JP2006051285A - Ultrasonic diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a blood vessel wall with high precision without being affected by a noise. <P>SOLUTION: An envelope signal 50 is obtained as a result of detection of a receiving RF signal of an ultrasonic beam passing through the blood vessel. Thus, the envelope signal 50 has two peaks on each of a blood vessel front wall and a blood vessel rear wall. The added waveform 52 of the envelope signal is obtained by cumulative addition processing of the envelope signals 50 toward one or both in the beam directions letting the blood vessel inner cavity center O as a starting point, and, either one of the blood vessel front wall and the blood vessel rear wall or both blood vessel walls are detected by the threshold value 54 of the blood vessel wall detection. Also, the position of the corresponding peak P1, namely, the blood vessel wall can be detected by detecting an inflection point M1 from the change of the inclination of the added waveform 52 of the envelope signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to detection of a blood vessel wall on an ultrasonic beam.

  Recently, an ultrasonic diagnostic apparatus is used to measure and diagnose vascular arteriosclerosis, circulatory function, and the like. For example, the probe is brought into contact with the neck, and in this state, an ultrasonic beam is formed so as to be orthogonal to the carotid artery. An RF reception signal obtained by forming an ultrasonic beam is detected, and a blood vessel wall is searched for along the beam direction from the center point inside the blood vessel in the received signal after detection. Since the amplitude of the echo is generally large at the edge corresponding to the boundary between the blood vessel lumen and the blood vessel wall, the edge is detected by, for example, differentiation processing or threshold processing. Specifically, the blood vessel wall is detected in the intima, media and adventitia. In the received signal after detection, one or both of the peak corresponding to the inner membrane and the peak corresponding to the boundary surface between the media and the outer membrane are specified. When a blood vessel wall is detected, for example, a tracking gate is set for the position, and the time displacement of the blood vessel wall is measured. In addition, the diameter of the blood vessel or its temporal change can be measured.

  Patent Document 1 below discloses a technique for detecting a blood vessel wall on a tomographic image. However, there is no disclosure of a technique for detecting the blood vessel wall by eliminating the influence of noise.

Japanese Patent Laid-Open No. 11-318896

  The received signal includes various noises. For example, as the noise, multiple echoes inside the blood vessel can be given. If it is attempted to detect a blood vessel wall by applying differential processing, threshold processing, or the like to the received signal in a state where such noise is included, there is a possibility that the noise is mistaken as a blood vessel wall.

  An object of the present invention is to detect a blood vessel wall with high accuracy without being affected by noise.

  Another object of the present invention is to detect a blood vessel wall with high accuracy without being affected by noise with a simple configuration.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a transmission / reception unit that forms an ultrasonic beam through a blood vessel in a living body, and a time axis received by the ultrasonic beam. Means for processing the above signal, an addition processing means for generating a cumulative addition signal by cumulatively adding the signal on the time axis from one or both of the beam directions from the start point set inside the blood vessel And a blood vessel wall detecting means for detecting a blood vessel wall based on the cumulative addition signal.

  In the above configuration, the signal on the time axis is, for example, an envelope signal generated by detecting an RF reception signal obtained by ultrasonic transmission / reception, or a positive signal obtained by rectifying the RF reception signal. Or a rectified signal having only a negative unipolar component. The start point set inside the blood vessel is, for example, the center point inside the blood vessel, and the cumulative addition processing is, for example, integration processing in the beam direction.

  In the above configuration, the influence of noise in the blood vessel can be reduced by the cumulative addition process. In other words, noise is generally accompanied by drastic changes and may have a transiently large amplitude. On the other hand, before performing cumulative addition processing, noise is detected by differential processing or threshold processing. Then, there is a possibility that noise is mistaken as a blood vessel wall. On the other hand, in the cumulative addition signal after the cumulative addition processing is performed, a drastic change in noise or a transiently large amplitude is smoothed, and the influence of noise when detecting a blood vessel wall is reduced.

  Preferably, the signal on the time axis is an envelope signal generated by detecting an RF reception signal obtained by transmitting and receiving ultrasonic waves. Preferably, the signal on the time axis is a rectified signal having only a positive or negative unipolar component obtained by rectifying an RF reception signal obtained by ultrasonic transmission / reception. And Preferably, the RF received signal is a digital RF received signal, and the rectified signal is generated by performing bit conversion with a complement relationship on each digital data having both positive and negative polarities in the digital RF received signal. And a bit conversion processing unit. Desirably, the blood vessel wall detecting means detects the blood vessel wall with reference to at least one of a level and a slope of the cumulative addition signal.

  According to the present invention, it is possible to detect a blood vessel wall with high accuracy without being affected by noise.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof.

  The probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves into a living body. The probe 10 forms an ultrasonic beam 40 so as to pass through a blood vessel in the living body. As necessary, the probe 10 scans the ultrasonic beam 40 over a two-dimensional plane, or scans over a three-dimensional space.

  The transmission / reception unit 12 supplies a transmission signal to the probe 10 and acquires a reception signal from the probe 10. The transmission / reception unit 12 operates based on an instruction from the transmission / reception control unit 14. The transmission / reception unit 12 supplies transmission signals to a plurality of vibration elements included in the probe 10 to scan the ultrasonic beam 40 in a predetermined direction, and arranges the reception signals for each vibration element output from the probe 10. A phase addition process or the like is performed to form a received RF signal (received beam). That is, the transmission / reception unit 12 functions as a so-called transmission beam former and reception beam former, and forms a reception RF signal for each ultrasonic beam. The received RF signal formed by the transmitting / receiving unit 12 is output to the tomographic image forming unit 16 and the quadrature detector 18.

  The tomographic image forming unit 16 forms an in-vivo tomographic image including blood vessels based on the received RF signal. A well-known technique is used to form a tomographic image, and a so-called B-mode image is formed. The formed image is output to the display unit 30, and the image is displayed on the display unit 30. In the present embodiment, a received RF signal may be used to form a 3D image, a Doppler image, or the like. A well-known technique is also used for forming these images.

  The quadrature detector 18 performs quadrature detection of the received RF signal using the reference signal. In quadrature detection, detection is performed using a reference signal and a reference signal obtained by shifting the phase of the reference signal by π / 2. In place of the quadrature detector 18, a detector that performs detection with one reference signal may be used.

  The envelope detector 20 detects the envelope signal of the received RF signal based on the detection result in the quadrature detector 18. The detected envelope signal is output to the blood vessel wall detection unit 22 configured by the adder 24 and the blood vessel wall detector 26.

  The adder 24 performs cumulative addition processing on the envelope signal from the start point set inside the blood vessel toward one or both of the beam directions to generate a cumulative addition signal. The start point is set by the start point setting unit 28. The blood vessel wall detector 26 detects the blood vessel wall based on the cumulative addition signal.

  FIG. 2 is a view for explaining blood vessel wall detection processing in the ultrasonic diagnostic apparatus of FIG. Hereinafter, the blood vessel wall detection process will be described with reference to FIG. 1 for the portions shown in FIG.

  The envelope signal 50 is a signal detected by the envelope detector 20. That is, the envelope signal 50 is obtained as a result of detection of the received RF signal for each ultrasonic beam. In the present embodiment, an ultrasonic beam is formed through the blood vessel. The envelope signal 50 in FIG. 2 corresponds to one ultrasonic beam passing through the blood vessel, and includes portions corresponding to the blood vessel front wall, the blood vessel lumen, and the blood vessel rear wall. The blood vessel wall includes an intima, an intima, and an adventitia, and in general, a peak corresponding to the intima and a peak corresponding to an interface between the intima and the adventitia are observed by detection with an ultrasonic beam. . For this reason, the envelope signal 50 in FIG. 2 has two peaks in each of the blood vessel front wall and the blood vessel rear wall. Furthermore, the blood vessel lumen contains noise associated with the influence of multiple echoes.

  By the way, if this envelope signal 50 is used to detect a blood vessel wall based on the threshold value of the blood vessel wall detection threshold 54 ′, for example, the noise exceeds the threshold value 54 ′ of the blood vessel wall detection. Therefore, it is impossible to accurately detect only the blood vessel wall. In addition, when differential processing is used, a drastic change in the noise portion has a large influence on the differential processing, and it is difficult to accurately detect only the blood vessel wall. Therefore, in the present embodiment, the addition waveform 52 of the envelope signal obtained by performing the addition process on the envelope signal 50 is used.

  The added waveform 52 of the envelope signal is generated in the adder 24. The adder 24 performs cumulative addition processing of the envelope signal toward one or both of the beam directions starting from the blood vessel lumen center O.

  The vascular lumen center O as the start point is set by the start point setting unit 28. The start point setting unit 28 uses, for example, the position of the central part of the blood vessel lumen set by the user using an input device such as a trackball while viewing the tomographic image of the blood vessel as the blood vessel lumen center O, and the position information thereof. Output to the adder 24. The start point setting unit 28 may determine the blood vessel lumen center O based on the blood vessel ROI (region of interest) set in the blood vessel portion by the user. Note that, in the addition process described later, the start point does not need to be located exactly at the center of the blood vessel lumen. For this reason, the start point may be set near the center of the blood vessel lumen, or may be set at a position deviated from the center within a range not hindering the addition process.

  The adder 24 performs cumulative addition processing on the envelope signal 50 from the blood vessel lumen center O as the set start point toward one or both of the addition direction on the front wall side and the addition direction on the rear wall side. . That is, the amplitude value of the envelope signal 50 is integrated toward one or both. As a result, an added waveform 52 of the envelope signal is obtained. In FIG. 2, the addition waveform 52 of the envelope signal is shown as the addition result of both the addition direction on the front wall side and the addition direction on the rear wall side. Only the waveform is obtained.

  When the envelope signal 50 is compared with the added waveform 52 of the envelope signal, a large difference is seen in the noise portion. The noise of the envelope signal 50 has a transiently large amplitude, but its spread in the time axis direction (the direction of integration processing) is small. For this reason, the integration processing result of the noise portion becomes extremely small with respect to the integration processing result on the blood vessel wall. For example, the blood vessel wall portion and the noise portion are accurately detected by the blood vessel wall detection threshold 54 in the blood vessel wall detector 26. Can be distinguished. In this way, for example, by appropriately setting the blood vessel wall detection threshold 54 according to the target portion (intima, media, outer membrane, etc.) of the blood vessel wall, the blood vessel wall can be highly accurate without being affected by noise. It becomes possible to detect.

  The blood vessel wall detector 26 detects the blood vessel wall of one of the blood vessel front wall and the blood vessel rear wall, or both blood vessel walls based on the blood vessel wall detection threshold value 54. By detecting both blood vessel walls, blood vessel diameter can be measured. Note that the value of the blood vessel wall detection threshold 54 may be set to be different between the blood vessel front wall and the blood vessel rear wall.

  The blood vessel wall detector 26 can also detect the blood vessel wall from the change in the slope of the added waveform in addition to the detection process using the threshold value. For example, in FIG. 2, the peak P <b> 1 on the blood vessel front wall of the envelope signal 50 corresponds to the inflection point M <b> 1 in the added waveform 52 of the envelope signal. That is, since the progress of the addition process changes before and after the peak P1, an inflection point M1 corresponding to the position of the peak P1 occurs in the addition waveform 52 of the envelope signal. Since the inclination of the inflection point M1 changes greatly, the blood vessel wall detector 26 detects the refraction point from the change in the inclination of the added waveform 52 of the envelope signal, and thus the corresponding peak position, that is, the blood vessel. A wall can be detected.

  Note that the inflection points are also generated in the noise portion. For this reason, the blood vessel wall detector 26 detects a portion where the inclination is substantially constant for a predetermined period (a predetermined length in the integration processing direction) when determining a change in the inclination, and determines from the inclination that the portion is not a noise portion. To do. Noise has a small spread in the time axis direction (integration processing direction), and the slope of the added waveform 52 of the envelope signal changes in a short period in the noise portion. For this reason, the noise part is excluded from the detection target by extracting only the part having the substantially constant slope for the predetermined period.

  Returning to FIG. 1, the position information of the blood vessel wall detected by the blood vessel wall detector 26 is output to the display unit 30, and the cursor indicating the position of the blood vessel wall on the tomographic image formed by the tomographic image forming unit 16. Are superimposed and displayed on the display unit 30. Of course, in addition to the cursor display or the like, or separately from the cursor display, a blood vessel diameter measurement value using the position of the blood vessel wall may be displayed.

  FIG. 3 shows another preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 3 is a block diagram showing the overall configuration thereof. The ultrasonic diagnostic apparatus of FIG. 3 is equivalent to the apparatus in which the quadrature detector 18 and the envelope detector 20 in the ultrasonic diagnostic apparatus of FIG. 3, the same reference numerals as those shown in FIG. 1 are the same as those in FIG.

  That is, the transmission / reception unit 12 supplies a transmission signal to the probe 10 and acquires a reception signal from the probe 10 to form a reception RF signal. The received RF signal is output to the tomographic image forming unit 16 and the full-wave rectifier 21. The tomographic image forming unit 16 forms an in-vivo tomographic image including blood vessels based on the received RF signal.

  The full-wave rectifier 21 performs full-wave rectification on the received RF signal and outputs a rectified signal having only a positive or negative unipolar component (absolute value). The rectified signal is output to the blood vessel wall detection unit 22 including the adder 24 and the blood vessel wall detector 26. The adder 24 performs a cumulative addition process on the rectified signal from the start point set inside the blood vessel toward one or both of the beam directions to generate a cumulative addition signal. The start point is set by the start point setting unit 28. The blood vessel wall detector 26 detects the blood vessel wall based on the cumulative addition signal.

  FIG. 4 is a view for explaining blood vessel wall detection processing in the ultrasonic diagnostic apparatus of FIG. Hereinafter, the blood vessel wall detection process will be described with reference to FIG. 3 for the portions shown in FIG.

  The received RF signal 51 in FIG. 4 corresponds to one ultrasonic beam that passes through the blood vessel, and includes portions corresponding to the blood vessel front wall, the blood vessel lumen, and the blood vessel rear wall. The blood vessel wall includes an intima, an intima, and an adventitia, and in general, a peak corresponding to the intima and a peak corresponding to an interface between the intima and the adventitia are observed by detection with an ultrasonic beam. . Therefore, the received RF signal 51 in FIG. 4 has a relatively large amplitude in each of the blood vessel front wall and the blood vessel rear wall. Furthermore, the blood vessel lumen contains noise associated with the influence of multiple echoes.

  The rectified signal 53 of the reception RF signal is a signal obtained as a result of rectification by the full-wave rectifier 21, and is obtained by folding the negative direction component of the reception RF signal 51 in the positive direction. The rectified signal addition waveform 55 is generated in the adder 24. The adder 24 performs cumulative addition processing on the rectified signal 53 of the received RF signal toward one or both of the beam directions with the blood vessel lumen center O as the starting point. The vascular lumen center O as the start point is set by the start point setting unit 28.

  The adder 24 accumulates the rectified signal 53 of the received RF signal from the blood vessel lumen center O as the set start point toward one or both of the addition direction on the front wall side and the addition direction on the rear wall side. Addition processing. That is, the amplitude value of the rectified signal 53 of the received RF signal is integrated toward one or both. As a result, an added waveform 55 of the rectified signal is obtained. In FIG. 4, the addition waveform 55 of the rectified signal is shown as the addition result of both the addition direction on the front wall side and the addition direction on the rear wall side, but in only one addition process, the waveform corresponding to that direction is shown. Only can be obtained.

  Then, the blood vessel wall detector 26 determines either the blood vessel wall of the blood vessel front wall or the blood vessel rear wall according to the blood vessel wall detection threshold value (corresponding to the blood vessel wall detection threshold value 54 in FIG. 2), or Detect both vessel walls. By detecting both blood vessel walls, blood vessel diameter can be measured. The blood vessel wall detector 26 can also detect the blood vessel wall from the change in the slope of the added waveform, in addition to the detection process using the threshold value. That is, the blood vessel wall detector 26 detects the blood vessel wall by detecting the refraction point from the change in the slope of the added waveform 55 of the rectified signal. This principle is the same as the principle of detecting the refraction point from the change in the slope of the added waveform 52 of the envelope signal described with reference to FIG. 2 and detecting the corresponding peak position, that is, the blood vessel wall.

  Returning to FIG. 3, the position information of the blood vessel wall detected by the blood vessel wall detector 26 is output to the display unit 30, and the cursor indicating the position of the blood vessel wall on the tomographic image formed by the tomographic image forming unit 16. Are superimposed and displayed on the display unit 30. According to the configuration of FIG. 3, the quadrature detector and the envelope detector are unnecessary as compared with the configuration of FIG.

  In the apparatus of FIG. 3, when the RF reception signal formed by the transmission / reception unit 12 is a digital RF reception signal, each digital data having both positive and negative polarities in the digital RF reception signal has a complement relationship. A rectified signal can be generated by performing bit conversion. For example, a bit conversion processing unit (not shown) executes the conversion process.

  FIG. 5 is a diagram for explaining bit conversion processing for a digital RF reception signal. The digital RF reception signal indicates the amplitude of the RF reception signal at each time and includes amplitude magnitude information and amplitude polarity (positive / negative sign) information.

  In FIG. 5, 4-bit data is shown as an example of the digital RF reception signal. For example, when 4 bits from the most significant bit to the least significant bit are 0111, the amplitude is +7, 0110 is +6, and 0001 is +1. 0000 indicates that the amplitude is zero.

  5 is a 2's complement digital signal. For example, if 4 bits from the most significant bit to the least significant bit are 1111, the amplitude is -1. 1010 indicates -6, and 1001 indicates -7. Incidentally, as shown in FIG. 5, when the most significant bit is 0, it is a positive number (including 0), and when the most significant bit is 1, it corresponds to a negative number, so the most significant bit is a sign bit. Have a role. Also, since the data is a two's complement digital signal, if two data having the same absolute value but different signs are added, the result of the addition is 0000 when the carried bits are ignored.

  Therefore, when the most significant bit is 1, each of the four bits of the digital RF signal is bit-inverted and 1 is added to obtain a digital RF signal with the polarity inverted. For example, when the magnitude of the amplitude is −6, 0101 is obtained by bit-inverting each bit of 1010, and by adding 1 to 0110, the result is 0110. This corresponds to data having an amplitude of +6. Thus, the rectification process for the digital RF reception signal is executed.

  When the most significant bit is 1, the rectification process may be executed only by bit inverting each of the four bits of the digital RF signal, that is, adding 1 after that is omitted. . In this case, an error corresponding to 1 occurs in the magnitude of the amplitude, but if the amplitude is large, the error can be ignored.

  As described above, by realizing the rectification process by the bit inversion process, the full-wave rectifier 21 in FIG. 3 can be realized by the bit inversion circuit, so that the circuit can be further downsized. For example, a configuration in which a bit inverting circuit is provided in the adder 24 and the full-wave rectifier 21 is omitted is also possible.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a figure for demonstrating the blood vessel wall detection process in the ultrasonic diagnosing device of FIG. It is a block diagram which shows the whole structure of another ultrasonic diagnostic apparatus which concerns on this invention. It is a figure for demonstrating the blood vessel wall detection process in the ultrasonic diagnosing device of FIG. It is a figure for demonstrating the bit conversion process with respect to a digital RF received signal.

Explanation of symbols

  18 quadrature detector, 20 envelope detector, 21 full-wave rectifier, 24 adder, 26 blood vessel wall detector, 28 start point setting unit.

Claims (5)

A wave transmitting / receiving means for forming an ultrasonic beam through a blood vessel in a living body;
A means for processing a signal on the time axis received by the ultrasonic beam, wherein the signal on the time axis is cumulatively added from one start point set in the blood vessel toward one or both of the beam directions. Addition processing means for generating a cumulative addition signal;
Blood vessel wall detecting means for detecting a blood vessel wall based on the cumulative addition signal;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The signal on the time axis is an envelope signal generated by detecting an RF reception signal obtained by transmitting and receiving ultrasonic waves.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The signal on the time axis is a rectified signal having only a positive or negative unipolar component obtained by rectifying an RF reception signal obtained by ultrasonic transmission / reception.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
The RF reception signal is a digital RF reception signal;
A bit conversion processing unit for generating the rectified signal by performing bit conversion on each digital data having both positive and negative polarities in the digital RF reception signal with a complement relationship;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The blood vessel wall detecting means detects the blood vessel wall with reference to at least one of a level and a slope of the cumulative addition signal;
An ultrasonic diagnostic apparatus.

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