JP2991212B2 - Ultrasonic medium characteristic value measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 【Overview】

A method and a device for quantitatively measuring the acoustic characteristic value of an inhomogeneous medium such as a living body using an ultrasonic pulse. The analysis permission signal is set to “0” in all scanning lines where an unsteady signal exists, and the medium characteristic is set. It is an object of the present invention to provide an ultrasonic medium characteristic value measuring method and apparatus capable of improving the accuracy of a value, transmitting an ultrasonic pulse to a medium, receiving a reflected wave thereof,
An ultrasonic medium characteristic value measuring method for analyzing a received echo signal and measuring an acoustic characteristic of a medium, wherein a received echo obtained by each scanning line is separated into a stationary signal and a non-stationary signal, and a binary result is added to the separated result. A signal is provided and stored for at least one frame as matrix information in which each scanning line corresponds to the scanning beam depth. Then, the storage result is read out in the scanning line direction, and the scanning beam depth corresponding to the read position is read out. The signal region indicating the presence of the non-stationary signal is expanded by an amount corresponding to the beam width in the range, and in the expansion result, only the received echo signal in which the presence of the stationary signal is recognized is analyzed. An unsteady signal is detected from the received echo in a device that transmits the sound wave pulse to the medium, receives the reflected wave, and analyzes the received echo signal to measure the acoustic characteristics of the medium. Means for recording at least one frame of the unsteady signal detection result, means for reading out the recorded unsteady signal detection result in the scanning direction, means for enlarging a portion determined to be the unsteady signal, There are means for recording, in the scanning direction, an unsteady signal detection result obtained by enlarging the portion determined to be a signal, and means for reading out the unsteady signal detection result obtained by enlarging the recorded unsteady signal to the depth direction. And configure.

[Industrial applications]

The present invention relates to an ultrasonic medium characteristic value measuring device that quantitatively measures using an ultrasonic pulse. A so-called ultrasonic echo diagnostic device that transmits an ultrasonic pulse to a living body and visualizes the internal structure of the living body from a reflected wave, such as a radar, is widely used. However, there is a strong demand for quantitatively measuring characteristic values such as an acoustic attenuation coefficient, a reflection coefficient, an acoustic impedance, and a non-linear propagation coefficient in order to indicate the quality of a living tissue (lesion status). In obtaining these characteristic values, a reflected wave having a large amplitude particularly returning from the wall of a blood vessel or an organ (hereinafter, referred to as “specular echo”).
A large error is caused by an unsteady signal such as a reflected wave having a small amplitude (hereinafter, referred to as “low echo”) returning from the inside of the blood vessel. Therefore, when calculating the characteristic value, it is necessary to perform the calculation while excluding such specular echo and low echo.

[Prior art]

Applicant first removed the non-stationary signal from the received echo,
An ultrasonic medium characteristic value measuring device capable of calculating the attenuation coefficient slope β has been proposed (see Japanese Patent Application Laid-Open No. Sho 63-105742). FIG. 6 shows an example of the device proposed here. The induction amount calculation circuit 7 calculates the logarithmic envelope of the echo signal, the logarithm of the envelope of the echo signal, or the derivation of the instantaneous frequency and the instantaneous spectral moment from the echo signal. After calculating the amount, the non-stationary signal is detected by the weight function calculating circuit 22, the echo signal of the portion detected as the non-stationary signal is removed, and the weighted averaging circuit 8 performs the averaging process.
The β value was obtained by a calculation circuit. As a weight function when a CFAR output calculation circuit is used as the weight function calculation circuit 22, for example, “1” is output for a signal within the allowable range of the CFAR output, and “0” is output for signals in the other range. A signal having a binary output that outputs "" is used, and the output value is used as an analysis permission signal to calculate a weighted average value.

[Problems to be solved by the invention]

However, in the above-described conventional example, since the thickness of the ultrasonic beam itself is generally thicker than the adjacent scanning line, not only the scanning line on the point where specular echo or low echo occurs, but also the scanning line in the vicinity thereof However, since the amplitude increases or decreases to such an extent that it cannot be detected, there is a problem that an error occurs in the characteristic value finally obtained. SUMMARY OF THE INVENTION The present invention has been made to address the above problems, and it is an object of the present invention to improve the accuracy of a medium characteristic value by setting an analysis permission signal to "0" in all scanning lines where a specular echo or a low echo exists. It is an object of the present invention to provide an ultrasonic medium characteristic value measuring device that can perform the measurement.

[Means for Solving the Problems]

FIG. 1 shows a principle diagram of the present invention. An unsteady signal detecting means 1 for detecting an unsteady signal from a received echo, a recording means 2 for recording at least one frame of the unsteady signal detection result, A reading means 3 for reading out the unsteady signal detection result in the scanning direction; an enlarging means 4 for enlarging the area of the unsteady judgment signal; a recording means 5 for recording the enlarging judgment result in the scanning direction; And reading means 6 for reading in the vertical direction. Further, the means for enlarging the portion determined as the unsteady signal may include means for changing the number of scanning lines to be enlarged according to the depth.

[Action]

Based on the above configuration, in the present invention, the non-stationary signal in the received echo obtained by each scanning line is separated by the non-stationary signal detecting means 1, and a binary signal is assigned according to the state, and the non-stationary signal is assigned. The detection result is output to the recording unit 2. The unsteady signal detection result S1 is composed of “0” indicating the presence of the unsteady signal and “1” indicating the presence of the steady signal, and only the received echo information corresponding to the steady signal is the data to be analyzed by the calculation circuit or the like at the subsequent stage. Used as a specular echo,
Alternatively, errors are prevented from being mixed into the analysis result due to the presence of low echo or the like. The output from the unsteady signal detection means 1 is output as a bit string indicating the mixing time of the unsteady signal based on the position of the unsteady determination signal "0", and is stored by the recording means 2 for at least one frame. The bit matrix stored in the recording means 2 is read by the reading means 3 in the scanning direction. The bit string read by the reading means 3 is a bit string indicating a signal state of a reception echo from a portion at the same depth from the body surface obtained by a plurality of scanning lines. The signal detection result is determined based only on each scanning line information, and does not take into account the influence of the ultrasonic beam in the width direction. That is, although the signal does not exist on the beam scanning line, the non-stationary signal detection means does not exist even for a received echo including a reflected echo component from a blood vessel wall or the like due to the spread of the beam in the width direction. Those that fall within the determination range of 1 are in the state of the steady-state determination signal “1”, and are used as analysis data, causing an error in the calculation result in the subsequent calculation circuit or the like. The enlarging means 4 avoids mixing of the error due to the spread of the beam width by enlarging the unsteady state determination signal area, and the area of the unsteady state determination signal includes a beam known in advance with respect to the beam depth. It is enlarged in the range corresponding to the width. The enlargement determination result obtained as described above is recorded on the recording means 5 in the scanning line direction, and is read out by the reading means 6 as an analysis permission signal in the depth direction. The analysis of the reception beam is performed by the calculation circuit and the like. As a result, the analysis permission signal can be set to “0” in all the scanning lines where specular echo and low echo exist, and accurate analysis is performed.

【Example】

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 shows an embodiment of the present invention, in which the amount of induction of the logarithm of the logarithm of the echo signal, the logarithm of the envelope of the echo signal, or the instantaneous frequency and the instantaneous spectral moment is calculated by the induction amount calculation circuit 7 from the echo signal. Is calculated, an averaging circuit 8 performs a process, and a β calculation circuit 9 calculates a β value. The averaging process is performed with reference to the analysis permission signal so that the calculation result by the β calculation circuit 9 does not include an error due to the presence of an unsteady signal such as a specular echo. In this embodiment, the unsteady signal is detected by using a CFAR processing system as shown in FIG. That is, first, the echo signal is passed through a logarithmic amplifier 10 and then output to an output envelope detection circuit 11 to obtain a signal equivalent to the logarithm of the envelope. The average is obtained, and a signal (logarithmic CFAR output) obtained by subtracting the short-time average of itself from the logarithm of the envelope by the subtraction circuit 15 is obtained. This output is input to two comparators 16 and 17. Two comparators 16,
17 sets the upper and lower limits of the allowable CFAR output. When the CFAR output is larger than the limit value, it outputs "1", and when it is smaller, it outputs "0" and sets the upper limit value.
The output of the NOT circuit 18 passes the output of the NOT circuit 18 and the output of the NOT circuit 18 and the output of the comparator 16 for which the lower limit is set.
Thus, the non-stationary signal detection means 1 which outputs the steady-state determination signal "1" only when the CFAR output is between the upper limit and the lower limit is configured. As shown in FIG. 1, the steady state determination signal and the unsteady state determination signal generated as described above are recorded in the recording unit 2 for at least one frame for each scanning line, and are read out in the scanning line direction. . As shown in FIG. 4, the expanding means 4 comprises a plurality of flip-flops FF1, FF2,... Synchronized with the clock CK, a gate circuit 20, and a ROM 21, and operates as follows. That is, the gate circuit control signal in consideration of the beam width at the depth is stored in the ROM 21 for the address corresponding to the depth. When the information is input to the ROM 21, the beat circuit control signal stored at the address corresponding to the bit string is called and output. On the other hand, the gate circuit 20 selects appropriate flip-flops FF1, FF2,... Based on the output from the ROM 21 as shown in FIG. The output is obtained by taking a logical sum, and at or near the beam convergence depth, the output of one or a small number of flip-flops is logically ORed to perform an operation for enlarging a small unsteady decision signal. At a position distant from the beam focusing point, the logical sum of a large number of flip-flop outputs is obtained and a large enlarging operation is performed. The unsteady determination signal expanded in this manner is stored in the scanning line direction, read out as an analysis permission signal in the depth direction by the reading means 6, processed by the averaging circuit 8, and processed by the β calculation circuit 9. A value is calculated.

【The invention's effect】

As is clear from the above description, according to the present invention, the analysis permission signal can be set to “0” in all the scanning lines where specular echo and low echo exist, so that the reliability of the analysis result can be improved. Can be.

[Brief description of the drawings]

 FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing a non-stationary signal detecting means, FIG. FIG. 6 is a diagram showing a function table of a gate circuit, and FIG. 6 is a diagram showing a conventional example. In the figure, 1 is means for detecting an unsteady signal, 2 is recording means, 3 is reading means, 4 is enlarging means, 5 is recording means, and 6 is reading means.

Claims (2)

(57) [Claims] An apparatus for transmitting an ultrasonic pulse to a medium, receiving a reflected wave thereof, analyzing a received echo signal and measuring an acoustic characteristic of the medium, detecting a non-stationary signal from the received echo, Means for recording at least one frame of the unsteady signal detection result, means for reading out the recorded unsteady signal detection result in the scanning direction, means for enlarging a portion determined to be the unsteady signal, Means for recording, in the scanning direction, the unsteady signal detection result obtained by enlarging the portion that has been enlarged, and means for reading out the unsteady signal detection result obtained by enlarging the portion determined to be the recorded unsteady signal in the depth direction. Ultrasonic medium characteristic value measuring device. 2. The ultrasonic medium characteristic value according to claim 1, wherein the means for enlarging the portion determined as the unsteady signal includes means for changing the number of scanning lines to be enlarged according to the depth. measuring device.