JPH0323052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of a Doppler signal analysis and display device used in a Doppler ultrasonic diagnostic apparatus.

(Prior art) When an ultrasonic pulse is emitted to a subject, an echo returns from a reflector, but if this reflector moves, the frequency of the received echo is different from the transmitting frequency, and the reflector is detected. The receiving frequency is higher than the transmitting frequency when moving towards the tentacle, and lower when moving away. And the frequency shift is proportional to the moving speed of the reflector. This Doppler effect can be used to determine, for example, the direction and speed of blood flowing within the heart and blood vessels. As a method, the beat frequency Δf _B is created by subtracting the frequency obtained by subtracting the offset frequency f ₁ from the sine wave f _T of the same frequency as the transmitted signal to the receiving frequency f _R for analysis.

Δf _B = f _R - (f _T - f ₁ ) = f ₁ + 2f _T Vcosθ/C ...(1) where C: Speed of sound in the medium V: Velocity of the reflector (velocity toward the probe is considered positive) ) θ: Angle between the direction of the sound wave beam and the direction of movement of the reflector Since the blood flowing through the heart and blood vessels changes its direction and speed from moment to moment, this can be measured moment by moment, and CRT It would be convenient if it could be displayed in or,
Blood flow at a given time does not flow at the same speed, but at various speeds, and especially in the case of turbulence, blood flow exists in both forward and reverse directions at the same time. Calculate this flow distribution at high speed,
A Doppler signal analysis and display device is used for real-time display on a CRT.

A fast Fourier transform (hereinafter referred to as FFT) device is used as the Doppler signal analysis and display device. When the Doppler beat signal Δf _B obtained by the Doppler device is input to this FFT device, the device calculates the flow velocity distribution and average flow velocity after AD conversion. The calculation results are converted back into analog signals and displayed on a CRT.

(Problems to be Solved by the Invention) However, general-purpose processor systems are not sufficient for real-time analysis using Doppler signal analysis and display devices.
Since it requires a considerable amount of specialized hardware, the device is large-scale and expensive.

The present invention has been made in view of the above points, and its purpose is to reduce the accuracy of real-time processing and perform precision processing not in real time, thereby reducing the need for hardware in a frequency analyzer and displaying Doppler signal analysis. The purpose is to realize the device.

(Means for Solving the Problems) The present invention solves the above problems by providing a high-speed analysis unit that coarsely performs frequency analysis calculations on reflected Doppler signal data at high speed in real time, and a frequency analysis calculation unit on Doppler signal data. frequency analysis means consisting of a precision analysis section that accurately performs the analysis at low speed; a digital scan converter consisting of a video buffer that temporarily stores the calculation results of the high-speed analysis section; and a frame memory that stores the calculation results of the precision analysis section; A waveform memory that stores reflected Doppler signal data corresponding to the image being output from the video buffer, and a precision analysis section that freezes the output image from the video buffer and causes the precision analysis section to calculate the data stored in the waveform memory at that time. The present invention is characterized by comprising a control means for outputting the image stored in the frame memory instead of the image stored in the video buffer after the calculation of .

(Function) The data of the input Doppler signal is processed in real time by a high-speed analysis unit that does not require the precision of a frequency analyzer, and is displayed on the screen on the display device, and the data is written in the waveform memory, and the display screen is changed as necessary. The frozen display screen is frozen, and the data written in the storage means is read out and subjected to precise analysis by the precise analysis section, and the frozen display screen is corrected and written using the precise analysis data.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The figure is a configuration block diagram showing one embodiment of the present invention. The reflected Doppler signal has both the i signal (in-phase) and the q signal (quadrature), but only one channel will be explained here. In the figure, 1 converts the analog Doppler signal to be analyzed into digital. The AD converters 2a, 2b, 2c, 2d, and 2e are switching circuits that operate in conjunction with control signals from the controller 3. When the switch S is on, the controller 3 operates the switching circuits 2a to 2e from the position shown in the figure to the opposite position. 4 is a frequency analyzer that analyzes the input Doppler signal and displays the output on the CRT monitor described later.
4a is WHT (Walsh Hadamard transformation) part,
4b is an FFT section. 5 is a waveform memory that stores the output of AD converter 1, and 6 is a clock oscillator 7.
a write address generator that generates a write address to the waveform memory 5 according to a clock from
A read address generator 8 generates a read address for data stored in the waveform memory 5 in response to a clock from a clock oscillator 9. 10 is a video buffer 10a for the WHT section 4a and a frame memory 1 for the FFT section 4b.
0b, its output signal is converted into an analog signal by the DA converter 11 and sent to the CRT monitor 1.
2.

Next, the operation of the circuit configured in this manner will be explained. First, during real-time operation, the switch S is in the OFF position as shown in the figure, and the switching circuits 2a to 2e are in the positions shown. Doppler signal input is AD converter 1
is converted into a digital signal by the switching circuit 2.
It enters the frequency analyzer 4 and waveform memory 5 via a.
In the frequency analyzer 4, the WHT section 4a processes the input signal in real time. WHT is a transformation that uses trigonometric functions as orthogonal functions, whereas WHT is a transformation of ±2 obtained when trigonometric functions are completely saturated.
Since the conversion is performed using a sequence of value functions, there is a lack of precision, but all calculations are only addition and subtraction, and the circuit configuration is easy and high-speed calculations are possible. Therefore, the frequency analyzer 4 can demonstrate processing power that cannot be achieved by FFT.
In practice, it can be run on rather slow hardware.
The WHT unit 4a processes a certain length section of the input Doppler signal and converts it into a frequency spectrum, and the output signal is sent to the video buffer 10a of the DSC 10.
The signal is then converted into an analog signal by the DA converter 11 via the contacts of the switching circuit 2e, and displayed on the CRT monitor 12. On the other hand, the write address generator 6 generates a write address by the clock of the clock oscillator 7 and writes the Doppler signal into the waveform memory 5. The waveform memory 5 is taken into the DSC 10,
It holds data for the section displayed on the CRT monitor 12.

When a signal of a certain length is displayed on the CRT monitor 12, or if necessary, the screen is frozen. Immediately after freezing or when a separate instruction is output, the switch S is turned on, the controller 3 is operated, the switching circuits 2a to 2e are switched, and the contacts are placed on the side opposite to the position shown in the figure. At this time, the clock from the clock oscillator 9 passes through the switching circuit 2d, causes the read address generator 8 to generate a read address, and reads the Doppler signal data stored in the waveform memory 5 during real-time operation.
The read data enters the FFT section 4b of the frequency analyzer 4 via the switching circuit 2d, where it is subjected to precise analysis processing. In this process, the previously displayed and frozen data is precisely analyzed by the FFT unit 4b, and the precisely analyzed data is sequentially transferred to the DSC1.
0 frame memory 10b, and when precise analysis is completed, the switching circuit 2e and the DA converter 11
After that, the frozen display on the CRT monitor 12 is precisely rewritten with the time and frequency axes aligned exactly. The process of performing this precise analysis and engraving is not displayed in real time, so there is some time leeway, so the FFT section does not need to be as fast as the one shown. During this time, the switching circuit 2a is cut off so that the output of the AD converter 1 does not enter the waveform memory 5. There is no problem in reading the waveform memory 5 in the forward or reverse direction.

In the case of FFT processing, direction separation was possible by performing frequency analysis on the i and q signals and then taking a linear combination, but in WHT processing, direction separation was first performed into i and q signals due to high sidelobes. It will be analyzed and processed later.

As explained above, the real-time processing and precision analysis processing are processed separately by the WHT unit, and precision analysis is performed only when necessary, reducing the need for hardware in the analyzer.

Note that the present invention is not limited to the above embodiments. In the example, the combination of high-speed processing that does not require precision and precise low-speed processing is "WHT processing - FFT processing"
However, various combinations are possible.

For example, real-time processing = FFT processing that reduces the number of data words (resolution on the frequency axis is coarser than the theoretical value considering the sampling rate of the original data), resulting in data interval thinning.Precise analysis A good combination is also a combination of processing = FFT processing that uses all data words, has the resolution on the frequency axis as the theoretical value, and does not perform data section thinning. Also, the same
Data word resolution (effective number of bits) in FFT
It is also possible to differentiate between fixed-point and floating-point numbers, whether overflow is allowed or not, etc. by using different types or using them together.

Furthermore, a combination of real-time processing = zero cross time interval histogram method or filter bank method precision low-speed processing = FFT processing is also good.

Furthermore, in the engraving process after precision processing, it would be effective to not only engrave the CRT monitor but also write the spectrum image to the striptease recorder at the same time.

(Effects of the Invention) As described in detail above, according to the present invention, accuracy can be reduced in real-time processing, so the necessity of the frequency analyzer hardware is reduced.

[Brief explanation of the drawing]

The figure is a block diagram of an embodiment of the present invention. 1...AD converter, 2a to 2e...switching circuit,
3... Controller, 4... Frequency analyzer, 4a...
WHT section, 4b...FFT section, 5... Waveform memory,
6...Write address generator, 7, 9...Clock oscillator, 8...Read address generator, 1
0...DSC, 10a...Video buffer, 10
b...Frame memory, 11...DA converter, 1
2...CRT monitor.

Claims (1)

[Scope of Claims] 1. A high-speed analysis unit 4 that roughly performs frequency analysis calculations on reflected Doppler signal data at high speed in real time, and a precision analysis unit 4b that performs frequency analysis calculations on reflected Doppler signal data precisely at low speed. a digital scan converter 10 consisting of a video buffer 10a that temporarily stores the calculation results of the high-speed analysis section 4a and a frame memory 10b that stores the calculation results of the precision analysis section 4b; The output image from the video buffer 10a and the waveform memory 5 that stores the data of the reflected Doppler signal corresponding to the image being displayed is frozen, and the precise analysis section 4b calculates the data stored in the waveform memory 5 at that time. 4b
1. A Doppler signal analysis and display device comprising a control means 3 for outputting an image stored in a frame memory 10b instead of an image stored in a video buffer 10a after completion of the calculation.