JPH03133439A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To obtain the B mode image of high S/N and high resolution by providing a frequency analyzer for analyzing the frequency component of a pulse echo signal in order to change the passing frequency band of a band pass filter to the band of a received pulse echo signal. CONSTITUTION:In a frequency analyzer 11, the data of several pieces of scanning lines is extracted with regard to a pulse echo signal, and the signal of the extracted scanning lines is brought to FET operation. As for the result of calculated frequency analysis, the measuring part is different by each scanning line used for the operation, therefore, frequency band data of the same load of each scanning line are averaged by an adder 7, respectively, and based on the averaged frequency band data, a passing data of a band pass filter 6 is controlled. Subsequently, to the band pass filter 6 whose passing band is set to the band of the pulse echo signal, a pulse echo signal is inputted from a pre-amplifier 5 and passes therethrough, by which a noise component except a signal band is filtered, and the S/N is improved. The pulse echo signal from which noise component is eliminated is inputted as a luminance signal to a CRT 8 through a log amplifier 7, and displayed as a B mode image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus used to obtain a B-mode diagnostic image of a subject by pulse echo method.

Conventional technology It has been well known that the higher the frequency of ultrasound waves, the greater the attenuation, which is a frequency-dependent attenuation. Therefore, the pulse echo signal from the living body has fewer high-frequency components as the reflection position gets deeper, and the apparent
The energy of the pulse echo signal appears to have shifted to the lower frequency side. Conventionally, even with this frequency-dependent attenuation,
As an ultrasonic diagnostic device that can maintain good image resolution in both near and far ranges, a dynamic filter method is used, for example, as described in Japanese Patent Laid-Open No. 100050/1983. The configuration is known.

Hereinafter, the above conventional example will be explained with reference to FIG. 2. In Fig. 2, 1 is an array transducer, which consists of ultrasonic transducers made of piezoelectric ceramic material such as PZT and arranged in an array, and emits ultrasonic pulses and receives pulse echo signals. do. 2 is a scanner, 3
is a transmitting/receiving circuit which generates a driving signal for the array transducer 1 and converts the pulse echo signal received by the array transducer 1 into an electrical signal. Reference numeral 4 denotes a transmission trigger generation circuit, which also generates a trigger signal for the transmission/reception circuit 3 to generate a drive signal. 5 is a preamplifier (preamplifier) that amplifies the received signal output from the transmitter/receiver circuit 3, 6 is a bandpass filter whose passband is set to the pulse echo signal band, and 7 is a log that outputs the received signal as a luminance signal. An amplifier (logarithmic amplifier); 8, a CRT for displaying ultrasonic tomographic images; 9, a scanning circuit for controlling scanning of the scanner 2 and 0RT8; 10, controlling the transmission trigger generation circuit 4, bandpass filter e, and scanning circuit 9; It is a control circuit.

The operation of the above configuration will be described below.

The array transducer 1 is synchronized with a trigger signal generated by a transmission trigger generation circuit 4, is excited by a drive signal from a transmission/reception circuit 3 transmitted via a scanner 2, and transmits constant ultrasonic pulses to a living body, which is a subject. Send at regular intervals. A pulse echo signal from a living tissue is received by an array transducer 1, passed through a scanner 2, converted into an electrical signal by a transmitting/receiving circuit 3, amplified by a preamplifier 5, and inputted to a bandpass filter 6. The passband characteristic of the bandpass filter 6 is controlled by the control circuit 1°, and it passes only the band of the received pulse echo signal and removes noise outside the band of the received signal.
/N is improved.

This pulse echo signal is passed through the log amplifier 7 and 0RT8
can be input as a luminance signal to display a B-mode image.

Problems to be Solved by the Invention However, in the conventional dynamic filter method described above, the characteristic control of the bandpass filter 6 by the control circuit 1o is performed only based on the passage of time. If the attenuation characteristics of living tissues are the same for all tissues, there is no problem with control based only on the passage of time, but attenuation characteristics vary depending on each part of the living tissue, such as muscle, fat, kidney, liver, etc. Changes to Therefore, it is impossible to adapt to the state where the signal energy component of the pulse echo signal decreases due to attenuation by controlling the bandpass filter 6 based only on the passage of time. As a result, the passband characteristics of the bandpass filter 60 and the signal component band of the pulse echo signal do not match, and not only is it not possible to obtain a sufficient noise removal effect, but conversely the S/N ratio is degraded, and the high-resolution B mode There was a problem in that it was not possible to obtain images.

The present invention solves the problems of the prior art as described above, and no matter how much attenuation occurs in any tissue, the passband characteristics of a bandpass filter can be changed from a short distance to a long distance from the signal component band of a pulse echo signal. Ultrasound diagnostics that allows the bandpass filter to be set to always have the optimum band characteristics, and therefore to obtain high-resolution B-mode images with a high S/N ratio. The purpose is to provide a device.

Means for Solving the Problems The technical solution of the present invention for achieving the above object is as follows:
The device is equipped with a frequency analyzer that analyzes the frequency components of the pulse echo signal in order to change the pass frequency band of the pan-pass filter to the band of the received pulse echo signal.

Therefore, according to the present invention, the frequency components of the received pulse echo signal are analyzed by a frequency analyzer, and based on the analysis results, the pass frequency band of the bandpass filter is controlled so that only the pulse echo signal components are passed. By doing so, noise components included in the pulse echo signal can be removed.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing an ultrasonic diagnostic apparatus in one embodiment of the present invention.

In this embodiment, the same parts as those in the conventional example described above are given the same reference numerals, and the explanation thereof will be omitted, and the different configuration will be explained. The feature of this embodiment is that, as shown in FIG. 1, the pulse echo signal of each scanning line constituting the B-mode image amplified by the preamplifier is sampled in time series in correspondence with the distance. A frequency analyzer 11 that analyzes the frequency components of this sampled signal, and an adder that is controlled by the control circuit 10 and averages the frequency band data of the same depth of each scanning line to control the passband of the bandpass filter 60. 12 are provided.

The operation of the above configuration will be described below.

The array transducer 1 is synchronized with a trigger signal generated by a transmission trigger generation circuit 4, is excited by a drive signal from a transmission/reception circuit 3 transmitted via a scanner 2, and transmits constant ultrasonic pulses to a living body, which is a subject. Send at regular intervals. A Nohalus echo signal from a living tissue is received by an array transducer 1, passed through a scanner 2, converted into an electrical signal by a transmitter/receiver circuit 3, and amplified by a preamplifier 5. The output of the preamplifier 6 is input to a bandpass filter 6 and a frequency analyzer 11. The frequency analyzer 11 performs frequency analysis on the pulse echo signal. There are various methods for frequency analysis, and any method may be used, but one of them is FF T (Fast F
There is an operation method (Transformation). In order to perform the FFT algorithm, it is first necessary to convert the pulse echo signal into a digital signal. According to Nyquist's sampling theorem, the sampling frequency of this A/D conversion must be at least twice the highest frequency component of the signal, and the frequency of ultrasound used in ultrasound diagnostic equipment is usually 2 to 7. Considering that the frequency is .5 MHz, a frequency of about 20 MHz is required as the sampling frequency for A/D conversion. If the F'FT calculation is performed using 128 points of data, the time required for sampling is 6.4 μsec, the frequency resolution of FFT is 156.25 ktlz, and the resolution converted to distance on the image is 4.93 sn. Become. Microcomputer or DS as a processor for FFT calculation
If it is performed using P, etc., the calculation time for 1280F'FT calculation is 1 to 5 m5 ec, and even if the FFT calculation is configured with hardware or a processor dedicated to FFT calculation is used, it takes 60 to SOO μsec.

calculation time is required. Therefore, it is understood that it is impossible to perform real-time calculations using all data of all scanning lines constituting a B-mode image. But at least 1
Since data for controlling the bandpass filter 6 cannot be obtained unless the data of the scanning lines are calculated, data of several scanning lines are extracted 1, and the signals of the extracted scanning lines are subjected to FFT calculation. The number of scanning lines to extract depends on values such as the FFT calculation time, the number of data points used for FF'T calculation, the image frame rate, the A/D conversion sampling rate, and the center frequency of the ultrasonic pulse. Determined comprehensively. Since the frequency analysis results calculated in this way differ in the measurement area depending on each scanning line used in the calculation, the frequency band data of the same depth of each scanning line is averaged by an adder 7. The passband of the bandpass filter 60 is controlled based on the frequency band data obtained.

Then, the pulse echo signal is inputted from the preamplifier 5 to the band pass filter 6 whose pass band is set to the pulse echo signal band, and passes through it, thereby filtering out noise components outside the signal band and improving the S/N. do. The pulse echo signal from which the noise component has been removed is input as a luminance signal to the CRT 8 via the log amplifier 7 and displayed as a B-mode image.

Therefore, this B-mode image is a good image at any depth and in any biological tissue.

Effects of the Invention As described above, according to the present invention, the frequency components of the received pulse echo signal are analyzed by a frequency analyzer, and based on the analysis results, the frequency components of the received pulse echo signal are passed through a bandpass filter so that only the pulse echo signal components are passed. By controlling the frequency band, it is possible to remove noise components contained in the pulse echo signal. Therefore, good images with high S/N and high resolution can be obtained over the entire diagnostic region of any living tissue.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram showing a conventional ultrasonic diagnostic apparatus. DESCRIPTION OF SYMBOLS 1...Array transducer, 2...Scanner, 3...Transmission/reception circuit, 4...Transmission trigger generation circuit,
6...Preamplifier, 6...Band pass filter, 7
...Log amplifier, 8...CRT, 9...Scanning circuit, 1o...Control circuit, 11...Frequency analyzer, 12
...adder.

Claims (1)

[Claims] An ultrasonic diagnostic apparatus comprising a frequency analyzer that analyzes frequency components of the pulse echo signal to change the pass frequency band of the bandpass filter to the band of the received pulse echo signal.