JP2012045318A - Radiological imaging system, image processing apparatus, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate superposition of images even when a bed top sags.SOLUTION: In a radiological imaging system, a calculation unit calculates the position of the bed top rendered in a plurality of X-ray CT images of a subject which is tomographically generated by an X-ray CT apparatus. A determination unit determines the positions of overlapped parts of the subject between nuclear medicine images having adjacent imaged parts in a plurality of overlapped nuclear medicine images of the subject which are generated at predetermined intervals, and determines the shift between the nuclear medicine images. A positioning unit positions the X-ray CT images and nuclear medicine images which have substantially the same position of the subject, based on the shift between the position of the bed top in the plurality of the X-ray CT images calculated by the calculation unit and the plurality of nuclear medicine images determined by the determination unit.

Description

  Embodiments described herein relate generally to a radiation imaging apparatus, an image processing apparatus, and an image processing program.

  Conventionally, as a medical image diagnostic apparatus capable of performing functional diagnosis in a living tissue of a subject, a single photon emission CT apparatus (SPECT apparatus, SPECT: Single Photon Emission Computed Tomography) or a positron emission CT apparatus (PET apparatus, PET: Nuclear medicine imaging devices such as Positron Emission Computed Tomography) are known.

  Specifically, a nuclear medicine imaging device detects gamma rays emitted from an isotope or a labeled compound selectively taken into a living tissue by a detector, and a nuclear medicine image obtained by imaging a dose distribution of the detected gamma rays. Is a device for reconfiguring.

  In recent years, an apparatus (for example, a PET-CT apparatus or a SPECT-CT) in which a nuclear medicine imaging apparatus is integrated with an X-ray CT (Computed Tomography) apparatus for imaging morphological information in a living tissue of a subject. Devices) have been put into practical use. For example, in a PET-CT apparatus, a fusion image obtained by superimposing a PET image and an X-ray CT image is generated, and what kind of disease (for example, tumor) occurs in which part of the body. Inspection is being conducted. In addition, in a radiotherapy plan using an X-ray CT image, it is known that the accuracy of the radiotherapy plan is improved by using a PET image in addition to the X-ray CT image.

  By the way, in an apparatus in which a nuclear medicine imaging apparatus and an X-ray CT apparatus are integrated, different imaging methods are used when images are captured by the respective apparatuses. For example, in a PET-CT apparatus, a PET image is captured by a step-and-shoot method in which a top plate on which a subject is placed is moved stepwise in the body axis direction and images are taken for each part. An X-ray CT image is captured by a continuous movement method in which the top plate on which the specimen is placed is moved while moving in the body axis direction.

JP 2010-99396 A

  However, in the prior art, there is a case where it is difficult to superimpose images due to the top board droop.

  The radiation imaging apparatus according to the embodiment includes a calculation unit, a determination unit, and an alignment unit. The calculation unit calculates the position of the top plate depicted in each X-ray CT image in a plurality of X-ray CT images of the subject taken by tomography with the X-ray CT apparatus. In the plurality of nuclear medicine images obtained by overlappingly imaging the subject at a predetermined interval, the determining unit determines the position of the overlapping part of the subject between the nuclear medicine images adjacent to the imaging part. Determine the gap between. The alignment unit images substantially the same position of the subject based on the position of the top plate in the plurality of X-ray CT images calculated by the calculation unit and the deviation between the plurality of nuclear medicine images determined by the determination unit. The obtained X-ray CT image and nuclear medicine image are aligned.

FIG. 1 is a diagram for explaining the overall configuration of the PET-CT apparatus according to the first embodiment. FIG. 2 is a diagram for explaining the configuration of the PET gantry device. FIG. 3 is a diagram for explaining the configuration of the CT gantry device. FIG. 4 is a diagram for explaining the bed apparatus 3. FIG. 5 is a diagram for explaining the configuration of the console device. FIG. 6 is a view for explaining the top board droop in the PET-CT apparatus according to the first embodiment. FIG. 7 is a diagram for explaining the position of the top board in the image for each bed. FIG. 8 is a diagram for explaining the configuration of the correction unit according to the first embodiment. FIG. 9 is a diagram schematically illustrating an example of processing by the top position calculation unit. FIG. 10 is a diagram for explaining an overlapping area between beds. FIG. 11 is a diagram for explaining an example of processing by the pattern matching unit. FIG. 12 is a diagram illustrating an example of attenuation map correction processing by the position correction unit. FIG. 13 is a diagram illustrating an example of a PET image correction process performed by the position correction unit. FIG. 14 is a flowchart illustrating a procedure of image processing performed by the PET-CT apparatus according to the first embodiment. FIG. 15 is a flowchart of the attenuation map correction process performed by the PET-CT apparatus according to the first embodiment. FIG. 16 is a flowchart illustrating a procedure of PET image correction processing by the PET-CT apparatus according to the first embodiment. FIG. 17 is a flowchart of a pattern matching process performed by the PET-CT apparatus according to the first embodiment.

  First, the overall configuration of the PET-CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining the overall configuration of the PET-CT apparatus according to the first embodiment. As illustrated in FIG. 1, the PET-CT apparatus according to the first embodiment includes a PET gantry device 1, a CT gantry device 2, a couch device 3, and a console device 4.

  The PET gantry 1 detects gamma ray projection data (gamma ray projection) for reconstructing a PET image by detecting a pair of gamma rays emitted from a biological tissue that has taken in a positron emitting nuclide administered to a subject P. Data). FIG. 2 is a diagram for explaining the configuration of the PET gantry device.

  As shown in FIG. 2A, the PET gantry device 1 includes a PET detector 11, a coincidence counting circuit 12, and the like. The PET detector 11 is a photon counting detector that detects gamma rays emitted from the subject P. Specifically, the PET detector 11 is configured by arranging a plurality of PET detector modules 111 so as to surround the subject P in a ring shape.

  For example, the PET detector module 111 is an anger-type detector having a scintillator 111a, a photomultiplier tube (PMT) 111c, and a light guide 111b, as shown in FIG. .

  In the scintillator 111a, a plurality of NaIs, BGOs, and the like that convert gamma rays emitted from the subject P and incident into visible light are two-dimensionally arranged as shown in FIG. The photomultiplier tube 111c is a device that multiplies the visible light output from the scintillator 111a and converts it into an electrical signal. As shown in FIG. 2B, the photomultiplier tube 111c is densely packed via the light guide 111b. A plurality are arranged. The light guide 111b is used to transmit visible light output from the scintillator 111a to the photomultiplier tube 111c, and is made of a plastic material having excellent light transmittance.

  The photomultiplier tube 111c includes a photocathode that receives scintillation light and generates photoelectrons, a multistage dynode that provides an electric field that accelerates the generated photoelectrons, and an anode that serves as an electron outlet. Electrons emitted from the photocathode due to the photoelectric effect are accelerated toward the dynode, collide with the surface of the dynode, and knock out a plurality of electrons. By repeating this phenomenon over multiple dynodes, the number of electrons is avalancheally increased, and the number of electrons at the anode reaches about 1 million. In such an example, the gain factor of the photomultiplier tube 111c is 1 million times. In addition, a voltage of 1000 volts or more is usually applied between the dynode and the anode for amplification using the avalanche phenomenon.

  In this way, the PET detector module 111 converts gamma rays into visible light by the scintillator 111a, and converts the converted visible light into an electrical signal by the photomultiplier tube 111c, whereby the gamma rays emitted from the subject P are converted. Count the number.

  The coincidence counting circuit 12 shown in FIG. 2A is connected to each of the plurality of photomultiplier tubes 111c included in each of the plurality of PET detector modules 111. Then, the coincidence circuit 12 generates coincidence information for determining the incident direction of the pair of gamma rays emitted from the positrons from the output result of the PET detector module 111. Specifically, the coincidence counting circuit 12 calculates the position of the center of gravity from the position of the photomultiplier tube 111c obtained by converting the visible light output from the scintillator 111a into an electric signal at the same timing and the intensity of the electric signal, The incident position of gamma rays (the position of the scintillator 111a) is determined. In addition, the coincidence circuit 12 calculates the energy value of the incident gamma rays by performing arithmetic processing (integration processing and differentiation processing) on the intensity of the electric signal output from each photomultiplier tube 111c.

  The coincidence circuit 12 then selects a combination in which the gamma ray incident timing (time) is within a certain time window width and the energy values are both within a certain energy window width from the output results of the PET detector 11. Search (Coincidence Finding). For example, a time window width of 2 nsec and an energy window width of 350 keV to 550 keV are set as search conditions. Then, the coincidence counting circuit 12 generates coincidence count information (Coincidence List) on the basis of the output result of the searched combination as information obtained by simultaneously counting two annihilation photons. The coincidence counting circuit 12 transmits coincidence counting information to the console device 4 shown in FIG. 1 as gamma ray projection data for PET image reconstruction. A line connecting two detection positions obtained by simultaneously counting two annihilated photons is called a LOR (Line of Response). Further, the coincidence counting information may be generated by the console device 4.

  Returning to FIG. 1, the CT gantry device 2 detects X-rays transmitted through the subject P, and thereby X-ray projection data for reconstructing an X-ray CT image, and X for generating a scanogram. This is a device for generating line projection data (X-ray projection data). FIG. 3 is a diagram for explaining the configuration of the CT gantry device.

  As shown in FIG. 3, the CT gantry device 2 includes an X-ray tube 21, an X-ray detector 22, a data collection unit 23, and the like. The X-ray tube 21 is an apparatus that generates an X-ray beam and irradiates the subject P with the generated X-ray beam. The X-ray detector 22 is a device that detects X-rays transmitted through the subject P at a position facing the X-ray tube 21. Specifically, the X-ray detector 22 is a two-dimensional array type detector that detects two-dimensional intensity distribution data (two-dimensional X-ray intensity distribution data) of X-rays transmitted through the subject P. More specifically, in the X-ray detector 22, 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 P. The X-ray tube and the X-ray detector are supported inside the CT gantry device 2 by a rotating frame (not shown).

  The data acquisition unit 23 is a DAS (Data Acquisition System) and performs an amplification process, an A / D conversion process, etc. on the two-dimensional X-ray intensity distribution data detected by the X-ray detector 22 to obtain an X-ray. Generate projection data. Then, the data collection unit 23 transmits the X-ray projection data to the console device 4 shown in FIG.

  Returning to FIG. 1, the bed apparatus 3 is a bed on which the subject P is placed, and includes a top board 31 and a bed 32. The couch device 3 is sequentially moved to the respective imaging openings of the CT gantry device 2 and the PET gantry device 1 on the basis of instructions from the operator of the PET-CT apparatus received via the console device 4. That is, the PET-CT apparatus first captures an X-ray CT image by moving the bed apparatus 3, and then captures a PET image. FIG. 4 is a diagram for explaining the bed apparatus 3.

  The couch device 3 moves the couchtop 31 and the couch 32 in the body axis direction of the subject by a driving mechanism (not shown). For example, the PET-CT apparatus rotates the rotating frame of the CT gantry 2 and horizontally moves the top 31 in the direction of the CT gantry 2 as shown in FIG. An X-ray CT image is picked up by a helical scan that continuously scans the P imaging region spirally with X-rays.

  In addition, after the X-ray CT image is captured, the PET-CT apparatus horizontally moves the bed 32 with the top 31 being fed out of the bed 32 as shown in FIG. Thus, the imaging region of the subject P is inserted into the imaging port of the PET gantry device 1. Here, the bed 32 moves the same distance as the distance “a” between the center positions of the detectors of the PET gantry device 1 and the CT gantry device 2 as shown in FIG. That is, the couch 32 moves the distance “a”, so that the top plate 31 when imaging the same part in the body axis direction of the subject P between the imaging of the X-ray CT image and the imaging of the PET image. The feeding amount from the bed 32 is the same.

  Then, the PET-CT apparatus captures a PET image by horizontally moving the top plate 31 in the direction opposite to that when capturing an X-ray CT image. In such a case, after imaging a part of the subject, the PET-CT apparatus horizontally moves by a predetermined movement amount in a state where the imaging is stopped, further images another part, and performs the movement and imaging. A wide range of the subject is imaged by the repeated step-and-shoot method.

  Returning to FIG. 1, the console device 4 is a device that receives an instruction from an operator and controls an imaging process in the PET-CT apparatus. FIG. 5 is a diagram for explaining the configuration of the console device.

  As shown in FIG. 5, the console device 4 includes an X-ray projection data storage unit 41, a CT image reconstruction unit 42, an attenuation map generation unit 43, a gamma ray projection data storage unit 44, and a PET image reconstruction unit 45. And have. Further, the console device 4 includes a control unit 48 and correction data 47 as shown in FIG.

  The X-ray projection data storage unit 41 stores the X-ray projection data transmitted from the data collection unit 23. Specifically, the X-ray projection data storage unit 41 stores X-ray projection data for reconstructing an X-ray CT image. The CT image reconstruction unit 42 performs a back projection process on the reconstruction X-ray projection data stored in the X-ray projection data storage unit 41 by, for example, an FBP (Filtered Back Projection) method, thereby converting the X-ray CT image. Reconfigure.

  For example, the CT image reconstruction unit 42, in a whole body examination using a PET-CT apparatus, based on imaging conditions (for example, slice width) determined from an imaging plan, A plurality of X-ray CT images obtained by imaging a plurality of cross sections orthogonal to the body axis direction of the specimen P are reconstructed.

  The attenuation map generation unit 43 generates an attenuation map for correcting gamma ray attenuation generated in the body of the subject P using the X-ray CT image reconstructed by the CT image reconstruction unit 42. The gamma ray projection data storage unit 44 stores gamma ray projection data transmitted from the coincidence counting circuit 12. The PET image reconstruction unit 45 reconstructs a PET image from the gamma ray projection data stored in the gamma ray projection data storage unit 44 by, for example, a successive approximation method.

  The correction unit 46 performs attenuation correction of the PET image using the attenuation map generated by the attenuation map generation unit 43, and the X-ray CT image reconstructed by the CT image reconstruction unit 42 and the PET image reconstruction unit 45 reconstructs the PET image. Corrections when fusing the configured PET image are performed. The correction data 47 stores the processing result of the correction unit 46. The processing content of the correction unit 46 and the correction data 47 will be described in detail later.

  The control unit 48 controls processing of the entire PET-CT apparatus. Specifically, the control unit 48 controls imaging by the PET-CT apparatus by controlling the PET gantry apparatus 1, the CT gantry apparatus 2, the top plate 31, and the bed 32. The control unit 48 also controls the processing of the PET image reconstruction unit 45 using the data stored in the gamma ray projection data storage unit 44. The control unit 48 also controls the processing of the CT image reconstruction unit 42 and the attenuation map generation unit 43 using the data stored in the X-ray projection data storage unit 41. Further, the control unit 48 controls the processing of the correction unit 46. The control unit 48 receives an operator's instruction from an input / output device (not shown). Further, the control unit 48 controls an input / output device (not shown) to display a GUI (Graphical User Interface) for an operator to input an instruction, an X-ray CT image, and a PET image.

  The overall configuration of the PET-CT apparatus according to the first embodiment has been described above. With this configuration, the PET-CT apparatus according to the first embodiment aligns the X-ray CT image reconstructed by the CT image reconstruction unit 42 and the PET image reconstructed by the PET image reconstruction unit 45. Correction processing is executed.

  Specifically, the PET-CT apparatus according to the first embodiment corrects a positional shift between images in a PET image and an X-ray CT image caused by the sinking of the top 31 due to the weight of the subject P. Execute. In the following, the state in which the top plate 31 has been sunk may be referred to as the top plate.

  Here, the top plate droop in the PET-CT apparatus according to the first embodiment will be described first. FIG. 6 is a view for explaining the top board droop in the PET-CT apparatus according to the first embodiment. In FIG. 6, after the bed 32 is moved to the PET gantry device 1 side, the top plate when the PET image is picked up while returning the table 31 that has been fed back to the bed 32 by the step-and-shoot method is shown. Yes. The scan area of FIG. 6 shows the scan area of the PET gantry device 1. Moreover, the bed 1, the bed 2, and the bed 3 shown in FIG. 6 have shown the imaging position of the image by a step-and-shoot system. Although the subject is not shown in FIG. 6, actually, the top of the top when the subject is placed on the top 31 is shown.

  As shown in FIG. 6, the degree of the top plate dripping varies depending on the amount of the top plate 31 fed from the bed 32. That is, as shown in FIG. 6A, when the bed 1 is scanned, the weight applied by the subject has a great influence on the top plate 31, and the degree of the top plate in the scan region also increases. However, as shown in FIGS. 6B and 6C, every time the amount of the top 31 fed out of the bed 32 decreases, the influence of the subject on the weighted top 31 is reduced, and scanning is performed. The extent of the top plate in the area is also reduced.

  FIG. 7 is a diagram illustrating the position of the top board in the image for each bed. In FIG. 7, the sagittal (sagittal) surface of the image imaged for each bed is shown. That is, FIG. 7 shows a cross section of the subject in the body axis direction. As shown in FIG. 7, when a PET image is captured by the step-and-shoot method, a top plate droop occurs, resulting in a step between the beds, that is, the seam of the image.

  Such a step in the seam of the image makes it difficult to superimpose the PET image and the X-ray CT image. Measures have been taken to prevent the top plate from dripping. However, even if the rigidity of the top plate is improved, it does not completely prevent the top plate from dripping. For example, when the detector field of view expands in the body axis direction, the amount of feeding of the top plate further increases from the current level, and as a result, the top plate droops. Further, if a column or rail supporting the top plate is provided in the field of view of the detector, it will affect the absorption of X-rays and gamma rays, causing artifacts.

  Therefore, the PET-CT apparatus according to the first embodiment performs correction processing by the correction unit 46, which will be described in detail below, so that images can be easily superimposed even when the top board droops. enable. FIG. 8 is a diagram for explaining the configuration of the correction unit 46 according to the first embodiment. As shown in FIG. 8, the correction unit 46 includes a top position calculation unit 46a, a pattern matching unit 46b, and a position correction unit 46c. Then, the correction unit 46 stores the processing result in the correction data 47.

  The top-plate position calculation unit 46a calculates the position of the top plate depicted in each X-ray CT image in a plurality of X-ray CT images of the subject taken by tomography by the X-ray CT apparatus. Specifically, the top panel position calculation unit 46a has a plurality of cross-sections imaged by a continuous movement method in which the imaging part of the subject P is continuously scanned by X-rays while moving the top panel 31 in the body axis direction. Using the position of the top plate depicted in the image, the position of the top plate in the CT image is calculated.

  FIG. 9 is a diagram schematically illustrating an example of processing performed by the top position calculation unit 46a. FIG. 9 shows a sagittal plane image generated by using a plurality of cross-sectional images captured by the continuous movement method and reconstructed from the X-ray projection data by the CT image reconstruction unit 42. Moreover, the arrow shown in FIG. 9 has shown the moving direction of the top plate 31. FIG. In addition, a plurality of rectangles illustrated in FIG. 9 indicate slice widths of the cross-sectional image.

  As shown in FIG. 9, the top panel position calculation unit 46a calculates a top panel position L1 in the CT image based on the top panel 31 depicted in each cross-sectional image. Here, calculation of the top board position L1 by the top board position calculation unit 46a will be described. The slice width of the X-ray CT image when the X-ray CT image taken by the continuous movement method is viewed on the sagittal plane is actually very thin without the thickness shown in FIG. Therefore, when the width of each cross-sectional image shown in FIG. 9 is made as thin as possible (when the slice width is made close to 0), the cross-sectional image converges at the center of the X-ray detector 22. Therefore, when calculating the top plate position in the CT image based on the top plate 31 depicted in each cross-sectional image, as shown in FIG. 9, a straight line passing through the center of the top plate 31 depicted in each cross-sectional image. L1 is the top plate position.

  The pattern matching unit 46b determines the position of the overlapping part of the subject between the nuclear medicine images adjacent to each other in the plurality of nuclear medicine images obtained by imaging the subject at predetermined intervals. Determine the deviation between medical images. Specifically, the pattern matching unit 46b determines the position of the overlapping portion of the subject between the nuclear medicine images where the imaging portions are adjacent by performing pattern matching. For example, the pattern matching unit 46b calculates the deviation of the subject region depicted in each of the regions that are imaged in duplicate on each of the two consecutive beds, and detects the calculated deviation as the bed deviation.

  Here, first, a PET image for each bed imaged by the step-and-shoot method will be described. FIG. 10 is a diagram for explaining an overlapping area between beds. FIG. 10 shows a sagittal plane of a PET image in two beds imaged by the step-and-shoot method and reconstructed from the gamma ray projection data by the PET image reconstruction unit 45. The slice shown in FIG. 10 means a portion where one PET image is captured.

  As shown in FIG. 10, the bed includes a plurality of slices, and a part of the area imaged on the nth bed is imaged again on the (n + 1) th bed. That is, in the step-and-shoot method, the top plate 31 is moved horizontally so as to overlap a predetermined region between successive beds, and a plurality of PET images are captured. This is because the detection sensitivity in the body axis direction of the subject is different. Note that R1 shown in FIG. 10 indicates a position where gamma rays in the subject are accumulated. That is, R1 indicates the position where gamma rays are emitted.

  FIG. 11 is a diagram for explaining an example of processing by the pattern matching unit 46b. FIG. 11A shows a sagittal plane of a PET image in two beds imaged by the step-and-shoot method and reconstructed from the gamma ray projection data by the PET image reconstruction unit 45. As shown in FIG. 11A, the pattern matching unit 46b translates the n-th bed stepwise in the vertical direction in steps, and the subject portion of the (n + 1) -th bed and the subject of the n-th bed. The position where the overlap with the part is maximized is calculated.

  For example, as shown in FIG. 11B, the pattern matching unit 46b performs parabolic fitting in which a parabola is associated with the pixel movement amount and the distance between the subject parts when the nth bed is moved stepwise. According to the method, the position of the nth bed that maximizes the overlap of the subject region is determined in subpixel units with higher accuracy than pixel units. That is, using the following equation (1), the pixel movement amount that minimizes the distance between the subject parts is calculated in the sub-pixel order.

  The pattern matching unit 46b determines the calculated pixel movement amount as a step between successive beds. In Expression (1), the distance between the detection sites is obtained by the sum of the differences between the movement amount j of the i-th pixel in the n-th bed and the i-th pixel in the (n + 1) -th bed.

  Returning to FIG. 8, the position correction unit 46 c includes the position of the top plate in the plurality of X-ray CT images calculated by the top plate position calculation unit 46 a and the plurality of nuclear medicine images determined by the pattern matching unit 46 b. Based on the deviation, the X-ray CT image and the nuclear medicine image obtained by imaging the substantially same position of the subject are aligned. Further, the position correction unit 46c is based on the position of the top plate in the plurality of X-ray CT images calculated by the top plate position calculation unit 46a and the deviation between the plurality of nuclear medicine images determined by the pattern matching unit 46b. Then, an attenuation map for correcting a nuclear medicine image obtained by imaging substantially the same part as each X-ray CT image is created.

  Below, the production | generation of the fusion image of the X-ray CT image and PET image by the PET-CT apparatus which concerns on Example 1 is demonstrated. First, in the PET-CT apparatus according to the first embodiment, when CT examination and PET examination are performed on the subject P, the CT image reconstruction unit 42 stores the X-ray projection stored in the X-ray projection data storage unit 41. An X-ray CT image is reconstructed using the data. Then, the attenuation map generation unit 43 generates an attenuation map using the X-ray CT image reconstructed by the CT image reconstruction unit 42.

  The PET image reconstruction unit 45 reconstructs a PET image using the gamma ray projection data stored in the gamma ray projection data storage unit 44 and the attenuation map generated by the attenuation map generation unit 43. Here, in the attenuation map used for the reconstruction of the PET image, the top plate position is calculated by the top plate position calculation unit 46a, and is stored in the correction data 47 together with the information on the top plate position.

  On the other hand, pattern matching by the pattern matching unit 46b is executed on the PET image reconstructed by the PET image reconstruction unit 45. That is, a step between adjacent beds in the PET image reconstructed by the PET image reconstruction unit 45 is determined.

  Here, the position correction unit 46c corrects the attenuation map using the PET image in which the level difference between the beds is determined by the pattern matching unit 46b and the attenuation map stored together with the information on the top board position by the correction data 47. Execute.

  FIG. 12 is a diagram illustrating an example of attenuation map correction processing by the position correction unit 46c. As shown in FIG. 12, the position correction unit 46c first arranges the top panel position L1 in the attenuation map calculated by the top panel position calculation unit 46a on the PET image based on the vertical and horizontal widths of the image. And the position correction | amendment part 46c arrange | positions the level | step difference between the adjacent beds determined by the pattern matching part 46b based on the top-plate position L1.

  For example, the position correction unit 46c arranges a step between the bed 1 and the bed 2 by arranging “b” and “c” illustrated in FIG. 12 at positions where the distances from the L1 are equal. Similarly, a step “df” between the bed 2 and the bed 3 is arranged. Then, the position correction unit 46c determines a top plate position in the bed 1 by arranging a straight line L2 connecting “c” and “g” so as to intersect L1 at the center of the bed 1. The top plate position in the bed 2 is determined by a straight line connecting “b” and “g”. The same applies to the bed 3.

  Since the attenuation map generated by the attenuation map generation unit 43 is generated using the X-ray CT image reconstructed by the CT image reconstruction unit 42, the top plate position in the attenuation map is the X-ray CT. The same position as the image. Therefore, as shown in FIG. 12, the top plate position in the attenuation map is obtained by performing correction for superimposing the attenuation map generated from the reconstructed X-ray CT image on the PET image. It becomes the same as L1 which is a top plate position.

  Then, as shown in FIG. 12, the position correction unit 46c slides the attenuation map for each slice so that the top position L1 of the attenuation map matches the top position L2 of the PET image. Perform alignment. Then, the position correction unit 46 c stores the attenuation map that has been aligned in the correction data 47.

  When the attenuation map that has been aligned with the PET image is stored in the correction data 47, the PET image reconstruction unit 45 again reconstructs the PET image using the gamma ray projection data. Here, the PET image reconstruction unit 45 reconstructs a PET image using the attenuation map stored by the correction data 47. That is, the PET image reconstruction unit 45 performs reconstruction of the PET image using the attenuation map that has been aligned with the PET image.

  Then, the pattern matching unit 46b performs pattern matching on the PET image reconstructed by the PET image reconstruction unit 45 again. The top panel position calculation unit 46 a calculates the top panel position in the X-ray CT image reconstructed by the CT image reconstruction unit 42. Here, the position correction unit 46c performs correction of the PET image on which pattern matching has been executed, using the X-ray CT image from which the top board position has been calculated.

  FIG. 13 is a diagram illustrating an example of a PET image correction process performed by the position correction unit 46c. As illustrated in FIG. 13, the position correction unit 46 c arranges the top position L1 of the X-ray CT image and the top position L2 of the PET image. Then, as shown in FIG. 13, the position correction unit 46c slides the slice so that the top position L2 of the PET image matches the top position L1 of the X-ray CT image for each slice, and the X-ray CT Perform registration of the PET image to the image.

  Then, the position correction unit 46 c stores the PET image on which the alignment with the X-ray CT image has been executed in the correction data 47. Based on an instruction from an operator of the PET-CT apparatus input from an input unit (not shown), the control unit 48 performs, for example, the PET image on which the alignment with the X-ray CT apparatus stored by the correction data 47 has been executed. The read image and the merged image of the read PET image and X-ray CT image are displayed on a display unit (not shown).

  As described above, the PET-CT apparatus according to the first embodiment determines the top plate positions of the X-ray CT image and the PET image, and performs image correction so that one of the determined top plate positions matches the other. As a result, it is possible to easily superimpose images even when the top sag occurs.

  Next, processing of the PET-CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 14 is a flowchart illustrating a procedure of image processing performed by the PET-CT apparatus according to the first embodiment. Note that FIG. 14 shows processing after the X-ray CT inspection by the continuous movement method and the PET inspection by the step-and-shoot method are performed on the subject. As shown in FIG. 14, in the PET-CT apparatus according to the first embodiment, the CT image reconstruction unit 42 reconstructs an X-ray CT image using the X-ray projection data stored in the X-ray projection data storage unit 41. Configure (step S101).

  Then, the attenuation map generation unit 43 generates an attenuation map using the X-ray CT image reconstructed by the CT image reconstruction unit 42 (step S102). Thereafter, the PET image reconstruction unit 45 reconstructs a PET image using the attenuation map generated by the attenuation map generation unit 43 and the gamma ray projection data stored by the gamma ray projection data storage unit 44 (step S103). . Then, the correction unit 46 corrects the deviation between the attenuation map and the PET image (step S104). Specifically, the correction unit 46 corrects the attenuation map so as to match the shift of the PET image, and stores the correction map 47 in the correction data 47.

  Then, the PET image reconstruction unit 45 executes attenuation correction of the PET image using the corrected attenuation map (step S105). Specifically, the PET image reconstruction unit 45 performs reconstruction of the PET image using the attenuation map stored by the correction data 47. Then, the correction unit 46 corrects the deviation between the PET image after attenuation correction and the X-ray CT image (step S106).

  Specifically, the correction unit 46 corrects the PET image reconstructed using the attenuation map that has been aligned with the PET image so as to match the shift of the X-ray CT image. Thereafter, the control unit 48 overlaps the overlapping area between the beds of the PET image (step S107), and fuses the corrected PET image and the X-ray CT image generated by the CT image reconstruction unit 42 (step S108). ), Display on a display device (not shown), and the process ends.

  Next, an attenuation map correction process performed by the PET-CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 15 is a flowchart of the attenuation map correction process performed by the PET-CT apparatus according to the first embodiment. The process shown in FIG. 15 corresponds to step S104 in FIG.

  As illustrated in FIG. 15, in the PET-CT apparatus according to the first embodiment, the top panel position calculation unit 46a renders the position of the top panel in the attenuation map based on the X-ray CT image (step S201). And the pattern matching part 46b calculates the level | step difference between beds by the pattern matching of the reconstruction image which adjoins (step S202).

  Then, the position correction unit 46c arranges the position of the top plate of the attenuation map on the PET image (step S203), and determines the position of the top plate of the PET image (step S204). Specifically, the position correction unit 46c determines the top plate position of the PET image using the step between the beds calculated by the pattern matching unit 46b and the top plate position of the attenuation map. Thereafter, the position correction unit 46c matches the position of the top plate of the attenuation map with the position of the top plate of the PET image for each slice (step S205), and ends the processing.

  Next, a PET image correction process performed by the PET-CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 16 is a flowchart illustrating a procedure of PET image correction processing by the PET-CT apparatus according to the first embodiment. The process shown in FIG. 16 corresponds to step S106 in FIG.

  As illustrated in FIG. 16, in the PET-CT apparatus according to the first embodiment, the top panel position calculation unit 46a renders the position of the top panel in the X-ray CT image (step S301). And the pattern matching part 46b calculates the level | step difference between beds by the pattern matching of the reconstruction image which adjoins (step S302).

  Then, the position correction unit 46c arranges the position of the top plate of the X-ray CT image on the PET image (step S303), and determines the position of the top surface of the PET image (step S304). Specifically, the position correction unit 46c determines the top plate position of the PET image using the step between the beds calculated by the pattern matching unit 46b and the top plate position of the X-ray CT image. Thereafter, the position correction unit 46c matches the position of the top of the PET image with the position of the top of the X-ray CT image for each slice (step S305), and ends the process.

  Next, the pattern matching process by the PET-CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 17 is a flowchart of a pattern matching process performed by the PET-CT apparatus according to the first embodiment. Note that the process shown in FIG. 17 corresponds to step 202 shown in FIG. 15 and step S302 shown in FIG.

  As shown in FIG. 17, in the PET-CT apparatus according to the first embodiment, first, the pattern matching unit 46b extracts adjacent reconstructed images (step S401). Specifically, the pattern matching unit 46b extracts an overlapping area between adjacent beds. Then, the pattern matching unit 46b extracts the subject part in the overlapping region (step S402), and moves the adjacent beds stepwise (step S403).

  Thereafter, the pattern matching unit 46b calculates the amount of movement of the pixel that minimizes the displacement of the subject region (step S404), determines the amount of movement of the pixel as a step between adjacent beds (step S405), The process ends.

  As described above, according to the first embodiment, the top plate depicted in each X-ray CT image in a plurality of X-ray CT images of the subject whose tomographic imaging is performed by the top plate position calculation unit 46a by the X-ray CT apparatus. The position of is calculated. Then, the pattern matching unit 46b determines the position of the overlapping part of the subject between the nuclear medicine images adjacent to each other in the plurality of nuclear medicine images obtained by imaging the subject at predetermined intervals. The deviation between each nuclear medicine image is determined. Then, the position correcting unit 46c is based on the position of the top plate in the plurality of X-ray CT images calculated by the top plate position calculating unit 46a and the deviation between the plurality of nuclear medicine images determined by the pattern matching unit 46b. Then, the X-ray CT image and the nuclear medicine image obtained by imaging substantially the same position of the subject are aligned. Therefore, the PET-CT apparatus according to the first embodiment makes it possible to easily superimpose the PET image and the X-ray CT image even when the top board droop occurs.

  Further, according to the first embodiment, the pattern matching unit 46b performs pattern matching to determine the position of the overlapping portion of the subject between the nuclear medicine images in which the imaging portions are adjacent. Therefore, the PET-CT apparatus according to the first embodiment makes it possible to accurately detect the degree of the top board dripping.

  In addition, according to the first embodiment, the position correction unit 46c includes a plurality of nuclear medicines determined by the position of the top plate in the plurality of X-ray CT images calculated by the top plate position calculation unit 46a and the pattern matching unit 46b. Based on the shift between the images, an attenuation map for reconstructing a nuclear medicine image obtained by imaging substantially the same site as each X-ray CT image is created. Therefore, the PET-CT apparatus according to the first embodiment can reconstruct a high-quality PET image.

  In addition, according to the first embodiment, even when the top plate droops, it is possible to easily superimpose images, and thus it is possible to perform alignment according to the radiation treatment top plate, which is conventionally achieved. Even an accurate radiation treatment plan becomes possible.

  Although the first embodiment has been described above, the present invention may be implemented in various different forms other than the first embodiment described above.

(1) Nuclear medicine imaging apparatus In Example 1 mentioned above, the case where a PET-CT apparatus was used as a nuclear medicine imaging apparatus was demonstrated. However, the present embodiment is not limited to this. For example, another nuclear medicine imaging apparatus such as a SPECT-CT apparatus may be used.

(2) Correction In the first embodiment described above, the case where the PET image is aligned with the X-ray CT image has been described. However, the present embodiment is not limited to this. The case where it aligns with respect to a PET image may be sufficient.

(3) Attenuation Map In the first embodiment described above, the case where the registration is performed on the PET image after the attenuation map is generated has been described. However, the present embodiment is not limited to this, and for example, An attenuation map may be generated after aligning the X-ray CT image with the PET image.

  The above-described embodiment is an exemplification, and the scope of the invention is not limited to this.

  As described above, according to the first and second embodiments, it is possible to easily superimpose images even when the top plate droops.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 PET mount apparatus 2 CT mount apparatus 3 Bed apparatus 4 Console apparatus 31 Top plate 32 Bed 42 CT image reconstruction part 43 Attenuation map generation part 45 PET image reconstruction part 46 Correction part 46a Top plate position calculation part 46b Pattern matching 46c Position correction unit

Claims (5)

In a plurality of X-ray CT images of a subject taken by tomography with an X-ray CT apparatus, a calculation unit that calculates the position of the top plate depicted in each X-ray CT image;
In a plurality of nuclear medicine images obtained by overlappingly imaging the subject at a predetermined interval, by determining the position of the overlapping part of the subject between the nuclear medicine images where the imaging parts are adjacent, between each nuclear medicine image A determination unit for determining a shift;
Based on the position of the top plate in the plurality of X-ray CT images calculated by the calculation unit and the deviation between the plurality of nuclear medicine images determined by the determination unit, the substantially same position of the subject is imaged. An alignment unit for aligning the X-ray CT image and the nuclear medicine image,
A radiation imaging apparatus comprising:   The radiation imaging apparatus according to claim 1, wherein the determination unit determines a position of an overlapping portion of the subject between nuclear medicine images adjacent to the imaging portion by performing pattern matching.   Based on the position of the top plate in the plurality of X-ray CT images calculated by the calculation unit and the deviation between the plurality of nuclear medicine images determined by the determination unit, substantially the same site as each X-ray CT image The radiation imaging apparatus according to claim 1, further comprising: a creation unit that creates an attenuation map for reconstructing a nuclear medicine image obtained by imaging the image. In a plurality of X-ray CT images of a subject taken by tomography with an X-ray CT apparatus, a calculation unit that calculates the position of the top plate depicted in each X-ray CT image;
In a plurality of nuclear medicine images obtained by overlappingly imaging the subject at a predetermined interval, by determining the position of the overlapping part of the subject between the nuclear medicine images where the imaging parts are adjacent, between each nuclear medicine image A determination unit for determining a shift;
Based on the position of the top plate in the plurality of X-ray CT images determined by the calculation unit and the deviation between the plurality of nuclear medicine images determined by the determination unit, the substantially same position of the subject is imaged. An alignment unit for aligning the X-ray CT image and the nuclear medicine image,
An image processing apparatus comprising: In a plurality of X-ray CT images of a subject taken by tomography with an X-ray CT apparatus, a calculation procedure for calculating the position of the top plate depicted in each X-ray CT image;
In a plurality of nuclear medicine images obtained by overlappingly imaging the subject at a predetermined interval, by determining the position of the overlapping part of the subject between the nuclear medicine images where the imaging parts are adjacent, between each nuclear medicine image A decision procedure to determine the deviation;
Imaging substantially the same position of the subject based on the position of the top plate in the plurality of X-ray CT images calculated by the calculation procedure and the deviation between the plurality of nuclear medicine images determined by the determination procedure An alignment procedure for aligning the acquired X-ray CT image and nuclear medicine image;
An image processing program for causing a computer to execute.

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