JP4763588B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an imaging technique for tissue that moves periodically.

  A scanning plane formed by scanning an ultrasonic beam is electronically or mechanically scanned in a direction intersecting with the scanning plane to form a three-dimensional echo data capturing space, and a three-dimensional data group is acquired from the space. Image forming volume data is configured. In order to obtain one volume data, it is necessary to form a very large number of ultrasonic beams, which requires a certain amount of time. Therefore, it is generally difficult to form a three-dimensional moving image of an organ that moves at high speed. It is.

  Therefore, for an organ that moves periodically (for example, the heart), the frame sequence is taken out for each time phase from the frame sequence at a high speed over a plurality of heartbeats while moving the scanning plane at a low speed. Thus, a technique for reconstructing volume data for each time phase has also been proposed. According to this technique, it is also possible to construct a three-dimensional moving image of a moving tissue as a result. However, since it is indispensable to specify the time phase, it is difficult to apply this technique to fetuses in the womb. This is because the maternal electrocardiogram signal is stronger than the fetal electrocardiogram signal, and the latter signal is buried in the former signal.

JP 2005-74225 A

  In the above-mentioned Patent Document 1, when displaying the fetal heart as a three-dimensional moving image, observation points are fixedly set on the scanning surface to be scanned, and the time axis direction (and the scanning direction of the scanning surface) is set. It is described that information on the heartbeat period is obtained by observing fluctuations in the luminance value of, and extracting periodically changing components therefrom.

  However, even if the variation of the luminance value is observed at one or a plurality of observation points, a periodically changing component cannot be obtained with high accuracy unless the setting position of each observation point is appropriate. That is, according to the above method, it is possible to point out a problem that an error is apt to be generated and the calculation accuracy of heartbeat information greatly varies depending on the setting of the observation point.

  An object of the present invention is to make it possible to accurately obtain heart rate information necessary for three-dimensional image processing of a moving tissue.

  The present invention provides an acquisition means for acquiring a frame sequence in time series by moving a beam scanning plane in a three-dimensional space including a target tissue that moves periodically, and a tissue for each frame constituting the frame sequence. Profile calculation means for quantifying the form and calculating a profile representing a periodic time change of the form quantity, period calculation means for calculating the movement period of the tissue based on the profile, and using the calculated movement period And reconstructing means for reconstructing the volume data of each time phase from the frame sequence, and image forming means for forming an ultrasonic image of each time phase based on the volume data of each time phase. The present invention relates to a characteristic ultrasonic diagnostic apparatus.

  According to the above configuration, a frame sequence (frame data sequence) is obtained along the moving direction by mechanical, electronic or manual movement of the beam scanning plane. Usually, one beam scanning plane corresponds to one frame. Each frame is usually composed of a plurality of beam data or an array of luminance data groups obtained by coordinate conversion of a plurality of beam data. From the viewpoint of volume data reconstruction to be described later, it is desirable that the moving speed of the beam scanning plane be set sufficiently lower than the moving speed of the target tissue. If the target tissue is a heart, a moving scan at a low speed is desired so that one moving scan corresponds to, for example, 5 to 30 heartbeats. Since the ultrasonic beam is scanned electronically, a plurality of frame data can be obtained substantially at each moving scanning position. The moving speed may be determined according to the target number of frames constituting each time phase volume data. When the frame sequence is acquired, the morphological amount is calculated for all or a specific portion of the target tissue for each frame. The form quantity is desirably information indicating the size of the area, length, and the like. If form quantities that are easy to measure are used, volume data for each time phase can be reconstructed more accurately. Since information such as area and length is not easily affected by noise, it is desirable to refer to the information, and particularly in the case of area, there is an advantage that it is difficult to be influenced by the pulsation or translation of the heart. In this case, if the lumen such as the left ventricle is set as the calculation target, the area can be calculated with high accuracy because the region can be easily extracted with a luminance difference from the myocardium. When a profile representing the temporal change of the morphological amount is calculated, it is possible to calculate the movement cycle by paying attention to the periodic component included in the profile. That is, the time phase can be specified for each frame. One volume data can be constructed by extracting and assembling a plurality of frames for the same time phase. It is also possible to construct a moving image by imaging volume data of each time phase.

  Desirably, the profile calculation means calculates a tissue area as the morphological quantity. Preferably, the target tissue that moves periodically is a fetal heart. Although it is difficult to directly measure an electrocardiogram signal for the fetal heart, according to the above method, heartbeat period information corresponding to the electrocardiogram signal can be obtained. Preferably, the tissue area is a lumen area in the fetal heart. Desirably, the ultrasonic image of each said time phase is displayed as a moving image.

  As described above, according to the present invention, heart rate information necessary for three-dimensional image processing of a moving tissue can be obtained with high accuracy.

  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 ultrasonic diagnostic apparatus according to the present embodiment has a function of displaying a three-dimensional moving image of a fetal heart as a target tissue. However, the target tissue may be other than the fetal heart.

  The 3D probe 10 is a probe for forming a three-dimensional echo data capturing space (three-dimensional space). Specifically, the 3D probe 10 has a function of forming a scanning surface (corresponding to a frame) by electronic scanning of an ultrasonic beam and a function of moving the scanning surface in a direction perpendicular to the scanning surface. The scanning plane can be moved mechanically or electronically. Of course, the scanning plane may be moved by manual scanning using a position detector or the like. When the three-dimensional space is mechanically formed, the 1D array transducer is mechanically driven. When forming a three-dimensional space electronically, a 2D array transducer is used. In any case, ultrasonic waves are transmitted and received so that a time-series frame sequence can be acquired as will be described later.

  Incidentally, the 3D probe 10 may be a probe used in contact with the body surface, or may be a probe inserted into a body cavity, for example, the esophagus. When the fetal heart is to be measured, the 3D probe 10 is brought into contact with the abdomen of the mother's womb, thereby forming the above three-dimensional space.

  The transmission unit 12 functions as a transmission beam former. The transmitter 12 supplies a plurality of transmission signals in parallel to the array transducer included in the 3D probe 10. As a result, a transmission beam is formed. On the other hand, a plurality of reception signals output from the array transducer in the 3D probe 10 are processed in the reception unit 14. The reception unit 14 functions as a reception beam former, and executes phasing addition processing for a plurality of reception signals. A reception beam is formed by the phasing addition processing, and a reception signal corresponding to the reception beam, that is, beam data is output to the signal processing unit 16.

  The signal processing unit 16 is a module that performs necessary signal processing on the received signal. For example, detection, logarithmic compression processing, and the like are executed. A frame to be described later is configured by a data group after the detection processing is performed in the present embodiment, but may be configured by an RF data group.

  The coordinate conversion unit 18 performs a coordinate conversion process on each echo data constituting the input beam data, thereby constituting a frame (frame data). As the coordinate conversion unit 18, a known DSC (digital scan converter) can be used. As a result, a plurality of frames are obtained in time series order on the output side of the coordinate conversion unit 18. These frames constitute a frame sequence, and the frame sequence is stored in the frame sequence memory 20. The frame sequence memory 20 has a storage space corresponding to a time space for storing the frame sequence.

The heart chamber extraction unit 22 executes processing for discriminating the myocardium from the heart chamber for each frame. In this process, the process is performed within a region of interest (ROI) set for each frame, or the process is executed within a three-dimensional ROI set in a three-dimensional space. In general, there is a significant difference in brightness level between the myocardium and the heart chamber, and since it is generally easy to detect the edge of the myocardium, this heart chamber extraction process has the advantage of being able to acquire morphological information with high accuracy. There is. It is also possible to extract cash forte other specific sites heart chamber.

  The area estimation unit 24 estimates the heart chamber area based on the heart chamber (image information) extracted for each frame. In this case, the area can be calculated by a method such as counting the number of pixels corresponding to the heart chamber. By estimating the area as described above, a profile (graph) including area values for each frame is obtained.

  The cycle calculation unit 26 acquires cycle information about the fetal heart from the profile obtained as described above. For example, frequency analysis such as FFT analysis is performed on the profile, and the period can be easily obtained by referring to the analysis result. It is also possible to obtain period information by applying a correlation method after removing DC components and low frequency components included in the profile by a filter. Other methods may be used.

  Based on the heartbeat information identified as described above, that is, the motion period, the reconstruction unit 28 extracts and aligns frame sets corresponding to the same time phase from a plurality of frames constituting the frame sequence. To reconstruct volume data for each time phase. This will be described later. Based on the volume data reconstructed for each time phase, the 3D image forming unit 30 forms a 3D image using a volume rendering method or the like. The three-dimensional images obtained in chronological order constitute a moving image, and the image data of the moving image is stored in the moving image memory 31. Data read therefrom is displayed on the display unit 32. That is, a three-dimensional ultrasonic image is displayed as a moving image on the screen of the display unit 32.

  It is desirable to determine the moving speed of the scanning plane in accordance with a target value as the number of frames constituting each volume data. In general, the scanning plane is moved and scanned with a sufficiently low moving speed with respect to a fetal heart that moves at high speed. Since the electronic scanning speed of the ultrasonic beam, that is, the scanning surface formation rate is extremely high, a plurality of frames can be acquired at substantially the same position or within the same minute region. For example, you may make it take time for 5 to 30 heartbeats per moving scan of the scanning surface. By the way, when moving and scanning the scanning surface by manual operation, the direction of each frame data may not be parallel. In such a case, volume data is reconstructed in consideration of the direction of each frame. Is desirable.

  FIG. 2 shows the frame sequence 50 described above. In FIG. 2, the X axis also corresponds to the time axis t. That is, the heart Q is moving, and the scanning of the scanning surface S is performed along with the movement. Therefore, the horizontal axis is an axis corresponding to the moving scanning and also corresponds to the time axis. The scanning plane is defined by a depth direction Z and a beam scanning direction Y. In FIG. 2, the frame at a certain time is indicated by F, and the area of the heart chamber corresponding to the left ventricle is indicated by S on the frame F crossing the heart Q. The heart itself moves with a heartbeat and performs a translational motion and the like. By referring to the area, there is an advantage that heart rate information can be obtained with high accuracy by eliminating the influence of such movement as much as possible.

  FIG. 3A shows a profile representing the time change of the area. The horizontal axis is the X axis, which corresponds to the time axis t. The vertical axis represents the area S. The area periodically increases and decreases according to the cardiac cycle. Here, T corresponds to a heartbeat cycle. If the period is obtained directly from such a profile, it can be observed. If it is difficult to specify the period directly, frequency analysis is performed on the profile as shown in FIG. The period T may be specified on the graph. In the graph shown in (B), peaks periodically occur, and the peaks occur on a frequency corresponding to the heartbeat cycle.

FIG. 4 shows a reconstruction processing method. As described above, for the frame sequence 50 acquired over a plurality of heartbeats, a plurality of sections 50a corresponding to one heartbeat are set based on the period T. If the moving speed of the scanning plane is constant within each section, the time phase of each frame can be easily specified. On the time axis, there are frames corresponding to the same time phase for each section 50a. Therefore, if a plurality of frames corresponding to each time phase are collected and arranged, volume data corresponding to each time phase can be configured. The volume data is represented by V ₁ , V ₂ ,..., V _i ,. If each of a plurality of volume data existing in such a time-series order is expressed as a three-dimensional image, it is possible to observe a three-dimensional image of the heart as a moving image by displaying it as an image. This technique itself is known.

  For the fetal heart, it is very difficult to directly measure the electrocardiogram signal from it, but according to the above method, heart rate information corresponding to the electrocardiogram signal can be obtained using image processing, It is possible to apply a reconstruction calculation to the frame sequence based on such heartbeat information. In addition, since the area information on each frame is used in the calculation of the heart rate information in the above method, it is possible to realize measurement that is hardly affected by noise and hardly affected by heart motion (for example, translational motion). There is. In the method of Patent Document 1 described above, since a change in luminance value was observed for one or a plurality of pixels, a large error factor was generated when the heart itself moved. Advantageous problems can be solved or alleviated and high-precision heart rate calculation can be performed.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present embodiment. It is a conceptual diagram which shows a frame row | line | column. It is a figure which shows the profile showing the profile showing the time change of an area, and the result of having analyzed the frequency of it. It is a figure for demonstrating the reconstruction calculation of volume data.

Explanation of symbols

  10 3D probe, 12 transmission unit, 14 reception unit, 18 coordinate conversion unit, 20 frame sequence memory, 22 heart chamber extraction unit, 24 area estimation unit, 26 period calculation unit, 28 reconstruction unit, 30 three-dimensional image formation unit

Claims (5)

Acquisition means for acquiring a frame sequence in time series by moving a beam scanning plane in a three-dimensional space including a target tissue that moves periodically;
A profile calculating means for extracting a specific part for each frame constituting the frame sequence, quantifying a tissue form for the specific part, and calculating a profile representing a periodic time change of the form quantity;
A cycle calculating means for calculating a motion cycle of the tissue based on the profile;
Reconstructing means for reconstructing the volume data of each time phase from the frame sequence using the calculated motion period;
Image forming means for forming an ultrasonic image of each time phase based on the volume data of each time phase;
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 1.
The ultrasonic diagnostic apparatus, wherein the profile calculation means calculates a tissue area as the morphological quantity. The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein the target tissue that moves periodically is a fetal heart. The apparatus of claim 3.
The specific site is a lumen in the fetal heart;
The ultrasonic diagnostic apparatus, wherein the tissue area is a lumen area in the fetal heart. The apparatus of claim 1.
The ultrasonic diagnostic apparatus, wherein the ultrasonic images of the respective time phases are displayed as moving images.

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