected echo signal from within the living body is received again by the probe 1 and input to the wave transmitting/receiving circuit 2. In the wave transmitting/receiving circuit 2, processing such as amplification is performed on the reflected echo signal, and the signal is sent to the Doppler detection circuit 3. The Doppler detection circuit 3 performs orthogonal detection of the obtained reflected echo signal, removes high frequency components with a filter (not shown), performs A/D conversion, and generates two digital signals: a real part and an imaginary part obtained by shifting the phase of the signal by 90 degrees. generate Doppler data.

The generated Doppler signal is temporarily stored in the buffer memory 4. The buffer memory 4 has a capacity capable of storing 128 Doppler signals for each of the real and imaginary parts. FIG. 3 is a timing chart of each signal during averaging processing of the Doppler signals stored in the buffer memory 4, and FIG.
is a flowchart showing a processing procedure for average processed values.

There are 128 Doppler data in the buffer memory 4.
When the number is stored, in step S10, the variable n is set to "1".
, the read signal S2 from the control circuit 13 becomes active (negative logic), and in step S11, the 128 Doppler data stored in the buffer memory 4 are sequentially read out. Subsequently, in step S12, a weighting process is performed in which each of the read Doppler data is multiplied by the window data WD1 output from the window data output circuit 7.

[0021] When the weighting process is completed, step S1
3, Fourier transform processing using FFT8 is performed to generate a power spectrum of weighted Doppler data. The generated power spectrum is processed in step S14.
Then, the sum of squares of the real part and the imaginary part is calculated by the power conversion circuit 9, and the power for each frequency of the power spectrum is determined. The obtained power for each frequency is stored in the averaging circuit 10 in step S15.

The averaging circuit 10 has an address for each frequency, and the power for each frequency is stored in the corresponding address. The averaging circuit 10 also has an accumulator function and adds up each input.

Subsequently, in step S16, the variable n is incremented by 1, and in step S17, it is checked whether the variable n is smaller than "4". When reading the buffer memory 4 for the first time, the variable n is smaller than "4", so "NO" is returned.
”, the process returns to step S11, and the buffer memory 4 is read out for the second time. Then, window data WD2 is output from the window data output circuit 7, and step S
A second weighting process is performed in step 12. Thereafter, the processes from step S13 to step S17 are performed, and step S
11, the processing from steps S11 to S17 is repeated, weighting processing is performed on window data WD3 and window data WD4, respectively, and the results of the four weighting processings are added up in the averaging circuit 10. When the four additions are completed, the determination in step S17 becomes "YES", and the process proceeds to step S18, where averaging processing is performed. This averaging process is started by the output of the output signal S1 from the control circuit 13,
The power stored in each address in the averaging circuit 10 is
” and prints the result.

The execution result is output to the DSC 11, and a smooth frequency spectrum subjected to averaging processing is output to the CRT 10.

As described above, in this embodiment, the smoothing effect can be obtained without significantly changing the hardware configuration by simply increasing the capacity of the memory in which window data is stored and increasing the number of address lines.

[Other Embodiments] (a) In the above embodiments, unimodal window data was used for weighting, but wavy window data such as a flat top window or bimodal window data may also be used. good.

(b) Furthermore, in the above embodiment, 128 points of Doppler data were once stored in the buffer memory and multiplied by the window data, but the present invention is not limited to this, and the multiplier and the window data output As many circuits and FFTs as there are types of window data are provided, and the Doppler data obtained by the Doppler detection circuit is processed in parallel.
You may also calculate the average of them. In this case, the time for writing and reading from the buffer memory is saved.

(c) In the above embodiment, one type of data stored in the buffer memory 4 was weighted using four types of windows, but a portion of the data stored in the buffer memory 4 (an amount equivalent to the calculation time) was weighted using four types of windows. ) are updated sequentially,
Different window processing may be applied to each updated data.

[0029]

According to the present invention, by applying a plurality of different weighting processes to the Doppler signal of one diagnostic site,
Since the update rate of the data input to the FFT increases dramatically, frequency speckles due to uncorrelated distributions of reflected echo signals can be canceled out, and the resulting power spectrum becomes smoother and less complex. A smooth and easy-to-see image can be obtained without using a spatial averaging circuit or the like.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing an example of window data of a window data output circuit.

FIG. 3 is a timing chart of each signal during averaging processing.

FIG. 4 is a flowchart showing a processing procedure during averaging processing.

[Explanation of symbols]

1 Probe 2 Transmission/reception circuit 3 Doppler detection circuit 5, 6 Multiplication circuit 7 Window data output circuit 8 FFT 9 Power conversion circuit 10 Average circuit

Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus that emits an ultrasonic beam into a living body and obtains blood flow information from reflected echo signals from the living body, wherein received analog signals obtained from the reflected echo signals are sequentially received. A/D to convert to digital signal
1 sequentially output from the converting means and the A/D converting means.
a weighting unit that performs a plurality of different weighting processes on digital signals for one diagnostic site; and a high-speed Fourier transformer that performs a fast Fourier transform on the digital signal weighted by the weighting unit to generate multiple types of power spectrum data regarding the blood flow information. An ultrasonic diagnostic apparatus comprising: a Fourier transform means; and an average calculation means for performing averaging processing on a plurality of power spectrum data generated by the fast Fourier transform means.