JP4847684B2 - Diagnostic imaging equipment - Google Patents

Description

  The present invention relates to a motion tracking display method of a biological tissue applied to an ultrasound diagnostic image, a magnetic resonance image, or an X-ray CT image, and an image diagnostic apparatus using the tracking display method.

  Image diagnostic apparatuses such as an ultrasonic diagnostic apparatus, a magnetic resonance imaging (MRI) apparatus, and an X-ray CT apparatus are all provided for diagnosis by displaying a tomographic image related to an examination site of a subject on a monitor. For example, in the case of a circulatory system such as the heart and blood vessels and other organs with movement, the movement of living tissues (hereinafter referred to as tissues) constituting them is observed by a tomographic image, and the functions of the organs and the like are observed. Diagnosis is going on.

In particular, if the function of the heart or the like can be quantitatively evaluated, the accuracy of diagnosis is expected to be further improved. For example, conventionally, the contour of the heart wall is extracted from the image obtained by the ultrasonic diagnostic apparatus, and the heart function (heart pump function) is calculated based on the heart wall contour based on the area and volume of the ventricle and the rate of change thereof. Attempts have been made to evaluate or evaluate local wall motion (Patent Document 1). In addition, the displacement of the tissue is measured based on a measurement signal such as a Doppler signal, and for example, a local contraction or relaxation distribution is imaged. Based on this, the location where the ventricular motion is activated is accurately determined. Or a method for quantitatively measuring tissue motion, such as measuring the thickness (wall thickness) of the heart wall during systole (Patent Document 2). Furthermore, a technique has been proposed in which the contours of the atria and ventricles that change from moment to moment are extracted, the contours are superimposed on the image, and the volume of the ventricles and the like is calculated based on the contours (Patent Document 3).
JP 9-13145 A Special table 2001-518342 USP5,322,067

  However, any of the above conventional techniques is only a method for evaluating the overall function of the heart, and no consideration is given to measuring the movement of each tissue such as the myocardium. In particular, the prior art that extracts the contour of the heart wall by image processing and measures changes in the thickness of the heart wall based on the contour does not necessarily achieve sufficient accuracy.

  In general, for example, if blood does not pass through the myocardium due to a thrombus or the like, the movement of the myocardium is said to decrease. Therefore, if the movement of each tissue of the heart, such as the movement of the myocardium constituting the ventricle and the change in thickness, can be measured quantitatively, it is possible to provide effective diagnostic information for determining a treatment method and the like. For example, if the degree of ischemia is known, it is effective as an index for selecting a treatment method for the heart such as coronary artery regeneration and specifying a treatment site. In addition, if the movement of the valve annulus can be measured quantitatively, research has been conducted to help evaluate the overall cardiac function in heart diseases such as hypertensive cardiac hypertrophy. The target for quantitatively measuring the movement of such a tissue is not limited to the heart, but is also demanded for blood vessels. That is, if a pulse wave of a large blood vessel wall such as a carotid artery can be measured quantitatively, it is effective for diagnosis of arteriosclerosis.

Therefore, the inventors of the present invention set a tracking point (mark) on the myocardial wall where the motion is to be tracked on a monitor on which a tomographic image of the heart is displayed, for example, and the myocardium of the region including the tracking point on the moving image It has been proposed to detect the movement of the wall by image processing, and to observe the movement of the myocardium by moving the tracking point according to the movement of the myocardial wall and displaying it superimposed (Japanese Patent Application No. 2002-266864). According to this, by measuring the movement of the tracking point, various information relating to the movement of the tissue can be obtained quantitatively.
However, the movement of each part of the myocardium when the doctor visually observes and the result tracked by the image processing may be slightly different. This is because the position of the tissue image determined by a human is different from the estimated movement position using the nature of the image.

  An object of the present invention is to make the movement of a tracking point displayed by following the movement of a living tissue coincide with the tissue image position of a human appearance.

An image diagnostic apparatus according to the present invention that solves the above-described problems includes an image storage unit (1) that stores a moving image obtained by imaging a cross section of a living body, a display unit (2) that displays the moving image, and the display. And an operation unit (3) for setting a mark on a desired tracking region of a living tissue with respect to one still image of the moving image, the diagnostic imaging apparatus including the desired tracking region on which the mark is set The cut-out image and the local image corresponding to the mark portion other than the one still image of the moving image are calculated, and the movement destination coordinates of the living tissue are tracked by the degree of coincidence between the cut-out image and the local image. A tracking unit (4) for calculating the movement destination of the mark based on the movement destination coordinates and displaying the movement destination of the mark on the display unit (2), and sequentially storing the movement destination of the mark according to the moving image. A tracking image storage unit (5) for performing the biological assembly A movement calculation unit (6) for calculating a physical quantity related to the movement destination coordinates of the tracking part as measurement information based on the movement destination coordinates, and displaying the change of the measurement information on the display unit (2) in a diagram, the display control unit for displaying on the display unit the destination sequentially read out the mark from the tracking image storage unit and to a line diagram display (5) (2) by the motion calculating section (6) and (11), the moving picture Image enhancement means for emphasizing image features, wherein the biological tissue is a myocardium, and the operation unit (3) faces the heart muscle wall along the myocardium with the plurality of marks as tracking points. The line diagram is a wall thickness graph, and the display control unit (11) adds the same label to each measurement location of the tracking point and each graph line of the wall thickness graph for display. Display in part (2) .

  According to the present invention, it becomes easy to observe the movement of the tracking point displayed following the movement of the living tissue.

(Embodiment 1)
An image diagnostic apparatus according to an embodiment to which the biological tissue motion tracking display method of the present invention is applied will be described with reference to FIGS. FIG. 1 shows the procedure of the biological tissue motion tracking display method of this embodiment, and FIG. 2 is a block diagram of an image diagnostic apparatus to which the biological tissue motion tracking display method of FIG. 1 is applied. As shown in FIG. 2, the diagnostic imaging apparatus includes an image storage unit 1 that stores a moving image obtained by photographing a tomogram of a living body that is a subject, a display unit 2 that can display a moving image, and various commands. An automatic console 4 for tracking the movement of a living tissue of a moving image displayed on the display unit 2, a tracking image storage unit 5 for storing a tracking image generated by the automatic tracking unit 4, and The motion calculation unit 6 calculates various measurement information based on the tracking result of the automatic tracking unit 5 and the signal transmission path 7 formed by connecting them.

  In the image storage unit 1, a moving image obtained by capturing a tomographic image of a subject from the diagnostic image capturing apparatus 8 indicated by a broken line is stored on-line or off-line. As the diagnostic image imaging apparatus 8, diagnostic apparatuses such as an ultrasonic diagnostic apparatus, a magnetic resonance imaging (MRI) apparatus, and an X-ray CT apparatus are applicable.

  The console 3 superimposes a mark (mark) on the part of the living tissue whose movement is desired to be tracked on the still image displayed on the display unit 2, and a command to display one frame image (still image) on the display unit 2. Various commands such as a command to be displayed and a command to select the type of image to be displayed on the display unit 2 can be input.

  The automatic tracking unit 4 includes a control unit 10 that controls the entire diagnostic imaging apparatus, a display control unit 11 that switches and controls an image displayed on the display unit 2, and a mark position of one frame image displayed on the display unit 2. Cutout image setting means 12 for setting a cutout image having a size including the corresponding tracking part, image feature enhancement means 13a for reading out other frame images of the moving image from the image storage unit 1 and emphasizing the features of the image, The image from the image feature enhancement means 13a with enhanced features is extracted, and the extracted image tracking means 13 for extracting a local image of the same size having the highest degree of coincidence between the image and the local image having the highest degree of coincidence is extracted. A movement amount calculation means 14 for obtaining a coordinate difference, a movement tracking means 15 for obtaining a movement destination coordinate of the tracking part based on the coordinate difference, and a tracking image in which the mark display position is changed based on the movement destination coordinate is created. The tracking image generation means 16 is provided. The tracking image generation means 16 has a function of generating a tracking image of a moving image by sequentially storing the movement destination of the tracking portion (mark) according to the moving image and storing the tracking image in the tracking image storage unit 5.

  In addition, the motion calculation unit 6 quantitatively calculates measurement information, which is a physical quantity related to movement such as the movement amount, movement speed, and movement direction of the tracking part, based on the movement destination coordinates of the tracking part obtained by the automatic tracking part 4. It has a function of obtaining and displaying the change of the measurement information on the display unit 2 in a diagram.

  The present embodiment is characterized in that image feature enhancement means 13a is provided. The image feature enhancement means 13a reads out the moving image data stored in the image storage unit 1 to enhance the feature of the image, and sends the enhanced image to the cutout image tracking means 13. For example, a moving average filter or triangular weight filter that blurs the image is used as a means to enhance the image characteristics, and a differential filter or Laplacian filter that enhances the edge is used. Various filters such as a Laplacian / Gaussian filter or a Gaussian / Gaussian filter having an effect of emphasizing can be used, and features can be enhanced by combining these filters.

An example of a typical typical two-dimensional filter is shown. First, as an example of the 8-direction Laplacian filter, there are weights of the center pixel -8 and the peripheral pixel +1, and as an example of the 4-direction Laplacian filter, there is a weight of 1 at the center -4. Further, examples of the Gaussian filter include a center 1.0, up and down, left and right 0.61, diagonal 0.37 (requires normalization), and the like. These filters are weighted so that the absolute value of the weight is greater at the center than at the end. Needless to say, the moving average filter and the triangular weight filter are not described here.
The filter type, dimension, coefficient, and multiplication method are not limited to this. It may be isotropic or anisotropic. Further, these filters may be used in combination, whereby the features of the image can be arbitrarily enhanced and extracted.

  Next, the detailed functional configuration of the diagnostic imaging apparatus of the present embodiment will be described along with the operation according to the processing procedure shown in FIG. First, the movement tracking operation of the living tissue starts when a command for selecting the movement tracking mode of the tissue is input from the console 3 (S1). The display control means 11 reads the first frame image ft (t = 0) of the moving image from the image storage unit 1 and displays it on the display unit 2 (S2). For example, it is assumed that a tomographic image of the heart ventricle 21 shown in FIG. 3 is displayed as the first frame image f0. In FIG. 3, when the operator wants to select a specific part of the myocardium 22 as a tracking part of the biological tissue whose movement is to be tracked, the operator operates the mouse or the like of the operation unit 3 to superimpose the tracking part on the frame image f0. The tracking point 23, which is a mark for setting, is displayed. Then, the tracking point 23 is moved and displayed in a superimposed manner on a desired tracking part, and the tracking part is input and set. In FIG. 3, reference numeral 24 denotes a mitral valve.

  When the tracking point 23 is input and set, the control means 10 takes in the coordinates of the tracking point 23 on the frame image f0 and sends it to the image feature enhancement means 13a provided in front of the cutout image setting means 12 (S3). The image feature enhancement means 13a performs the process of enhancing the image features as described above, and sends the image with the features enhanced to the image setting means 12 (S4a). As shown in FIG. 4A, the cut-out image setting unit 12 sets a rectangular area having a size of 2 (A + 1) pixels (A is a natural number) around the image of the tracking point 23 as a cut-out image 25. (S4). Here, the size of the cut-out image 25 is preferably set to a region having a size including a living tissue different from the living tissue at the tracking point 23.

  The image feature enhancement means 13a reads the next frame image f1 of the moving image from the image storage unit 1 (S5a), emphasizes the feature of the image, and sends it to the cutout image tracking means 13 (S5b). The cutout image tracking means 13 extracts a local image of the same size having the highest degree of matching between the cutout image 25 and the image (S5). This extraction process is image processing called a so-called block matching method or correlation method. If this extraction process is performed for the entire region of the frame image f1, it takes too much processing time. Therefore, in order to shorten the extraction processing time, in the present embodiment, the search area 26 shown in FIG. 4B, which is sufficiently smaller than the frame image f1, is performed. That is, the search area 26 is a rectangular area in which the number B of pixels having a constant swing width is added to the cutout image 25 in the vertical and horizontal directions. The number of pixels B is larger than the amount of movement of the tissue related to the tracking region, and is set to 3 to 10 pixels, for example. This is because the range of movement of the circulatory system such as the heart is limited to a narrow region in a normal visual field. In this way, local images 27 of the same size in the search area 26 are sequentially shifted to obtain the degree of coincidence with the cut image 25. FIG. 5 shows a specific example of image tracking processing by the correlation method. In this example, in order to simplify the description, the size of the cut-out image 25 is described as a rectangular 9-pixel area, and the search area 26 is also described as a rectangular 25-pixel area. That is, the cutout image 25 shown in FIG. 10A is an example in which A = 1 pixel is set around the pixel of the tracking point 23, and the search area 26 shown in FIG. This is an example. According to this, as shown in FIG. 6B, the image coincidence is obtained for nine local regions 27. Various known methods can be applied to the method for obtaining the degree of coincidence of images.

  Next, a local image 27max having the highest degree of coincidence among the plurality of searched local images 27 is extracted, the local image 27max is set as a movement destination of the cut image 25, and the coordinates of the local image 27max are obtained (S6). The coordinates of these images are represented by the coordinates of the center pixel or the coordinates of any corner of the rectangular area. Then, a coordinate difference between the local image 27max and the cut-out image 25 is obtained, and a movement destination coordinate of the tracking point 23 is obtained based on the coordinate difference and stored in the tracking image storage unit 5. Usually, the display control means 11 reads the tracking image from the tracking image storage unit 5 and displays it on the frame image f1 of the display unit 2 (S7). Note that the relative position of the tracking point 23 in the local image 27max and the cutout image 25 is treated as not changing.

The motion calculation unit 6 calculates various measurement information related to the movement of the tracking point 23, that is, the movement of the tissue of the tracking part, based on the movement destination coordinates of the tracking point 23 obtained in S7 (S8). That is, the movement direction and the movement amount can be quantitatively measured based on the coordinates of the tracking part before and after the movement. In addition, measurement information, which is a physical quantity related to movement such as the movement amount, movement speed, and movement direction of the tracking part, can be obtained quantitatively.
Based on the measurement information thus obtained, the motion calculation unit 6 further displays various measurement information related to the movement of the tracking point 23 and changes thereof on the display unit in a graph (S9). Thereby, the viewer can easily observe the movement of the tracking portion.

  Next, the process proceeds to step S10, where it is determined whether or not tracking of the tracking point 23 has been completed for all frame images of the moving image. If there is an unprocessed frame image, the process returns to step S5 to perform the processes of S5 to S10. repeat. When the tracking of the tracking point 23 is completed for all the frame images, the tracking processing operation is ended. At this time, a tracking image indicating the movement history of the tracking point 23 is stored in the tracking image storage unit 5.

  As described above, according to the present embodiment, since the coordinates of the movement destination of the tracking point 23 can be obtained sequentially, the movement of the tracking part can be easily measured quantitatively and accurately, and the diagnosis can be performed. Information can be provided accurately.

  Here, a specific example of measuring the movement of the tracking portion of the living tissue using the above embodiment will be described with reference to FIGS. Figure 6 shows two tracking points 23 set across the heart wall of the myocardium 22, and the distance between the two tracking points 23, that is, the wall thickness, is measured, the change in the wall thickness is measured, and these are graphed. This is an example displayed on the display unit 2. Thereby, the wall thickness of the myocardium and the change in the wall thickness can be grasped quantitatively. FIG. 7A shows an example in which a plurality of tracking points 23 are set to face each other across the myocardial wall along the myocardium 22. According to this, the shape change and the wall thickness change of the heart wall accompanying the expansion and contraction and expansion of the heart can be easily observed by the movement of the mark.

  Here, in FIG. 7B, when a plurality of tracking points 23 are designated along the myocardium 22, the correspondence between the tracking points 23 and the wall thickness graph becomes difficult to understand. In this case, a command to switch to a display mode for displaying the same label on the tracking point 23 and the wall thickness graph is input from the console 3. As a result, the display control means 11 operates to add the same label to each measurement location of the corresponding tracking point 23 and each graph line of the wall thickness graph, and display the display unit 2 together with these added labels. As a result, the relationship between each trace location and each graph line of the wall thickness is clarified, and it is possible to easily determine which graph line is the wall thickness measured at which location. It is possible to accurately diagnose the unbalanced movement of the heart caused by badness.

  A mode that displays the wall thickness change rate at a specific time phase of the cardiac phase as shown in Fig. 7 (b), or displays the maximum wall thickness change rate instead of Fig. 7 (b) By providing this, it is possible to switch to an image display that makes it easy to observe the movement of the myocardium 22 according to the intention of the operator. These tracking images are created by the tracking image generation means 16 on the basis of a command from the console 3 and stored in the tracking image storage unit 5.

  As described above, according to the above-described embodiment, the following effects can be obtained. First, if the heart motion is biased to only one side after the heart surgery, or if the site where the change in the wall thickness of the myocardial wall is small is examined to examine the site where blood circulation is poor, Being confused makes it difficult to observe subtle differences in wall thickness changes. In this case, a tracking point is specified for the wall thickness part to be measured, the wall thickness change is displayed as a graph, and a label is attached to each measurement line and each graph line of the wall thickness, so that the movement of the heart is lost. Accordingly, the difference in change in the wall thickness of the myocardium depending on the site can be easily observed by associating the measurement location with the wall thickness graph. At this time, since the features of the image are emphasized, the movement of the part to be tracked and the tracking position track a part close to the appearance of human eyes.

  In addition, since the movement of each part of the heart can be measured quantitatively, for example, by tracking myocardial motion or quantitatively measuring changes in myocardial wall thickness, for example, an ischemic site is identified in ischemic heart disease. be able to. In addition, since the myocardial motion can be quantified, the degree of ischemia can be known, and can be used as an index for selecting a treatment method such as coronary artery regeneration and specifying a treatment site. In addition, quantitatively tracking the movement of the valve annulus may be useful in evaluating overall cardiac function in heart diseases such as hypertensive cardiac hypertrophy. Since the feature of the image is emphasized, this quantification standard is easily compared with a method that has been judged visually by a doctor in the past, so that verification is easy.

  Further, the present invention is not limited to measuring the movement of each part of the heart, but is obviously applicable to any part of the biological tissue as long as the movement of the biological tissue is desired to be observed. For example, it can be applied to pulse wave measurement of a large blood vessel wall such as a carotid artery. In this case, the degree of arteriosclerosis can be determined by setting a plurality of tracking parts in the longitudinal direction of the blood vessel wall and quantitatively measuring and comparing the movement amounts of these tracking parts. At this time, the image features are similarly emphasized, so that the blood vessel wall position of the doctor's appearance matches the tracking position well, and a result that is difficult to deviate from the experience of the doctor can be expected.

  Further, in the above-described embodiment, in order to observe the movement of the myocardium finely, the number of tracking points 23 that are marks of tracking parts is input and set from the console 3, and the setting work is complicated. Therefore, when setting the tracking point 23 along the myocardial wall, an appropriate interval is provided for a part where the tissue shape changes gently according to the operator's judgment, and an interval is provided for a part where the tissue shape changes greatly. You may make it set narrowing. In this case, it is preferable that the tracking points 23 are automatically complemented and set at a close interval by the control means 10.

  In the above-described embodiment, an example of performing offline has been described. However, if the speed related to the image tracking process is improved, the embodiment can be applied to an online or real-time moving image. Further, although a two-dimensional tomographic image has been described as an example, it goes without saying that the present invention can also be applied to a three-dimensional tomographic image.

The figure which shows the process sequence of one Embodiment of the movement tracking display method of the biological tissue of this invention. FIG. 2 is a block configuration diagram of an image diagnostic apparatus to which the biological tissue motion tracking display method of FIG. 1 is applied. The figure for applying and explaining the movement tracking of the biological tissue of this invention to the tomogram of a heart. It is a figure explaining one Embodiment of the image tracking processing method concerning this invention, (a) is an example of a cut-out image, (b) is a figure which shows an example of a search area | region. The figure explaining the image tracking process by a correlation method using a specific example. An example of measuring and displaying the distance between two marks set across the heart wall and the change in the distance. The figure which shows the example which displays the example which displays the tracking point set on the inner and outer wall of the heart so as to overlap the moving image of the heart, the example which displays only the tracking point, and the tracking point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image memory | storage part 2 Display part 3 Console 4 Automatic tracking part 5 Tracking image memory | storage part 6 Motion calculation part 7 Signal transmission path 8 Diagnostic image imaging device 10 Control means 11 Display control means 12 Cutout image setting means 13 Cutout image tracking means 13a Image enhancement means 14 Movement amount calculation means 15 Movement tracking means 16 Tracking image generation means

Claims (3)

An image storage unit (1) for storing a moving image obtained by imaging a cross section of a living body;
A display unit (2) for displaying the moving image;
An operation unit (3) for setting a mark on a desired tracking region of a living tissue with respect to one still image of the displayed moving image;
A diagnostic imaging apparatus comprising:
The cut-out image including the desired tracking region where the mark is set and the local image corresponding to the mark portion other than the one still image of the moving image are calculated, and the living tissue is determined by the degree of coincidence between the cut-out image and the local image A tracking unit (4) for tracking the movement destination coordinates of the mark, calculating the movement destination of the mark based on the tracked movement destination coordinates, and displaying the movement destination of the mark on the display unit (2);
A tracking image storage unit (5) for sequentially storing the movement destination of the mark according to the moving image;
Based on the movement destination coordinates of the living tissue, a physical quantity related to the movement destination coordinates of the tracking part is calculated as measurement information, and a movement calculation unit (6) for displaying a change of the measurement information on the display unit (2) in a diagram. )When,
A display control unit (11) for causing the display unit (2) to display the diagram displayed by the motion calculation unit (6) and the movement destination of the marks sequentially read from the tracking image storage unit (5);
Image enhancement means for enhancing the feature of the moving image,
The living tissue is myocardium,
The operation section (3) sets a plurality of the marks as tracking points, facing each other across the myocardial wall along the myocardium,
The diagram is a wall thickness graph,
The display control unit (11) adds the same label to each measurement location of the tracking point and each graph line of the wall thickness graph, and displays the same on the display unit (2) . The said display control part (11) switches the image displayed on a display part (2) according to the command which switches the display mode input from the said operation part (3), The display part (2) is characterized by the above-mentioned. Diagnostic imaging device. The display control unit (11) causes the display unit (2) to display the wall thickness change rate or the maximum value of the wall thickness change rate in a specific time phase of the cardiac phase together with the tracking point. Item 3. The diagnostic imaging apparatus according to Item 2.

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