JP4660356B2 - X-ray CT apparatus, image data area extraction system, and image data area extraction program - Google Patents

Description

  The present invention relates to an X-ray CT apparatus, an image data region extraction system, and an image data region extraction program for creating three-dimensional projection image data from X-ray CT (computed tomography) image data obtained by irradiating a subject with X-rays. In particular, the present invention relates to an X-ray CT apparatus, an image data region extraction system, and an image data region extraction program having a function of extracting a region and deleting three-dimensional projection image data inside and outside the extracted region.

  Conventionally, there is an X-ray CT apparatus as an image diagnostic apparatus that irradiates a subject with X-rays, detects transmitted X-rays, and reconstructs X-ray CT image data. Imaging is often performed for the purpose of observing an organ such as a blood vessel by administering a contrast medium to a subject using this X-ray CT apparatus. In imaging for the purpose of blood vessel observation, X-ray CT image data of a contrasted blood vessel is reconstructed by administration of a contrast medium, and three-dimensional (3D) projection image data is created from the X-ray CT image data. Is done.

  Typical methods for creating 3D projection image data include methods such as Maximum Intensity Projection (MIP), Minimum Intensity Projection, and Addition Average Projection (X-ray Projection). Can be mentioned. For the purpose of observing contrast blood vessels, 3D projection images (MIP images) created by MIP are frequently used.

  However, since the CT values of the bone and contrasted blood vessel both have a portion that is in the same range, even if an MIP image is created for the purpose of blood vessel observation, the bone is imaged together with the blood vessel and reflected. There is a problem that the image of the bone gets in the way of clinical diagnosis.

  Therefore, in the past, prior to the observation of contrast-enhanced blood vessels using MIP images, 3D images such as surface display (SR: Surface Rendering) images and volume display (VR: Volume Rendering) images using voxels are created separately from MIP images. Then, a so-called bone removal operation is performed in which image data in the bone region is extracted and deleted via the SR image or the VR image (see, for example, Patent Document 1).

  FIG. 9 is a diagram for explaining a procedure of a bone removal operation performed prior to observation of a contrasted blood vessel using a conventional MIP image.

  FIG. 9A is a diagram illustrating an example of a shaded volume rendering (SVR) image created as a 3D image for the bone removal operation. As shown in FIG. 9A, the SVR image includes bones having the same CT value as well as blood vessels.

  Therefore, in the SVR image, a threshold value based on the CT value and an opacity (Opacity) with respect to the CT value are set and used as a reference for discriminating between the bone and the contrasted blood vessel. Then, bones and contrasted blood vessels are displayed so that they can be identified by threshold values and opacity, and the SVR image data of the bone region is divided or extracted by a commonly used connected region extraction method, and is selectively deleted. Is implemented.

As a result, as shown in FIG. 9B, an SVR image of the contrasted blood vessel from which the bone has been deleted is obtained. Further, an MIP image is generated from the X-ray CT image data included in the blood vessel extraction region of the SVR image from which the bone has been deleted.
JP-A-9-73557

  However, in the observation of contrast blood vessels using a conventional X-ray CT apparatus, there is a problem that the bone removal operation cannot be performed efficiently. That is, the CT value of the bone takes a value within a certain range, but there is a bone CT value that is close to the soft tissue. Therefore, when the threshold value and the opacity are set so that the CT value becomes low at the start of the bone removal operation, an organ close to the soft tissue is displayed together with the bone.

  However, there are many contact sites between an organ close to a soft tissue and a contrasted blood vessel, and it is difficult to extract a bone region by a generally used connected region extraction method. As a result, if the threshold value and the opacity are set so that the CT value becomes low at the start of the boning operation, efficient boning operation becomes difficult.

  Therefore, at the start of the boning operation, the thresholding and the opacity are set so that the CT value becomes high, and the boning operation is performed. Therefore, even if an MIP image is created from X-ray CT image data after a bone removal operation, the MIP image is an image including bone (particularly cartilage) having a CT value close to that of soft tissue.

  FIG. 9C is a diagram illustrating an example in which cartilage is displayed on the MIP image after the bone removal operation. As shown in the curved frame in FIG. 9C, cartilage having a CT value close to the soft tissue often remains in the MIP image after the bone removal operation.

  For this reason, in order to delete the bone remaining in the MIP image, the 3D image such as the SR image or the SVR image is displayed again, and the bone removal operation is resumed. Then, in the resumed bone removal operation, the threshold value is lowered and an organ with a lower CT value is displayed. Furthermore, after the cartilage displayed with the newly set threshold is selectively deleted by the connected region extraction method, an MIP image is created.

  However, cartilage with a lower CT value may be displayed in the re-created MIP image. In such a case, a bone removal operation using a 3D image is performed in order to obtain a clinically effective MIP image. Then, complicated operations such as confirmation by the MIP image and threshold setting of the boning operation are repeated.

  In addition to blood vessel observation, the problem that such a complicated operation occurs can also occur when a specific organ or organ is selectively deleted or displayed depending on the CT value. .

  The present invention has been made to cope with such a conventional situation, and more easily extracts a region from X-ray CT image data according to a CT value, and creates three-dimensional projection image data inside and outside the extracted region. An object of the present invention is to provide an X-ray CT apparatus, an image data region extraction system, and an image data region extraction program that can be used.

  In order to achieve the above object, an X-ray CT apparatus according to the present invention, as described in claim 1, includes image reconstruction means for collecting raw data of a subject and reconstructing three-dimensional image data. 3D reference image display means for displaying the 3D image data included in the first area of the 3D image data as a 3D reference image, and the 3D image data is in the first area of the 3D image data. 3D projection image display means for displaying 3D image data included in the second area as a 3D projection image, and a connected area to be deleted from the second area via the 3D reference image A connected area specifying means for acquiring the position of the connected area, a connected area extracting means for obtaining a connected area connected to the position acquired by the connected area specifying means as a threshold area based on a preset threshold, and the second area. It is characterized in that it has a connection area deleting means for updating the second region by removing the coupling region determined by the coupling region extracting means from.

  Moreover, in order to achieve the above-mentioned object, the image data region extraction system according to the present invention includes the first region in the three-dimensional image data collected by the image diagnostic apparatus as described in claim 5. Three-dimensional reference image display means for displaying the three-dimensional image data to be displayed as a three-dimensional reference image, and three-dimensional image data included in a second region within the first region of the three-dimensional image data. 3D projection image display means for displaying as a projection image, connected area specifying means for acquiring a position for specifying a connected area to be deleted from the second area via the 3D reference image, and the connected area A connected area extracting means for obtaining a connected area connected to the position acquired by the specifying means as a threshold area based on a preset threshold; and from the second area to the connected area extracting means. Ri is characterized in that it has a connection area deleting means for updating the second region by removing the coupling region obtained.

  In order to achieve the above-mentioned object, the image data region extraction program according to the present invention, as described in claim 6, causes the computer to execute the first of the three-dimensional image data collected by the image diagnostic apparatus. 3D reference image display means for displaying the 3D image data included in the region as a 3D reference image, and 3D image data included in the second region in the first region of the 3D image data. 3D projection image display means for displaying as a 3D projection image, connected area specifying means for acquiring a position for specifying a connected area to be deleted from the second area via the 3D reference image, the connected area A connected area extracting means for obtaining a connected area connected to the position acquired by the specifying means as a threshold area based on a preset threshold, and the connected area from the second area; It is characterized in that to function as a connecting area deleting means for updating the second region by removing the coupling region determined by the region extraction means.

  In the X-ray CT apparatus, the image data region extraction system, and the image data region extraction program according to the present invention, the region is more easily extracted from the X-ray CT image data according to the CT value, and the three-dimensional projection inside and outside the extracted region is performed. Image data can be created.

  Embodiments of an X-ray CT apparatus, an image data region extraction system, and an image data region extraction program according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a functional block diagram showing an embodiment of an X-ray CT apparatus according to the present invention.

  The X-ray CT apparatus 20 includes a gantry unit 21 and a computer device 22. The gantry unit 21 includes an X-ray tube 23, a high voltage generator 24, an X-ray detector 25, and a data acquisition unit 26 (DAS; Data Aquisition System). The X-ray tube 23 and the X-ray detector 25 are mounted at positions facing each other with the subject P sandwiched between rotating rings (not shown) that rotate continuously at high speed.

  The high voltage generator 24 is configured to supply a tube current and a tube voltage to the X-ray tube 23 according to a control signal from the computer device 22 so that the X-ray detector 25 can detect the X-ray transmitted through the subject P. Is done. Further, the X-ray detection signal detected by the X-ray detector 25 is supplied to the data acquisition unit 26, digitized, and supplied to the computer device 22 as raw data. That is, the X-ray CT apparatus 20 functions as a raw data collection unit that collects raw data that is biological information of the subject P by the high voltage generator 24, the X-ray tube 23, the X-ray detector 25, and the data collection unit 26. Prepared for.

  The computer device 22 includes an image processing device 27, an image display unit 28, and an input unit 29. The image processing device 27 has a control unit 30 as a center, a pre-processing unit 31 that converts raw data output from the data collection unit 26 into projection data through correction processing and the like, a memory unit 32 that stores projection data, and projection data The image reconstruction unit 33 for reconstructing the 3D image data from the storage device 34 for temporarily storing the 3D image data and the raw data output from the data collection unit 26, and the 3D image data is read from the storage device 34 and specified. An image data area extraction system 35 that creates 3D projection image data in the area is configured.

  That is, the X-ray CT apparatus 20 is provided with a function as image reconstruction means for reconstructing 3D image data from raw data by the preprocessing unit 31 and the image reconstruction unit 33 of the image processing device 27.

  An image data area extraction system 35 is built in the X-ray CT apparatus 20. However, the image data region extraction system 35 may be provided individually without being incorporated in the X-ray CT apparatus 20. When the image data area extraction system 35 is configured separately from the X-ray CT apparatus 20, 3D image data and SVR image data captured by the X-ray CT apparatus 20 can be input to the image data area extraction system 35. Configured to be able to.

  According to this image data area extraction system 35, while referring to a 3D reference image such as an SVR image displayed on the image display unit 28, a specific area is specified to generate 3D projection image data such as MIP image data. be able to. Examples of projection methods for creating 3D projection image data include projection methods such as a maximum value projection method (MIP), a minimum value projection method (MinIP), and an addition average projection method. Here, a case where MIP image data, which is an example of 3D projection image data, is created while referring to an SVR image, which is an example of a 3D reference image, will be described.

  FIG. 2 is a functional block diagram of the image data region extraction system 35 built in the X-ray CT apparatus 20 shown in FIG.

  The image data area extraction system 35 is constructed by reading an image data area extraction program into the computer device 22, and is configured by an SVR data management unit 35a, an MIP data management unit 35b, an SVR image creation unit 35c, an MIP image creation unit 35d, A connected region specifying unit 35e, a connected region extracting unit 35f, a MIP connected region deleting unit 35g, a connected region extraction determining unit 35h, and an SVR connected region deleting unit 35i are provided. However, all or part of the image data region extraction system 35 may be configured by a circuit. The input unit 29 is provided with a mouse 29a, an extraction button 29b, and a process start button 29c.

  The SVR data management unit 35a has a function of managing an existing region (existing region) to be generated and displayed as an SVR image as existing region information for SVR, and an SVR image generating unit every time the existing region information for SVR is updated. 35c.

  Specifically, the SVR data management unit 35a gives the location information on the SVR image received from the connected region specifying unit 35e described later to the connected region extracting unit 35f together with the existing region information for SVR, while the connected region extracting unit 35f. And the function of providing the connected area information received from the SVR image creating unit 35c. In addition, when the SVR data management unit 35a receives the connection region extraction confirmation information from the connection region extraction confirmation unit 35h, the SVR data management unit 35a gives the connection region information together with the SVR existing region information to the SVR connection region deletion unit 35i. It has a function. Further, the SVR data management unit 35a has a function of updating the existing area information for SVR according to the notified update information when the update information of the existing area information for SVR is notified from the connected area deleting unit for SVR 35i. When an area extraction process start instruction is received from the process start button 29c of the input unit 29, the existing area information for SVR is given as initialization process information to the MIP data management unit 35b, thereby performing the initialization process of the MIP image. It has a function to instruct the start.

  The MIP data management unit 35b has a function of managing the existing area of the MIP image as existing area information for MIP and a function of providing the function of the existing area information for MIP to the MIP image creating unit 35d.

  Specifically, when the MIP data management unit 35b receives the SVR existing area information as the initialization processing information from the SVR data management unit 35a, the MIP data management unit 35b uses the same area as the SVR existing area as the MIP existing area. By providing it to the image creating unit 35d, it has a function of creating MIP image data in the same area as the SVR image data as an initialization process. Further, when the area to be deleted from the existing area of the MIP image is notified as the connection area information from the connection area extraction section 35f, the MIP data management section 35b provides the MIP existing area information to the MIP connection area deletion section 35g. At the same time, it provides a function of updating the existing area information for MIP according to the notified update information when the update information of the existing area information for MIP is notified from the connected area deletion unit 35g for MIP.

  When receiving the SVR existing area information from the SVR data management section 35a, the SVR image creating section 35c reads the 3D image data included in the existing SVR area from the storage device 34, and creates SVR image data. And the function of causing the image display unit 28 to display the SVR image by giving the created SVR image data to the image display unit 28.

  The SVR image creation unit 35c, when receiving the connection region information from the SVR data management unit 35a, displays a connection region image for visually displaying the connection region on the SVR image displayed on the image display unit 28. It has a function of creating data and a function of causing the image display unit 28 to display a connected region by giving the generated connected region image data to the image display unit 28. For example, the connected area image data can be created so that the connected area is displayed in color on the SVR image. The connected region image data created by the SVR image creating unit 35c may be SVR image data as long as the connected region can be identified on the SVR image. The connected region image data created by the SVR image creation unit 35c can be, for example, image data displayed in a single color or color projection image data with contrast.

  The MIP image creation unit 35d, when receiving the MIP existing area information from the MIP data management unit 35b, reads the 3D image data included in the existing MIP area from the storage device 34 and creates the MIP image data And a function of displaying the MIP image on the image display unit 28 by giving the created MIP image data to the image display unit 28.

  The connected area designating unit 35e is designated by the input unit 29 such as the mouse 29a via the SVR image displayed on the image display unit 28 as information for obtaining an area to be deleted from the existing area for the SVR image and the existing area for the MIP image. The acquired position is acquired, and the acquired position is provided to the data management unit 35a for SVR. The connection area designating unit 35e is configured to refer to 3D image data stored in the storage device 34 when acquiring position information.

  Further, if necessary, the connection area designating unit 35e gives the position information designated by the input unit 29 to the image display unit 28 so that the designated position can be displayed on the image display unit 28 in an identifiable manner. it can.

  The connected region extraction unit 35f refers to the 3D image data stored in the storage device 34 based on the positional information on the SVR image received from the SVR data management unit 35a and the existing region information for SVR, thereby existing SVR images. It has a function of obtaining a connected area (connected area) including a position determined by position information in the area and providing the obtained connected area to the SVR data management unit 35a and the MIP data management unit 35b.

  That is, the connected region extraction unit 35f regards the region occupied by the threshold region connected to the position (starting point) specified by the position information in the 3D image data in the existing region for SVR as an object, and performs general connected region extraction. It is configured to obtain as a connected region by law.

  A CT value can be used as a threshold used when obtaining a connected region. A pixel value (CT value) representing a point or range where the opacity of the 3D image data changes from 0 (transparent) to 0 and 1 (semi-transparent), or from 0 to 1 (opaque). As the threshold value, for example, an area that is greater than or less than the threshold value among the 3D image data stored in the storage device 34 can be obtained as a connected area.

  The threshold area thus obtained can be regarded as an object in the 3D image data. That is, the boundary surface of the threshold area representing the area in which the opacity of the 3D image data is a certain value or more can be set as the object detection position. The threshold used for extracting the connected area can be arbitrarily set by operating the input unit 29. The set threshold value is notified from the input unit 29 to the connected region specifying unit 35e and the connected region extracting unit 35f.

  Further, the connection area extraction unit 35f expands or contracts the obtained connection area as necessary, and the connection area after the expansion or contraction is converted into the SVR data management unit 35a and the MIP data management. You may make it provide to the part 35b.

  Even if the connection area and the area occupied by the object do not match with sufficient accuracy because the threshold setting for the 3D image data is inappropriate, the connection area is expanded or contracted to make the connection area an object. It is possible to approach the area occupied by. Therefore, an expansion rate (or contraction rate) or expansion width (or contraction width) is set in advance, the connected region extracted as the threshold region is expanded or contracted, and the connected region after the expansion or contraction is used as the existing SVR-use region. The SVR data management unit 35a and the MIP data management unit 35b can be given as an area to be deleted from the area or the existing MIP area.

  The MIP linked area deletion unit 35g updates the existing MIP area by subtracting the linked area from the existing MIP area based on the existing MIP area information and the linked area information received from the MIP data management unit 35b. And a function of giving the updated MIP existing area to the MIP data management unit 35b as update information of the existing MIP area information.

  The connected area extraction / determination unit 35h is a function for providing the connection determination of the connected area to the SVR data management unit 35a when a request for actually subtracting the connected area from the existing area for SVR is received from the extraction button 29b of the input unit 29. Have

  The SVR linked area deletion unit 35i updates the existing area for SVR by subtracting the linked area from the existing area for SVR based on the existing area information for SVR and the linked area information received from the data management unit 35a for SVR. And a function of giving the updated SVR existing area to the SVR data management unit 35a as update information of the SVR existing area information.

  Furthermore, the SVR image data and the MIP image data can be rotated, moved, and enlarged so that the SVR image data and the MIP image data can be displayed on the SVR image data generation unit 35c and the MIP image data generation unit 35d as needed. It is also possible to provide a function that is generated and given to the image display unit 28. By doing so, the SVR image and the MIP image displayed on the image display unit 28 can be rotated, moved, or enlarged by the operation of the input unit 29.

  Next, the operation and action of the X-ray CT apparatus 20 will be described.

  FIG. 3 is a flowchart showing a procedure when the X-ray CT apparatus 20 shown in FIG. 1 extracts a region from X-ray CT image data and creates three-dimensional projection image data inside and outside the extracted region. Reference numerals with numbers added to S indicate steps in the flowchart.

  First, in step S1, for example, in order to collect contrast-enhanced blood vessel images of the subject P, a scan with contrast medium administration is executed to reconstruct 3D image data of the subject P. That is, a tube current and a tube voltage are supplied from the high voltage generator 24 to the X-ray tube 23 by a control signal from the computer device 22, and the subject P is irradiated with X-rays. Then, X-rays that have passed through the subject P are detected by the X-ray detector 25. The X-ray detection signal detected by the X-ray detector 25 is supplied to the data collecting unit 26 and digitized, and is supplied to the computer device 22 as raw data.

  In the computer device 22, the raw data is converted into projection data by the correction processing in the preprocessing unit 31, and is temporarily stored in the memory unit 32. Then, 3D image data is reconstructed from the projection data by the image reconstruction unit 33, and the reconstructed 3D image data is stored in the storage device 34.

  Then, the 3D image data including the contrasted blood vessels stored in the storage device 34 is read into the image data region extraction system 35 and used for creating MIP image data of the contrasted blood vessels.

  Next, in step S <b> 2, SVR image data is created from 3D image data including contrasted blood vessels and bone regions and displayed on the image display unit 28. That is, the SVR data management unit 35a provides the entire region of the three-dimensional space to the SVR image creation unit 35c as the existing region for SVR. The SVR image creation unit 35c reads 3D image data of the entire area from the storage device 34, and generates SVR image data. The SVR image creation unit 35 c gives the generated SVR image data to the image display unit 28. For this reason, the SVR image of the entire region is displayed on the image display unit 28.

  Next, in step S3, when an instruction to start the area extraction application to start the area extraction process is given to the image data area extraction system 35 from the process start button 29c of the input unit 29, the area extraction process start instruction is issued. The data is given to the SVR data management unit 35a. Then, the SVR data management unit 35a gives the MIP data management unit 35b SVR existing region information indicating all regions as initialization processing information.

  Thereby, the initialization process of the MIP image is started. That is, the MIP data management unit 35b provides the same area as the existing area for SVR to the MIP image creation section 35d as the existing area for MIP. The MIP image creation unit 35d creates MIP image data for the entire area by reading 3D image data included in the existing area for MIP, which is the entire area, from the storage device 34 and performing MIP processing. The MIP image creation unit 35d gives the created MIP image data to the image display unit 28. For this reason, the MIP image is displayed on the image display unit 28.

  The displayed MIP image includes the MIP image of the bone region to be deleted in clinical diagnosis of the blood vessel together with the contrasted blood vessel. Therefore, it is necessary to perform a so-called bone removal operation for deleting the bone region image from the MIP image. This boning operation can be performed by operating the input unit 29 while referring to both the SVR image and the MIP image displayed on the image display unit 28 by the function of the image data region extraction system 35.

  Therefore, in step S4, a threshold for extracting a bone region is set. The threshold value is notified from the input unit 29 to the connected region specifying unit 35e and the connected region extracting unit 35f.

  FIG. 4 is a diagram for explaining an example of the procedure of the boning work by the X-ray CT apparatus 20 shown in FIG.

  As shown in FIG. 4A, for example, when contrasted blood vessels, bones, and cartilage are close to each other, the profile image of the CT value at the line position indicated by the solid line is as shown in FIG. 4B. That is, the CT value of the contrast blood vessel and the bone region exceeds 200, and the CT value of the cartilage region is between 100 and 200. The CT values of the region between the contrasted blood vessel and the bone and the region between the bone and the cartilage are smaller than the CT values of the contrasted blood vessel, the bone region, and the cartilage region.

  Then, the contrasted blood vessel, the bone region, and the cartilage region are identified and separated using such a difference in CT value. The MIP image is basically displayed by assigning the entire range of CT values to the Gray Level corresponding to the CT values. For this reason, a portion having a small CT value is black, while a portion having a high CT value is white.

  In the case of a MinIP image, if air with a CT value of −1000 is present around the body of the subject, the value of the MinIP image becomes −1000. Therefore, the CT of 3D image data is usually performed prior to MinIP processing. Threshold processing is performed so that the value is about −900 to −500.

  That is, the CT value is set as a threshold value so that contrast blood vessels, bone regions, and cartilage regions can be extracted as threshold regions and separated as separate objects. Here, if the CT value set as the threshold is set too low, the contrasted blood vessel and the bone region cannot be properly separated. That is, in the case of the MIP image having the CT value profile image shown in FIG. 4B, the CT value of the region between the contrasted blood vessel and the bone and the region between the bone and the cartilage exceeds 100. . Therefore, when the threshold value is set to 100, which is smaller than the CT value of cartilage, for example, and an area where the CT value exceeds 100 is extracted as the threshold value region, the contrasted blood vessel, bone region, and cartilage region are integrated as shown in FIG. End up.

  Therefore, at the start of the bone removal operation, a large CT value is set as a threshold value in order to separate the contrasted blood vessel and the bone region. For example, the user can designate a CT value 200 larger than the CT value of the region between the contrasted blood vessel and the bone and the region between the bone and the cartilage as the threshold value by operating the input unit 29. Then, the threshold value for setting the CT value 200 is notified from the input unit 29 to the connected region specifying unit 35e and the connected region extracting unit 35f.

  As a result, in the case of the MIP image having the CT value profile image shown in FIG. 4B, as shown in FIG. 4D, the contrast blood vessels having a CT value of 200 or more and the bone region are separated from each other. A region can be formed on the 3D image data.

  In step S5, the user selects (clicks) a threshold region to be deleted on the SVR image displayed on the image display unit 28 with the mouse 29a. If it does so, the position selected with the mouse | mouth 29a will be acquired by the connection area | region designation | designated part 35e. The connection area designation unit 35e gives the acquired position to the SVR data management unit 35a.

  In step S6, the SVR data management unit 35a provides the location information received from the connected region designating unit 35e together with the existing region for SVR to the connected region extracting unit 35f. And the connection area | region extraction part 35f calculates | requires the threshold value area | region containing the provided position as a connection area | region. At this time, the connection area extraction unit 35f expands or contracts the connection area as necessary. This connected area is notified from the connected area extracting unit 35f to the SVR data managing unit 35a and the MIP data managing unit 35b.

  Then, in step S7, the MIP data management unit 35b provides the connection region information received from the connection region extraction unit 35f to the MIP connection region deletion unit 35g together with the existing MIP region information. The MIP linked area deletion unit 35g updates the existing area for MIP by subtracting the linked area from the existing area for MIP images. As a result, the existing area for the newly updated MIP image is provided as update information to the MIP data management unit 35b.

  The MIP data management unit 35b gives the updated MIP existing region information to the MIP image creation unit 35d, and the MIP image creation unit 35d stores the 3D image data included in the updated MIP existing region from the storage device 34. Read and create MIP image data. The created MIP image data is given to the image display unit 28 from the MIP image creation unit 35d. As a result, the image display unit 28 displays the MIP image from which the threshold region (connected region) selected on the SVR image by the mouse 29a has been deleted.

  On the other hand, in step S8, the SVR data management unit 35a gives the connected region information received from the connected region extracting unit 35f to the SVR image creating unit 35c. Then, the SVR image creation unit 35c creates connected region image data for visually displaying the connected region on the SVR image displayed on the image display unit 28. Then, the SVR image creation unit 35 c gives the created connected region image data to the image display unit 28. As a result, the connected area is visually displayed on the image display unit 28 as, for example, a color display.

  For this reason, the user can confirm the MIP image in which the connected area is actually deleted while selecting the SVR image with the mouse 29a and referring to the connected area displayed in color. That is, the connected area is deleted from the MIP image, while the connected area is not deleted from the SVR image.

  Then, the user refers to the MIP image, and if the intended MIP image can be obtained, the user operates the extraction button 20b of the input unit 29 to extract a request for actually subtracting the connected region from the existing region for SVR. It gives to the determination part 35h. The connected region extraction confirmation unit 35h provides the connection confirmation of the connected region to the SVR data management unit 35a.

  Then, in step S9, the SVR data management unit 35a determines that there is an instruction to delete the connected region from the SVR image from the connected region extraction confirmation unit 35h.

  In step S10, the SVR data management unit 35a provides the connected region information to the SVR connected region deleting unit 35i together with the existing region information for SVR. The SVR linked area deletion unit 35i updates the existing area for SVR by subtracting the linked area from the existing area for SVR based on the existing area information for SVR and the linked area information received from the data management unit 35a for SVR. . Then, the SVR linked region deletion unit 35i gives the updated SVR existing region to the SVR data management unit 35a as update information. The SVR data management unit 35a updates the existing region information for SVR according to the update information notified from the SVR linked region deletion unit 35i.

  In step S1, the SVR data management unit 35a provides the updated SVR existing area information to the SVR image creation unit 35c. For this reason, the SVR image creation unit 35c creates the SVR image data by reading the 3D image data included in the existing area for SVR after the update after deleting the connected area from the storage device 34. Then, the SVR image creation unit 35 c gives the created SVR image data to the image display unit 28. As a result, the SVR image from which the connected area is deleted is displayed on the image display unit 28.

  On the other hand, if there is no instruction to delete the connected region on the SVR image in step S9, a new threshold can be set again in step S4. Then, threshold areas formed by different threshold values are selected on the common SVR image and deleted from the MIP image in the same procedure.

  For example, when it is determined that the threshold setting is inappropriate such as when the bone region and the contrasted blood vessel are not properly separated, the threshold value is increased to the CT value 250 so that the threshold region is appropriately created. Can be set. Then, the bone removal operation is started with reference to the SVR image in the same procedure by selecting a threshold region determined by the newly set threshold.

  In addition, although the deletion of the threshold region has been completed to some extent with the high CT value as a threshold, if it is determined that there is still an unnecessary organ for clinical diagnosis with a lower CT value, the threshold can be set small. Then, until the MIP image having no problem in clinical diagnosis, that is, having no unnecessary organs, is created, the CT value can be lowered repeatedly to perform operations such as a bone removal operation.

  For example, in the case of the MIP image having the CT value profile image shown in FIG. 4B, even if the bone region is deleted with the threshold value CT value 200, it is necessary to further delete the cartilage region having a CT value of less than 200. There is. Therefore, it is necessary to lower the threshold value to the CT value 100 so that the cartilage region is included in the threshold value region.

  However, usually, for example, by setting the threshold value to the CT value 200 and extracting the bone region as the threshold region, and deleting the extracted bone region from the MIP image, the CT value is less than 200 but a bone value close to 200 The tissue around the region remains without being deleted from the MIP image. For this reason, when the threshold value is lowered from the CT value 200 to the CT value 100, the contrasted blood vessel and the cartilage region are integrated as shown in FIG.

  Therefore, as shown by the hatched portion in FIG. 4 (f), the bone region selected as the connected region is deleted after being expanded by the connected region extracting unit 35f, and regions other than the connected region including the expanded bone region are included. This is a new existing area for MIP. For this reason, as shown in FIG. 4G, the contrasted blood vessel and the cartilage region can be separated even if the threshold value is lowered to the CT value 100 in step S4 in order to delete the cartilage region from the MIP image.

  FIG. 5 shows the SVR by expanding the connected region selected in the SVR image when the head of the subject P is viewed from the front by the function of the image data region extraction system 35 incorporated in the X-ray CT apparatus 20 shown in FIG. It is the figure which compared the case where it deletes from an image, and the case where it deletes as it is from a SVR image as it is, without expanding the selected connection area | region. FIG. 6 illustrates a case where the connected region selected in the SVR image when the head of the subject P shown in FIG. 5 is viewed from the right side is expanded and deleted from the SVR image, and the selected connected region is not expanded. It is the figure compared with the case where it deletes from an SVR image as it is. The SVR image in FIG. 6 corresponding to the SVR image in FIG.

  When the bone region is deleted from the SVR image 1 (D1) of the blood vessel surrounded by the skull as shown in FIGS. 5 and 6, a threshold value based on the CT value of the bone is set, and the SVR image 2 (D2 Only bones are selectively displayed as shown in FIG. However, if the threshold value is set high in order to reliably extract only the bone, the bone region having a low CT value is excluded as shown in the SVR image 2 (D2) in FIG. Extracted as a connected region.

  Here, when the extracted connected region, that is, the displayed bone is designated by the mouse 29a and deleted from the original SVR image 1 (D1) as it is, the SVR image 3 (returning the threshold value to the original and displaying the blood vessel) ( In D3), an image of a bone that was not displayed with a low CT value remains.

  Therefore, if the displayed bone is designated and the connected region is expanded, the connected region that covers the bone region that is low in CT value and not displayed as shown in the SVR image 4 (D4) of FIG. Is set. Then, if the reset connected region after the expansion is deleted from the original SVR image 1 (D1), when the blood vessel is displayed with the threshold restored, the bone is almost as shown in the SVR image 5 (D5). It is possible to obtain an image of a blood vessel in which no water remains.

  In this way, the cartilage region is selected as a connected region in the same procedure from step S5, and is deleted from the MIP image. That is, the threshold value is sequentially reset to a smaller value, and a process of extracting a connected region by selecting a cartilage region, expanding a connected region, and deleting a connected region after expansion is repeatedly performed. As a result, it is possible to create MIP image data such as contrast-enhanced blood vessel images from which images in areas such as unnecessary bones and cartilage are deleted without any problem in clinical diagnosis.

  FIG. 7 is a diagram showing an example of the SVR image and the color MIP image displayed in parallel on the image display unit 28 by the function of the image data region extraction system 35 built in the X-ray CT apparatus 20 shown in FIG.

  As shown in FIG. 7, the image display unit 28 displays the SVR image (upper right) and the MIP image (upper left) in parallel. Moreover, a cross-sectional reconstruction (MPR: multi-planar reconstruction) image (lower right) can be displayed in parallel for reference. With such a screen configuration, the user changes the threshold value on a common SVR image that visually displays the connected area while referring to the MIP image from which the connected area has been deleted. By selecting, the bone region can be easily deleted from the MIP image.

  FIG. 8 is a diagram comparing a procedure for creating an MIP image and a conventional procedure for creating an MIP image by the function of the image data region extraction system 35 built in the X-ray CT apparatus 20 shown in FIG. is there.

  FIG. 8A is a diagram for explaining a procedure for creating an MIP image by the function of the image data region extraction system 35 built in the X-ray CT apparatus 20 shown in FIG. 1, and FIG. FIG. 10 is a diagram for explaining a conventional MIP image creation procedure.

  As shown in FIG. 8B, conventionally, after generating and displaying an SVR image and extracting an unnecessary bone region on the SVR image, a MIP image is generated from 3D image data outside the extracted region. . However, only a series of operations of displaying an SVR image, extracting an area, and displaying an MIP image may not delete a sufficiently unnecessary area on the MIP image, and an MIP image intended by the user may not be obtained. Therefore, the operation of displaying the SVR image again, extracting the region, and displaying the MIP image is repeated. Such a similar operation is repeated a plurality of times until a sufficiently unnecessary area is deleted. For this reason, the water removal operation requires time and labor for the user.

  On the other hand, as shown in FIG. 8A, according to the image data region extraction system 35 of the X-ray CT apparatus 20, once the SVR image is displayed, the threshold value is changed on the SVR image a plurality of times. A region can be extracted over the whole area. For this reason, it is not necessary to perform SVR image data generation processing each time the threshold value is changed, which can lead to reduction in processing time. Further, when an area is extracted on the SVR image, a visually extracted threshold area is displayed on the SVR image, while the MIP image displayed in parallel is reflected in real time to confirm the MIP image after the area is deleted. Can do. For this reason, a user's effort can also be reduced.

  That is, the X-ray CT apparatus 20 as described above, when executing region extraction on a three-dimensional reference image such as an SVR image over a plurality of times, MIP images and the like in which each extracted region is reflected in real time. This is an apparatus provided with an image processing function capable of referring to the three-dimensional projection image.

This is an apparatus having a function of extracting a specific region by a connected region extraction method based on a reference value such as a CT value.

  For this reason, when the user designates an unnecessary area on the SVR image, what kind of image the MIP image becomes is updated and displayed in real time. As a result, it is not necessary to repeat the display switching process and the area extraction process between the SVR image and the MIP image, so that the user can create 3D projection image data such as the intended MIP image data in a simpler and shorter time. Will be able to.

  It should be noted that some components and functions of the X-ray CT apparatus 20 and the image data region extraction system 35 may be omitted.

  The image data region extraction system 35 can also be used to create 3D projection image data from 3D image data obtained by not only the X-ray CT apparatus 20 but also other image diagnostic apparatuses.

1 is a functional block diagram showing an embodiment of an X-ray CT apparatus according to the present invention. FIG. 2 is a functional block diagram of an image data region extraction system built in the X-ray CT apparatus shown in FIG. 1. FIG. 3 is a flowchart showing a procedure when an area is extracted from X-ray CT image data by the X-ray CT apparatus shown in FIG. The figure explaining an example of the procedure of the bone removal operation | work by the X-ray CT apparatus shown in FIG. The function of the image data region extraction system built in the X-ray CT apparatus shown in FIG. 1 expands the connected region selected in the SVR image when the head of the subject is viewed from the front and deletes it from the SVR image; The figure which compared with the case where the selected connection area | region is deleted as it is from an SVR image, without expanding. When the selected connected area is expanded and deleted from the SVR image in the SVR image when the head of the subject shown in FIG. 5 is viewed from the right side, and when the selected connected area is deleted from the SVR image without being expanded. FIG. The figure which shows an example of the SVR image and color MIP image which were displayed in parallel by the image display part by the function of the image data area | region extraction system incorporated in the X-ray CT apparatus shown in FIG. The figure which compared the procedure in the case of producing a MIP image by the function of the image data area | region extraction system incorporated in the X-ray CT apparatus shown in FIG. 1, and the creation procedure of the conventional MIP image. The figure explaining the procedure of the bone removal work implemented prior to the observation of the contrast blood vessel by the conventional MIP image.

Explanation of symbols

20 X-ray CT device 21 Gantry unit 22 Computer device 23 X-ray tube 24 High voltage generator 25 X-ray detector 26 Data collection unit 27 Image processing device 28 Image display unit 29 Input unit 29a Mouse 29b Extraction button 29c Processing start button 30 Control unit 31 Preprocessing unit 32 Memory unit 33 Image reconstruction unit 34 Storage device 35 Image data region extraction system 35a SVR data management unit 35b MIP data management unit 35c SVR image creation unit 35d MIP image creation unit 35e Connection region designation unit 35f Connected region extracting unit 35g Connected region extracting unit 35h for MIP Connected region extracting and determining unit 35i Connected region deleting unit for SVR P Subject

Claims (6)

Image reconstruction means for collecting raw data of a subject and reconstructing three-dimensional image data;
3D reference image display means for displaying 3D image data included in the first region of the 3D image data as a 3D reference image;
3D projection image display means for displaying, as a 3D projection image, 3D image data included in a second area within the first area of the 3D image data;
Connected region specifying means for acquiring a position for specifying a connected region to be deleted from the second region via the three-dimensional reference image;
A connected area extracting means for obtaining a connected area connected to the position acquired by the connected area specifying means as a threshold area based on a preset threshold;
Connected region deleting means for updating the second region by deleting the connected region obtained by the connected region extracting means from the second region;
An X-ray CT apparatus comprising: The X-ray CT apparatus according to claim 1, wherein the three-dimensional projection image display unit is configured to display the three-dimensional projection image in parallel with the three-dimensional reference image. 2. The X-dimensional image according to claim 1, wherein the three-dimensional reference image display means is configured to display the connected area obtained by the connected area extracting means in an identifiable manner on the three-dimensional reference image. Line CT device. The connected area extracting means is configured to be able to expand or contract the connected area, while the connected area deleting means is configured to delete the connected area after being expanded or contracted from the second area. The X-ray CT apparatus according to claim 1, wherein: 3D reference image display means for displaying 3D image data included in the first region among the 3D image data collected by the image diagnostic apparatus as a 3D reference image;
3D projection image display means for displaying, as a 3D projection image, 3D image data included in a second area within the first area of the 3D image data;
Connected region specifying means for acquiring a position for specifying a connected region to be deleted from the second region via the three-dimensional reference image;
A connected area extracting means for obtaining a connected area connected to the position acquired by the connected area specifying means as a threshold area based on a preset threshold;
Connected region deleting means for updating the second region by deleting the connected region obtained by the connected region extracting means from the second region;
An image data area extraction system comprising: Computer
3D reference image display means for displaying 3D image data included in the first region among the 3D image data collected by the image diagnostic apparatus as a 3D reference image;
3D projection image display means for displaying, as a 3D projection image, 3D image data included in a second area within the first area of the 3D image data;
Connected region specifying means for acquiring a position for specifying a connected region to be deleted from the second region via the three-dimensional reference image;
A connected area extracting means for obtaining a connected area connected to the position acquired by the connected area specifying means as a threshold area based on a preset threshold; and the connected area obtained by the connected area extracting means from the second area Connected region deletion means for updating the second region by deleting the region;
An image data area extraction program characterized in that it functions as a program.

Images