JPWO2015136853A1 - Image processing apparatus, image processing method, and program - Google Patents

Abstract

Based on information obtained by tomographic imaging of the tubular object, information on the branch pipe portion branched from the tubular object is automatically provided. Of the tubular object image obtained by scanning the inside of the first tubular object using the probe, the part corresponding to the first tubular object and the second tubular object branched from the first tubular object The information which distinguishes the site | part to perform is acquired. The information is used to generate quantitative information indicative of the morphology of the second tubular object at the bifurcation from the first tubular object.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program.

  2. Description of the Related Art Conventionally, an apparatus that performs tomography by inserting a probe into a tubular object is known for image diagnosis of a tubular object such as a blood vessel. For example, such diagnostic imaging apparatuses are widely used for diagnosis of arteriosclerosis, preoperative diagnosis at the time of endovascular treatment with a high-function catheter such as a balloon catheter or a stent, or confirmation of postoperative results. . As typical image diagnostic apparatuses, for example, an intravascular ultrasonic diagnostic apparatus (IVUS), an optical coherence tomographic image diagnostic apparatus (OCT / OFDI), and the like have been developed.

  Techniques have also been developed that allow doctors to easily confirm blood vessel images taken with these devices. Citation 1 discloses a technique for associating a three-dimensional image reconstructed from a tomographic image obtained by IVUS or OCT with a three-dimensional image obtained by CT or MRI. In the technique described in the cited document 1, a blood vessel bifurcation is automatically extracted from an image obtained by IVUS or OCT for matching.

JP2012-075752A

  In some cases, it may be desirable to check not only information about the tubular object into which the probe is inserted, but also information about the branch pipe portion branched from the tubular object. For example, when a stent is placed at a branch portion of a blood vessel, it is desired to check not only information on the main blood vessel but also information on the branch blood vessel branched from the main blood vessel. However, no technology has been developed that makes it possible to easily acquire information on the branch pipe section.

  An object of the present invention is to automatically provide information on a branch pipe portion branched from a tubular object based on information obtained by tomographic imaging of the tubular object.

In order to solve the problems of the present invention, for example, an image processing apparatus according to an embodiment of the present invention comprises the following arrangement. That is,
Of the tubular object image obtained by scanning the inside of the first tubular object using a probe, a portion corresponding to the first tubular object and a second tubular object branched from the first tubular object An information acquisition means for acquiring information for distinguishing the portion corresponding to
Generating means for generating quantitative information indicating the form of the second tubular object at a branch from the first tubular object using the information;
Is provided.

  Based on information obtained by tomographic imaging of the tubular object, information about the branch pipe portion branched from the tubular object can be automatically provided.

  Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same reference numerals.

The accompanying drawings are included in the specification, constitute a part thereof, show an embodiment of the present invention, and are used to explain the principle of the present invention together with the description.
FIG. 1 is a diagram showing a schematic configuration of an image processing apparatus 100 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic configuration of the boundary extraction unit 200 according to an embodiment. FIG. 3 is a flowchart of processing performed by the boundary extraction unit 200 in one embodiment. FIG. 4A is a diagram illustrating processing performed by the boundary extraction unit 200 in one embodiment. FIG. 4B is a diagram illustrating processing performed by the boundary extraction unit 200 in an embodiment. FIG. 4C is a diagram illustrating processing performed by the boundary extraction unit 200 in one embodiment. FIG. 4D is a diagram illustrating processing performed by the boundary extraction unit 200 in one embodiment. FIG. 4E is a diagram illustrating processing performed by the boundary extraction unit 200 in one embodiment. FIG. 4F is a diagram illustrating processing performed by the boundary extraction unit 200 in one embodiment. FIG. 5A is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 5B is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 5C is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 6A is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 6B is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 6C is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 7A is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 7B is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 7C is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 8A is a diagram illustrating processing performed by the determination update unit 250 in one embodiment. FIG. 8B is a diagram illustrating processing performed by the determination update unit 250 according to an embodiment. FIG. 9 is a diagram illustrating an example of a screen that displays the determination result by the boundary extraction unit 200. FIG. 10 is a diagram illustrating a schematic configuration of the information calculation unit 1000 according to an embodiment. FIG. 11 is a flowchart of processing performed by the information calculation unit 1000 in one embodiment. FIG. 12A is a diagram for explaining an example of a method for approximating a boundary point group between a main blood vessel and a branch blood vessel. FIG. 12B is a diagram for explaining an example of an approximation method for a boundary point group between a main blood vessel and a branch blood vessel. FIG. 12C is a diagram for explaining an example of an approximation method of a boundary point group between a main blood vessel and a branch blood vessel. FIG. 12D is a diagram for explaining an example of an approximation method of a boundary point group between a main blood vessel and a branch blood vessel. FIG. 12E is a diagram for explaining an example of a method for approximating a boundary point group between a main blood vessel and a branch blood vessel. FIG. 13 is a diagram illustrating an example of the definition of the branch angle of the branch blood vessel. FIG. 14A is a diagram for explaining a method of selecting points projected onto a cross section of a branch blood vessel. FIG. 14B is a diagram for explaining a method of selecting points to be projected onto the cross section of the branch blood vessel. FIG. 14C is a diagram for explaining a method of selecting points projected onto the cross section of the branch blood vessel. FIG. 14D is a diagram for explaining a method of selecting points to be projected onto the cross section of the branch blood vessel. FIG. 15 is a diagram illustrating an example of a display screen for information generated by the information calculation unit 1000. FIG. 16 is a diagram illustrating a basic configuration of a computer according to an embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments.

  FIG. 1 shows an image processing apparatus 100 according to an embodiment of the present invention. The image processing apparatus 100 includes a display control unit 110, a boundary extraction unit 200, and an information calculation unit 1000. The image processing apparatus 100 may be part of an imaging system that includes an imaging apparatus (not shown) that acquires the blood vessel image 190.

  The image processing apparatus 100 receives a tubular object image obtained by scanning the inside of the tubular object using a probe. The type of the tubular object is not particularly limited. In the following description, it is assumed that the tubular object is a blood vessel, and a blood vessel image 190 is input to the image processing apparatus 100.

  The blood vessel image 190 is image information indicating the form of the blood vessel, and the form is not particularly limited. The blood vessel image acquisition method is not particularly limited, and for example, an existing ultrasonic diagnostic apparatus (IVUS), an optical coherent tomographic image diagnostic apparatus (OCT), an optical coherent tomographic image diagnostic apparatus (OFDI), or the like can be used. Hereinafter, the blood vessel into which the probe is inserted is called a main blood vessel.

  The blood vessel image 190 can be acquired as follows. That is, a plurality of line data is acquired by inserting a probe into a blood vessel and scanning the inside of the blood vessel. Each line corresponds to one scan, and one line data indicates the relationship between the distance from the probe in the depth direction of the blood vessel and the obtained signal intensity. A plurality of line data can be obtained by scanning while changing the probe direction and the position of the probe in the blood vessel length direction. In one embodiment, the blood vessel image 190 is composed of the plurality of line data. For example, the blood vessel image 190 may be an image in which one-dimensional images indicated by line data are arranged side by side. The blood vessel image 190 is a plurality of cross-sectional images obtained by arranging one-dimensional images indicated by line data in a circle (cross-sectional images in a direction crossing the blood vessel axis, for example, tomographic images perpendicular to the blood vessel axis). It may be constituted by. Further, the blood vessel image 190 may be subjected to gain correction, contrast correction, γ correction, or the like. In the present embodiment, the blood vessel image 190 is composed of a plurality of cross-sectional images whose gain and contrast are adjusted.

  The blood vessel image 190 is not limited to a combination of a plurality of transverse cross-sectional images, and may be a combination of a plurality of cross-sectional images in the blood vessel axis direction (tomographic images in a cross section parallel to the blood vessel axis), or a 3D image of a blood vessel. May be. As already known, these cross-sectional images, vascular axial cross-sectional images, and 3D images can be transformed into each other.

  The boundary extraction unit 200 detects a portion corresponding to the main blood vessel from the blood vessel image 190. Further, the boundary extraction unit 200 detects a portion corresponding to the branched blood vessel that branches off from the main blood vessel from the blood vessel image 190. In this way, the boundary extraction unit 200 detects the boundary portion between the main blood vessel and the branch blood vessel. According to the detection result, the boundary extraction unit 200 outputs information indicating a part corresponding to the main blood vessel in the blood vessel image 190 and information for distinguishing a part corresponding to the branch blood vessel to the information calculation unit 1000. However, as will be described later, it is not essential to detect a portion corresponding to the main blood vessel and a portion corresponding to the branch blood vessel before detecting the boundary portion between the main blood vessel and the branch blood vessel. A detailed configuration of the boundary extraction unit 200 will be described later. Here, the branch blood vessel is a structure connected to the main blood vessel into which the probe is inserted, and includes not only a tubular shape but also a umbilical shape.

  The information calculation unit 1000 refers to the information obtained from the boundary extraction unit 200 and generates quantitative information indicating the shape of the branch blood vessel in the branch portion from the main blood vessel. Then, the information calculation unit 1000 causes the display unit 120 to display the generated information via the display control unit 110.

  The display control unit 110 controls the display unit 120 to display desired information. The display unit 120 is a device that can display an image. The type of the display unit 120 is not particularly limited, and may be a liquid crystal display, for example.

[Boundary extraction part]
First, a schematic configuration of the boundary extraction unit 200 will be described with reference to FIG. The boundary extraction unit 200 includes an image acquisition unit 210, a position acquisition unit 220, a detection unit 230, and a determination unit 240.

  The image acquisition unit 210 acquires a blood vessel image 190. In the present embodiment, the image acquisition unit 210 acquires a plurality of tomographic images. Each tomographic image is processed by each unit described later, and information indicating a part corresponding to the main blood vessel and information identifying a part corresponding to the branch blood vessel are generated. The image acquisition unit 210 also performs preprocessing on the acquired tomographic image.

  The position acquisition unit 220 acquires the estimated position of the central point of the main blood vessel on the tomographic image. In the present embodiment, the position acquisition unit 220 calculates the estimated position of the central point of the main blood vessel by image processing on the tomographic image. However, the center point of the main blood vessel may be designated by a user input via an input unit (not shown).

  In one embodiment, the position acquisition unit 220 acquires the estimated positions of the guide wire and the catheter sheath image on the tomographic image. The position acquisition unit 220 calculates these estimated positions by image processing on the tomographic image. However, these positions may be designated by user input via an input unit (not shown).

  The detection unit 230 detects a plurality of points indicating the inner surface of the blood vessel on the tomographic image. Although various methods such as template matching can be considered as the detection method, in the present embodiment, the detection unit 230 extracts the position of the inner wall of the blood vessel on the tomographic image by scanning the tomographic image. Specifically, the detection unit 230 extracts a crossing point with the blood vessel when proceeding outward from the center point of the main blood vessel as the position of the blood vessel inner wall.

  The determination unit 240 determines whether each of the plurality of points detected by the extraction unit 230 indicates a main blood vessel. Further, the determination unit 240 determines whether or not the intersection detected by the extraction unit 230 indicates a branch blood vessel. The determination unit 240 can also determine whether each of the plurality of points detected by the extraction unit 230 indicates the boundary between the main blood vessel and the branch blood vessel. These determinations are made based on the positions of a plurality of points detected by the extraction unit 230. In one embodiment, these determinations are made based on the positional relationship between a plurality of consecutive points detected by the extraction unit 230. For example, as described later, based on a change in the distance from the center of the main blood vessel for a plurality of consecutive points, it is determined whether the point detected by the extraction unit 230 indicates a main blood vessel or a branch blood vessel. be able to. As will be described later, whether each point indicates a main blood vessel or a branch blood vessel based on a comparison between the distance from the center of the main blood vessel and a threshold value for a plurality of consecutive points detected by the extraction unit 230 Is also included in the determination based on the positional relationship between a plurality of consecutive points. Further, it can be determined that a branch blood vessel is present at a point where a plurality of continuous points are interrupted, and it can be determined that the ends of the plurality of continuous points indicate a boundary between the main blood vessel and the branch blood vessel.

  These determinations can be made independently. That is, the determination unit 240 indicates whether the point detected by the extraction unit 230 indicates a main blood vessel and a branch blood vessel, or whether the point detected by the extraction unit 230 indicates a boundary between the main blood vessel and the branch blood vessel, At least one of them can be determined. By these determinations, the boundary between the main blood vessel and the branch blood vessel is detected.

  For the determination by the determination unit 240, the distance between the center point of the main blood vessel and the intersection is mainly used. However, the determination unit 240 performs this determination using various other criteria. For example, in one embodiment, the determination unit 240 performs determination in consideration of the positions of the guide wire and the catheter sheath image on the tomographic image.

  In one embodiment, the boundary extraction unit 200 further includes a determination update unit 250. The determination update unit 250 updates the determination result by the determination unit 240. For example, the determination update unit 250 can correct the determination result by the determination unit 240. The determination update unit 250 can detect a new intersection and determine that the detected intersection indicates a main blood vessel or a branch blood vessel. Further, the determination update unit 250 can update the determination result by the determination unit 240 for another tomographic image based on the determination result by the determination unit 240 for one tomographic image constituting the blood vessel image 190.

  Next, the processing performed by the boundary extraction unit 200 will be described in detail with reference to the flowchart of FIG.

  In step S305, the image acquisition unit 210 acquires the blood vessel image 190. In this embodiment, it is assumed that the image acquisition unit 210 acquires a blood vessel image 190 including a plurality of tomographic images at a time. However, the image acquisition unit 210 may sequentially acquire tomographic images that are sequentially generated while performing blood vessel scanning using a probe. The following processing from step S310 is sequentially performed on each tomographic image. FIG. 4A shows a tomographic image to be processed in the following description.

  In step S310, the image acquisition unit 210 performs preprocessing on the acquired tomographic image. However, the image acquisition unit 210 may acquire a tomographic image that has already been preprocessed. The type of pre-processing is not particularly limited, but in one embodiment, filtering processing and binarization processing are performed. Although the kind of filter used is not specifically limited, For example, a smoothing filter process can be used, and the isolated point contained as noise can be reduced by performing a smoothing filter process with respect to a tomogram. The tomographic image after the filter processing is shown in FIG. 4B.

  Moreover, the process mentioned later can be simplified by performing a binarization process using a predetermined threshold value. In the binarization processing, a threshold value is used such that the inner wall of the blood vessel becomes a white pixel and the blood vessel lumen becomes a black pixel. Such a threshold value may be set in advance or may be automatically determined by the image acquisition unit 210 with reference to a tomographic histogram. The threshold value may be input by the user via an input unit (not shown). Below, it demonstrates on the assumption that the binarization process was performed in step S310. However, it is not essential to perform binarization processing. When performing binarization processing, a pixel having a pixel value within a predetermined range defined by the threshold is determined to be a white pixel, and a pixel having a pixel value outside the predetermined range is determined to be a black pixel. . Even if the binarization processing is not performed, for example, in step S325 described later, it is determined that a pixel having a pixel value within a predetermined range is a white pixel, and a pixel having a pixel value outside the predetermined range is It can be determined that the pixel is a black pixel. The tomographic image after binarization is shown in FIG. 4C.

  In step S315, the position acquisition unit 220 acquires the estimated position of the central point of the main blood vessel on the tomographic image. As described above, the estimated position of the center point may be input by the user, but in the present embodiment, the position acquisition unit 220 calculates the estimated position of the center point by image processing on the tomographic image.

  The calculation method of the estimated position of the center point is not particularly limited. In one embodiment, the main blood vessel on the tomographic image is detected, and the center of gravity is used as the estimated position of the central point of the main blood vessel. In the present embodiment, Hough transform is used as a main blood vessel detection method. That is, the position acquisition unit 220 performs a Hough transform process on the binarized tomographic image to detect a circle that approximates the inner wall shape of the main blood vessel. Then, the position acquisition unit 220 acquires the center position of the detected circle as the estimated position of the center point. An example of a circle detected by the Hough transform is shown in FIG. 4D.

  The center point estimation method using the Hough transform will be described in detail below. First, the position acquisition unit 220 extracts a black pixel circle (a circle having a black pixel inside the outline and a white pixel outside the outline (background)) by Hough transform. And the position acquisition part 220 specifies the largest thing among the circles which contain the center of a tomogram as a circle (henceforth a blood vessel circle) which shows the inner wall of a main blood vessel. The center of this blood vessel circle is treated as the estimated position of the central point of the main blood vessel. The position acquisition unit 220 also calculates the radius of the blood vessel circle.

  However, when the lumen of the main blood vessel is not substantially circular, there is a possibility that the blood vessel circle cannot be extracted by the Hough transform. In this case, the position acquisition unit 220 can use the center of the blood vessel circle extracted from the tomographic image at another position of the main blood vessel as the estimated position of the center point. The same applies to the radius of the blood vessel circle. In one embodiment, a tomographic image in which a blood vessel circle can be extracted by the Hough transform, and the center of the blood vessel circle extracted from the closest tomographic image is used as the estimated position of the center point. In another embodiment, the estimated position of the center point in the tomographic image at the adjacent position is used as the estimated position of the center point.

  As a further method, when the blood vessel circle cannot be extracted by the Hough transform, the position acquisition unit 220 may detect the inscribed circle of the blood vessel and treat the center of the inscribed circle as the estimated position of the center point of the main blood vessel. For example, a circle that is inscribed in three or more white pixels and does not pass through the white pixels on the binarized tomographic image can be detected as an inscribed circle of the blood vessel. Further, for example, the maximum circle among the circles inscribed in the blood vessel can be detected using Euclidean distance conversion. The distance conversion is not limited to Euclidean and may be weighted. As yet another method, the center of gravity of a plurality of points detected by the extraction unit 230 may be treated as the estimated position of the center point of the main blood vessel.

  As will be described later, after the intersection indicating the main blood vessel in the tomographic image is determined, the barycentric position of the intersection indicating the main blood vessel can also be calculated. In this case, the position acquisition unit 220 may use the barycentric position of the intersection indicating the main blood vessel calculated for the tomographic image at another position of the main blood vessel as the estimated position of the central point. In a further embodiment, if the blood vessel circle cannot be extracted by the Hough transform, the position acquisition unit 220 calculates the barycentric position of the intersection indicating the main blood vessel in a tomographic image at another position of the main blood vessel, and estimates the center point It can be used as a position.

  As described above, when the center of the blood vessel circle extracted from the tomographic image at the other position of the main blood vessel is used as the estimated position of the center point, there is a possibility that an erroneous determination of the intersection may occur. Therefore, for such a tomographic image, the determination unit 240 may determine an intersection serving as a wire shadow boundary pair with reference to the wire shadow boundary pair detected for the adjacent tomographic image. As a specific example, the determination unit 240 can determine that a wire shadow boundary pair exists in the same angular direction as the wire shadow boundary pair detected for the adjacent tomographic images. Further, the determination unit 240 can determine that a wire shadow boundary exists at the center in the angular direction of each wire shadow boundary detected for two adjacent tomographic images.

  In step S320, the position acquisition unit 220 further detects the estimated positions of the guide wire and the catheter sheath image from the tomographic image. Normally, when a blood vessel image is taken, a guiding catheter (not shown) is inserted into the main blood vessel via a guide wire, and a probe covered with a catheter sheath is inserted into the guiding catheter. . For this reason, the tomographic image includes an image of the guide wire and catheter sheath inserted into the main blood vessel. In the present embodiment, the determination unit 240 performs determination in consideration of the positions of the guide wire and catheter sheath images on the tomographic image.

  Specifically, the position acquisition unit 220 extracts a white pixel circle (a circle in which the outline is a white pixel and the outline is a black pixel) by Hough transform. The position acquisition unit 220 identifies the circle closest to the center of the tomographic image as a circle indicating the catheter sheath (hereinafter referred to as a sheath circle). The position acquisition unit 220 may treat only the extracted circles inside the circle indicating the inner wall of the main blood vessel as circle candidates indicating the catheter sheath. The center of this sheath circle is treated as the estimated position of the catheter sheath image.

  Further, the position acquisition unit 220 detects a pixel having the highest luminance among the pixels between the sheath circle and the blood vessel circle in the tomographic image before binarization. The detected pixel is treated as a pixel indicating a part of the guide wire (hereinafter referred to as a guide wire pixel), and the position of the guide wire pixel is treated as an estimated position of the guide wire image.

  In step S325, the detection unit 230 extracts a crossing point with the blood vessel as it goes outward from the center point of the main blood vessel as the position of the inner wall of the blood vessel. The specific process will be described below.

  First, the detection unit 230 performs preprocessing on the binarized tomographic image. Specifically, the detection unit 230 sets all pixels within a predetermined distance from the center of the blood vessel circle as black pixels. This predetermined distance is determined to be equal to or less than the radius of the blood vessel circle. By this processing, it is possible to reduce the possibility that a pixel that is close to the center of the blood vessel circle and is not the inner wall of the blood vessel is erroneously detected as the inner wall of the blood vessel. On the other hand, by making this predetermined distance smaller than the radius of the blood vessel circle, it is possible to reduce the possibility of failing to detect pixels indicating the inner wall of the blood vessel located near the blood vessel circle. The predetermined distance is not particularly limited, and may be 0.95 times or less of the radius of the blood vessel circle, or may be 0.50 times or more of the radius of the blood vessel circle, for example.

  By this processing, for example, a guide wire image, a catheter sheath image, and blood vessel lumen noise can be erased from the tomographic image. For this reason, the intersection is not detected from the region where the distance from the center point of the main blood vessel is equal to or less than the predetermined distance. Other methods can be used to eliminate guide wire images, catheter sheath images, and vessel lumen noise. For example, a guide wire image or a catheter sheath image can be recognized using template matching, and the recognized image can be erased. Furthermore, noise or a catheter sheath image may be recognized and erased by using morphological processing. A tomographic image immediately before the intersection detection is shown in FIG. 4E.

  Thereafter, the detection unit 230 performs scanning from the central point of the main blood vessel in each angle direction, and detects an intersection with the blood vessel, that is, an intersection with the white pixel. In other words, for each of a plurality of half lines extending in the respective angular directions from the central point of the main blood vessel, the detection unit 230 selects a pixel closest to the central point among the white pixels on the half line as an intersection corresponding to the angular direction. Detect as. By performing 360 ° scanning, pixels indicating the inner wall of the blood vessel are extracted. The detection unit 230 stores each detected intersection in association with the angular direction and the distance from the center point of the main blood vessel. Using the stored information, a graph can be created in which the horizontal axis indicates the scanning angle and the vertical axis indicates the distance from the center point of the main blood vessel.

  An example of detection by the detection unit 230 is shown in FIG. 4F. In FIG. 4F, scanning is performed for each of the angular directions 411, 412, and 413 from the center 400 of the blood vessel circle. As a result, intersections 421, 422, and 423 are detected.

  In step S330, the determination unit 240 determines whether the intersection indicates the main blood vessel based on the distance from the center point of the main blood vessel to the intersection. The determination unit 240 determines whether the intersection indicates a branch blood vessel. Generally, in the tomographic image, the branch blood vessel is separated from the main blood vessel, so that the inner wall of the branch blood vessel is considered to be further away from the center point of the main blood vessel than the inner wall of the main blood vessel. Therefore, the determination unit 240 determines that the intersection indicates the inner wall of the main blood vessel when the distance from the central point of the main blood vessel to the intersection is equal to or less than the threshold value. This threshold is determined based on the radius of the blood vessel circle. A specific threshold value determination method is not particularly limited, and may be, for example, 0.90 times or more of the radius of the blood vessel circle or 1.10 times or less of the radius of the blood vessel circle.

  In one embodiment, the determination unit 240 determines that the intersection indicates the inner wall of the branch blood vessel when the distance from the center point of the main blood vessel to the intersection exceeds a threshold value. However, the inner wall of the main blood vessel located behind the guide wire as viewed from the probe is not shown in the tomographic image. Then, there is a possibility that an unrecognized region 430 (hereinafter referred to as a guide wire shadow) shown in FIG. 4F is erroneously recognized as a branch blood vessel. Therefore, in the present embodiment, the determination unit 240 further considers the positions of the catheter sheath image and the guide wire image, and guides whether an intersection whose distance from the center point of the main blood vessel exceeds the threshold indicates a branch blood vessel. It is determined whether the shadow of the wire is shown.

  Specifically, the determination unit 240 indicates that an intersection near the extension from the center of the sheath circle to the position of the guide wire pixel indicates a shadow of the guide wire, and an intersection not near the extension line indicates a branch blood vessel. judge. For example, the determination unit 240 has an intersection within a predetermined angle range from the direction from the catheter sheath image to the guide wire image on the tomographic image when the distance between the central point of the main blood vessel and the intersection exceeds a threshold value. Is determined to show the shadow of the guide wire. In addition, the determination unit 240 is such that the distance between the center point of the main blood vessel and the intersection exceeds the threshold and is not within a predetermined angle range from the direction from the catheter sheath image to the guide wire image on the tomographic image. It is determined that the intersection indicates a branch vessel. This angle range is not particularly limited, and can be set as appropriate.

  The determination method by the determination unit 240 is not limited to this method. For example, when the distance from the center point of the main blood vessel to the intersection is greatly changed at two intersections located in the adjacent angular directions, the determination unit 240 determines whether the two intersections are a shadow of a guide wire or a branched blood vessel. Can be determined. And the determination part 240 can determine with the intersection which was not determined to show the shadow of a guide wire or a branch blood vessel showing a main blood vessel. This method can be applied to, for example, a tomographic image in which a blood vessel circle cannot be detected by the Hough transform.

  In step S335, the determination unit 240 detects an intersection indicating the boundary between the main blood vessel and the branch blood vessel according to the determination result. The determination unit 240 also detects an intersection indicating the boundary between the main blood vessel and the guide wire shadow. In this embodiment, when it is determined that one of the intersections in the adjacent angular direction indicates the main blood vessel and the other indicates the branch blood vessel, the determination unit 240 determines that the intersection indicating the main blood vessel is the main blood vessel. It is determined that the boundary with the branch vessel is indicated. However, in this case, it may be determined that the intersection indicating the branch blood vessel indicates the boundary between the main blood vessel and the branch blood vessel. If the resolution of scanning in the angular direction by the detection unit 230 is sufficiently high, there is no great difference in information obtained by either method. When it is determined that one of the intersections in the adjacent angular direction indicates the main blood vessel and the other indicates the shadow of the guide wire, the determination unit 240 determines that the intersection indicating the main blood vessel is the main blood vessel and the guide wire. It is determined to indicate the boundary with the shadow of. However, in this case, it may be determined that the intersection indicating the shadow of the guide wire indicates the boundary between the main blood vessel and the shadow of the guide wire.

  In addition, there is a possibility that an intersection indicating a shadow of a branch blood vessel or a guide wire is not detected at a portion where the inner wall of the main blood vessel is interrupted. For example, in the case shown in FIG. 4F, an intersection indicating a guidewire shadow may not be detected in the angular direction in which the guidewire shadow is located. Further, depending on the angle formed by the inner wall of the main blood vessel and the inner wall of the branch blood vessel, there is a possibility that the intersection indicating the branch blood vessel is not detected around the branch position. Therefore, the determination unit 240 determines that the point indicating the inner surface is located at the boundary between the main blood vessel and the branch blood vessel (or the shadow of the guide wire) based on the position of the location where the inner surface of the main blood vessel is interrupted on the tomographic image. You can decide whether to do it.

  As a specific example, when the determination unit 240 has an intersection indicating a main blood vessel in one direction with respect to adjacent angular directions, but does not have an intersection indicating a main blood vessel in the other direction, the determination unit 240 Can be determined to indicate the boundary between the main blood vessel and the branch blood vessel or the shadow of the guide wire (this is the boundary candidate point). More specifically, when there is a boundary candidate point within a predetermined angle range from the direction from the catheter sheath image to the guide wire image, the determination unit 240 determines that the boundary candidate point is the main blood vessel and the guide wire. It is determined to indicate the boundary with the shadow. Further, when there is no boundary candidate point within a predetermined angle range from the direction from the catheter sheath image to the guide wire image, the determination unit 240 indicates the boundary between the main blood vessel and the branch blood vessel. Is determined. By such a method, the determination unit 240 can determine whether each of the plurality of points detected by the extraction unit 230 indicates the boundary between the main blood vessel and the branch blood vessel. In the present embodiment, whether the point detected by the extraction unit 230 indicates the boundary between the main blood vessel and the branch blood vessel is determined by whether the point detected by the extraction unit 230 indicates the main blood vessel and the branch blood vessel. This is done after judging. However, the determination of whether the point detected by the extraction unit 230 indicates the boundary between the main blood vessel and the branch blood vessel is the determination of whether the point detected by the extraction unit 230 indicates the main blood vessel and the branch blood vessel. Can be done independently.

  In step S340, the determination unit 240 detects an intersection pair indicating the boundary between the main blood vessel and the branch blood vessel that sandwiches the branch blood vessel portion. Specifically, the determination unit 240 indicates a boundary between the main blood vessel and the branch blood vessel, and is a set of two intersections existing in two different angular directions, and the intersection existing between the two angular directions is A set of intersections that all show branch vessels (or no intersection exists) is detected. Hereinafter, the pair of intersections thus detected is referred to as a branch boundary pair. Further, the determination unit 240 indicates a boundary between the main blood vessel and the shadow of the guide wire, and is a set of two intersections existing in two different angular directions, and all the intersections existing between the two angular directions are all A set of intersections showing a shadow of the guide wire (or no intersection exists) is detected. Hereinafter, the detected intersection pair is referred to as a wire shadow boundary pair. Such detected branch boundary pairs and wire shadow boundary pairs are used for processing by the determination update unit 250.

  In step S345, the determination update unit 250 updates the determination result by the determination unit 240 in step S330. Here, the determination update unit 250 refers to at least one of the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel and the position of the intersection indicating the boundary between the main blood vessel and the shadow of the guide wire. For example, the determination update unit 250 can determine whether or not a parameter determined based on the position of an intersection indicating these boundaries matches a predetermined condition, and can correct the determination result if they match. Further, the determination update unit 250 can detect a new intersection based on the position of the intersection indicating these boundaries, and can determine the detected intersection. In the following, five examples of the determination result update method will be described. However, various methods can be considered for the determination result update method, and the determination result update method is not limited to the following example.

(1) False detection of crescent main blood vessel When the main blood vessel has the shape shown in FIG. 5A (a crescent shape), an intersection is not detected for a part of the blood vessel inner wall of the main blood vessel, or a branched blood vessel is indicated. There is a possibility of being detected as an intersection. For example, in the case of FIG. 5A, since the intersection 502 has a large distance from the center point of the main blood vessel or a large change in the distance, there is a possibility that the intersection 502 is detected as an intersection indicating a branch blood vessel. In such a case, it is conceivable that the difference in distance from the center point of the main blood vessel to each of the branch boundary pairs 501 and 503 increases. On the other hand, as shown in FIG. 5B, when the main blood vessel has a substantially circular shape and an intersection 512 indicating a branch blood vessel is detected, from the center point of the main blood vessel to each of the branch boundary pairs 511 and 513. Often the distances are similar.

  Therefore, in the present embodiment, the determination update unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel, and determines that the determination unit 240 indicates the branch blood vessel when the predetermined condition is met. It is determined that the crossing point indicates the main blood vessel. Then, the determination update unit 250 updates the determination by the determination unit 240. Specifically, the determination update unit 250 determines that the intersection determined to indicate a branch blood vessel by the determination unit 240 when the difference in distance from the center point of the main blood vessel to each of the branch boundary pairs is equal to or greater than a threshold value. It is determined that the main blood vessel is indicated. In the case of FIG. 5A, the determination update unit 250 determines that the intersection 502 determined by the determination unit 240 to indicate a branch blood vessel indicates a main blood vessel. In addition, the determination update unit 250 determines that the intersections 501 and 503 do not indicate the boundary between the main blood vessel and the branch blood vessel and are not a branch portion boundary pair.

  When the main blood vessel has the shape shown in FIG. 5A, the number of intersections indicating the main blood vessel detected near the intersection 502 is reduced even if scanning is performed in each angular direction from the central point of the main blood vessel. . Therefore, in the present embodiment, the determination update unit 250 additionally detects an intersection indicating a main blood vessel that exists between the intersections 501 and 503 determined not to be a branch boundary pair. An example of the additional detection method will be described with reference to FIG. 5C. For example, the determination update unit 250 calculates a straight line 505 obtained by translating a straight line 502 that passes through the intersections 501 and 503 determined not to be a branch boundary pair by a predetermined distance in a direction away from the central point of the main blood vessel. Set. Then, the determination update unit 250 detects the intersections 504 and 506 between the parallel line 505 and the blood vessel as the intersections indicating the main blood vessel. Specifically, the determination updating unit 250 moves a point 505s obtained by moving the middle point 502m of the intersections 501 and 503 by a predetermined distance in a direction perpendicular to the straight line 502 passing through the intersections 501 and 503 and away from the center point of the main blood vessel. Set as a reference point. Then, the determination update unit 250 performs scanning on the straight line 505 in both directions from the set reference point 505s, and detects pairs of intersections with blood vessels, that is, pairs 504 and 506 of intersections with white pixels.

  The intersections 504 and 506 thus detected may be intersections indicating the main blood vessels. Therefore, the determination update unit 250 considers the size of the blood vessel in the upstream or downstream cross-sectional image, and determines whether or not the determination that the detected intersections 504 and 506 indicate the main blood vessel is appropriate. judge. In one embodiment, an upstream or downstream cross-sectional image that is substantially circular is referenced. For example, a cross-sectional image in which an intersection indicating a main blood vessel is additionally detected because it has the shape shown in FIG. 5A is not considered in this determination. As an example of the determination method, by updating the determination that the intersections 504 and 506 are intersections indicating the main blood vessels, the updated blood vessel size is the approximate size of the blood vessel in the upstream or downstream cross-sectional image. Can be determined to be valid. If the determination update unit 250 determines that the intersection is appropriate, the determination update unit 250 updates the determination by the determination unit 240 if the intersections 504 and 506 indicate main blood vessels.

  The determination update unit 250 can sequentially detect the intersections indicating the main blood vessels by setting, translating, and scanning the straight line passing through the pair of intersections indicating the newly detected main blood vessels. That is, the determination update unit 250 sets a straight line 508 obtained by translating a straight line 505 passing through the intersections 504 and 506 by a predetermined distance in a direction away from the central point of the main blood vessel. In addition, the determination update unit 250 uses, as a reference point, a point 508s obtained by moving the middle point 505m of the intersections 504 and 506 by a predetermined distance in a direction perpendicular to the straight line 505 passing through the intersections 504 and 506 and away from the center point of the main blood vessel. Set. Then, the determination update unit 250 performs scanning on the straight line 508 in both directions from the set reference point 508s, and detects a pair of intersections with blood vessels, that is, pairs 507 and 509 of intersections with white pixels. The determination update unit 250 determines the detected intersections 507 and 509 as intersections indicating main blood vessels. If the reference point becomes a white pixel when this process is repeated, the repetition may be terminated, or the distance to be translated may be made smaller.

(2) False detection of gourd-shaped main blood vessel Even when the main blood vessel is narrowed and has the shape (gourd shape) shown in FIG. 6B, no intersection is detected for a part of the blood vessel inner wall of the main blood vessel. Or as an intersection indicating a branch vessel. For example, in the case of the tomographic image 620 shown in FIG. 6B, the intersections 622 and 623 have a large distance from the center point of the main blood vessel, and thus may be detected as an intersection indicating a branch blood vessel. In this case, the intersections 621 and 624 are determined to be a branch boundary pair.

  Thus, there is a possibility that an intersection indicating a branch blood vessel is erroneously detected in a plurality of tomographic images in the vicinity of the stenosis site. Comparing the stenosis site with the tomographic images before and after, generally, the main blood vessel becomes narrower as it approaches the stenosis site from the upstream side, and the main blood vessel becomes wider as it progresses from the stenosis site to the downstream side. FIG. 6B shows a tomographic image 620 at a site where the stenosis is the highest, and 625 shows a distance between the branch boundary pairs 621 and 624 in the tomographic image 620. On the other hand, FIG. 6A shows a tomographic image 610 upstream from the tomographic image 620, and 612 shows the distance between the branch boundary pairs 611 and 613 in the tomographic image 610. 6C shows a tomographic image 630 downstream of the tomographic image 620, and 632 shows the distance between the branch boundary pairs 631 and 633 in the tomographic image 630. As described above, the distance between the branch boundary pairs becomes shorter as it approaches the stenosis site from the upstream side, and becomes longer as it advances from the stenosis site to the downstream side. On the other hand, when the main blood vessel has a substantially circular shape and there are branch blood vessels, the distance between the branch boundary pairs increases as it approaches the center of the branch blood vessel from the upstream side and approaches the downstream side from the center of the branch blood vessel. As it gets shorter.

  Therefore, in this embodiment, the determination update unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel, and determines that the determination unit 240 indicates a branch blood vessel when the predetermined condition is met. It is determined that the crossing point indicates the main blood vessel. Specifically, the determination update unit 250 determines whether or not the distance 612 between the branch boundary pairs detected from the tomogram 610 is greater than the distance 625 between the branch boundary pairs detected from the tomogram 620. judge. Further, the determination update unit 250 determines whether or not the distance 632 between the branch boundary pairs detected from the tomogram 630 is larger than the distance 625 between the branch boundary pairs detected from the tomogram 620. When both of these conditions are satisfied, there is a possibility that an intersection determined to indicate a branch blood vessel by the determination unit 240 in the tomographic images 610, 620, and 630 may indicate a main blood vessel. In addition, in the tomographic image between the tomographic image 610 and the tomographic image 630, there is a possibility that an intersection determined to indicate a branch blood vessel by the determination unit 240 may also indicate a main blood vessel.

  Then, the determination update unit 250 considers whether or not it is appropriate to determine that the detected intersections 622 and 623 indicate a main blood vessel in consideration of the size of the blood vessel in the upstream or downstream cross-sectional image. judge. This determination can be performed in the same manner as the determination for the intersections 504 and 506 described with reference to FIGS. If the determination update unit 250 determines that the intersection is appropriate, the determination unit 240 updates the determination by the determination unit 240 if the intersections 622 and 623 indicate main blood vessels. In addition, the determination update unit 250 determines that the intersections 621 and 624 do not indicate the boundary between the main blood vessel and the branch blood vessel and are not a branch portion boundary pair.

  The number of intersections indicating the main blood vessels detected near the intersections 622 and 623 even when the main blood vessels have the shape shown in FIG. 6B and when scanning is performed in the respective angular directions from the central point of the main blood vessels. Will be less. Therefore, in the present embodiment, the determination update unit 250 additionally detects an intersection indicating a main blood vessel that exists between the intersections 621 and 624 determined not to be a branch boundary pair. Additional detection can be performed in the same manner as when the main blood vessel has the shape shown in FIG. 5A.

(3) False detection when the branch vessel and wire shadow overlap When the branch vessel and guide wire shadow overlap, depending on the position of the guide wire, the intersection that originally shows the branch vessel may be If it shows a shadow, it may be misjudged. For example, in the tomographic image 720 shown in FIG. 7B, the intersection 723 indicates a branched blood vessel, but is erroneously determined to indicate a shadow of a guide wire. In FIG. 7B, it is determined that the intersection 722 also shows the shadow of the guide wire, and the intersections 721 and 724 are determined as wire shadow boundary pairs. When such an erroneous determination is made, the shadow size of the guide wire indicated by the wire shadow boundary pair 721, 724 increases.

  On the other hand, in the tomographic images at positions adjacent to each other, the shadow size of the guide wire is usually not so different. FIG. 7A is a tomographic image 710 at a position in the vicinity of the tomographic image 720 shown in FIG. 7B. FIG. 7C is also a tomographic image 730 at a position near the tomographic image 720 shown in FIG. 7B. In the tomographic image 710 and the tomographic image 730, the branch blood vessel and the shadow of the guide wire do not overlap. In this case, the size of the guide wire shadow indicated by the wire shadow boundary pair 711 and 712 is not significantly different from the size of the guide wire shadow by the wire shadow boundary pair 731 and 732.

  Therefore, the determination update unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the guide wire shadow, and the intersection determined by the determination unit 240 to indicate the guide wire shadow indicates a branch blood vessel. judge. Specifically, the determination updating unit 250 determines that the shadow of the guide wire and the branch blood vessel overlap when the size of the shadow of the guide wire is larger than the tomographic image at the neighboring position, and the guide It is determined that some of the intersections determined to indicate the shadow of the wire indicate the branch blood vessel.

  Hereinafter, an example of specific processing performed by the determination update unit 250 will be described. First, the determination update unit 250 calculates an angle width and a center angle for the detected wire shadow boundary pair. The angle width represents a difference between an angle direction from the center point of the main blood vessel to one of the wire shadow boundary pairs and an angle direction from the center point of the main blood vessel to the other of the wire shadow boundary pairs. The central angle is the angular direction located at the center of the angle direction from the center point of the main blood vessel to one of the wire shadow boundary pairs and the angle direction from the center point of the main blood vessel to the other of the wire shadow boundary pairs. Represents. 7A and 7C, 713 and 733 indicate angular widths, and 714 and 734 indicate central angles.

  Then, the determination update unit 250 detects a tomographic image in which the angle width of the wire shadow boundary pair is clearly wide. Specifically, the determination update unit 250 detects a tomographic image in which the angle width of the wire shadow boundary pair exceeds a threshold value. The threshold value may be set in advance or may be calculated by the determination update unit 250. For example, this threshold value can be calculated based on the average value of the angular widths calculated for a predetermined number of tomographic images adjacent to the tomographic image to be detected. In one example, the threshold value may be a value obtained by adding a predetermined value to the average value thus calculated. Hereinafter, for the tomographic image 720 illustrated in FIG. 7B, the determination update unit 250 determines that the angular width 725 exceeds the threshold value.

  When the tomographic image 720 in which the angle width of the wire shadow boundary pair exceeds the threshold is detected, the determination update unit 250 determines the position of the shadow of the guide wire in the tomographic image 720, that is, the position of the wire shadow boundary pair. presume. The determination update unit 250 performs this estimation based on the position of the wire shadow boundary pair calculated for the tomographic images 710 and 730 located in the vicinity of the tomographic image to be processed. Specifically, the determination update unit 250 refers to the positions of the wire shadow boundary pairs 711 and 712 detected from the tomographic image 710 and the positions of the wire shadow boundary pairs 731 and 732 detected from the tomographic image 730. The position of the wire shadow boundary pair in the second tomographic image is estimated. Here, the tomographic image 710, the tomographic image 720, and the tomographic image 730 are tomographic images at the first, second, and third positions of the blood vessel, respectively, and the second position is the first position and the third position. Exists between.

  More specifically, the determination update unit 250 performs linear interpolation between the center angle 714 of the wire shadow boundary pair detected from the tomographic image 710 and the center angle 734 of the wire shadow boundary pair detected from the tomographic image 730. Can be calculated. In this case, the determination update unit 250 can estimate the calculated value as the center angle 727 of the wire shadow boundary pair for the tomographic image 720. Further, the determination update unit 250 calculates a value by linear interpolation between the angle width 713 of the wire shadow boundary pair detected from the tomographic image 710 and the angle width 733 of the wire shadow boundary pair detected from the tomographic image 730. Can do. In this case, the determination update unit 250 can estimate the calculated value as the angle width 728 of the wire shadow boundary pair for the tomographic image 720. Here, the linear interpolation may be weighted according to the distance, or may be nonlinear interpolation from three or more frames.

  Using the center angle 727 and the angle width 726 of the wire shadow boundary pair thus estimated, the determination update unit 250 selects a part of the intersections determined to show the shadow of the guide wire in the tomographic image 720. Specifically, the determination update unit 250 determines the region 728 specified by the estimated center angle 727 and angular width 726 of the wire shadow boundary pair among the intersections determined to show the shadow of the guide wire in the tomographic image 720. An intersection 723 that does not exist within can be selected. However, the determination update unit 250 considers the calculation error of the estimated angle width 726 of the wire shadow boundary pair, adds a predetermined angle value to the angle width 726, and then selects the intersection 723. May be. Then, the determination update unit 250 determines that the selected intersection 723 indicates a branch blood vessel. Further, the determination update unit 250 can detect the intersection 724 indicating the boundary point between the main blood vessel and the branch blood vessel in the same manner as the determination unit 240 according to the new determination.

  In order to accurately estimate the position of the wire shadow boundary pair, the determination update unit 250 can select a tomographic image in which the shadow of the branch vessel and the guide wire do not overlap as a tomographic image used for estimation. That is, in one embodiment, the angle width 713 of the wire shadow boundary pair in the tomographic image 710 detected by the detection unit 230 is equal to or smaller than the threshold, and the angle width 733 of the wire shadow boundary pair in the tomographic image 730 is equal to or smaller than the threshold.

(4) Additional detection in the vicinity of the branch start portion of the branch blood vessel The detection unit 230 detects an intersection with the blood vessel when proceeding in each angular direction from the center point of the main blood vessel according to a predetermined angular direction resolution. However, when the resolution is rough, there is a possibility that the branch blood vessel cannot be extracted in the vicinity of the branch start portion of the branch blood vessel, that is, at a position away from the center of the branch blood vessel. Therefore, in the present embodiment, the determination update unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel, and detects a portion where there is a possibility that an undetected branch blood vessel exists. And the determination update part 250 detects an intersection according to higher angular direction resolution about the detected part, and determines whether the detected intersection shows a branch blood vessel.

  Specifically, the determination update unit 250 first detects a combination of a tomographic image 810 in which a branch boundary pair is detected and a tomographic image 820 in which a branch boundary pair is not detected. Here, the tomographic image 810 is a tomographic image at a first position of the blood vessel, and the tomographic image 820 is a tomographic image at a second position adjacent to the first position. Since the branch blood vessel is shown in a plurality of adjacent tomographic images, there is a possibility that the branch blood vessel is shown although the branch blood vessel was not detected from the tomographic image 820.

  Next, the determination update unit 250 refers to the angle direction 814 of the branch boundary pair 811 and 812 calculated from the tomogram 810 as shown in FIG. 8A, and detects the detection range in the tomogram 820 as shown in FIG. 8B. 825 is set. This detection range 825 is defined by a detection start angle and a detection end angle. Specifically, the detection range 825 is set to include the angular direction 814. The width of the set detection range 825 is not particularly limited. In one embodiment, the width of the detection range 825 is set to match the angular width 813 of the branch boundary pair 811 812. That is, the detection start angle coincides with the angular direction from the main blood vessel center point to the intersection 811, and the detection end angle coincides with the angular direction from the main blood vessel center point to the intersection 812. In another embodiment, in order to confirm the trend of the change in the distance from the center point of the main blood vessel to the intersection, the width of the detection range 825 is a predetermined value than the angular width 813 of the branch boundary pair 811 812. Is set to be only larger. The angular width and the angular direction of the branch boundary pair can be calculated in the same manner as the angular width and the angular direction of the wire shadow boundary pair.

  Then, the determination update unit 250 detects an intersection in the set detection range 825 using a detection method with higher sensitivity while using the same method as the detection unit 230. Hereinafter, an example of increasing the detection sensitivity of an intersection will be described, but the method of increasing the sensitivity is not limited to the following example.

  As an example, the determination update unit 250 can detect an intersection according to an angular direction resolution higher than the angular direction resolution when the detection unit 230 performs scanning. In one example, if the detection unit 230 scans every 1 °, the determination update unit 250 can scan every 0.25 °. Then, similarly to the determination unit 240, the determination update unit 250 determines whether the detected intersection indicates a main blood vessel or a branch blood vessel.

  Further, as described above, when the distance from the central point of the main blood vessel to the intersection is greatly changed at two intersections located in adjacent angular directions, the determination unit 240 determines that the two intersections are branched blood vessels. (Or a shadow of a guide wire). The determination update unit 250 can also determine that the intersection indicates a branch blood vessel using the same method, but the determination threshold used in this case is made smaller than the threshold used when the determination unit 240 performs the determination. Can do. For example, the determination unit 240 determines that the two intersections indicate a branch blood vessel (or a shadow of a guide wire) when the difference in distance from the center point of the main blood vessel to the two intersections is greater than the first threshold. Can do. The determination update unit 250 determines that the two intersections indicate a branch blood vessel (or a shadow of a guide wire) when the distance difference from the center point of the main blood vessel to the two intersections is larger than the second threshold. be able to. Here, the second threshold value is smaller than the first threshold value.

  In another method, for an intersection located in an adjacent angular direction, a trend of a change in the distance from the center point of the main blood vessel is detected, and an intersection where the change in the distance is greater than a threshold is determined to indicate a branch vessel. The For example, for the first, second, and third intersections located in adjacent angular directions, the distance difference from the central point of the main blood vessel to the first and second intersections, and the second and second points from the central point of the main blood vessel. The difference between the distance difference to the three intersections and the difference is calculated. When the difference is larger than the first threshold, the determination unit 240 can determine that the first intersection indicates a branch blood vessel (or a shadow of a guide wire). Moreover, the determination update part 250 can determine with the 1st intersection showing a branch blood vessel, when this difference is larger than a 2nd threshold value. Again, the second threshold is smaller than the first threshold.

(5) Additional extraction of branch blood vessels In the method of detecting intersections by scanning in the respective angular directions from the central point of the blood vessels used by the detection unit 230, the number of intersections detected in the branch blood vessel portion is reduced. Can be considered. Therefore, the determination update unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel, specifically, the position of the branch boundary boundary pair, and detects and detects a further intersection indicating the branch blood vessel. It is determined that a branch blood vessel is indicated at the intersection.

  A specific method is the same as the method of additionally detecting the intersection indicating the main blood vessel described with reference to FIG. 5C. That is, the determination update unit 250 sets a straight line obtained by translating a straight line passing through an intersection determined to be a branch boundary pair by a predetermined distance in a direction away from the central point of the main blood vessel. Then, the determination update unit 250 detects an intersection between the translated straight line and the blood vessel as an intersection indicating a branch blood vessel.

  In a further embodiment, the determination updating unit 250 refers to the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel that does not form the branch boundary pair, and detects and detects a further intersection indicating the branch blood vessel. It is determined that a branched blood vessel is indicated at the intersection. For example, as shown in FIG. 7B, when the branch blood vessel and the shadow of the guide wire overlap, an intersection indicating a boundary between the main blood vessel and the branch blood vessel that does not form a branch boundary pair may occur. In this case, the determination update unit 250 sets a straight line that passes through the intersection 724 indicating the boundary between the main blood vessel and the branch blood vessel and is orthogonal to the direction indicated by the estimated center angle 727 of the wire shadow boundary pair to the center point of the main blood vessel. A straight line obtained by translating a predetermined distance in the direction away from the center is set. Then, the determination update unit 250 can detect an intersection between the translated straight line and the blood vessel as an intersection indicating a branch blood vessel.

  In this case, the determination update unit 250 determines a point away from the intersection 724 by a predetermined distance in a direction approaching the central point of the main blood vessel along a straight line orthogonal to the direction indicated by the central angle 727. Then, the determination update unit 250 sets, as a reference point, a point that has been moved by a predetermined distance in the direction indicated by the center angle 727 in the direction away from the center point of the main blood vessel. Further, the determination update unit 250 performs scanning on a straight line set in a direction approaching the intersection 724 from the set reference point, and uses the intersection with the blood vessel, that is, the intersection with the white pixel as an intersection indicating a branch blood vessel. Can be detected.

  In another embodiment, instead of the intersection determined to be a branch boundary pair, the determination update unit 250 includes an intersection 721 indicating a boundary between the main blood vessel and the shadow of the guide wire, a main blood vessel, and a branch blood vessel. It is also possible to use a pair with an intersection 724 indicating the boundary of. That is, the determination update unit 250 sets a straight line obtained by translating a straight line passing through the pair by a predetermined distance in a direction away from the central point of the main blood vessel. Then, the determination update unit 250 detects, as an intersection indicating a branch blood vessel, an intersection closer to the intersection 724 out of a pair of intersections of the translated straight line and the blood vessel.

  The determination updating unit 250 refers to the position of the wire shadow boundary pair in the same manner, detects a further intersection indicating the guide wire shadow, and determines that the detected intersection indicates the guide wire shadow. Good.

  The determination update unit 250 may use only one of the above methods (1) to (5), or may use a plurality of methods in combination. The order in which the above methods are applied is not particularly limited. In one embodiment, in order to extract many intersections indicating branch blood vessels, the determination update unit 250 performs the process (5) after performing the processes (1) to (4). In the methods (2) to (4), the position of the intersection indicating the boundary between the main blood vessel and the branch blood vessel and the shadow of the main blood vessel and the guide wire in the tomographic image at a position different from the tomographic image to be processed. Processing is performed with reference to at least one of the positions of intersections indicating boundaries. Thus, by referring to a plurality of tomographic images, the boundary between the main blood vessel and the branch blood vessel can be detected with higher accuracy.

  The boundary extraction unit 200 sends the determination result thus obtained to the information calculation unit 1000 in order to calculate quantitative information about the branch blood vessel. Specifically, the position information about each intersection and the determination result by the determination unit 240 or the determination update unit 250 are sent to the information calculation unit 1000. In one embodiment, this position information includes the angular direction from the central point of the main blood vessel and the distance from the central point. In this case, the boundary extraction unit 200 can send the estimated position of the central point of the main blood vessel in the tomographic image to the information calculation unit 1000. In another embodiment, this position information may include the XY coordinates of the intersection on the tomographic image. As described above, the boundary extraction unit 200 generates determination results for a plurality of intersections for each tomographic image and sends the determination results to the information calculation unit 1000.

  However, it is not essential to send all the determination results, and the boundary extraction unit 200 stores information that distinguishes at least a portion corresponding to the main blood vessel and a portion corresponding to the branch blood vessel branching from the main blood vessel. This is sent to the calculation unit 1000. For example, the boundary extraction unit 200 may send only the position information about the intersection indicating the boundary between the main blood vessel and the branch blood vessel to the information calculation unit 1000. Further, the boundary extraction unit 200 may send only the position information about the intersection indicating the branch blood vessel to the information calculation unit 1000.

  Further, the boundary extraction unit 200 can cause the display unit 120 to display the determination result via the display control unit 110. An example of the display screen is shown in FIG. In the display screen 900 shown in FIG. 9, a cross-sectional image 910 and a blood vessel axis direction cross-sectional image 920 are displayed. In the cross-sectional image 910, dots 911 to 915 that indicate the detected intersections and are displayed in different colors are superimposed and displayed. Each of the dots 911 to 915 includes an intersection indicating a main blood vessel, an intersection indicating a branch blood vessel, an intersection indicating a shadow of the guide wire, an intersection indicating a boundary point between the main blood vessel and the branch blood vessel, and a shadow of the main blood vessel and the guide wire. The intersection which shows the boundary point of is represented. The user can stop the display of these dots 911 to 915 by operating the check box 916, for example. Similarly, dots 911 to 915 are also superimposed on the blood vessel axis direction cross-sectional image. In this manner, by displaying the determination result automatically generated by the determination unit 240 or the determination update unit 250, the user can easily identify a portion corresponding to the branch blood vessel or the shadow of the guide wire in the blood vessel image. Is possible.

[Information calculation unit]
Next, a schematic configuration of the information calculation unit 1000 will be described with reference to FIG. The information calculation unit 1000 includes an information acquisition unit 1010 and a generation unit 1020.

  The information acquisition unit 1010 acquires information that distinguishes a portion corresponding to the main blood vessel and a portion corresponding to a branch blood vessel that branches from the main blood vessel in the blood vessel image 190. As described above, the information acquisition unit 1010 acquires the determination result obtained by the boundary extraction unit 200. In this embodiment, the information acquisition unit 1010 acquires from the boundary extraction unit 200 at least position information about an intersection indicating a boundary between a main blood vessel and a branch blood vessel or position information about an intersection indicating a branch blood vessel. The information acquisition unit 1010 can also acquire a blood vessel image 190.

  The generation unit 1020 uses the information acquired by the information acquisition unit 1010 to generate quantitative information indicating the morphology of the branch blood vessel at the branch portion from the main blood vessel. Examples of the quantitative information include information indicating the size of the branch blood vessel at a branch portion from the main blood vessel, information indicating the branch direction of the branch blood vessel from the main blood vessel, and the like. In the present embodiment, the generation unit 1020 generates both information indicating the size of the branch blood vessel and information indicating the branch direction, but the generation unit 1020 may generate one of these pieces of information.

  Next, the processing performed by the information calculation unit 1000 will be described in detail with reference to the flowchart of FIG.

  In step S1110, as described above, the information acquisition unit 1010 acquires information for distinguishing between a portion corresponding to the main blood vessel and a portion corresponding to a branch blood vessel branching from the main blood vessel in the blood vessel image 190.

  In step S1120, the generation unit 1020 detects a branch portion of the branch blood vessel included in the blood vessel image 190. The generation unit 1020 determines that one branch portion exists for continuous tomographic images in which branch blood vessels exist. Whether or not a branch blood vessel exists in the tomographic image can be easily determined by confirming the presence of an intersection indicating the boundary between the main blood vessel and the branch blood vessel or an intersection indicating the branch blood vessel. When a plurality of branch portions are detected, the following processing is performed for each branch portion.

  In steps S1130 to S1140, the generation unit 1020 calculates the branch plane information for the branch portion detected in step S1120. The branch plane is a plane connecting the main blood vessel and the branch blood vessel. Examples of the branch plane information include the position, direction, size, and the like of the branch plane. The size of the branch surface corresponds to the size of the branch blood vessel at the branch portion from the main blood vessel. The size of the branch surface includes not only the area of the branch surface, but also the length indicating the characteristics of the branch surface (radius and diameter for a circle, minor axis and major axis for an ellipse, etc.) and the length of the circumference of the branch surface Also included.

  In step S1130, the generation unit 1020 derives an approximate polygon or approximate ellipse that approximates the boundary point group between the main blood vessel and the branch blood vessel. For example, FIG. 12A shows a boundary point group 1201 that is an intersection group indicating a boundary between a main blood vessel and a branch blood vessel. In the present embodiment, the generation unit 1020 derives an approximate plane 1202 that approximates the boundary point group 1201 as illustrated in FIG. 12B. Furthermore, as illustrated in FIG. 12C, the generation unit 1020 obtains a projection point group 1203 by projecting each boundary point group 1201 onto the approximate plane 1202 perpendicularly. Thus, as shown in FIG. 12D, an approximate polygon 1204 configured by the projected point group 1203 is derived. The approximate polygon 1204 is obtained by linearly connecting adjacent projection point groups 1203. However, instead of the approximate polygon 1204, an approximate curve obtained by nonlinearly connecting the projection point group 1203 using, for example, a spline curve or the like may be derived. Then, the generation unit 1020 derives an approximate ellipse 1205 that approximates the approximate polygon 1204 as illustrated in FIG. 12E. The algorithm used for the approximation is not particularly limited, and a conventionally known method such as least square approximation can be used.

  In step S1140, the generation unit 1020 determines the size of the derived approximate polygon (or approximate curve), the size of the maximum inscribed circle of the derived approximate polygon (or approximate curve), or the derived approximate ellipse. Is calculated as quantitative information. For example, the generation unit 1020 can calculate the area of the derived approximate polygon. Further, the generation unit 1020 can calculate the radius, diameter, or area of the maximum inscribed circle of the derived approximate polygon. Furthermore, the generation unit 1020 can calculate the short axis length, the long axis length, the area, or the like of the derived approximate ellipse. Further, the generation unit 1020 can calculate the circumference of the derived approximate polygon or approximate ellipse. The generation unit 1020 further calculates the center of the maximum inscribed circle of the derived approximate polygon, the intersection of the major axis and the minor axis of the derived approximate ellipse, or the center of gravity of the derived approximate polygon or approximate ellipse. May be. Here, it is considered that the short axis length of the approximate ellipse approximates the diameter of the branch blood vessel at the branch portion. The area of the approximate polygon or approximate ellipse is considered to approximate the area of the branch plane.

  The branch surface information thus obtained is used as reference information for selecting a device such as a balloon or a stent to be inserted into the branch blood vessel. In steps S1130 and S1140, the generation unit 1020 derives the maximum inscribed sphere inscribed in the boundary point group between the main blood vessel and the branch blood vessel, and calculates the size and position of the derived maximum inscribed sphere. Good. The value calculated in this way is also branch information and represents the size and position of the branch portion.

  In steps S1150 to S1170, the generation unit 1020 calculates the branch direction of the branch blood vessel from the main blood vessel for the branch portion detected in step S1120.

  In step S1150, the generation unit 1020 calculates the direction of the main blood vessel at the branch portion. For example, the generation unit 1020 can calculate the center of gravity of the lumen of the main blood vessel in two or more tomographic images in the vicinity of the branch portion, and can derive a vector that approximates the position of the center of gravity. For this calculation, it is possible to use position information about the intersection indicating the main blood vessel acquired from the boundary extraction unit 200. The vector derived in this way represents the direction of the main blood vessel. The calculation of the center of gravity can be performed using position information about the intersection indicating the main blood vessel. The tomographic image used for calculating the direction of the main blood vessel may be a tomographic image in which a branched portion is reflected, or a tomographic image within a predetermined range from the branched portion. However, the center of the approximate ellipse of the lumen of the main blood vessel or the center of the maximum inscribed circle of the lumen of the main blood vessel can be used instead of the center of gravity of the lumen of the main blood vessel.

  When a lesion is present in the vicinity of the bifurcation, the lumen of the main blood vessel becomes narrow and the position of the center of gravity moves in the lesion. In one embodiment, when a lesion is present in the vicinity of the branch portion, a tomographic image closer to the branch portion than the lesion is used. In this case, the influence of the lesion when calculating the direction of the main blood vessel can be suppressed. The detection method of the lesion is not particularly limited. For example, when the lumen of the main blood vessel is smaller than the threshold value, it can be determined that the lesion is reflected in the tomographic image. In another embodiment, the generation unit 1020 identifies a tomographic image in which the maximum inscribed circle of the lumen of the main blood vessel is the smallest among the tomographic images in which the lesion is reflected. The center of the inscribed circle in the identified tomographic image can be used instead of the center of gravity of the lumen of the main blood vessel. According to such a configuration, the calculated branching direction approximates the traveling direction of the branching blood vessel relative to the traveling direction of the catheter or the like in the blood vessel, which is useful in making a treatment plan.

  In step S1160, the generation unit 1020 calculates the branch direction of the branch blood vessel at the branch portion. In the present embodiment, the generation unit 1020 calculates the branch direction of the branch blood vessel with reference to the position information about the intersection indicating the branch blood vessel. For example, the generation unit 1020 can derive an inscribed sphere inscribed in the branch blood vessel. Then, the generation unit 1020 determines the branch direction of the branch blood vessel based on the direction from the center of the approximate polygon (or approximate curve) or approximate ellipse derived in step S1140 toward the center of the derived inscribed sphere. Can be calculated.

  Specifically, the generation unit 1020 derives the maximum inscribed sphere inscribed in the intersection group indicating the branch blood vessel. Here, the maximum inscribed sphere is derived so as not to protrude from the space surrounded by the intersection group indicating the branch blood vessel on the branch portion side or the open portion side (downstream side) away from the branch portion. Alternatively, the maximum inscribed sphere may be derived after adding a point group representing the start point of the branch blood vessel and a point group on the open side (downstream side) away from the branch portion to the intersection group indicating the branch blood vessel. Good. Then, the generation unit 1020 calculates a vector from the approximate polygon (or approximate curve) or approximate ellipse calculated in step S1140 toward the center of the maximum inscribed sphere as a vector indicating the branch direction of the branch blood vessel. . However, the generation unit 1020 may use the center of the maximum inscribed circle of the approximate polygon (or approximate curve) derived in step S1140 instead of the approximate polygon (or approximate curve) or the center of gravity of the approximate ellipse. . In one embodiment, in order to increase the calculation accuracy, a predetermined number of point groups that are further away from the branch portion are selected from the intersection group indicating the branch blood vessel, and the maximum inscribed inscribed in the selected point group is selected. A sphere is derived.

  In another embodiment, the generation unit 1020 derives two or more inscribed spheres inscribed in the intersection group indicating the branch blood vessel, and the direction from the center of one inscribed sphere toward the center of the other inscribed sphere May be calculated as the branch direction of the branch vessel. In this case, the branch direction of the branch blood vessel can be calculated based only on the position information about the intersection indicating the branch blood vessel. In one embodiment, in order to improve the calculation accuracy of the branch direction of the branch vessel, one inscribed sphere is the maximum inscribed sphere, and the distance between the centers of the two inscribed spheres is equal to or greater than a threshold value. Two inscribed spheres are derived such that the difference between the inscribed sphere radii is equal to or less than a threshold value.

  When a lesion is present in a branch blood vessel, the same processing as when a lesion is present in the main blood vessel can be performed. The generation unit 1020 can quantitatively represent the branch direction of the branch blood vessel in the branch portion thus obtained using an angle. In one embodiment, this branch direction can be expressed as an angle with respect to the scanning direction when the blood vessel image 190 is captured. The branch direction thus obtained can be used as reference information when a guide wire or the like is inserted into the branch blood vessel.

  On the other hand, in step S1170 of the present embodiment, the generation unit 1020 calculates the branch angle of the branch blood vessel from the main blood vessel in order to provide more useful information. The branch angle calculated in this way corresponds to quantitative information indicating the form of the branch blood vessel in the branch portion from the main blood vessel. The method for calculating the branch angle is not particularly limited. For example, the generation unit 1020 may calculate an angle between a vector representing the direction of the main blood vessel and a vector representing the branch direction of the branch blood vessel.

  In another embodiment, the angles Φ and Θ shown in FIG. 13 are calculated so that the user can more easily understand the branch angle. In FIG. 13, an xyz coordinate system (right-handed Cartesian coordinate system) is set so that a vector 1301 representing the direction of the main blood vessel is on the xy plane and is parallel to the x-axis. Further, the xyz coordinate system of the vector 1302 representing the branch direction of the branch blood vessel is set so that the start point is located at the origin and the end point is located in the first quadrant of the xy plane. In FIG. 13, a projection point 1303 is a point obtained by projecting the end point of a vector 1302 onto the xy plane.

  The branch angle thus obtained can be used as reference information when a guide wire or the like is inserted into the branch blood vessel.

  In step S1180, the generation unit 1020 calculates information indicating the size of the branch blood vessel in the cross section orthogonal to the branch direction calculated in step S1160. The information calculated in this way also corresponds to quantitative information indicating the shape of the branch blood vessel in the branch portion from the main blood vessel. Examples of the information indicating the size of the branch blood vessel include a cross-sectional area, a circumference, a radius or a diameter of the maximum inscribed circle, and the like. The generation unit 1020 can generate information indicating the size of the branch blood vessel according to the intersection group indicating the branch blood vessel. Here, a cross-sectional image of a branch blood vessel can also be generated by projecting the luminance of the intersection group. The brightness of the projected intersection group is the brightness value of the corresponding pixel in the blood vessel image 190 (for example, a cross-sectional image).

  For example, the generation unit 1020 may project the intersection group indicating the branch blood vessel onto a cross section orthogonal to the branch direction, and can calculate information indicating the size of the branch blood vessel according to the position of the projected point. In this case, it is possible to project a point group having a distance from the cross section within a predetermined range from the cross point group indicating the branch blood vessel onto the cross section.

  In another embodiment, a point cloud to be projected is selected as follows. This selection method will be described with reference to FIGS. A vector 1401 representing the branch direction of the branch blood vessel comes on the plane, and a plane orthogonal to the imaging section 1402 when the blood vessel image 190 is captured is defined as an XY plane. The X axis represents the scanning direction when the blood vessel image 190 is captured. On the XY plane, the angle formed by the scanning direction X and the vector representing the branch direction is Ω. Here, the i-th imaging section at the time of imaging the blood vessel image 190 is referred to as a section i, and a projection target section 1403 orthogonal to the vector 1401 representing the branch direction is referred to as a section j. These relationships are shown in FIG. 14A.

First, for each cross-section i, a point closest to the cross-section j is selected from the intersection group indicating the branch blood vessel. The selected point is called P _{i, j} . Next, when the points P _{i, j} and P _{i + 1, j} are vertically projected onto the XY plane, a vertical bisector 1404 that divides the two projection points is calculated. FIG. 14B shows the position of the vertical bisector 1404. Then, an intersection group indicating a branch blood vessel on the cross section i between the vertical bisector 1404 and a plane passing through _{Pi, j} parallel to the vertical bisector 1404 is projected onto the cross section j. Selected as a point. Further, an intersection group indicating a branch vessel on the cross section i + 1 between the vertical bisector 1404 and a plane parallel to the vertical bisector 1404 and passing through P _{i + 1, j} is projected onto the cross section j. Selected as a point. In FIG. 14C, the selected point 1405 is represented.

However, when a plurality of cross-sectional images are created and the interval Ds of the cross-section j and the interval Dm of the cross-section i satisfy the relationship Ds <Dm · cosΩ, one of the intersection groups indicating the branch blood vessels The part is projected on both the cross section i and the cross section i + 1. In order to avoid this, the following processing may be performed. That is, when P _{i, j} and P _{i, j + 1} are vertically projected onto the XY plane, a vertical bisector 1406 that divides the two projection points is calculated. Then, as shown in FIG. 14D, the intersection group indicating the branch blood vessel on the cross section i between the vertical bisector 1406 and the plane passing through P _{i, j} parallel to the vertical bisector 1406 is , Selected as a point that is projected onto section j but not onto section j + 1. Further, an intersection group indicating a branching vessel on the cross section i between the vertical bisector 1406 and a plane parallel to the vertical bisector 1406 and passing through P _{i, j + 1} is projected onto the cross section j + 1. However, it is selected as a point that is not projected onto the section j.

  However, a method for creating a tomographic image at an arbitrary cross section from the blood vessel image 190 is known as a multi-section reconstruction method. Therefore, the method in which the generation unit 1020 reconstructs the blood vessel image 190 to create a tomographic image in a cross section orthogonal to the branch direction of the branch blood vessel is not limited to the above method.

  As a specific example of the calculation method of the information indicating the size of the branch blood vessel in the cross section orthogonal to the branch direction, an approximate ellipse, approximate curve and approximate polygon that approximate the projected point are derived, and the area and the length of the circumference are derived. And a method of deriving the maximum inscribed circle of the projected point and determining its radius, diameter, or area.

  As described above, the generation unit 1020 can also create and output a tomographic image in a cross section orthogonal to the branch direction of the branch blood vessel. For example, the generation unit 1020 can create a tomographic image that passes through the approximate polygon (or approximate curve) or approximate ellipse center of gravity calculated in step S1140. The generation unit 1020 can also create a tomographic image that passes through the position of the most upstream side or the most downstream side of the branch plane. The generation unit 1020 can also generate a surface rendering image or a volume rendering image of the branch blood vessel in the line-of-sight direction along the branch direction of the branch blood vessel or in the line-of-sight direction orthogonal to the branch direction.

  According to such a configuration, it is possible to easily confirm the degree of stenosis of the branch vessel due to the plaque moving in the direction of the branch vessel after the main vessel is treated using a balloon, a stent, or the like. it can. Further, according to the above method, even if the intersection indicating the branch blood vessel cannot be sufficiently detected for some tomographic images, for example, because the branch blood vessel and the shadow of the guide wire overlap each other, one There is a possibility that quantitative information indicating the shape of the branch blood vessel may be obtained using the intersection of the parts.

  When the stent is indwelled at the branch portion, in step S1140, the generation unit 1020 may calculate the size, for example, the width or thickness of the stent strut (stent strut). Stent struts appear as high-luminance points on the tomographic image. Therefore, similarly to the estimated position of the guide wire image, the detection unit 230 can extract the stent strut morphologically as an object, and can detect the position. In this case, the generation unit 1020 can project the object representing the stent strut vertically onto the branch plane. And the production | generation part 1020 can calculate the area of the division area produced by dividing | segmenting a branch surface with a stent strut, or the magnitude | size of the maximum inscribed circle. Based on the information thus obtained, the width or thickness of the stent strut after the stent is placed in the main blood vessel can be confirmed.

  In step S1180, the generation unit 1020 can project the object representing the stent strut onto a cross section orthogonal to the branch direction of the branch blood vessel. And the production | generation part 1020 can calculate the magnitude | size of the division | segmentation area | region divided | segmented by the stent strut, a perimeter, or the largest inscribed circle on this cross section. The information thus obtained corresponds to the width of the stent struts in the direction perpendicular to the catheter when manipulating the catheter through the stent strut gap. Thus, this information is useful for manipulating a guidewire or the like through the stent strut gap, for example, to select a balloon to be used to perform a kissing balloon technique.

  Furthermore, when the stent is arranged at the branch portion, the generation unit 1020 corrects quantitative information indicating the form of the branch blood vessel in the branch portion from the main blood vessel using the information indicating the size of the stent. Can do. Information indicating the size of the stent is acquired by the information acquisition unit 1010. Information indicating the size of the stent may be input by the user via an input unit (not shown), or may be recorded in the information calculation unit 1000 in advance.

  For example, the information acquisition unit 1010 can acquire information indicating the width or thickness (I1) of the stent strut. In this case, the generation unit 1020 can calculate the correction parameter (I1 / I2) using the calculated width or thickness (I2) of the stent strut. The calculated width or thickness of the stent strut may be an average value of values measured for each of the plurality of stent struts. The generation unit 1020 more accurately multiplies the correction parameter (I1 / I2) calculated in this way by quantitative information indicating the morphology of the branching blood vessel, for example, the short axis length of the approximate ellipse calculated in step S1140. Can be obtained. For example, when the width of the stent strut is used, the length in the blood vessel axis direction can be corrected. Further, when the thickness of the stent strut is used, the length in the scanning line direction can be corrected.

  The information calculation unit 1000 can cause the display unit 120 to display quantitative information indicating the shape of the obtained branch blood vessel via the display control unit 110. For example, the display control unit 110 can display a display screen including quantitative information on the display unit 120. The display control unit 110 can also cause the display unit 120 to display a display screen that includes at least one of the cross-sectional image of the blood vessel, the axial cross-sectional image, and the three-dimensional image. FIG. 15 shows an example of a display screen including both quantitative information and a blood vessel image. However, it is not essential that the display screen includes both quantitative information and a blood vessel image.

  The display screen 1500 displays a blood vessel axis direction cross-sectional image 1510, and the blood vessel axis direction cross-sectional image 1510 shows branch portions SB1 to SB5 from the detected main blood vessel to the branch blood vessel. The user can specify a branching portion for which information is desired via an input unit (not shown). The display control unit 110 updates the display screen so as to include quantitative information indicating the morphology of the branch blood vessel in the designated branch portion in response to an input designating one of the plurality of branch portions. Can do. In addition, the display control unit 110, in response to an input designating one of the plurality of branch portions, includes a cross-sectional image of the blood vessel including the specified branch portion, an axial cross-sectional image, and a three-dimensional image. The display screen can be updated to include at least one.

  For example, on the display screen 1500, the branch portion SB5 is selected. In a region 1520 of the display screen 1500 shown in FIG. 15, the branch angle (Θ5, Φ5) of the branch blood vessel, the diameter of the branch blood vessel (D5), and the area of the branch surface (S5) are displayed. Further, the region 1520 further displays the diameter (D5) of the branch blood vessel and the area (S5) of the branch surface after correction by the width or thickness of the stent strut.

  In addition, the display screen 1500 displays enlarged images 1530, 1540, and 1550 of the vascular axis direction cross-sectional image including the branch portion SB5, and a cross-sectional image 1560 including the branch portion SB5. The cross-sectional position of the displayed enlarged image 1530 can be changed in the screen depth direction. The orientation of the cross section of the enlarged image 1530 can be controlled using the user interface 1580 at the lower right of the display screen 1500. The enlarged image 1540 is a cross section in the blood vessel axis direction parallel to the xz plane shown in FIG. 13 and passing through the center (probe). In the enlarged image 1550, the position of the detected stent strut is highlighted. The display screen 1500 displays the blood vessel axial direction cross-sectional image and the cross-sectional image of the main blood vessel, but the blood vessel axial direction cross-sectional image or the cross-sectional image of the branch blood vessel in the branch portion SB5 may be displayed. .

  The 3D image 1570 displays a three-dimensional image of a blood vessel including the branch portion SB5. In one embodiment, the line-of-sight direction of the displayed three-dimensional image is determined according to the branch direction of the branch blood vessel in the designated branch portion. For example, the display control unit 110 can determine the line-of-sight direction of the 3D image 1570 so as to match the branch direction vector of the branch blood vessel in the selected branch portion SB5. The method of determining the line-of-sight direction is not limited to this method. For example, the display control unit 110 determines the line-of-sight direction of the 3D image 1570 so as to be orthogonal to the branch direction vector of the branch blood vessel in the selected branch portion SB5. Also good.

[Other Embodiments]
The image processing apparatus 100 including the boundary extraction unit 200 and the information calculation unit 1000 has been described above. However, the image processing apparatus including the boundary extraction unit 200 and the image processing apparatus including the information calculation unit 1000 may be separate devices. In this case, the image processing apparatus including the boundary extraction unit 200 can acquire the blood vessel image 190 and output the determination result by the determination unit 240 or the determination update unit 250. Based on the output information, the user can easily identify the portion of the blood vessel image 190 corresponding to the branch blood vessel or the shadow of the guide wire. In addition, the image processing apparatus including the information calculation unit 1000 is information that distinguishes between a part corresponding to the main blood vessel and a part corresponding to the branch blood vessel generated by a method different from the method used by the boundary extraction unit 200. May be obtained. Even if such information is used, the image processing apparatus including the information calculation unit 1000 can generate and output quantitative information indicating the shape of the obtained branched blood vessel.

  The functions of the units included in the image processing apparatus 100 illustrated in FIG. 1 can be realized using a general-purpose computer. As described above, even when the image processing apparatus including the boundary extraction unit 200 and the image processing apparatus including the information calculation unit 1000 are separate apparatuses, the functions of the respective apparatuses are realized using a general-purpose computer. be able to.

  FIG. 16 is a diagram showing a basic configuration of a computer. In FIG. 16, a processor 1610 is a CPU, for example, and controls the operation of the entire computer. The memory 1620 is, for example, a RAM, and temporarily stores programs, data, and the like. The computer-readable storage medium 1630 is, for example, a hard disk or a CD-ROM, and stores programs, data, and the like for a long time. In the present embodiment, a program that realizes the function of each unit stored in the storage medium 1630 is read into the memory 1620. Then, when the processor 1610 executes the program on the memory 1620, the processing of each step described above is performed, and the function of each unit is realized.

  In FIG. 16, an input interface 1640 is an interface for acquiring information from an external device. The output interface 1650 is an interface for outputting information to an external device, and is connected to the display unit 120, for example. A bus 1660 connects the above-described units and enables data exchange.

  The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

  This application claims priority on the basis of Japanese Patent Application No. 2014-052371 filed on Mar. 14, 2014, the entire contents of which are incorporated herein by reference.

Claims (14)

Of the tubular object image obtained by scanning the inside of the first tubular object using a probe, a portion corresponding to the first tubular object and a second tubular object branched from the first tubular object An information acquisition means for acquiring information for distinguishing the portion corresponding to
Generating means for generating quantitative information indicating the form of the second tubular object at a branch from the first tubular object using the information;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the generation unit calculates a size of the second tubular object at a branch portion from the first tubular object as the quantitative information. .   The generation means derives an approximate polygon or an approximate ellipse that approximates a boundary point group between the first tubular object and the second tubular object, and determines the size of the approximate polygon and the maximum of the approximate polygon. The image processing apparatus according to claim 2, wherein a size of an inscribed circle or a size of the approximate ellipse is calculated as the quantitative information. The information acquisition means further acquires, in the tubular object image, information indicating a portion corresponding to a strut of a stent placed at a branch portion from the first tubular object to the second tubular object,
The image processing apparatus according to claim 1, wherein the generation unit calculates a size of a gap between struts of the stent. The information acquisition means further acquires information indicating the size of the gap between the stent struts,
The generating unit corrects the quantitative information based on the information indicating the size of the stent strut gap acquired by the information acquiring unit and the calculated size of the stent strut gap. The image processing apparatus according to claim 4, wherein:   The image processing apparatus according to claim 1, wherein the generation unit calculates a branching direction of the second tubular object from the first tubular object. The generating means includes
Deriving an approximate polygon or approximate ellipse that approximates a boundary point group between the first tubular object and the second tubular object;
Deriving an inscribed sphere inscribed in the second tubular object;
The image processing apparatus according to claim 6, wherein the branch direction is calculated based on a direction from a center of gravity of the approximate polygon or approximate ellipse toward a center of the inscribed sphere.   The said generation means calculates the branch angle of the said 2nd tubular object from the said 1st tubular object as said quantitative information based on the said branch direction, The Claim 6 or 7 characterized by the above-mentioned. The image processing apparatus described.   The said generation means calculates the information which shows the magnitude | size of the said 2nd tubular object in the cross section orthogonal to the said branch direction as said quantitative information, The any one of Claim 6 thru | or 8 characterized by the above-mentioned. The image processing apparatus according to item.   The image processing apparatus according to claim 6, wherein the generation unit generates a cross-sectional image of the second tubular object in a cross section orthogonal to the branch direction. The information acquisition means further acquires, in the tubular object image, information indicating a portion corresponding to a strut of a stent placed at a branch portion from the first tubular object to the second tubular object,
The generation means calculates a size of a gap between the stent struts on the cross section when the stent struts are vertically projected onto a cross section perpendicular to the branch direction. Item 11. The image processing apparatus according to any one of Items 6 to 10.   The image processing apparatus according to claim 1, wherein the first tubular object and the second tubular object are blood vessels. An image processing method performed by an image processing apparatus,
Of the tubular object image obtained by scanning the inside of the first tubular object using a probe, a portion corresponding to the first tubular object and a second tubular object branched from the first tubular object An information acquisition step of acquiring information for distinguishing the portion corresponding to
Generating using the information to generate quantitative information indicative of the morphology of the second tubular object at a branch from the first tubular object;
An image processing method comprising:   A program for causing a computer to execute each step of the image processing method according to claim 13.