JP3078569B2 - Ultrasound diagnostic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an ultrasonic diagnostic apparatus that corrects phase distortion of an ultrasonic pulse based on non-uniformity of sound velocity in a subject.

(Prior Art) In a conventional ultrasonic diagnostic apparatus, an ultrasonic echo detected by focusing a transmission ultrasonic pulse on a certain region in a subject using a probe in which many transducers are arranged in an array. 2. Description of the Related Art An ultrasonic image is reconstructed based on a signal and displayed on a display.

Here, various tissues are present in the body, and the sound speed of these tissues with respect to ultrasonic waves is not uniform. For this reason, a phase distortion is generated in the ultrasonic pulse based on the non-uniformity of the sound velocity in the body, thereby deteriorating the image quality. It is necessary to correct this phase distortion.

For this reason, conventionally, the ultrasonic pulse transmitted from the probe is concentrated on a certain region in the subject, and an ultrasonic echo signal, which is a reflected wave from a small scattering group in the vicinity, is obtained for each transducer in the receiving port, A cross-correlation function is calculated based on a signal between at least two transducers of the reception transducer group, and phase distortion in the propagation time of the ultrasonic pulse caused by the non-uniformity of the speed of sound in the subject is detected and corrected. Such a method is performed.

(Problems to be Solved by the Invention) The conventional ultrasonic diagnostic apparatus has the following problems.

In order to detect the phase distortion of an ultrasonic pulse, an echo signal from the inside of the subject is required, but a part where the echo signal such as a gallbladder or a blood vessel does not return inside the body (referred to as a structure).
, The phase distortion may not be detected.

It has been reported that the phase distortion can be detected when the echo signal consists only of the reflected component from the small scatterer group (called speckle). Therefore, there is a possibility that a means for removing is required, or sufficient detection cannot be performed.

The present invention has been made in view of the above problems, and has an ultrasonic diagnostic apparatus capable of correcting a phase distortion of an ultrasonic pulse based on non-uniformity of a sound velocity in a body even when a structure exists. The purpose is to provide.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention focuses a transmission ultrasonic pulse on a certain region in a subject and reflects the pulse from a small scatterer group in the vicinity thereof. Incoming ultrasonic echoes are received for each transducer, and phase distortion between the ultrasonic echo signals caused by non-uniformity in the subject is corrected based on the ultrasonic echo signals output from each transducer. A correction value for performing the cross-correlation processing, and based on this correction value, in an ultrasonic diagnostic apparatus that corrects at least one of the transmission delay characteristic and the reception delay characteristic, performs a histogram analysis of the intensity of the ultrasonic echo signal. A means for determining whether or not the phase distortion correction value is valid based on the analysis result is provided.

(Operation) For example, a histogram analysis of the intensity of the ultrasonic echo signal is performed, and based on the analysis result, it is determined whether or not the correction value of the phase distortion of the ultrasonic pulse is valid. By correcting the phase distortion in this manner, even when a structure exists in the ultrasonic transmission region, the phase distortion of the ultrasonic pulse based on the non-uniformity of the sound velocity in the body can be corrected.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a probe in which a number of transducers 1a, 1b, 1c,. To transmit an ultrasonic pulse and receive the reflected ultrasonic echo signal. In the body of the subject 2, for example, the abdominal wall 3, the liver 4,
Blood vessels 5 and gallbladder 6 are present. The blood vessel 5 and the gallbladder 6 constitute a structure that does not reflect ultrasonic echo signals. 7
Is an ultrasonic beam transmitted from the probe 1 so that the ultrasonic pulse is focused on a predetermined area. 9 is probe 1
A pulser 10 for driving the ultrasonic pulse transmitted from the probe 1 to give a desired delay characteristic, and a rate pulse generator 11 for generating a rate pulse (reference signal).

Reference numeral 12 denotes a preamplifier for amplifying the ultrasonic echo signal received by the probe 1, and reference numeral 13 denotes a reception delay circuit for giving a desired delay characteristic to the ultrasonic echo signal. Reference numeral 14 denotes a phase distortion detection circuit that detects phase distortion from the ultrasonic echo signal, and 15 denotes an addition circuit and an envelope detection circuit that perform phasing addition of the received echo signal for each transducer and detect an echo component. 16 is CPU
(Central processing unit) controls the overall control operation.
Reference numeral 17 denotes a DSC (Digital Scan Converter) for converting an ultrasonic echo signal into a TV scanning system, which has an A / D converter 18 and a memory 19, and 20 denotes a display for displaying an ultrasonic image.

Reference numeral 21 denotes a one-line memory for storing one-line data of the output of the A / D converter 18, which is segmented (# 1, # 2,...) For each length corresponding to the depth in the subject. This is for storing data in each segment. Numeral 22 denotes an arithmetic unit provided corresponding to each segment (# 1, # 2,...), Which analyzes data of each segment and sends it to the CPU 16. The CPU 16 determines this analysis result to determine whether the data in each segment can be used for correcting the phase distortion of the ultrasonic pulse,
For a segment determined to be usable, a transmission delay circuit 10 is set so that the transmission is focused on the position (depth) of the segment.
Set delay data for that. As a result, the transmission ultrasonic pulse is focused and transmitted to the focal position by the pulsar 9.

 Next, the operation of the present embodiment will be described.

First, a desired delay characteristic is given by the transmission delay circuit 10 under the control of the CPU 16 so that the transmission ultrasonic pulse from the probe 1 is focused on a certain region in the subject, and an ultrasonic echo signal from a tissue existing near this region. Is transmitted by the probe 1. The reception signal is amplified by the preamplifier 12, and after a desired delay characteristic is given by the reception delay circuit 13, the phasing addition and the envelope detection are performed by the addition circuit and the envelope detection circuit 15, and then the signal is applied to the DSC 17. . Next, one line of data output from the A / D converter 18 is segmented into lengths corresponding to the depth of the body and stored in the memory 21 for one line. Is analyzed and sent to the CPU 16.

The CPU 16 determines an analysis result for each segment, and determines whether data in each segment can be used for correcting phase distortion of an ultrasonic pulse. Then, the CPU 16 sets delay data for the segment determined to be usable in the transmission delay circuit 10 so that the transmission focus is set at the position of the segment. As a result, the transmitted ultrasonic pulse from the probe 1 is focused on the focal position by the pulsar 9, and the ultrasonic echo signal (reflected wave) from this position is transmitted to the probe 1
Received at. This echo signal is applied to a phase distortion detection circuit 14 via a preamplifier 12 and a reception delay circuit 13, where the phase distortion in each transducer constituting the probe 1 is detected.

This detection result is sent to the transmission delay circuit 10 or the reception delay circuit 13 under the control of the CPU 16, and the phase distortion is corrected by the transmission delay circuit 10 giving a desired delay characteristic, and the ultrasonic pulse is again transmitted from the probe 1 to the probe 1. Is transmitted. Alternatively, after being corrected by providing a desired delay characteristic only in the reception delay circuit 13, the addition circuit and the envelope detection circuit
The image is sent to the DSC 17 via 15, and finally the image whose phase distortion has been corrected is displayed on the display 20. The operations from the determination of each segment data to the correction are serially added to each segment.

In this case, if the transmission focus is fixed and only the amount of delay is corrected for reception only, the degree of correction is relatively incomplete, but the rate of the ultrasonic pulse transmitted once goes back and forth at a certain depth, and
Since the correction can be performed in the time required for detecting the data for the line), there is an advantage that the correction can be performed without deteriorating the real-time property. On the other hand, if the method of focusing the transmission on each effective segment (determined to be usable for correction of phase distortion as a result of the determination) is adopted, on the other hand, the real-time property is reduced, but the correction is performed in a more complete manner. Will be

When it is determined that the data of the segment cannot be used for correction as a result of the determination, the correction value of the portion determined to be usable for the determination result in the segment at a position shallower or deeper than that position is used, or Using the correction values obtained by estimation based on those correction values, correction is performed so that the position (for the segment whose determination result cannot be used) is focused.

Next, an algorithm for determining whether or not one line of data in the one line memory 21 can be used for correcting phase distortion will be described. This algorithm can be implemented in a way that performs a histogram analysis of the intensity of the echo signal in each segment. That is, as shown in FIGS. 2 (a) and 2 (b), a graph is created by plotting the luminance of each segment data on the horizontal axis and the frequency on the vertical axis, and by recognizing the pattern drawn on this graph. Can be determined.

This is because the reflected wave from the speckle region is considered to be a large number of reflected waves from the scatterer sufficiently small with respect to the wavelength added in a random phase relationship, and the histogram is a function determined statistically. (In this case, Rayleigh distribution). Accordingly, by performing an operation of changing the parameter for determining the curve of the Rayleigh distribution (in this case, the variance of the reflection intensity of each of the reflectors present in the speckle region) while changing the histogram, the histogram is changed to the one shown in FIG. ) Or a reflected wave from a structure as shown in FIG. 2B can be easily distinguished by recognizing the pattern.

In the case of FIG. 2 (b), since the reflection intensity is not random, a complex pattern generally largely different from the Rayleigh distribution is obtained.

As described above, according to the present embodiment, the determination can be easily performed by matching the patterns. Alternatively, it may be possible to simply determine the ratio of the average value and the variance value of the distribution, etc., so that the criterion is to examine the statistical properties of the reflected wave from the subject, and to use a simpler method within the range that does not make a mistake It is desirable to use the system from the viewpoints of miniaturization, low cost, and high speed of the system.

FIG. 3 shows another embodiment of the present invention, and the same parts as those in FIG. 1 are indicated by the same reference numerals. This embodiment shows an example in which the criterion is relaxed and the determination is made based on whether or not there is an ultrasonic echo signal which is a reflected wave.
Reference numeral 23 denotes a structural component removing circuit which is provided at a stage subsequent to the phase distortion detecting circuit 14.

, In which to perform the determination by calculating by comparison with the threshold level V _T with the average value of the received signal without performing a histogram analysis of the intensity of the echo signal as in the Example in the present embodiment . That the effective phase distortion detection considers that echo signal when the average value thereof is over the threshold level V _T, if it is not effective when the average value does not exceed the threshold level V _T It is to judge.

In the present embodiment, by providing the structural component removing circuit 23, an echo signal from the structure is removed to remove the influence of the structure on the phase distortion detection.

FIGS. 4 (a), (b) and (c) illustrate the operation of the present embodiment. In the case of the scanning line A in FIG. 4 (a), as shown in FIG. 4 (b). There is no problem because the received signal S _A having a uniform waveform can be obtained. However, in the case of the scanning line B in FIG. 4 (a), as shown in FIG. some received signal S _B waveform expires so obtained. Therefore, in this case, it can be determined that the phase distortion detection is not effective. Figure 4 (c) is a diagram for comparing with the threshold level V _T over time the level of each received signal shown in FIG. 4 (b), it is determined whether valid or not.

It is assumed that the reception signal used in this embodiment has already been removed from the influence of attenuation in the subject by means such as STC. FIG. 5 shows a simple configuration of a circuit for calculating an average value of a received signal, wherein 25 is a shift register, 26 and 27 are accumulators, and 28 is a difference circuit. According to this configuration, an average value between k samples can be obtained for each clock,
It is possible to easily determine whether each received signal is valid.

When it is determined that the region according to the present embodiment is inappropriate for the detection of phase distortion, a correction value of a surrounding effective region is used as in the above-described embodiment, or based on those correction values. The correction can be performed using the estimated correction value.

[Effects of the Invention] As described above, according to the present invention, an ultrasonic echo signal is analyzed and it is determined whether or not the correction value of the phase distortion of the ultrasonic pulse is valid based on the analysis result. Even when a structure exists, the phase distortion of the ultrasonic pulse based on the non-uniformity of the internal structure can be corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention, FIGS. 2A and 2B are histograms of echo signals for explaining the principle of the present embodiment, and FIG. Block diagram showing another embodiment, FIGS. 4 (a), (b), (c)
3 is an explanatory diagram of the operation of the embodiment of FIG. 3, and FIG. 5 is a block diagram showing a partial configuration of the embodiment of FIG. DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Subject, 10 ... Transmission delay circuit, 13 ... Reception delay circuit, 14 ... Phase distortion detection circuit, 16 ... CPU (Central processing unit), 17 ... DSC, 18 …… A / D converter, 21… 1 line memory, 22… Calculator, 23… Structure component removal circuit, 25… Shift register, 26,27… Cumulative adder, 28 …… Difference circuit .

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-79941 (JP, A) JP-A-4-64350 (JP, A) JP-A-3-286751 (JP, A) JP-A-1- 135333 (JP, A) JP-A-63-73937 (JP, A) W. Flax and M.S. O'Donnell, "Phase-Ablation Collection Using Signals From Point Reflectors and Diffuse Scratchers, Basic Electronics Contracts", IEEE Transactions, Inc. Vol. 35, No. 6, November 1988 (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (2)

(57) [Claims] 1. A transmission ultrasonic pulse is focused on a certain region in a subject, and an ultrasonic echo reflected from a small scatterer group in the vicinity thereof is received for each transducer, and output from each transducer. A correction value for correcting the phase distortion between the ultrasonic echo signals caused by the non-uniformity in the subject based on the ultrasonic echo signal is calculated by a cross-correlation process, and the transmission delay is determined based on the correction value. An ultrasonic diagnostic apparatus that corrects at least one of a characteristic and a reception delay characteristic, performs a histogram analysis of the intensity of the ultrasonic echo signal, and determines whether the phase distortion correction value is valid based on the analysis result. An ultrasonic diagnostic apparatus comprising means. 2. When the correction value is invalid as a result of the determination, the correction value obtained in a region near the region and determined to be valid is used or estimated based on those correction values. The ultrasonic diagnostic apparatus according to claim 1, wherein the correction is performed using the correction value.