JP5242235B2 - MRI diagnostic imaging apparatus and MR image forming method - Google Patents

Description

  The present invention relates to an MRI (magnetic resonance imaging) diagnostic imaging apparatus and an MR image forming method using a magnetic resonance phenomenon of a nuclear spin in a subject. More particularly, the present invention relates to an MRI diagnostic imaging apparatus and an MR image forming method capable of providing a blood vessel image without administering a contrast medium to a subject.

  Various medical image diagnosis such as an X-ray angiography device with an X-ray imaging diameter using an iodine contrast medium, an MRI (magnetic resonance imaging) image diagnosis device, a CT image diagnosis device, or an ultrasonic image diagnosis device for blood vessel image diagnosis A device (modality) is used. In diagnosis and treatment for blood vessels as a target site, treatment plans and treatment support for displaying blood vessel images in combination with captured images such as brain parenchyma and bone are widely and generally performed. In such a treatment plan and treatment support, images of various modalities as described above and composite images of these modalities are used. In particular, among the modalities described above, the MRI image diagnostic apparatus has a superior spatial resolution and is a non-invasive imaging method and is often used for blood vessel image diagnosis.

  This MRI diagnostic imaging apparatus uses a nuclear magnetic resonance (NMR) phenomenon to magnetically excite nuclear spins at a desired examination site of a subject placed in a static magnetic field with a Larmor frequency high frequency signal. A density distribution, a relaxation time distribution, and the like are measured based on an FID (free induction decay) signal and an echo signal generated along with excitation, and an arbitrary cross section of the subject is displayed as an image from the measurement data.

  An MRI apparatus includes an apparatus having an imaging function called MRA imaging (MR angiography) for drawing a blood flow. MRA imaging is roughly classified into a method that does not use a contrast agent (non-contrast MRA imaging) and a method that administers a contrast agent and images (contrast MRA imaging) (see, for example, Patent Document 1). .

  And in the method using the contrast agent as described in Patent Document 1, there is a heavy load on the patient such as injection pain and influence on the heart. Therefore, non-contrast-enhanced MRA imaging without using a contrast agent is performed in order to reduce the load on the patient.

  A typical technique for this non-contrast MRA imaging is a TOF method based on the effect of blood flowing into the imaging surface, and a phase contrast (hereinafter abbreviated as “PC”) based on a phase shift effect when blood moves in a gradient magnetic field. .) Method (see, for example, Patent Document 2). Especially in the head and neck, these two methods are mainly used.

JP 2004-008516 A JP 07-059747 A

  Both the above-described TOF method and the PC method such as Patent Document 2 have the advantage of observing blood vessels (blood flow) without requiring a contrast agent, but have a merit that blood vessels (blood flow) can be observed. It becomes a low signal at the location where the turbulent flow is generated. Therefore, in places where turbulence of blood flow occurs, the display brightness is depicted low, and in fact, false defects that appear to be broken even though blood vessels are connected, or false that appear to be stenotic There is a problem that stenosis occurs. For this reason, blood vessel extraction cannot be performed accurately, and blood vessels near the treatment path may not be displayed accurately. In the treatment using an MRI image, radiation is emitted so as not to hit an important blood vessel. In surgery using an MRI image, a scalpel is inserted while avoiding important blood vessels. In such a case, if the blood vessels near the treatment path are not accurately displayed, there is a risk that the diagnosis and treatment plan will be wrong. In particular, misidentifying blood vessels that feed important organs can lead to serious accidents. Furthermore, in the conventional blood vessel tracing technology, there is a problem that the automatic extraction processing cannot be performed in a portion where the blood vessel is interrupted, such as a defective portion in MRA imaging, and the blood vessel is displayed in an interrupted manner. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an MRI diagnostic imaging apparatus that extracts, corrects, and displays a false defect portion of a blood vessel that occurs in MRA imaging.

  In order to achieve the above object, the MRI diagnostic imaging apparatus according to claim 1 applies a gradient magnetic field and a high frequency magnetic field to a subject placed in a static magnetic field, and generates a nuclear magnetic resonance signal generated from the subject. Scanning means for detecting, reconstruction means for reconstructing an image based on the nuclear magnetic resonance signal to generate volume data, blood vessel extraction means for extracting blood vessels from the volume data, and end points of the extracted blood vessels An end point information creating means for obtaining end point information including the position of the blood vessel and the direction of the blood vessel at the end point; an interpolation place selecting means for selecting between the end points as an interpolation place from the end point information; and between the selected end points Interpolating means for interpolating a blood vessel wall, and display control means for displaying on the display means an image obtained by adding information on the intervening blood vessel wall to the volume data. A.

  The MR image forming method according to claim 8, wherein a gradient magnetic field and a high-frequency magnetic field are applied to an object placed in a static magnetic field, and a nuclear magnetic resonance signal generated from the object is detected; A reconstruction stage for reconstructing an image by processing nuclear magnetic resonance signals to generate volume data, a blood vessel extraction stage for extracting blood vessels from the volume data, a position of an end point of the extracted blood vessels, and a direction of the blood vessels An end point information creation step for obtaining end point information including: an interpolated portion selecting step for selecting between the end points as an interpolated portion from the end point information; an interpolating step for interpolating a blood vessel wall at the selected interpolated portion; and the volume A display control step of displaying on the display means an image obtained by adding the information of the blood vessel wall interpolated to the data to the display means.

  According to the MRI diagnostic imaging apparatus described in claim 1 and the MR image forming method described in claim 8, it is possible to create and display a blood vessel image obtained by interpolating a false defect portion of a blood vessel image. Thereby, an accurate MRI image of a blood vessel can be generated. By using the blood vessel image generated using the present invention for treatment planning and treatment support, it is possible to reduce oversight of important blood vessels in surgery and radiation route examination.

[First Embodiment]
Hereinafter, an MRI diagnostic imaging apparatus according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing functions of an MRI image diagnostic apparatus according to the present invention. The storage unit 100 shown in FIG. 1 is configured by a storage device such as a hard disk. The volume data storage unit 101, the segment data storage unit 102, the blood vessel core line storage unit 103, the end point information storage unit 104, and the blood vessel wall storage unit 105 are arranged in the same storage unit 100 in this embodiment. However, these storage units may be arranged in different storage devices.

  Details of the scanning unit 001 will be described with reference to FIG. FIG. 2 is a detailed block diagram of the scanning unit 001. The scanning unit 001 includes a bed 201 on which the subject P is placed, a static magnetic field magnet 202 that forms a uniform static magnetic field in a space where the subject P is placed, a gradient magnetic field generating unit 203 that applies a magnetic field gradient to the static magnetic field, A high-frequency magnetic field generation unit 204 that causes nuclear magnetic resonance to occur in atomic nuclei constituting the tissue of the specimen P, and a reception unit 205 that receives an echo signal generated from the subject P by nuclear magnetic resonance are provided. The scanning unit 001 generates a uniform static magnetic field around the subject P in the direction of the body axis or in a direction perpendicular to the body axis by the static magnetic field magnet 202. Further, the scanning unit 001 applies a gradient magnetic field to the subject P by the gradient magnetic field generation unit 203. Next, the scanning unit 001 causes the high-frequency magnetic field generation unit 204 to transmit a high-frequency pulse toward the subject P to cause nuclear magnetic resonance. The scanning unit 001 detects an echo signal emitted from the subject P by the nuclear magnetic resonance by the receiving unit 205. The scanning unit 001 outputs the detected echo signal to the reconstruction unit 002. This scanning unit 001 corresponds to “scanning means” in the present invention.

  The reconstruction unit 002 performs processing such as Fourier transform, correction coefficient calculation, and image reconstruction on the echo signal received by the scanning unit 001. Thereby, the reconstruction part 002 produces | generates the image showing the spatial density and spectrum of a nucleus. This reconstruction unit 002 corresponds to “reconstruction means” in the present invention.

  A cross-sectional image is generated by the processing of the scan unit 001 and the reconstruction unit 002 as described above. Then, the above-described processing is performed in a three-dimensional area to collect three-dimensional image data. This three-dimensional image data is “volume data”. In the present embodiment, the volume data is represented in a three-dimensional coordinate space with the center of the volume as the origin. Here, this coordinate space may take any origin. For example, a three-dimensional coordinate space having the origin set as the origin in the apparatus may be used. The volume data is composed of pixels (a minimum unit constituting a three-dimensional image, also referred to as “voxel”), and each pixel has a reconstruction unit 002 at a position of the pixel in the three-dimensional coordinate space. The value of the signal strength of the echo signal generated in is given. This signal intensity is referred to as a “pixel value” (or “voxel value”). In the case of the present embodiment, the scan unit 001 and the reconstruction unit 002 perform scanning and volume data generation by a method using the TOF (Time-Of-Flight) method, the PC method, or the like. By using the TOF method, the PC method, or the like, a three-dimensional image in which the blood vessel portion is emphasized can be generated.

  The reconstruction unit 002 stores the generated volume data in the volume data storage unit 101.

  The blood vessel extraction unit 003 has a segment data creation unit 004. The blood vessel extraction unit 003 stores a pixel value threshold range for extracting blood vessels. This blood vessel extraction unit 003 corresponds to the “blood vessel extraction means” in the present invention.

  The blood vessel extraction unit 003 receives an input of an approximate pixel value of the blood vessel portion in the volume data generated by the reconstruction unit 002. This pixel value is input by the operator using the input unit 014. For example, when the TOF method is used, the signal intensity is strong in the region of the blood vessel portion, and thus the operator inputs a high pixel value. Further, the blood vessel extraction unit 003 acquires volume data from the volume data storage unit 101. The blood vessel extraction unit 003 extracts, from the acquired volume data, pixels included in the threshold range stored with the input pixel value as a reference. Thereby, the blood vessel extraction unit 003 can create an image in which an area substantially corresponding to a blood vessel is extracted.

  In addition, another method may be used in combination for extracting only the region corresponding to the blood vessel more accurately in the blood vessel extraction unit 003. For example, the blood vessel extraction unit 003 receives the designation of a part other than the blood vessel using the input unit 014 by the operator, and deletes the designated part from the volume data to delete an object other than the blood vessel. Good. In addition, the blood vessel extraction unit 003 performs a connected region extraction process in which the operator designates a point on the region representing the blood vessel using the input unit 014 and extracts connected pixels from the point. May be. Furthermore, the blood vessel extraction unit 003 receives a volume data region (for example, a rectangular parallelepiped region including a certain blood vessel) specified by the operator using the input unit 014, and deletes regions other than the specified region. A processing space range limiting process may be performed. This blood vessel extraction unit 003 corresponds to the “blood vessel extraction means” in the present invention.

  The image segment data creation unit 004 sets the pixel value of the extracted portion to 1 and sets the pixel values of the other portions to 0 for the image obtained by extracting the region corresponding to the blood vessel. Image data that has been subjected to processing for representing the pixel value as 0 or 1 is referred to as segment data.

  The blood vessel extraction unit 003 stores the segment data in the segment data storage unit 102.

  The end point information creation unit 006 includes a structure line extraction unit 007 and a blood vessel core line extraction unit 008. This end point information creating unit 006 corresponds to “end point information creating means” in the present invention.

  The structural line extraction unit 007 acquires segment data from the segment data storage unit 102. The structural line extraction unit 007 obtains a structural line 301 of the blood vessel 300 by performing thinning processing such as morphology processing and distance conversion processing on the blood vessel 300 of the acquired segment data as shown in FIG. FIG. 3 is a diagram for explaining the extraction of the structural line. The structural line 301 is a point sequence that is a collection of pixels. That is, the data of the structural line 301 is represented as a collection of points in the three-dimensional coordinate space. Then, the structural line extraction unit 007 transmits the data of the structural line 301 to the blood vessel core line extraction unit 008.

  The blood vessel core line extraction unit 008 obtains a plane orthogonal to the structure line 301 at each point 302 (pixel) constituting the structure line 301 based on the received data of the structure line 301. Furthermore, the blood vessel core line extraction unit 008 obtains a cross section of the blood vessel 300 cut along the obtained plane as shown in FIG. Here, FIG. 4 is a diagram for explaining how to obtain the center of the inscribed circle. Then, the blood vessel core line extraction unit 008 obtains an inscribed circle 303 that is inscribed in the obtained cross section of the blood vessel 300. Then, the blood vessel core line extraction unit 008 obtains the center 304 of the obtained inscribed circle 303. Hereinafter, the obtained center is referred to as “the center point of the blood vessel 300”. The blood vessel core line extraction unit 008 repeats the above processing at each point 302 on the structural line 301 to obtain the center point of the corresponding blood vessel 300. Then, as shown in FIG. 5, a point sequence obtained by collecting the center points of the blood vessel 300 becomes a blood vessel core 400. FIG. 5 is a diagram for explaining how to obtain the blood vessel core line and the end points. The data of the blood vessel core line 400 is also expressed as a collection of points in the three-dimensional coordinate space. Here, in this embodiment, the center 304 of the inscribed circle 303 is the center point of the blood vessel 300, but this may be another method. For example, the center of gravity of the cross section of the blood vessel 300 may be obtained and used as the center point of the blood vessel 300. Further, an inscribed sphere of a blood vessel including a point on the structure line 301 in a great circle may be obtained, and the center of the inscribed sphere may be set as the center point of the blood vessel 300.

  The blood vessel core line extraction unit 008 stores the obtained blood vessel core line 400 data in the blood vessel core line storage unit 103.

  The end point information creation unit 006 confirms whether there are two other points constituting the blood vessel core line 400 in the pixels adjacent to the point constituting the blood vessel core line 400 obtained by the blood vessel core line extraction unit 008. Go. Then, the end point information creation unit 006 sets the position coordinates of the end points as the position coordinates of the points constituting the blood vessel core line 400 where only one other point constituting the blood vessel core line 400 exists in the adjacent pixel. For example, in FIG. 5, the point 500 is an end point. The position coordinates of the end point 500 become the position coordinates of the end point of the blood vessel 300. Further, the end point information creation unit 006 obtains the difference between the obtained position coordinates of the end point 500 and the coordinates of the pixels adjacent to the end point 500 to obtain the direction vector of the end point 500. Here, the point for obtaining the vector of the end point 500 may use another point in the vicinity of the end point 500 without using the adjacent point. Furthermore, the endpoint information creation unit 006 acquires volume data from the volume data storage unit 101 and extracts the pixel value at the position coordinate of the endpoint 500 as the pixel value of the endpoint 500.

  The endpoint information creation unit 006 stores endpoint information such as the position coordinates of the endpoint 500, the direction vector of the endpoint 500, and the pixel value of the endpoint 500 in the endpoint information storage unit 104. Also, the endpoint information creation unit 006 stores the inscribed circle diameter at the endpoint 500 in the endpoint information storage unit 104 as the blood vessel diameter at the endpoint.

  The interpolation location selection unit 010 sets the threshold value of the distance between the end points 500, the threshold value of the outer angle created by the direction vector at the two end points 500, the threshold value of the difference between the pixel values at the two end points 500, and the blood vessel diameter at the two end points 500. A difference threshold is stored in advance. In this embodiment, a distance threshold is 2 voxels, an outer angle threshold created by a direction vector is 1 °, a pixel value difference threshold is created as a pixel value histogram, and the difference between the maximum value and the minimum value in the histogram is 5 %, And the threshold value of the difference in blood vessel diameter is 2 voxels. Here, an example of how to obtain the pixel value threshold will be described. The interpolation location selection unit 010 acquires image data before the segment data from which the blood vessel is extracted by the blood vessel extraction unit 003 is obtained. The interpolation location selection unit 010 creates a histogram from the extracted pixel values in the blood vessel 300. Then, the interpolation location selection unit 010 extracts the maximum value and the minimum value from the created histogram and calculates 5% of the difference between them. The interpolation location selection unit 010 corresponds to “interpolation location selection means” in the present invention.

  The interpolation location selection unit 010 selects two end points 500 out of the end points 500 stored in the end point information storage unit 104, and acquires end point information of each end point 500. The interpolation location selection unit 010 calculates the distance between the two end points 500 acquired based on the acquired position coordinates. Then, the interpolation location selection unit 010 compares the calculated distance between the two end points 500 and 2 voxels that are threshold values of the stored distance. In addition, the interpolation location selection unit 010 calculates an outer angle between the direction vectors based on the obtained direction vectors at the two end points 500. Then, the interpolation location selection unit 010 compares the outside angle formed by the direction vectors at the calculated two end points 500 with 1 ° which is the threshold value of the outside angle created by the stored direction vector. Further, the interpolation location selection unit 010 calculates the difference between the pixel values at the acquired two end points 500. Then, the interpolation location selection unit 010 compares the difference between the calculated pixel values of the two end points 500 and the threshold value of the stored pixel value difference. Further, the interpolation location selection unit 010 calculates a difference in blood vessel diameter at the acquired two end points 500. Then, the interpolation location selection unit 010 compares the calculated difference in blood vessel diameter between the two end points 500 with 2 voxels that are threshold values for the stored difference in blood vessel diameter. Then, the interpolation point selection unit 010 has a distance between the two end points 500 of 2 voxels or less, an outer angle formed by a direction vector at the two end points 500 is 1 ° or less, and a difference between pixel values at the two end points 500 is If the difference in blood vessel diameter between the two end points 500 is less than the threshold and less than 2 voxels, a false defect has occurred at the two end points 500, that is, the two end points are connected blood vessels. Judge that there is. Then, the interpolation location selection unit 010 selects the two endpoints as a set of endpoints to be interpolated between the two endpoints.

  Comparison with the threshold value at the end point 500 by the interpolation location selection unit 010 will be specifically described with reference to FIG. FIG. 6 is a diagram for explaining the comparison with the threshold value at the end point 500 by the interpolation location selection unit 010. End points 500a and 500c are extracted as end points in the blood vessel core line 400a. Further, an end point 500b is extracted as an end point in the blood vessel core line 400b. Furthermore, an end point 500d is extracted as an end point in the blood vessel core line 400c. A sphere having a radius of 2 voxels centered on the end point 500 a is a sphere 601. An end point 500 b is included in the sphere 601. Therefore, the distance between the end point 500a and the end point 500b is within a threshold value. On the other hand, the end point 500 c and the end point 500 d are not included in the sphere 601. Therefore, the distance between the end point 500c and the end point 500d and the end point 500a is equal to or greater than the threshold value.

  In the present embodiment, the interpolation location selection unit 010 uses the distance between the end points, the outer angle formed by the vectors at the two end points, the difference in pixel values, and the difference in blood vessel diameter for comparison. A comparison may be made using several combinations.

  The interpolation unit 009 receives input of information on a set of end points to be interpolated, which are selected as objects to be interpolated by the interpolation location selection unit 010. Then, the interpolation unit 009 acquires the end point information of the end point set from the end point information storage unit 104 based on the input end point set information. This interpolation unit 009 corresponds to “interpolation means” in the present invention.

  The interpolating unit 009 creates a connection line connecting the two end points in the set from the end point information of the acquired set of end points by spline interpolation using the blood vessel core line 400 of the normal imaging unit. For example, in the case of FIG. 6, a connection line that connects the end points 500a and 500b and the end points 500c and 500d is created. Thereby, the blood vessel core wire 400a and the blood vessel core wire 400b are connected. The interpolation of the blood vessel core line 400 may be performed by any other method, and the blood vessel core line 400a and the blood vessel core line 400c are connected. The interpolation unit 009 stores the created blood vessel core line 400 in the blood vessel core line storage unit 103. Further, the interpolation unit 009 outputs the interpolated blood vessel core line 400 information to the interpolation target extraction unit 011.

  The interpolation unit 009 receives input of information on the blood vessel core 400 that is a target to interpolate the blood vessel wall from the interpolation target extraction unit 011. The interpolation unit 009 forms a circle using the blood vessel diameter at the end point around the blood vessel core line 400 connecting the two end points of the false defect portion of the blood vessel having the blood vessel core line 400 to be interpolated according to the distance on the blood vessel core line 400. Obtained by linear interpolation calculation. FIG. 9 is a diagram for explaining the interpolation of the blood vessel wall. This linear interpolation will be described in detail. When the blood vessel wall between the end point 500a and the end point 500b is interpolated as shown in FIG. 9, the intervening blood vessel wall 900 has a distance from the end point 500a and a distance from the end point 500b. Is u: v, the blood vessel diameter such that the difference between the blood vessel diameter at the blood vessel wall 900 and the blood vessel diameter at the end point 500a and the difference between the blood vessel diameter at the blood vessel wall 900 and the blood vessel diameter at the end point 500b are u vs. v. What is necessary is just to obtain | require the blood vessel diameter in 900. FIG.

  Here, in this embodiment, since it is only necessary to grasp the approximate position of the blood vessel, the blood vessel wall is interpolated using a circle using the blood vessel diameter at the end point so that the interpolation can be easily performed. May be other methods, for example, linear interpolation may be performed based on the blood vessel shape at the end points. In that case, the blood vessel wall extraction unit 005 in FIG. 1 acquires segment data from the segment data storage unit 102, and based on the information of the end points to be interpolated stored in the end point information storage unit 104, the shape of the blood vessel wall Find the blood vessel shape. Based on the blood vessel shape obtained by the blood vessel wall extraction unit 005, the interpolation unit 009 may perform interpolation between the end points.

  The interpolation unit 009 stores the interpolated blood vessel wall information in the blood vessel wall storage unit 105.

  The interpolation target extraction unit 011 receives information on the blood vessel core 400 from the interpolation unit 009. Further, the interpolation target extraction unit 011 is a region on the blood vessel (hereinafter, referred to as “important region”) that is considered important by the operator from the input unit 014 (hereinafter, referred to as “important region”) and the origin of the fine blood vessel connected to the important region. , “Starting point”). Specifically, the operator uses the user interface 015 to acquire segment data from the segment data storage unit 102 and display it on the display unit 013. Then, the operator uses the input unit 014 to specify an important area on the segment data. Hereinafter, the case where the brain stem is designated as the designated area will be described. As a method of designating this important area, there is a method of designating by an ellipsoid approximate shape and a typical shape, for example. In the case of an ellipsoidal approximation, the ellipsoid displayed on the screen is set so that the operator adjusts the position, angle, and size using the input unit 014 and wraps the brainstem with the ellipsoid. The brainstem area can be specified. In the case of a typical shape, segment data (hereinafter referred to as “typical data”) of a typical brainstem region shape created from past image data stored in the storage unit 100 in advance is used. By adjusting the position, angle, size, etc. and setting the brain stem of the currently displayed subject to be wrapped with the typical data, the brain stem region can be specified. For example, the operator designates an important region 700 including the brain stem on the screen of the display unit 013 as shown in FIG. FIG. 7 is a diagram for explaining extraction of blood vessels to be interpolated. Furthermore, the operator uses the user interface 015 to acquire volume data and MPR images from the volume data storage unit 101 and display them on the display unit 013. Then, the operator designates one or more start points on the blood vessel corresponding to the origin of the fine blood vessel connected to the brain stem. In the following, a case where a point on the posterior cerebral artery is designated as the start point will be described. For example, the operator designates a start point 701 on the blood vessel 703 corresponding to the major part of the fine blood vessel 702 connected to the important region 700 including the brain stem on the screen of the display unit 013 as shown in FIG. The reason for receiving the operator's designation as described above is that if there is a false defect in a blood vessel leading to an important area such as a brainstem or other vital part of life support, the treatment plan and treatment support will be greatly affected. This is because such false blood vessel defects are preferentially interpolated.

  The interpolation target extraction unit 011 receives the important region 700 including the brain stem designated by the operator and a point on the posterior cerebral artery (start point 701), and the posterior cerebral artery of the blood vessel core line 400 interpolated by the interpolation unit 009. A blood vessel core line 400 connecting from the upper start point 701 to the important region 700 including the brain stem is extracted as an object to interpolate the blood vessel wall. For example, the blood vessel core line 400a indicated by a dotted line in FIG. 7 is connected from the start point 701 to the important region 700 including the brain stem. On the other hand, the blood vessel core line 400b indicated by the alternate long and short dash line starts from the start point 701 but is not connected to the important region 700 including the brain stem. Accordingly, in the case shown in FIG. 7, the interpolation target extraction unit 011 extracts the blood vessel core line 400a as a target for interpolating the blood vessel wall.

  Further, in this extraction, in order to avoid erroneous extraction, the extraction may be limited in the direction of the blood vessel core 400, the length from the point on the posterior cerebral artery to the brain stem, a certain region, or the like. Specifically, the operator designates a limited range of a region from which blood vessels are extracted by designating a region 800 including a start point 701 and an important region 700 as shown in FIG. FIG. 8 is a diagram for explaining the restriction of the blood vessel extraction region that leads from the starting point 701 to the important region 700. Then, the interpolation target extraction unit 011 extracts the blood vessel core line 400c and the like included in the designated region 800 as a target for interpolating the blood vessel wall. Further, the interpolation target extraction unit 011 excludes the blood vessel core line 400d and the like that protrude from the designated region 800 from the extraction target. This is because it is highly likely that a blood vessel that is directly directed from the blood vessel including the start point 701 directly toward the brainstem (direction of the important region 700) is feeding blood to the brainstem. In other words, a blood vessel is rarely connected from the starting point 701 in a direction different from the important region 700 and then turned around to the important region 700, and interpolating it may generate a wrong blood vessel connection. It is because the nature is high. As a result, it is possible to improve the probability of interpolating correct blood vessels. In addition, when a length restriction is provided, the interpolation target extraction unit 011 sets an extraction target when the length of the blood vessel core line from the start point 701 to the important region 700 is equal to or less than the input length. This is also because the possibility that the path is not actually connected in the case of a blood vessel that is too long is empirically high.

  The interpolation target extraction unit 011 outputs information on the extracted blood vessel core line 400a to the interpolation unit 009. This interpolation target extraction unit 011 corresponds to “interpolation target extraction means” in the present invention.

  Here, in the present embodiment, a particularly important blood vessel is extracted by the interpolation target extraction unit 011 and the blood vessel wall is interpolated for the blood vessel. This is to simplify the interpolation process and generate a blood vessel image that is easy to refer to. However, the MRI diagnostic imaging apparatus of the present invention can operate even with a configuration in which interpolation is performed on all portions selected as interpolation locations by the interpolation location selection unit 010 without performing extraction of this important blood vessel.

  Based on the volume data stored in the volume data storage unit 101 and the interpolated blood vessel wall information stored in the blood vessel wall storage unit 105, the display control unit 012 performs a three-dimensional image of the blood vessel that has been interpolated. Is displayed on the display unit 013.

  Next, with reference to FIG. 10, a blood vessel image generation operation in the MRI image diagnostic apparatus according to the present embodiment will be described. FIG. 10 is a flowchart of blood vessel image generation in the MRI image diagnostic apparatus according to this embodiment.

  Step S001: The scanning unit 001 applies a magnetic field gradient by the gradient magnetic field generation unit 203 to the static magnetic field generated by the static magnetic field magnet 202, and applies a high frequency magnetic field generation unit to the subject P placed in the magnetic field. A high frequency pulse is transmitted by 204 to cause magnetic resonance, and an echo signal generated by the subject P is received by the receiving unit 205.

  Step S002: The reconstruction unit 002 performs processing such as Fourier transform, correction coefficient calculation, and image reconstruction on the echo signal received by the scanning unit 001, and generates volume data. Then, the reconstruction unit 002 stores the generated volume data in the volume data storage unit 101.

  Step S003: The operator inputs an approximate value of the pixel value of the blood vessel obtained empirically.

  Step S004: The blood vessel extraction unit 003 acquires the volume data stored in the volume data storage unit 101. Then, the blood vessel extraction unit 003 extracts a pixel having a pixel value within a threshold range stored in advance from the pixel value of the blood vessel input from the volume data, thereby generating an image in which the blood vessel is extracted.

  Step S005: The segment data creation unit 004 creates segment data by setting the pixel value of the blood vessel region to 1 and setting the pixel value of the other region to 0 in the extracted blood vessel image. The blood vessel extraction unit 003 stores the segment data in the segment data storage unit 102.

  Step S006: The end point information creation unit 006 acquires the segment data stored in the segment data storage unit 102. The structural line extraction unit 007 creates a structural line by performing thinning processing on the acquired segment data.

  Step S007: The blood vessel core line extraction unit 008 cuts the blood vessel along a plane orthogonal to the structural line including the point on the structural line created by the structural line extraction unit 007, and obtains a blood vessel cross section including the point on the structural line. Then, the blood vessel core line extraction unit 008 obtains an inscribed circle inscribed in the obtained blood vessel, and obtains the center of the inscribed circle. Furthermore, the blood vessel core line extraction unit 008 creates a blood vessel core line by collecting the centers of the inscribed circles described above. The blood vessel core line extraction unit 008 stores the created blood vessel core line information in the blood vessel core line storage unit 103.

  Step S008: The endpoint information creation unit 006 extracts a point having only one adjacent point from the points on the blood vessel core line, and obtains the position coordinates of the endpoint. Then, the endpoint information creation unit 006 obtains a direction vector at the endpoint from the location information of the endpoint and adjacent points. Further, the end point information creation unit 006 acquires the pixel value at the end point from the volume data of the volume data storage unit 101. In addition, the end point information creation unit 006 acquires the diameter of the inscribed circle at the end point as the blood vessel diameter at the end point obtained by the blood vessel core line extraction unit 008. The end point information creation unit 006 stores end point information such as the position coordinates of the end point, the direction vector at the end point, the pixel value of the end point, and the blood vessel diameter at the end point in the end point information storage unit 104.

  Step S009: The interpolation location selection unit 010 acquires the end point information from the end point information storage unit 104. The interpolation location selection unit 010 stores in advance a threshold value of the distance between the end points, a threshold value of the outer angle formed by the direction vector at the end point, a threshold value of the difference in luminance value at the end point, and a threshold value of the difference in blood vessel diameter at the end point, The values at any two of the acquired end points are compared, and a set of two end points within all threshold values is selected.

  Step S010: The operator inputs an important area and a starting point on the segment data using the user interface 015.

  Step S011: The interpolation target extraction unit 011 extracts the blood vessel core line connected from the start point designated by the operator to the important region based on the information on the blood vessel core line interpolated by the interpolation unit 009.

  Step S012: The interpolation unit 009 receives information on the blood vessel core line extracted by the interpolation target extraction unit 011. Further, the interpolation unit 009 acquires the size of the blood vessel diameter at the end point from the end point information storage unit 104. Then, the interpolation unit 009 interpolates the blood vessel wall between the end points of the blood vessel having the blood vessel core line extracted by the interpolation target extraction unit 011 based on the size of the blood vessel diameter at the two end points sandwiching the part to be interpolated.

  Step S013: The display control unit 012 acquires the interpolated data from the interpolation unit 009, and acquires blood vessel data from the volume data storage unit 101. The display control unit 012 displays the interpolated blood vessels on the display unit 013. Let

  As described above, in the MRI diagnostic apparatus according to the present embodiment, by extracting a blood vessel in which a false defect has occurred from the generated blood vessel image, and interpolating and displaying the false defect portion of the blood vessel, More accurate blood vessel display can be performed. This makes it possible to reduce oversight of blood vessels in treatment planning and treatment support using MRI images.

  Further, it is possible to interpolate a false defect portion by focusing on a blood vessel connected to an important region such as a brain stem. Therefore, it is possible to prevent an oversight of a blood vessel connected to an important part and to perform an interpolation process efficiently.

[Second Embodiment]
The MRI image diagnostic apparatus according to the second embodiment of the present invention will be described below. The MRI image diagnostic apparatus according to the present embodiment uses not only the information of the end points but also the information of the nearby points when performing the blood vessel interpolation (the blood vessel core line and the blood vessel wall interpolation) as in the first embodiment. Is different. Therefore, in the following, blood vessel interpolation will be mainly described. A block diagram of the MRI image diagnostic apparatus according to the present embodiment is also represented in FIG. 1 as in the first embodiment. Moreover, in this embodiment, the functional part to which the same code | symbol as 1st Embodiment is attached | subjected without description in particular has the same function.

  The operation until the segment data is stored in the segment data storage unit 102 is the same as that in the first embodiment also in the MRI image finger bullet apparatus according to the present embodiment.

  The end point information creation unit 006 acquires segment data from the segment data storage unit 102.

  The structural line extraction unit 007 extracts a structural line by thinning the segment data.

  The blood vessel core line extraction unit 008 slices the blood vessel along a plane orthogonal to the blood vessel including the point on the structural line, obtains a cross section of the blood vessel, and further obtains an inscribed circle inscribed in the cross section of the blood vessel. Then, the blood vessel core line extraction unit 008 generates a blood vessel core line by collecting the center points of the obtained inscribed circle. The blood vessel core line extraction unit 008 stores the obtained blood vessel core line in the blood vessel core line storage unit 103.

  The endpoint information creation unit 006 extracts, as endpoints, points that have only one adjacent point among the created points on the blood vessel core line. Then, the end point information creation unit 006 uses the position coordinate information of the end point and the position coordinates of a point on the blood vessel core line within 3 voxels from the end point (hereinafter simply referred to as “neighboring point”) as the blood vessel core line extraction unit 008. Get from. Also, the end point information creation unit 006 calculates a direction vector at the end point by obtaining a difference between the end point and the adjacent point. In addition, the endpoint information creation unit 006 acquires pixel values at nearby points from the volume data storage unit 101. Further, the end point information creation unit 006 acquires the blood vessel diameter at a nearby point based on the inscribed circle obtained by the blood vessel core line extraction unit 008. Then, the end point information creation unit 006 obtains the average value of the pixel value and the blood vessel diameter at the acquired nearby points.

  The end point information creation unit 006 stores the end point position information, the direction vector at the end point, the average value of the pixel values at the nearby points, and the average value of the blood vessel diameter at the nearby points in the end point information storage unit 104. The reason for using pixel values and blood vessel diameters at points other than the end points in this way is that the values at the end points themselves are inaccurate compared to the normal imaging unit in the case of pixel values and blood vessel diameters. This is because the interpolation point selection unit 010 may be inappropriate for use in comparison for interpolation because it cannot be said to be a pixel value or blood vessel diameter.

  Here, in the present embodiment, in order to obtain an average pixel value and a blood vessel diameter value in the vicinity of the end point, an average value of the pixel value and the blood vessel diameter in the vicinity point is taken. This may be another value, for example, the median value or the maximum value may be used. In the present embodiment, a plurality of points are used for calculation of pixel values and blood vessel diameters. This may be a point other than the end point in the vicinity of the end point. For example, a pixel value or a blood vessel diameter of a point at a position separated by 3 voxels may be used. Further, in the present embodiment, the point is within 3 voxels, but this may be a point near the end point, and may be within 2 voxels or within 4 voxels, for example.

  The interpolation location selection unit 010 has a threshold value of the distance between end points, a threshold value of an outer angle formed by a direction vector at the end points, a threshold value of an average value of pixel values at neighboring points, and a difference between average values of blood vessel diameters at neighboring points. Are stored in advance. The interpolation location selection unit 010 acquires the end point position information, the direction vector at the end point, the average value of the pixel values at the nearby points, and the average value of the blood vessel diameter at the nearby points from the end point information storage unit 104. The interpolation location selection unit 010 compares the acquired position information of the end points, the direction vector at the end points, the average value of the pixel values at the neighboring points, and the average value of the blood vessel diameter at the neighboring points with a threshold value stored in advance. To do. Then, the interpolation location selection unit 010 extracts a pair of two end points that fall within all threshold values as an interpolation location.

  The interpolation unit 009 interpolates the blood vessel core line at the interpolation location between the end point pairs extracted by the interpolation location selection unit 010 based on the blood vessel core data stored in the blood vessel core storage unit 103 using spline interpolation or the like. To do.

  The interpolation unit 009 receives input of information on the blood vessel core line that is a target for interpolating the blood vessel wall from the interpolation target extraction unit 011. The interpolation unit 009 acquires from the end point information storage unit 104 the average value of the blood vessel diameters of the neighboring points in the interpolation portion of the blood vessel having the input blood vessel core line. The interpolation unit 009 performs linear interpolation according to the distance on the blood vessel core line based on the acquired average value of the blood vessel diameters of neighboring points, thereby interpolating the blood vessel wall at the interpolation location. Here, in this embodiment, the average value of neighboring points is used for interpolation of the blood vessel wall in order to obtain an accurate blood vessel image. This is because the value of the blood vessel diameter at the end point itself is not clear with respect to the normal imaging unit and may be an inaccurate value. Therefore, by using the values of nearby points, it is possible to reduce the risk of damaging a blood vessel by a treatment plan or treatment support using an image corrected by the blood vessel based on such an inaccurate value.

  In the present embodiment, the average value of the blood vessel diameters at nearby points is used to interpolate the blood vessel wall with the average value of the blood vessel wall near the end points. This may be another value, for example, an intermediate value or a maximum value at nearby points may be used. Furthermore, since the value of the end point is inaccurate, the blood vessel diameter at a point 3 voxels away from the end point may be used if the use of the end point value should be avoided in the interpolation. Further, in the present embodiment, the point is within 3 voxels, but this may be a point near the end point, and may be within 2 voxels or within 4 voxels, for example.

  Furthermore, in the present embodiment, an inscribed circle is used for the interpolation of the blood vessel wall, but an actual blood vessel shape may be used for the interpolation. In this case, the interpolation unit 009 obtains an average blood vessel shape obtained from the blood vessel shape at a nearby point from the blood vessel wall extraction unit 005, and performs interpolation of the blood vessel wall using the blood vessel shape.

  The interpolation unit 009 interpolates the interpolated blood vessel wall data in the blood vessel wall storage unit 105.

  The interpolation target extraction unit 011 receives input of an important region and a start point from the operator. The interpolation target extraction unit 011 extracts a blood vessel core line connected from the start point to the important region from the blood vessel core lines interpolated by the interpolation unit 009. The interpolation target extraction unit 011 outputs the extracted blood vessel core line to the interpolation unit 009.

  The display control unit 012 creates an interpolated blood vessel image based on the interpolated blood vessel wall data stored in the blood vessel wall storage unit 105 and the blood vessel data stored in the volume data storage unit 101. Are displayed on the display unit 013.

  As described above, the MRI image diagnostic apparatus according to the present embodiment is configured to perform vascular core line interpolation and blood vessel interpolation using pixel values and blood vessel diameters at points near the end points. As a result, even when the pixel value or the blood vessel diameter value at the end point is inaccurate, it is possible to perform substantially accurate blood vessel interpolation. Therefore, by using the blood vessel image generated by the MRI image diagnostic apparatus according to the present embodiment, it becomes possible to perform treatment planning and treatment support more accurately.

  Further, in this embodiment, in order to generate a more accurate blood vessel image, interpolation is performed using pixel values and blood vessel diameters of neighboring points in both selection of an interpolation location and blood vessel wall interpolation. However, the MRI diagnostic imaging apparatus according to the present embodiment is operable even in a configuration in which interpolation is performed using pixel values and blood vessel diameters of neighboring points only in either one.

[Third Embodiment]
The MRI image diagnostic apparatus according to the third embodiment of the present invention will be described below. The MRI image diagnostic apparatus according to the present embodiment is different from the first embodiment in that the MRI image diagnostic apparatus according to the present embodiment displays an image of the interpolated blood vessel wall in a state that can be distinguished from other blood vessel walls. Therefore, the identification of the interpolated blood vessel wall will be mainly described below. A block diagram of the MRI image diagnostic apparatus according to the present embodiment is also represented in FIG. 1 as in the first embodiment. Moreover, in this embodiment, the functional part to which the same code | symbol as 1st Embodiment is attached | subjected without description in particular has the same function.

  The interpolation unit 009 interpolates a blood vessel core line at the interpolation location selected by the interpolation location selection unit 010 based on the end point information stored in the end point information storage unit 104. Further, the interpolation unit 009 attaches a flag indicating that interpolation has been performed to the data of the interpolated portion of the blood vessel core line.

  Further, the interpolation unit 009 interpolates the blood vessel wall based on the blood vessel diameter of the end point information storage unit 104 with respect to the blood vessel having the blood vessel core line to be interpolated with the blood vessel wall extracted by the interpolation target extraction unit 011. Further, the interpolation unit 009 attaches a flag indicating that interpolation has been performed to the data of the interpolated portion of the blood vessel wall. Here, as a method for searching which blood vessel wall is the interpolated blood vessel wall, for example, the interpolated blood vessel wall having a flag indicating that the interpolation is performed at the point on the blood vessel core line from which the interpolation is performed It is a method to judge.

  The interpolation unit 009 stores the blood vessel wall data with the flag indicating the interpolation in the blood vessel wall storage unit 105.

  The display control unit 012 causes the display unit 013 to display the normal imaging region and the interpolated blood vessel core line and the blood vessel wall portion (that is, the false defect portion of the blood vessel) with different settings such as opacity and color. For example, FIG. 11 is an example of an image in which the color of the blood vessel wall of the interpolated portion is made different. As shown in FIG. 11, blood vessel images are displayed with different colors of the blood vessel core lines 400a and 400b corresponding to the normal imaging unit and the blood vessel core line 400d corresponding to the interpolated portion. In this way, it is possible to easily grasp which part corresponds to the interpolated blood vessel.

  As described above, in the MRI image diagnostic apparatus according to the present embodiment, it is possible to display an image in which the opacity, color, and the like are different between the normal part and the interpolated part. Thus, the operator can easily grasp which part is interpolated. Therefore, it is easy to determine that the place is detected by the operator when a false-defective blood vessel is erroneously detected due to imaging conditions or the like.

Block diagram of an MRI diagnostic imaging apparatus according to the present invention Detailed block diagram of the scanning unit Diagram for explaining the extraction of structural lines Illustration for explaining how to find the center of an inscribed circle The figure for explaining how to find the blood vessel core and end points The figure for demonstrating the comparison with the threshold value in the end point by the interpolation location selection part A diagram for explaining extraction of blood vessels to be interpolated The figure for demonstrating the restriction | limiting of the extraction area | region of the blood vessel connected to an important area | region from a starting point Diagram for explaining interpolation of blood vessel wall FIG. 6 is a flowchart of blood vessel image generation in the MRI image diagnostic apparatus according to the present embodiment. Illustration of an example of an image with different colors of the blood vessel wall of the interpolated part

Explanation of symbols

001 Scan unit 002 Reconstruction unit 003 Blood vessel extraction unit 004 Segment data creation unit 005 Blood vessel wall extraction unit 006 Endpoint information creation unit 007 Structure line extraction unit 008 Blood vessel core line extraction unit 009 Interpolation unit 010 Interpolation location selection unit 011 Interpolation target extraction unit 012 Display control unit 013 Display unit 014 Input unit 015 User interface 100 Storage unit 101 Volume data storage unit 102 Segment data storage unit 103 Blood vessel core line storage unit 104 Endpoint information storage unit 105 Blood vessel wall storage unit

Claims (8)

Scanning means for applying a gradient magnetic field and a high-frequency magnetic field to a subject placed in a static magnetic field, and detecting a nuclear magnetic resonance signal generated from the subject;
Reconstructing means for reconstructing an image based on the nuclear magnetic resonance signal and generating volume data;
Blood vessel extraction means for extracting blood vessels from the volume data;
End point information creating means for obtaining end point information including the position of the end point of the extracted blood vessel and the direction of the blood vessel at the end point;
Interpolation point selection means for selecting between the end points as interpolation points from the end point information;
Interpolation means for interpolating a blood vessel wall between the selected end points;
Display control means for displaying on the display means an image obtained by adding information of the blood vessel wall interpolated to the volume data;
An MRI diagnostic imaging apparatus comprising: The blood vessel extraction means stores in advance a threshold value of a pixel value representing a blood vessel, compares the pixel value of the volume data with the threshold value, and extracts a blood vessel,
Furthermore, the pixel value of the extracted blood vessel region in three-dimensional coordinates is set to 1, and the pixel value of the other region is converted to segment data represented as 0.
The MRI image diagnostic apparatus according to claim 1. The end point information creating means includes:
A structural line is obtained by thinning the extracted blood vessel,
Determining an inscribed circle inscribed in a blood vessel in a cross section including pixels on the structure line and orthogonal to the structure line;
By connecting the centers of the inscribed circles, the blood vessel core line is obtained,
Finding the position of the end point based on the blood vessel core line and the direction vector of the direction of the blood vessel at the end point,
The MRI image diagnostic apparatus according to claim 1 or 2, wherein The interpolation location selection means includes
One or a combination of the distance between the two endpoints, the direction vector at each endpoint, the luminance value at each endpoint or a point adjacent to each endpoint, or the blood vessel diameter at each endpoint or a point adjacent to each endpoint. The MRI image diagnostic apparatus according to any one of claims 1 to 3, wherein an interpolation location is set between the two end points when the threshold value is less than or equal to a threshold value stored in advance. The interpolation means includes
Interpolating the blood vessel core line at the interpolation location;
Interpolating the blood vessel at the interpolation location by sequentially creating a blood vessel wall corresponding to a point on the blood vessel core line based on the blood vessel wall near the end point;
The MRI diagnostic imaging apparatus according to any one of claims 3 and 4. After the interpolating means interpolates the blood vessel core line, the blood vessel having the blood vessel core line connecting the start point and the specific area is received in accordance with designation of the specific area and the start point on the blood vessel in the volume data. Further comprising an interpolation object extracting means for extracting as an object for interpolation of the blood vessel wall,
The interpolation means interpolates a blood vessel with respect to a blood vessel extracted as an interpolation target of the blood vessel wall;
The MRI diagnostic imaging apparatus according to claim 5.   The MRI image diagnosis apparatus according to claim 1, wherein the display control unit displays the interpolated blood vessel wall image and the image based on the volume data in a distinguishable manner. . A scanning step in which a gradient magnetic field and a high-frequency magnetic field are applied to a subject placed in a static magnetic field, and a nuclear magnetic resonance signal generated from the subject is detected;
A reconstruction step of computing the nuclear magnetic resonance signal to reconstruct an image and generating volume data;
A blood vessel extraction step of extracting blood vessels from the volume data;
End point information creating step for obtaining end point information including the position of the extracted blood vessel end point and the direction of the blood vessel;
An interpolation location selection stage for selecting between the endpoints to be interpolation locations from the endpoint information;
An interpolation step of interpolating a blood vessel wall at the selected interpolation location;
A display control step of displaying on the display means an image obtained by adding information of the blood vessel wall interpolated to the volume data;
An MR image forming method comprising: