JP5461803B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus.

  Conventionally, an X-ray computed tomography apparatus (hereinafter referred to as an X-ray CT apparatus, CT; Computed Tomography) uses a projection data indicating an intensity distribution of X-rays transmitted through a subject to form a form of a body tissue in the subject. By reconstructing and providing tomographic images that indicate physical information, it plays an important role in many medical practices such as disease diagnosis, treatment, and surgical planning.

  An X-ray CT apparatus includes a gantry rotating unit having an X-ray tube and an X-ray detector disposed opposite to each other around an internal space into which a subject lying on a couch top is inserted, and a gantry rotating unit. And a gantry fixing portion that is rotatably supported. The X-ray CT apparatus rotates the gantry rotating unit around the subject at the time of imaging, and the X-ray tube disposed on the gantry rotating unit irradiates the subject with X-rays from multiple directions, The X-ray detector detects the intensities of X-rays irradiated from multiple directions and transmitted through the subject.

  Then, the X-ray CT apparatus performs X-ray intensity distribution data (pure raw data) from multiple directions detected by the X-ray detector as projection data after performing correction such as sensitivity correction by preprocessing, and then performing back projection. Image reconstruction is performed by (back projection) and convolution (convolution). Note that image capturing in which the X-ray tube and the X-ray detector are rotated once while the position of the subject is fixed is called a conventional scan.

  Currently, an X-ray detector in which a plurality of rows of detection elements (for example, 16 rows, 64 rows, etc.) are arranged along the body axis direction of the subject has been put into practical use, so that an image in a wide area of the subject can be obtained. Can be collected at high speed. When an X-ray detector in which a plurality of rows of detection elements are arranged is used, a plurality of tomographic images in units of columns can be obtained by back-projecting projection data generated from the collected pure raw data in units of columns. A wide range of three-dimensional images (volume images) can be obtained by synthesizing a plurality of reconstructed tomographic images.

  In addition, in the X-ray CT apparatus, a helical scan for imaging a wider area is performed by rotating the gantry rotating unit and continuously moving the bed in the body axis direction of the subject at the time of imaging. ing. By reconstructing a plurality of tomographic images in units of columns along the body axis direction of the subject by helical scanning, and synthesizing the reconstructed tomographic images, a wider range of three-dimensional images (volume images) are obtained. be able to.

  Here, in the helical scan, it is necessary to perform image reconstruction by immediately and reliably processing a large amount of detection data for a plurality of rows over a wide range. For this reason, a technique is disclosed in which an enormous amount of pure raw data is divided in units of columns, and then preprocessing and reconstruction processing are performed in parallel (see, for example, Patent Document 1).

  On the other hand, in recent years, an X-ray detector (for example, 256 rows) in which detection elements are arranged in more rows in the body axis direction has entered a practical stage. When such an X-ray detector is used, in order to reconstruct data including the entire region of interest (for example, the heart), that is, a three-dimensional image of the region of interest, by conventional scanning without performing imaging by helical scanning. It is possible to collect the data required for In addition, by performing conventional scanning continuously, it is possible to collect data for reconstructing a three-dimensional image along the time series of the region of interest at a time.

JP 2007-315 A

  By the way, in the above-described conventional technique, data required for reconstructing a three-dimensional image including a region of interest once by a conventional scan using X-ray detectors arranged in multiple rows in the body axis direction. 3D images cannot be immediately reconstructed.

  For example, the amount of pure raw data detected and collected by an X-ray detector in which 256 rows of detection elements are arranged in the body axis direction is the X-ray in which detection elements such as 16 rows and 64 rows are arranged in the body axis direction. Compared to the amount of pure raw data detected and collected by the detector, it becomes even larger. For this reason, the above-described conventional technique reconstructs a tomographic image by dividing projection data generated from pure raw data and performing parallel processing in units of columns, and generates a three-dimensional image from the reconstructed tomographic image. Even so, the time required is several seconds.

  On the other hand, in order to immediately reconstruct a three-dimensional image by conventional scanning, for example, a method of collectively processing projection data for all columns for each X-ray irradiation direction (for each view unit) can be considered. In other words, this is a method for instantly reconstructing a three-dimensional image by backprojecting projection data in units of views in units of cross sections having the same weight. However, if the method of batch processing of projection data in view units is adopted, parallel data processing in units of columns is required for immediate processing of helical scans (or conventional scans that reconstruct images in units of columns). It becomes impossible to execute.

  Thus, the above-described technique has a problem that the reconstruction speed cannot be optimized according to the image reconstruction method.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and provides an X-ray CT apparatus capable of optimizing the reconstruction speed in accordance with the image reconstruction method. With the goal.

In order to solve the above-described problems and achieve the object, the present invention provides an X-ray tube for irradiating X-rays and a detection element array formed by arranging X-ray detection elements for a plurality of channels. An X-ray detector arranged in a plurality of rows along the direction and detecting X-rays irradiated from the X-ray tube and transmitted through the subject, and the X-ray tube and the X-ray detector are rotated around the subject By doing so, a data collection unit that collects projection data groups corresponding to views in different projection directions, and a corrected projection data group obtained by performing correction processing on the projection data group collected by the data collection unit A pre-processing unit for generating, and a process for back-projecting the corrected projection data of a plurality of views by a plurality of back-projection processing units and combining the output data of the plurality of back-projecting units to generate one cross-sectional image Repeatedly different A first image reconstruction unit that generates a three-dimensional image from the corrected projection data group generated by the preprocessing unit by reconstructing a cross-sectional image of the position, and a corrected projection of one view; By repeating the process of back-projecting the data on each pixel of the three-dimensional image for a plurality of views, a second image reconstruction for generating a three-dimensional image from the corrected projection data group generated by the preprocessing means And a configuration means.

The present invention also relates to an X-ray CT apparatus for reconstructing an image based on a projection data group indicating an intensity distribution of X-rays transmitted through a subject, an X-ray tube for irradiating X-rays, and a plurality of channels. X-ray detection for detecting X-rays that are arranged in a plurality of rows along the body axis direction of the subject and that are irradiated from the X-ray tube and transmitted through the subject A data collection unit that collects the projection data group by rotating the X-ray tube and the X-ray detector around the subject, and the projection data group collected by the data collection unit. A pre-processing unit that generates a corrected projection data group that has been subjected to correction processing, and an image is reconstructed by performing back projection processing on the corrected projection data group generated by the pre-processing unit Image reconstruction A first image reconstruction method for reconstructing an image from projection data combined in units of columns based on the X-rays detected in each stage and the detection element rows, or X-rays emitted from the X-ray tube An operator using one of the second image reconstruction methods for reconstructing an image from projection data in units of X-ray irradiation directions based on X-rays detected by the plurality of detection element arrays in each irradiation direction. The projection data group and / or the corrected projection data group in units of columns or in the X-ray irradiation direction according to the input means that receives and inputs from the input means, and the reconstruction setting condition input by the input means The data collection means and / or the preprocessing means is controlled so as to be sorted and distributed in units, and the corrected projection data group distributed in units of columns is processed in advance. The first image reconstruction method is executed in parallel, and the second image reconstruction method is collectively executed for the corrected projection data group distributed in units of the X-ray irradiation direction. Control means for controlling the image reconstruction means.

According to the present invention, it is possible to select a reconstruction processing method according to the image reconstruction method, and it is possible to optimize the reconstruction speed according to the image reconstruction method.

According to the present invention, it is possible to select a data transmission method and a reconstruction processing method according to the image reconstruction method, and it is possible to optimize the reconstruction speed according to the image reconstruction method.

  Exemplary embodiments of an X-ray CT apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

  First, the structure of the X-ray CT apparatus in a present Example is demonstrated using FIG. FIG. 1 is a diagram for explaining the configuration of the X-ray CT apparatus in the present embodiment. As shown in FIG. 1, the X-ray CT apparatus in the present embodiment includes a gantry device 10, a couch device 20, and a console device 30.

  The gantry device 10 is a device that collects data by irradiating the subject P with X-rays, and includes a gantry rotating unit 12 and a gantry fixing unit 11.

  The gantry rotating unit 12 is an annular frame that rotates continuously at a high speed around the subject P. The X-ray tube 13 and the X-ray detector 14 are arranged to face each other, and the first data A collection unit 15 is provided.

  The X-ray tube 13 is a vacuum tube that generates X-rays by a high voltage supplied from a high voltage generation unit 17 described later. As the gantry rotation unit 12 rotates, an X-ray fan beam or cone beam is applied to the subject. Irradiate P from multiple directions.

  The X-ray detector 14 is a two-dimensional array type detector that detects X-ray intensity distribution data indicating the intensity distribution of X-rays that have passed through the subject P, and includes X-ray detection elements for a plurality of channels. A plurality of detection element arrays are arranged along the body axis direction of the subject P (the Z-axis direction shown in FIG. 1). Specifically, in this embodiment, the X-ray detector 14 has X-ray detection elements arranged in multiple rows such as 320 rows along the body axis direction of the subject P. It is possible to detect an X-ray intensity distribution data group transmitted through the subject P over a wide range, such as a range including the heart.

  The X-ray tube 13 in this embodiment irradiates the subject P with X-rays by narrowing the X-ray irradiation range (cone angle) in accordance with the reconstruction setting condition described later. For example, the detector 14 can detect the X-ray intensity distribution data group with only 64 detection element rows located in the center of the 320 rows.

  The first data collecting unit 15 installed in the gantry rotating unit 12 performs an amplification process, an A / D conversion process, etc. on the X-ray intensity distribution data group detected by the X-ray detector 14 to produce a projection data group. Is generated.

  The gantry fixing unit 11 rotatably supports the gantry rotating unit 12, and includes a second data collection unit 16, a high voltage generation unit 17, and a gantry driving unit 18.

  The second data collection unit 16 installed in the gantry fixing unit 11 receives the projection data group generated by the first data collection unit 15, and uses the received projection data group as a preprocessing unit 34 (described later) of the console device 30. Send to.

  The high voltage generating unit 17 is a device that supplies a high voltage to the X-ray tube 13, and the gantry driving unit 18 rotates the gantry rotating unit 12 to rotate the X on the circular orbit around the subject P. The tube 13 and the X-ray detector 14 are turned.

  The couch device 20 is a device on which the subject P is placed, and includes a couchtop 22 and a couch driving unit 21. The top plate 22 is a plate on which the subject P is placed at the time of imaging, and the bed driving unit 21 is a device that moves the top plate 22 in the Z direction shown in FIG.

  The console device 30 is a device that accepts the operation of the X-ray CT apparatus by the operator and reconstructs an image representing the internal form of the subject P from the projection data collected by the gantry device 10. Display unit 32, scan control unit 33, preprocessing unit 34, projection data storage unit 35, reconstruction auxiliary processing unit 36, image reconstruction unit 37, image storage unit 38, and system control unit 39 Is provided.

  The input unit 31 is used to input an instruction from an operator such as a mouse or a keyboard. For example, the reconstruction setting condition, the diameter of the effective field of view when collecting projection data, and the length in the body axis direction are used. The collection range and the image processing settings after reconstruction are received and input from the operator.

  Here, the reconstruction setting condition is the first image reconstruction in which an image is reconstructed by “helical scan in which imaging is performed by continuously rotating the gantry rotating unit 12 while moving the couchtop 22 by the bed driving unit 21”. A second image reconstruction method for reconstructing an image (volume data) by a configuration method and “a conventional scan in which imaging is performed by rotating the gantry rotating unit 12 once or continuously while the position of the subject P is fixed”. Either. The first image reconstruction method and the second image reconstruction method will be described in detail later.

  Further, the image processing after reconstruction includes processing for generating a two-dimensional image from the reconstructed three-dimensional image by volume rendering.

  The display unit 32 displays image data stored in an image storage unit 38 (to be described later) based on control by a system control unit 39 (to be described later).

  The scan control unit 33 controls the operations of the first data collection unit 15, the second data collection unit 16, the high voltage generation unit 17, the gantry drive unit 18, and the bed drive unit 21 under the control of the system control unit 39 described later. Control.

  That is, when the reconstruction setting condition is the second image reconstruction method, the scan control unit 33 drives the bed driving unit 21 and moves the subject P lying on the top plate 22 to the internal space of the gantry rotating unit 12. , The gantry driving unit 18 is driven to rotate the gantry rotating unit 12, a high voltage is generated from the high voltage generating unit 17, and X-rays are emitted from the X-ray tube 13.

  In addition, when the reconstruction setting condition is the first image reconstruction method, the scan control unit 33 drives the bed driving unit 21 and moves the subject P lying on the top plate 22 to the internal space of the gantry rotating unit 12. , The gantry driving unit 18 is driven to rotate the gantry rotating unit 12.

  Note that when the reconstruction setting condition is the first image reconstruction method, the scan control unit 33, for example, from the X-ray tube 13 based on the setting condition further input from the operator via the input unit 31. The high voltage generator 17 is controlled so as to narrow the X-ray irradiation range (fan angle and cone angle) and irradiate the subject P with X-rays. The first data collection unit 15 is controlled so that the X-ray intensity distribution data is detected only by the 64 detection element rows located in the X direction.

  Further, the scan control unit 33 is configured to transmit data from the first data collection unit 15 to the second data collection unit 16 based on the control of the system control unit 39 described later. The transmission format of data to the processing unit 34 is controlled.

  The pre-processing unit 34 performs corrections such as logarithmic conversion processing, offset correction, sensitivity correction, and beam hardening correction on the projection data group generated by the first data collection unit 15 and transmitted by the second data collection unit 16. Processing is performed to generate a corrected projection data group.

  The projection data storage unit 35 stores the corrected projection data group generated by the preprocessing unit 34.

  The reconstruction auxiliary processing unit 36 reads out the corrected projection data group from the projection data storage unit 35 via the preprocessing unit 34, and performs a convolution process using weighted data as preprocessing for image reconstruction. Then, a convolutionally processed projection data group (hereinafter referred to as a preprocessed projection data group) that has been subjected to convolution processing is transmitted to the image reconstruction unit 37 described later.

  The image reconstruction unit 37 reconstructs an image by back projection processing from the corrected projection data group received from the reconstruction assistance processing unit 36, and transmits the reconstructed image to the reconstruction assistance processing unit 36. This will be described in detail later.

  Here, the reconstruction auxiliary processing unit 36 receives the image reconstructed by the image reconstruction unit 37, performs post-processing such as artifact correction processing and image processing based on an operator's instruction, and performs image processing. The post-processed image data is stored in the storage unit 38. The post-processing performed by the reconstruction auxiliary processing unit 36 will be described in detail later.

  The system control unit 39 controls the X-ray CT apparatus as a whole by controlling the operations of the gantry device 10, the couch device 20, and the console device 30. That is, the system control unit 39 collects projection data groups from the gantry device 10 by controlling the scan control unit 33 based on the operator's instruction input by the input unit 31. Further, the system control unit 39 controls the preprocessing unit 34, the reconstruction auxiliary processing unit 36, and the image reconstruction unit 37 to control the entire data transmission and reconstruction processing, and the image data from the image storage unit 38. , And control is performed so that the image data is displayed on the monitor included in the display unit 32.

  The “input unit 31” described above corresponds to the “input unit” recited in the claims, and the “first data collection unit 15” and the “second data collection unit 16” are the same as the “data collection unit”. "Pre-processing unit 34" also corresponds to "Pre-processing means", and "Reconstruction auxiliary processing unit 36" and "Image reconstruction unit 37" also correspond to "Image reconstruction means". The “system control unit 39” corresponds to “control means”.

  Here, the X-ray CT apparatus in the present embodiment reconstructs an image based on the projection data group indicating the intensity distribution of the X-ray transmitted through the subject as described above, but the image is reconstructed according to the image reconstruction method. The main feature is that the configuration speed can be optimized.

  This main feature will be described with reference to FIGS. 2 is a diagram for explaining the first image reconstruction method, FIG. 3 is a diagram for explaining the second image reconstruction method, and FIGS. 4 and 5 are diagrams showing the first acquisition. FIG. 6 is a diagram for explaining the projection data storage unit, FIG. 6 is a diagram for explaining the data transmission between the unit, the second collection unit, the preprocessing unit, and the projection data storage unit. FIG. 8 is a diagram for explaining data transfer among the preprocessing unit, the projection data storage unit, and the reconstruction auxiliary processing unit, and FIG. 8 illustrates how the preprocessing unit transfers to the image reconstruction unit via the reconstruction auxiliary processing unit. FIG. 9 is a diagram for explaining the data transmission, FIG. 9 is a diagram for explaining the image reconstruction unit, and FIG. 10 is a diagram for explaining the data transmission from the image reconstruction unit to the reconstruction auxiliary processing unit. FIG. 11 illustrates data transmission from the reconstruction auxiliary processing unit to the image storage unit. A view fit, 12 and 13 are views for explaining the storage format and display format of the three-dimensional image reconstructed by the second image reconstruction method.

  Here, the first image reconstruction method and the second image reconstruction method will be described again with reference to FIGS.

  In the first image reconstruction method in which an image is reconstructed by a helical scan in which the gantry rotating unit 12 is continuously rotated while moving the couchtop 22 by the bed driving unit 21, each of the detection element arrays of the X-ray detector 14 The image is reconstructed from the projection data combined in units of columns generated from the X-ray intensity distribution data detected in step. For example, in the first image reconstruction method, a case will be described in which an X-ray intensity distribution data group is detected and a projection data group is generated by 64 detection element rows located in the center among 320 columns.

  That is, in the first image reconstruction method, an image in a three-dimensional region is reconstructed by successively reconstructing a two-dimensional section in the Z-axis direction by changing the position of the section. In order to reconstruct an image of a cross section at one position, the projection data of all the columns of the detector are not necessary, and only a part of the projection data necessary for the backprojection process is necessary. For this reason, the projection data group for all X-ray irradiation directions (all views) irradiated by the X-ray tube 13 while the gantry rotating unit 12 rotates is divided in columns, for example, as shown in FIG. “Projection data group for all views in columns 1 to 20”, “Projection data group for all views in columns 2 to 21”, “Projection data group for all views in columns 3 to 22”, “4 After the weighting process is performed on the projection data group for all the views in 20 column units such as “projection data group for all views in the ˜23rd column”, the tomographic image is reconstructed by performing the back projection process. The By repeating this reconstruction and generating a plurality of tomographic images, a three-dimensional image is generated.

  When reconstructing an image by helical scanning, scanning is performed while moving the X-ray tube 13 and the X-ray detector 13 relative to the subject P in the Z-axis direction. In order to display an image at the same time as scanning or in a short time after scanning, it is possible to collect and reconstruct the necessary projection data as described above, rather than performing reconstruction after all scanning is completed. The time until the image is displayed after scanning can be shortened by sequentially performing the images of the cross sections.

  On the other hand, in the second image reconstruction method (volume reconstruction method) in which an image is reconstructed by a conventional scan in which imaging is performed by rotating the gantry rotating unit 12 once or continuously while the position of the subject P is fixed. Then, an image is reconstructed from projection data in units of X-ray irradiation directions detected by all the plurality of detection element arrays in each X-ray irradiation direction irradiated from the X-ray tube 13. At that time, the second image reconstruction method does not sequentially reconstruct a two-dimensional cross-sectional image as in the first image reconstruction method, but performs a back projection process on each pixel of the image of the three-dimensional region. At the same time, the image of the three-dimensional area is reconstructed. That is, after predetermined weighting processing is performed on the projection data of a plurality of columns in one view, back projection processing is performed on each pixel of the image in the three-dimensional region. This process is sequentially repeated for the views for the angle range necessary for reconstruction, thereby reconstructing an image of the three-dimensional region.

  Hereinafter, in the second image reconstruction method, a case will be described in which an image is reconstructed by a conventional scan in which the gantry rotating unit 12 is rotated once to perform imaging. In the present invention, the gantry rotating unit 12 is continuously connected. The present invention is applicable even when an image is reconstructed by a conventional scan in which shooting is performed by rotating the image.

  That is, in the second image reconstruction method, X-rays generated from the X-ray tube 13 with a fan angle and a cone angle are spread to the subject P from multiple directions, and X-ray intensity distribution data is obtained. Is detected by the X-ray detector 14.

  In the first image reconstruction method, for example, as shown in FIG. 3, a view in which all 320 detection element rows (rows necessary for image reconstruction) are detected in each X-ray irradiation direction (view) is detected. 900 three-dimensional images are reconstructed for each projection data group of view units generated from the X-ray intensity distribution data group of units, and these are synthesized, and three-dimensional based on the X-ray intensity distribution data for 900 views. Reconstruct the image.

  When the reconstruction setting condition of any of the first image reconstruction method and the second image reconstruction method described above is input to the system control unit 39 via the input unit 31, the system control unit 39 The projection data group generated by one data collection unit 15 is rearranged in units of columns or units of X-ray irradiation direction according to the input reconstruction setting condition, and distributed and transmitted to the preprocessing unit 34. The second data collection unit 16 is controlled via the scan control unit 33. This will be described with reference to FIG. 4 and FIG.

  In the following description, it is assumed that the total number of detection element rows of the X-ray detector 14 is “n”. Also, the number of detection element rows used in the helical scan in the first image reconstruction method is “4k”, and the number of detection element rows used in the conventional scan in the second image reconstruction method is “n”. explain.

  That is, when the reconstruction setting condition input to the system control unit 39 via the input unit 31 is the first image reconstruction method, the system control unit 39 generates the projection data generated by the first data collection unit 15. The second data collection unit 16 is controlled so that the groups are rearranged in units of columns and distributed to the preprocessing unit 34 for transmission.

  Specifically, as shown in FIG. 4, the first data collection unit 15 is equipped with a Field Programmable Gate Array (FPGA) that executes high-speed processing, and this FPGA is detected by the X-ray detector 14. The acquired X-ray intensity distribution data group is collected, and the collected X-ray intensity distribution data group is subjected to amplification processing, A / D conversion processing, and the like to generate a projection data group. Then, the FPGA mounted on the first data collecting unit 15 transmits the generated projection data group to the second data collecting unit 16 through the high-speed data transmission path via the high-speed transmission I / F included in the FPGA. To do.

  As shown in FIG. 4, the second data collection unit 16 is equipped with an FPGA having the same processing capability as the FPGA installed in the first data collection unit 15, and this FPGA has the same high-speed transmission I / F. Provided. Further, the second data collection unit 16 includes a plurality of DDRs (Double Data Rates) that are large-capacity external memories for storing data before and after processing of the FPGA, and the plurality of DDRs are connected to the FPGA. .

  The FPGA mounted on the second data collection unit 16 receives the projection data group collected by the helical scan from the first data collection unit 15 through the high-speed transmission I / F included in the FPGA, and receives the received “4k” The projection data group for the column is divided into a plurality of DDRs, for example, the projection data group for all the views in the odd-numbered column and the projection data group for all the views in the even-numbered column. Store. As a result, the FPGA mounted on the second data collection unit 16 has the projection data group rearranged in units of columns stored in the two DDRs via another high-speed transmission I / F included in the FPGA. It adjusts so that it may be transmitted to the pre-processing part 34. FIG. 4 shows the case where the second data collection unit 16 is provided with two DDRs. In the present invention, the number of DDRs provided in the second data collection unit 16 is two. It is not limited to, and may be a case of three or more.

  As shown in FIG. 4, the preprocessing unit 34 is equipped with four CPUs, and each of these CPUs is provided with a high-speed transmission I / F. These high-speed transmission I / Fs are the same as those included in the FPGA mounted on the first data collection unit 15 and the second data collection unit 16, and each of the four CPUs mounted on the preprocessing unit 34. Receives a projection data group having the “k” column as one unit from the second data collection unit 16 via the high-speed transmission I / F included in each.

  That is, as shown in FIG. 4, each of the four CPUs mounted in the preprocessing unit 34 includes “# 1 to #k” columns and “# k + 1 to # 2k” columns in the “4k” columns of projection data. , Receiving projection data for “k” columns such as “# 2k + 1 to # 3k” and “# 3k + 1 to # 4k”, respectively, and performing logarithmic conversion processing, offset correction, sensitivity correction, beam hardening correction, etc. Correction processing is performed to generate a corrected projection data group for each column.

  Then, as shown in FIG. 4, each of the four CPUs mounted in the preprocessing unit 34 has a CPU-RAID transmission I / E provided for each of the generated projection data groups corresponding to the “k” columns. The data is stored in each of four RAIDs (Redundant Array of Inexpensive Disks) mounted on the projection data storage unit 35 through a general-purpose data transmission path (for example, fiber channel) via F.

  On the other hand, when the reconstruction setting condition input to the system control unit 39 via the input unit 31 is the second image reconstruction method, the system control unit 39 generates the projection data generated by the first data collection unit 15. The second data collection unit 16 is controlled so that the groups are rearranged in units of X-ray irradiation direction (view units), distributed to the preprocessing unit 34, and transmitted.

  Specifically, as shown in FIG. 5, as in the first image reconstruction method, the FPGA of the first data collection unit 15 collects the X-ray intensity distribution data group detected by the X-ray detector 14. Then, the projection data group is generated from the collected X-ray intensity distribution data group of the view unit, and the FPGA mounted on the second data collection unit 16 is connected to the first data collection unit via the high-speed transmission I / F included in the FPGA. 15 receives a group of projection data collected by conventional scanning. Then, as shown in FIG. 5, the FPGA mounted on the second data collection unit 16 divides the received “n” column projection data group into, for example, “# 0 to # n / 2−” for each view unit. The projection data group of the “1” column and the projection data group of the “# n / 2 to # n−1” column are divided into a plurality of “n / 2” columns and divided into a plurality of DDRs. Store. As a result, the FPGA mounted on the second data collection unit 16 has the projection data group rearranged in view units stored in the plurality of DDRs via another high-speed transmission I / F included in the FPGA. It adjusts so that it may be transmitted to the pre-processing part 34. Note that the second data collection unit 16 shown in FIG. 5 is the same as FIG. 4, and FIG. 5 also shows the case where the second data collection unit 16 includes two DDRs. As described above, in the present invention, the number of DDR provided in the second data collection unit 16 is not limited to two, and may be three or more. Further, the number of DDRs to be used can be arbitrarily changed between when the first image reconstruction method is executed and when the second image reconstruction method is executed.

  Then, as shown in FIG. 5, the four CPUs mounted in the preprocessing unit 34 receive “m” view as one unit from the second data collection unit 16 via the high-speed transmission I / F included in each CPU. Each projection data group to be received is received.

  That is, as shown in FIG. 5, each of the four CPUs mounted on the preprocessing unit 34 includes “# 0 to # m−1” views, “#m to # 2m−1” among the projection data of 900 views. ”View,“ # 2m to # 3m−1 ”view,“ # 3m to # 4m−1 ”view, etc., respectively, received projection data groups of“ m ”view, logarithmic conversion processing, offset correction, sensitivity Correction processing such as correction and beam hardening correction is performed to generate a corrected projection data group for each view.

  Then, as shown in FIG. 5, each of the four CPUs mounted in the preprocessing unit 34 has a CPU-RAID transmission I / F provided with the corrected projection data group of each generated “m” view. And stored in each of the four RAIDs mounted in the projection data storage unit 35 by a general-purpose data transmission path.

  Here, the system control unit 39 assigns rearrangement information indicating whether the rearrangement process performed by the second data collection unit 16 is in units of columns or in units of views, and then generates the corrected processed projection. The preprocessing unit 34 is controlled to store the data group in the projection data storage unit 35. This will be described with reference to FIG.

  For example, as shown in FIG. 6A, the system control unit 39 performs the rearrangement processing performed by the second data collection unit 16 in units of columns based on the first image reconstruction method based on the helical scan. Controls the preprocessing unit 34 to store the generated corrected projection data group in the projection data storage unit 35 after adding the accompanying information of “helical scan” to the generated corrected projection data. .

  In addition, as shown in FIG. 6B, the system control unit 39 performs the rearrangement processing performed by the second data collection unit 16 in units of columns based on the second image reconstruction method based on the conventional scan. Controls the pre-processing unit 34 to store the generated correction-processed projection data group in the projection data storage unit 35 after adding supplementary information of “conventional scan” to the generated correction-processed projection data. .

  Further, when a display request for the corrected projection data group stored in the projection data storage unit 35 is input via the input unit 31, the system control unit 39 selects the corresponding rearrangement information (“helical scan” or “ Control is performed so that “conventional scan” is displayed together with the corrected projection data group.

  Thereby, for example, an instruction to reconstruct an image in the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 again from the corrected projection data group stored in the projection data storage unit 35 via the input unit 31. The reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 can also reconstruct an image by a corresponding image reconstruction method with reference to the rearrangement information even when input from the operator.

  In addition, for example, an administrator who refers to the corrected projection data group stored in the projection data storage unit 35 together with the rearrangement information of “helical scan” uses a reconstruction condition (for example, a sequence) in the first image reconstruction method. It is possible to determine that the image is reconstructed again by changing the resolution of the cross-sectional image reconstructed from the unit projection data.

  Subsequently, each of the four CPUs mounted in the preprocessing unit 34 reads out the stored corrected projection data group from each of the four RAIDs mounted in the projection data storage unit 35, as shown in FIG. And transmitted to the reconstruction auxiliary processing unit 36.

  Here, as shown in FIG. 7, the preprocessing unit 34 includes a high-speed transmission I / F and a parallel processing transmission I / F. Based on the control of the system control unit 39, the preprocessing unit 34 uses the first image reconstruction method for the reconstruction setting condition to transmit the corrected projection data groups corresponding to the “k” columns for inter-CPU transmission. The I / F is divided by the parallel processing transmission I / F and transmitted to the reconstruction auxiliary processing unit 36.

  Further, based on the control of the system control unit 39, the pre-processing unit 34, when the reconstruction setting condition is the second image reconstruction method, sets the corrected projection data group for each “m” view between the CPUs. The transmission I / F and the high-speed transmission I / F are collectively transmitted to the reconstruction auxiliary processing unit 36.

  The above is the process related to the projection data before the image reconstruction process corresponding to the two image reconstruction methods. In addition, when the reconstruction setting condition input from the operator by the input unit 31 is changed, the second data collection unit 16 changes and rearranges the projection data group according to the changed reconstruction setting condition. Distribute. Thereby, for example, even when the three-dimensional image is changed from the projection data group collected by the helical scan by using the second image reconstruction method used in the conventional scan instead of the first image reconstruction method. This can be handled in the X-ray CT apparatus.

  In the present embodiment, the case has been described where rearrangement of projection data groups in units of columns or views is performed in the gantry device 10, that is, the second data collection unit 16, but the present invention is not limited thereto. Instead, the console device 30 may perform rearrangement of projection data groups in units of columns or in units of views.

  That is, the second data collection unit 16 simply divides the projection data group generated by the first data collection unit 15 into two DDRs, stores them in two DDRs, and then performs preprocessing while adjusting the data transmission speed. To the unit 34. Then, each of the four CPUs mounted on the preprocessing unit 34 sets the received projection data group as a corrected projection data group, and then performs reconfiguration via the inter-CPU transmission I / F shown in FIG. Depending on the conditions, the corrected projection data group is rearranged in column units or view units and stored in the projection data storage unit 35. As described above, by using the inter-CPU transmission I / F, the console device 30 can execute the rearrangement process of the projection data before the image reconstruction process corresponding to the two image reconstruction methods. .

  Even when the rearrangement process is performed by the preprocessing unit 34, if the reconfiguration setting condition input from the operator by the input unit 31 is changed, the preprocessing unit 34 is changed according to the changed reconfiguration setting condition. Changes and rearranges the corrected projection data group and distributes it. Even when this is changed, for example, when a three-dimensional image is reconstructed from the projection data group collected by the helical scan by the second image reconstruction method used in the conventional scan instead of the first image reconstruction method. However, it can be handled in the X-ray CT apparatus.

  In the present invention, both the second data collection unit 16 and the preprocessing unit 34 can be set so that data is rearranged. Accordingly, the reconfiguration setting condition changed by the second data collection unit 16 or the preprocessing unit 34 in response to the timing when the reconfiguration setting condition input from the operator by the input unit 31 is changed. It is possible to change and execute the data rearrangement process according to the above. In addition, the console device 30 receives the projection data group collected by the gantry device 10 and stores the corrected projection data, and then rearranges the gantry device 10 independently of the gantry device 10 even if the gantry device 10 is turned off. Thus, the image reconstruction process according to the reconstruction setting condition can be executed.

  When the reconstruction setting condition input from the operator by the input unit 31 is changed, the corrected projection data group stored in the projection data storage unit 35 is changed according to the changed reconstruction setting condition. Change the sort information as well. Accordingly, the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 can reliably reconstruct an image by referring to the rearrangement information and using the corresponding image reconstruction method.

  Below, the process regarding the image reconstruction process corresponding to two image reconstruction methods is demonstrated using FIGS.

  The reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 control the system control unit 39 for the corrected projection data group divided and distributed in units of columns via the parallel processing transmission I / F. Based on the above, the first image reconstruction method is executed in parallel.

  On the other hand, the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 perform correction processing of the projection data group distributed in units of view via the high-speed transmission I / F and the system control unit 39. Based on the control, the second image reconstruction method is collectively executed.

  As shown in FIG. 8, the reconfiguration auxiliary processing unit 36 includes one CPU having a high-speed transfer I / F connected to the high-speed transfer I / F of the pre-processing unit 34 via a high-speed data transmission path. , A parallel processing transmission I / F of the preprocessing unit 34 and a plurality of CPUs having a parallel processing transmission I / F connected via a plurality of branched general-purpose data transmission paths.

  Each of the plurality of CPUs having the parallel processing transmission I / F mounted in the reconfiguration auxiliary processing unit 36 receives ("k" columns) in units of columns received from the preprocessing unit 34 based on the control of the system control unit 39. The pre-processed projection data groups in minutes are generated in parallel to generate pre-processed projection data groups in units of columns, and the parallel processing in the image reconstruction unit 37 is performed by the parallel processing transmission I / F. Transmit to the transmission I / F.

  In addition, one CPU having the high-speed transfer I / F mounted on the reconstruction auxiliary processing unit 36 is configured to receive the “m” view in the view unit received from the preprocessing unit 34 based on the control of the system control unit 39. The pre-processed projection data group is corrected in batch, thereby generating a pre-processed projection data group for each view, and the high-speed transmission I / O in the image reconstruction unit 37 via the high-speed data transmission path. Send to F. Note that a CPU having a high processing capability is selected as the CPU having the high-speed transfer I / F as compared with the CPU having the parallel processing transmission I / F.

  As shown in FIG. 8, the image reconstruction unit 37 is an FPGA board having a high-speed transfer I / F connected via the high-speed transfer I / F of the reconstruction auxiliary processing unit 36 and a high-speed data transmission path. A plurality of FPGAs having a parallel processing transfer I / F of the reconfiguration auxiliary processing unit 36 and a parallel processing transfer I / F connected via a general-purpose data transmission path are mounted.

  Here, the FPGA shown in FIG. 8 is the same as the FPGA described in the first data collection unit 15 and the second data collection unit 16 described above, and the FPGA board shown in FIG. 8 is the first data collection unit described above. 15 and a plurality of FPGAs described in the second data collection unit 16 are arranged.

  The high-speed transmission I / F of each of the four CPUs mounted in the reconstruction auxiliary processing unit 36 and the high-speed transmission I / F in the image reconstruction unit 37 are the first data collection unit 15, This is the same as the high-speed transmission I / F provided in the second data collection unit 16 and the preprocessing unit 34. The high-speed data transmission path used for data transmission between the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 is data transmission between the first data collection unit 15 and the second data collection unit 16. And, it is the same as the high-speed data transmission path used for data transmission between the second data collection unit 16 and the preprocessing unit 34.

  The plurality of CPUs having the parallel processing transmission I / F in the reconstruction auxiliary processing unit 36 and the plurality of FPGAs having the parallel processing transfer I / F in the image reconstruction unit 37 are described in the claims. This corresponds to “first image reconstruction means”. In addition, a single CPU having a high-speed transfer I / F in the reconstruction auxiliary processing unit 36 and a plurality of FPGA boards having a high-speed transfer I / F in the image reconstruction unit 37 are also referred to as “second image reconstruction unit”. ".

  Each of the plurality of FPGAs having the parallel processing transfer I / F mounted on the image reconstruction unit 37 is preprocessed for a plurality of columns received from the reconstruction auxiliary processing unit 36 based on the control of the system control unit 39. By parallel reconstruction processing from the projection data group, sectional images as partial images for a plurality of columns are respectively generated by the first image reconstruction method.

  The plurality of FPGA boards having the high-speed transfer I / F mounted on the image reconstruction unit 37 are preprocessed for a plurality of views received from the reconstruction auxiliary processing unit 36 under the control of the system control unit 39. A three-dimensional image as a partial image for a plurality of views is generated by the second image reconstruction method by batch reconstruction processing from the already-projected projection data group.

  Here, when performing the second image reconstruction method, the image reconstruction unit 37 back-projects a preprocessed projection data group for a plurality of views collectively in a unit of a cross section having the same weighting, and the partial image As a three-dimensional image.

  For example, in order to reconstruct a three-dimensional image composed of “512 × 512 × 512” pixels by the second image reconstruction method, a view projected back on each pixel of “512 × 512 × 512” It is necessary to perform interpolation processing by weighting each unit of preprocessed projection data group.

  In the first image reconstruction method (that is, the image reconstruction method based on the helical scan), each pre-processed projection data group in units of columns is read and along the body axis direction of the subject P, that is, along the Z-axis direction. The tomographic images on the XY plane were reconstructed. In this case, as shown in FIG. 9, the weighting for the data back-projected on the XY plane at the same Z coordinate is different for all “512 × 512” pixels, and the weighting is changed every time the Z coordinate changes. It is necessary to read out data, perform interpolation processing, and perform back projection processing. For this reason, the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 optimize the reconstruction speed by executing the first image reconstruction method by parallel processing.

  However, in the second image reconstruction method (that is, the three-dimensional image reconstruction method by the conventional scan), since the tomographic image is not reconstructed, all projection data for a plurality of views are read. The projection data for a plurality of views can be backprojected collectively to generate a three-dimensional image as a partial image for a plurality of views consisting of “512 × 512 × 512” pixels.

  At that time, as shown in FIG. 9, “the weighting for the data backprojected on the YZ plane at the same X coordinate is the same”, and “the data backprojected on the XZ plane at the same Y coordinate” Is the same weight. That is, once the weighting data in the YZ plane or the XZ plane is read out, “512 tomographic images on all YZ planes” or “512 tomographic images on all XZ planes” are weighted together. By performing interpolation processing and backprojecting, it is possible to generate three-dimensional images as partial images for a plurality of views at a high speed in a batch, and the reconstruction speed of the three-dimensional image in the second image reconstruction method Can be optimized.

  Specifically, the plurality of FPGA substrates that perform the second image reconstruction method are partial images corresponding to 900 views generated by backprojecting collectively in units of cross sections having the same weighting. Three-dimensional images are respectively synthesized, and a three-dimensional image based on all X-ray intensity distribution data for 900 views is reconstructed. The plurality of FPGA boards that perform the second image reconstruction method sequentially store the generated partial images in a plurality of DDRs included in the FPGA substrate, and sequentially read out the partial images from the plurality of DDRs to synthesize the partial images. To do.

  The image reconstruction unit 37 that has completed the image reconstruction process by the first image reconstruction method or the second image reconstruction method, for image transmission, based on the control of the system control unit 39, as shown in FIG. Via the I / F, the reconstructed cross-sectional image or three-dimensional image is transmitted to the reconstruction auxiliary processing unit 36 by a general-purpose data transmission path (for example, PCI express). As shown in FIG. 10, each of the plurality of FPGAs performing the first image reconstruction method corresponds to each of the plurality of CPUs for the first image reconstruction method mounted in the reconstruction auxiliary processing unit 36. The generated tomographic image is transmitted. As shown in FIG. 10, the plurality of FPGA boards that perform the second image reconstruction method are configured so that the second image reconstruction mounted on the reconstruction auxiliary processing unit 36 based on the control of the system control unit 39. A three-dimensional image is transmitted to one legal CPU.

  Then, the reconstruction auxiliary processing unit 36 receives the cross-sectional image or the three-dimensional image reconstructed from the image reconstruction unit 37 via the image transmission I / F as shown in FIG. Or post-processing such as image processing based on an instruction from the operator. Note that the first image reconstruction method CPU mounted on the image reconstruction unit 37 generates a three-dimensional image by synthesizing a plurality of tomographic images after the artifact correction processing.

  Then, as shown in FIG. 11, one set CPU among the plurality of CPUs for the first image reconstruction method mounted on the reconstruction auxiliary processing unit 36 is based on the control of the system control unit 39. A three-dimensional image obtained by synthesizing a plurality of tomographic images or a rendering image generated from the three-dimensional image is transmitted to the image storage unit 38 via the image transmission I / F, and the image storage unit 38 receives the received image. Store image data.

  As shown in FIG. 11, one CPU for the second image reconstruction method mounted on the reconstruction auxiliary processing unit 36 is a three-dimensional image or the three-dimensional image based on the control of the system control unit 39. The rendered image generated from the dimensional image is transmitted to the image storage unit 38 via the image transmission I / F, and the image storage unit 38 stores the received image data.

  Then, the image data stored in the image storage unit 38 is displayed on the display unit 32 according to control by the system control unit 39.

  Here, the high-speed data transmission path used in the X-ray CT apparatus in the present embodiment will be described. High-speed data transmission path in “first data collection unit 15 to second data collection unit 16”, “second data collection unit 16 to preprocessing unit 34”, and “reconstruction auxiliary processing unit 36 to image reconstruction unit 37” For example, a transmission path having a transmission rate of 1 GB / sec is used. Furthermore, in data transmission using a high-speed data transmission path, a function for transmitting and receiving data retransmission processing corresponding to a data transmission error and time adjustment processing for transmitting data in units of views in a batch Performed between blocks.

  Now, the X-ray CT apparatus in the present embodiment post-processes the three-dimensional image reconstructed by the second image reconstruction method and stores it in the image storage unit 38, and stores the stored three-dimensional image in the display unit 32. In order to smoothly execute storage and display processing of the three-dimensional image reconstructed by the second image reconstruction method, processing described below is performed.

  The input unit 31 receives from the operator the reconstruction setting condition and the “collection range consisting of the diameter of the effective visual field and the length in the body axis direction when collecting projection data” and inputs them to the system control unit 39.

  When the input reconstruction setting condition is the second image reconstruction method based on the conventional scan, the system control unit 39 determines a predetermined value according to the collection range input together with the “second image reconstruction method”. Set a set cube frame consisting of sizes. For example, the system control unit 39 determines that the number of pixels on one side (X, Y, Z axes) is “32, 64, 128, 256, 512, 1024” or the like according to the diameter of the effective visual field. A set cube frame consisting of multiples of 32 is set. In the following, as shown in FIG. 12A, a case where a set cube frame of “512 × 512 × 512” is set will be described.

  Then, the system control unit 39 prepares in advance in the image storage unit 38 the amount of memory required to store the image data including the set cube frame of “512 × 512 × 512”. The display unit 32 prepares in advance the amount of memory required to display the image data including the set cube frame of “512 × 512 × 512”.

  Then, the system control unit 39 inserts the three-dimensional image by the second reconstruction method reconstructed by the image reconstruction unit 37 into the setting cube frame of “512 × 512 × 512” by the reconstruction reconstruction processing unit 36. In addition, the image storage unit 38 is controlled to store in a memory space prepared in advance.

  When the display request for the three-dimensional image reconstructed by the second reconstruction method is input via the input unit 31, the system control unit 39 stores “512 × 512 ×” stored in the image storage unit 38. Control is performed so that the three-dimensional image inserted into the set cube frame of “512” is displayed on the display unit 32 in a previously facilitated memory space.

  Here, the process of fitting the three-dimensional image into the set cube frame by the reconstruction auxiliary processing unit 36 controlled by the system control unit 39 will be specifically described.

  As shown in FIG. 12B, the system control unit 39 determines that the diameter (FOV diameter) of the effective field of view (FOV) at the time of projection data collection is the length in the body axis direction (that is, Z-axis imaging). In the first case larger than (range), the reconstruction auxiliary processing unit 36 is controlled so that the FOV diameter becomes one side of the set cube frame of “512 × 512 × 512”. That is, in the first case, the system control unit 39 controls the reconstruction auxiliary processing unit 36 so that the three-dimensional image reconstructed by the image reconstruction unit 37 is fitted into a cubic frame in which the FOV diameter is prioritized.

  Further, as shown in FIG. 12C, the system control unit 39 sets the Z-axis imaging range to “512 × 512 × 512” in the second case where the Z-axis imaging range at the time of projection data collection is larger than the FOV diameter. The image reconstruction unit 37 is controlled so as to be one side of the set cube frame. That is, in the second case, the system control unit 39 controls the reconstruction auxiliary processing unit 36 so that the three-dimensional image reconstructed by the image reconstruction unit 37 is fitted into a cubic frame giving priority to the Z-axis imaging range.

  In addition, when the FOV diameter at the time of projection data collection and the Z-axis imaging range match, the system control unit 39 reconstructs the three-dimensional image reconstructed by the image reconstruction unit 37 into the set cube frame of “512 × 512 × 512” The reconstruction auxiliary processor 36 is controlled so as to fit the image as it is.

  Note that the system control unit 39 sets the CT value of water “0” or air for pixels corresponding to the reconstructed image range (outlined portion) shown in FIGS. The reconstruction auxiliary processing unit 36 is controlled so as to fit the three-dimensional image reconstructed by the image reconstruction unit 37 into the set cube frame by padding the CT value “−1024”.

  Furthermore, the set cube frame used in the second image reconstruction method is also applied in the following cases.

  Specifically, when a request for split display of the three-dimensional image is input via the input unit 31 by an operator who refers to the three-dimensional image inserted in the set cube frame in the second case described above, the system control As shown in FIG. 13A, the unit 39 is centered on the split display center point specified in the split display request, and the FOV diameter is set to one side of the set cube frame of “512 × 512 × 512”. The reconstruction auxiliary processor 36 is controlled so that the image is cut out from the three-dimensional image. That is, the system control unit 39 controls the reconstruction auxiliary processing unit 36 so as to cut out and fit the three-dimensional image reconstructed by the image reconstruction unit 37 into a cubic frame giving priority to the FOV diameter. Then, the system control unit 39 controls the display unit 32 to display the divided image inserted into the “512 × 512 × 512” setting cube frame.

  In addition, when the operator who refers to the 3D image inserted in the setting cube frame in the second case described above inputs an enlarged display request for the 3D image via the input unit 31, the system control unit 39 As shown in FIG. 13B, the reconstruction auxiliary processing unit 36 is controlled so as to enlarge the enlarged region designated by the enlarged display request to the set cube frame. Then, the system control unit 39 controls the display unit 32 to display an enlarged image fitted in the set cube frame of “512 × 512 × 512”.

  Subsequently, a processing flow of the X-ray CT apparatus in the present embodiment will be described with reference to FIG. FIG. 14 is a flowchart for explaining processing of the X-ray CT apparatus in the present embodiment. Hereinafter, a case will be described in which the rearrangement process according to the image reconstruction method of the projection data group is performed in the second data collection unit 16 and the reconstruction setting condition is not changed.

  As shown in FIG. 14, in the X-ray CT apparatus according to the present embodiment, imaging conditions including a reconstruction setting condition, a collection range, and the like are input from the operator via the input unit 31 and imaging starts. Then (Yes at Step S1401), the first data collection unit 15 generates a projection data group from the X-ray intensity distribution data group detected by the X-ray detector 14 (Step S1402).

  Then, the system control unit 39 determines whether the reconstruction setting condition included in the imaging condition is the first image reconstruction method based on the helical scan or the second image reconstruction method based on the conventional scan (step S1403). .

  In the case of the second image reconstruction method based on the conventional scan (Yes at Step S1404), the system control unit 39 controls each functional block so as to execute the processing from Step S1405 to Step S1413.

  In other words, the second data collection unit 16 rearranges the projection data group received from the first data collection unit 15 into view units and transmits them to the preprocessing unit 34 (step S1405).

  The preprocessing unit 34 corrects the received projection data group in view units (step S1406). The preprocessing unit 34 stores the corrected projection data group in view units in the projection data storage unit 35.

  Subsequently, the preprocessing unit 34 collectively transmits the corrected projection data group in view units stored in the projection data storage unit 35 to the reconstruction auxiliary processing unit 36 in view units (step S1407).

  After that, the reconstruction auxiliary processing unit 36 pre-processes the received corrected projection data group for each view unit, and transmits the pre-processed projection data group to the image reconstruction unit 37 in units of view. (Step S1408).

  Further, the image reconstruction unit 37 performs batch reconstruction processing on the pre-processed projection data group received in batch by the first reconstruction method (step S1409), and generates the generated reconstructed image (three-dimensional). Image) is transmitted to the reconstruction assistance processor 36 (step S1410).

  Then, the reconstruction auxiliary processing unit 36 performs post-processing of the received reconstruction image (three-dimensional image) (step S1411). Specifically, the reconstruction auxiliary processing unit 36 performs a process of fitting from the collection range to the preset cube frame set in advance by the system control unit 39.

  Subsequently, the reconstruction auxiliary processing unit 36 stores the post-processed image data in the image storage unit 38 (step S1412), and the display unit 32 displays the image data stored in the image storage unit 38 (step S1412). S1413), the process is terminated.

  On the other hand, if it is not the second image reconstruction method by the conventional scan, that is, if it is the first image reconstruction method by the helical scan (No at Step S1404), the system control unit 39 performs the processing from Step S1414 to Step S1422. Each functional block is controlled to execute.

  That is, the second data collection unit 16 rearranges the projection data group received from the first data collection unit 15 in units of columns and transmits it to the preprocessing unit 34 (step S1414).

  Then, the preprocessing unit 34 corrects the received projection data group in units of columns (step S1415). The preprocessing unit 34 stores the corrected projection data group in units of columns in the projection data storage unit 35.

  Subsequently, the preprocessing unit 34 divides and transmits the corrected projection data group in view units stored in the projection data storage unit 35 to the reconstruction auxiliary processing unit 36 in units of columns (step S1416).

  After that, the reconstruction auxiliary processing unit 36 preprocesses the received corrected projection data group for each column unit in parallel, and divides the preprocessed projection data group into the image reconstruction unit 37 in column units. (Step S1417).

  Furthermore, the image reconstruction unit 37 performs parallel reconstruction processing on the pre-processed projection data group in units of columns received in a divided manner by the first reconstruction method (step S1418), and generates the reconstructed image (a plurality of reconstructed images). The tomographic image) is transmitted to the reconstruction auxiliary processing unit 36 (step S1419).

  Then, the reconstruction auxiliary processing unit 36 performs post-processing of the received reconstruction image (a plurality of tomographic images) (step S1420). Specifically, the reconstruction assistance processing unit 36 generates a three-dimensional image by combining a plurality of tomographic images, or generates a rendering image from the generated three-dimensional image.

  Subsequently, the reconstruction auxiliary processing unit 36 stores the post-processed image data in the image storage unit 38 (step S1421), and the display unit 32 displays the image data stored in the image storage unit 38 (step S1421). S1422), the process is terminated.

  As described above, in this embodiment, the system control unit 39 first reconstructs an image from projection data in units of columns collected by helical scanning as a reconstruction setting condition from the operator via the input unit 31. When the image reconstruction method is accepted, the following control processing is executed. That is, the second data collection unit 16 rearranges the projection data group received from the first data collection unit 15 in units of columns and transmits it to the pre-processing unit 34, and the pre-processing unit 34 receives the projections in column units received. Correction processing is performed on the data group to store the corrected projection data group in units of columns in the projection data storage unit 35, and the corrected projection data group in units of views stored in the projection data storage unit 35 is reconstructed in units of columns. The data is divided into auxiliary processing units 36 and transmitted. The reconstruction auxiliary processing unit 36 preprocesses the received corrected projection data group for each column unit in parallel, and divides the preprocessed projection data group into the image reconstruction unit 37 and transmits it. The image reconstruction unit 37 reconstructs the generated reconstructed image (a plurality of tomographic images) by performing parallel reconstruction processing on the preprocessed projection data group in units of columns received in a divided manner by the first reconstruction method. The reconstruction auxiliary processing unit 36 performs post processing on the received reconstructed image (a plurality of tomographic images), stores the post-processed image data in the image storage unit 38, and displays it. The unit 32 displays the image data stored in the image storage unit 38.

  In addition, when the system control unit 39 receives a second image reconstruction method for reconstructing an image from projection data in view units collected by a conventional scan as a reconstruction setting condition from the operator via the input unit 31 The following control process is executed. In other words, the second data collection unit 16 rearranges the projection data group received from the first data collection unit 15 into view units and transmits them to the preprocessing unit 34. The preprocessing unit 34 receives the projections in the received view units. The data group is corrected, the corrected projection data group in view unit is stored in the projection data storage unit 35, and the corrected projection data group in view unit stored in the projection data storage unit 35 is reproduced in view unit. The data is transmitted to the configuration auxiliary processing unit 36 at once. The reconstruction auxiliary processing unit 36 pre-processes the received corrected projection data group for each view unit in a lump, and transmits the pre-processed projection data group to the image reconstruction unit 37 in a lump for each view. The reconstruction unit 37 performs batch reconstruction processing on the preprocessed projection data group received in batch by the first reconstruction method, and performs reconstruction assistance processing on the generated reconstruction image (three-dimensional image). The reconstruction auxiliary processing unit 36 performs post-processing of the received reconstruction image (three-dimensional image), stores post-processed image data in the image storage unit 38, and the display unit 32 The image data stored in the image storage unit 38 is displayed. This makes it possible to select a data transmission method and a reconstruction processing method according to the image reconstruction method, and it is possible to optimize the reconstruction speed according to the image reconstruction method as described above. It becomes.

  In addition, since the rearrangement information is added and the corrected projection data group is stored, the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 refer to the rearrangement information by the corresponding image reconstruction method. The image can be reconstructed, and the reconstruction speed can be reliably optimized according to the image reconstruction method. In addition, since the corrected projection data group stored in the projection data storage unit 35 can be referred to together with the rearrangement information, the administrator can change the reconstruction condition in accordance with the image reconstruction method. Become.

  In addition, according to the present embodiment, it is possible to execute image processing corresponding to two image reconstructions by a single X-ray CT apparatus without installing a workstation for image processing.

  Further, when storing and displaying a three-dimensional image reconstructed by the second image reconstruction method, a preset cube frame is used, so that the second image reconstruction can be performed without using a complicated interface. It is possible to smoothly execute storage processing and display processing after generating a three-dimensional image by the method. Also, even when the displayed 3D image is divided or enlarged, the preset cube frame is used, so that the image processing after the generation of the 3D image by the second image reconstruction method is executed smoothly. It becomes possible to do.

  In the present embodiment, the case where the first image reconstruction method or the second image reconstruction method is executed based on the currently set reconstruction setting condition has been described. However, the present invention is limited to this. The first image reconstruction is performed for each of the plurality of corrected projection data groups according to the rearrangement information given to the plurality of corrected projection data groups stored in the projection data storage unit 35 instead of the one. The system control unit 39 may control the reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 so that the method or the second image reconstruction method is executed in parallel.

  For example, the system control unit 39 performs the first image reconstruction according to the rearrangement information “helical scan” assigned to the corrected projection data group stored in the projection data storage unit 35 by the helical scan at the present time. The reconstruction auxiliary processing unit 36 and the image reconstruction unit 37 are controlled to execute the method. Further, at the same time, when an image reconstruction request for the corrected projection data group already stored in the projection data storage unit 35 by the conventional scan is input via the input unit 31, the first image reconstruction is performed. In parallel with the configuration method, the reconstruction auxiliary processing unit 36 and the reconstruction correction processing unit 36 are configured to execute the second image reconstruction method with reference to the rearrangement information “conventional scan” for the specified corrected projection data group. The image reconstruction unit 37 is controlled.

  As a result, the X-ray CT apparatus alone can simultaneously execute two types of image reconstruction methods at an optimized reconstruction speed.

  Further, in this embodiment, the case where the projection data group collected by the helical scan is processed in units of columns has been described as the first image reconstruction method. For example, a conventional scan using only 64 detection element columns The present invention can also be applied to the case where the first image reconstruction method is used when the projection data group collected by the above is processed in units of columns.

  As described above, the X-ray CT apparatus according to the present invention is useful when reconstructing an image based on a projection data group indicating the intensity distribution of X-rays transmitted through a subject, and in particular, an image reconstruction method. It is suitable to optimize the reconstruction speed according to

It is a figure for demonstrating the structure of the X-ray CT apparatus in a present Example. It is a figure for demonstrating the 1st image reconstruction method. It is a figure for demonstrating the 2nd image reconstruction method. It is a figure (1) for demonstrating the data transmission between a 1st collection part, a 2nd collection part, a pre-processing part, and a projection data storage part. It is FIG. (2) for demonstrating the data transmission between a 1st collection part, a 2nd collection part, a pre-processing part, and a projection data storage part. It is a figure for demonstrating a projection data storage part. It is a figure for demonstrating the data transfer between a pre-processing part, a projection data storage part, and the reconstruction assistance process part. It is a figure for demonstrating the data transmission from the pre-processing part to the image reconstruction part via a reconstruction assistance process part. It is a figure for demonstrating an image reconstruction part. It is a figure for demonstrating the data transmission from an image reconstruction part to the reconstruction assistance process part. It is a figure for demonstrating the data transmission from a reconstruction assistance process part to an image memory | storage part. It is a figure (1) for demonstrating the storage format and display format of a three-dimensional image reconstructed by the 2nd image reconstruction method. It is FIG. (2) for demonstrating the storage format and display format of the three-dimensional image reconfigure | reconstructed by the 2nd image reconstruction method. It is a figure for demonstrating the process of the X-ray CT apparatus in a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mount apparatus 11 Mount fixing part 12 Mount rotation part 13 X-ray tube 14 X-ray detector 15 1st data collection part 16 2nd data collection part 17 High voltage generation part 18 Mount drive part 20 Sleeper apparatus 21 Sleeper drive part 22 Top Board 30 Console device 31 Input unit 32 Display unit 33 Scan control unit 34 Pre-processing unit 35 Projection data storage unit 36 Reconstruction auxiliary processing unit 37 Image reconstruction unit 38 Image storage unit 39 System control unit

Claims (10)

An X-ray tube that emits X-rays;
A plurality of detection element arrays each including X-ray detection elements for a plurality of channels are arranged in the body axis direction of the subject , and detects X-rays irradiated from the X-ray tube and transmitted through the subject. A line detector;
By rotating the X-ray tube and the X-ray detector around the subject, a data collection means for collecting the projection data groups corresponding to the different projection directions view,
Pre-processing means for generating a corrected projection data group obtained by performing correction processing on the projection data group collected by the data collecting means;
Cross-sections at different positions are obtained by repeatedly projecting the corrected projection data of a plurality of views by a plurality of back-projection processing means and combining the output data of the plurality of back-projection processing means to generate one cross-sectional image. First image reconstruction means for generating a three-dimensional image from the corrected projection data group generated by the preprocessing means by reconstructing an image;
The process of back-projecting the corrected projection data of one view onto each pixel of the three-dimensional image is repeated for a plurality of views each having the same weight for use in convolution, so that the pre-processing unit generates the projection data. Second image reconstruction means for generating a three-dimensional image from the corrected projection data group;
An X-ray CT apparatus comprising: An X-ray CT apparatus for reconstructing an image based on a projection data group indicating an intensity distribution of X-rays transmitted through a subject,
An X-ray tube that emits X-rays;
A plurality of detection element arrays each including a plurality of channels of X-ray detection elements are arranged along the body axis direction of the subject, and detects X-rays irradiated from the X-ray tube and transmitted through the subject. An X-ray detector;
Data collection means for collecting the projection data group by rotating the X-ray tube and the X-ray detector around a subject;
Pre-processing means for generating a corrected projection data group obtained by performing correction processing on the projection data group collected by the data collecting means;
Image reconstructing means for reconstructing an image by performing back projection processing on the corrected projection data group generated by the preprocessing means;
A first image reconstruction method for reconstructing an image from projection data combined in units of columns based on X-rays detected in each of the detection element columns, or X-ray irradiation directions irradiated from the X-ray tube, respectively Second image reconstruction in which projection data in units of X-ray irradiation directions based on X-rays detected by a plurality of the detection element arrays in FIG. 3 are back-projected for each section having the same weight used for convolution, thereby reconstructing an image An input means for accepting and inputting one of the methods from the operator as a reconstruction setting condition;
According to the reconstruction setting condition input by the input unit, the projection data group and / or the corrected projection data group are rearranged and distributed in units of columns or X-ray irradiation directions. The data collection means and / or the preprocessing means is controlled, and the first image reconstruction method is executed in parallel on the corrected projection data group distributed in units of columns. Control means for controlling the image reconstruction means to collectively execute the second image reconstruction method for the corrected projection data group distributed in irradiation direction units;
An X-ray CT apparatus comprising:   When the reconstruction setting condition input by the input unit is changed, the control unit may change the projection data group and / or the corrected projection data group according to the changed reconstruction setting condition. The X-ray CT apparatus according to claim 2, wherein the data collection unit and / or the pre-processing unit are controlled so as to be changed, rearranged, and distributed. A projection data storage unit for storing the corrected projection data group generated by the preprocessing unit;
The control means, after giving rearrangement information indicating whether the rearrangement processing performed by the data collection means and / or the preprocessing means is a column unit or an X-ray irradiation direction unit, Controlling the preprocessing means to store the generated corrected projection data group in the projection data storage means;
When the display request for the corrected projection data group stored in the projection data storage means is input via the input means, the corresponding rearrangement information is displayed together with the corrected projection data group. The X-ray CT apparatus according to claim 2, wherein the X-ray CT apparatus is controlled.   When the reconstruction setting condition input by the input unit is changed, the control unit stores the corrected projection data group stored in the projection data storage unit according to the changed reconstruction setting condition. The X-ray CT apparatus according to claim 4, wherein the preprocessing unit is controlled so as to change and rearrange the rearrangement information.   The control unit is configured to perform the correction processing on each of the plurality of corrected projection data groups according to the rearrangement information given to the plurality of corrected projection data groups stored in the projection data storage unit. 6. The X-ray CT apparatus according to claim 4, wherein the image reconstruction unit is controlled to execute one image reconstruction method or the second image reconstruction method in parallel. Image storage means for storing the image reconstructed by the image reconstruction means;
The input means accepts and inputs from the operator a collection range consisting of the diameter of the effective field of view and the length in the body axis direction when the projection data is collected by the data collection means together with the reconstruction setting condition,
When the reconstruction setting condition input via the input means is the second image reconstruction method, the control unit sets a predetermined value set according to the collection range input together with the reconstruction setting condition A set cube frame having a size of is set, and the image reconstructing unit is controlled to store the reconstructed image in the set cube frame and then stored in the image storage unit, and the image storage unit stores the image. 7. The control according to claim 2, wherein, when an image display request is input through the input unit, control is performed so as to display the image inserted in the setting cube frame. The X-ray CT apparatus described.   The control means is reconstructed by the image reconstruction means so that the diameter of the effective visual field is one side of the set cube frame in the first case where the diameter of the effective visual field is larger than the length in the body axis direction. In the second case, when the image is inserted and the length in the body axis direction is larger than the diameter of the effective visual field, the image reconstruction unit reconstructs the length in the body axis direction to be one side of the set cube frame. The X-ray CT apparatus according to claim 7, wherein the image reconstruction unit is controlled so as to fit the formed image.   When a split display request for the image is input through the input unit by the operator who refers to an image inserted in the setting cube frame in the second case, the control unit may The image reconstruction means is controlled so that an image having the center of the designated divided display as the center and the diameter of the effective visual field as one side of the set cube frame is cut out from the image, and the image reconstruction means The X-ray CT apparatus according to claim 8, wherein the X-ray CT apparatus is controlled to display a cut image.   When an enlargement display request for the image is input through the input unit by the operator who refers to an image inserted in the setting cube frame in the second case, the control unit may Controlling the image reconstruction unit so as to generate an enlarged image in which the designated enlarged region is enlarged to the set cube frame, and controlling to display the enlarged image generated by the image reconstruction unit. The X-ray CT apparatus according to claim 8, wherein

Images