JP2014083294A - Pet-ct apparatus and image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PET (Positron Emission computed Tomography)-CT (Computed Tomography) apparatus and an image processing apparatus capable of giving suitable information for specifying a target volume to a radiotherapy planner.SOLUTION: A PET-CT apparatus includes: an image reconfiguration part; an image generating part; and a display control part. The image reconfiguration part reconfigures a breath-hold CT image from a projection data collected in the breath-holding state by an X-ray CT scanner, and reconfigures a breath-free PET image from a projection data collected in the breath-free state by a PET scanner. The image generation part generates a breath-free PET image already subjected to deconvolution by deconvoluting the breath-free PET image by spatial resolution. The display control part displays the breath-holding CT image and the deconvoluted breath-free PET image on a display part.

Description

  Embodiments described herein relate generally to a PET (Positron Emission Computed Tomography) -CT (Computed Tomography) apparatus and an image processing apparatus.

  In radiotherapy, it is desirable to concentrate the dose on cancer tissue and reduce the dose on normal tissue. For this reason, prior to radiation treatment, a radiation treatment plan is formulated, and a site to be irradiated with radiation (hereinafter referred to as “target volume”) is determined. The target volume is defined by the International Commission on Radiation Units and Measurements, Inc. (ICRU). Target volumes include GTV (Gross Tumor Volume), CTV (Clinical Target Volume), ITV (Internal Target Volume), and PTV (Planning Target Volume).

  Conventionally, there is a method of formulating a radiation treatment plan using 4DCT images. This method classifies projection data using the phase and amplitude detected by the respiratory monitor during radiographing by an X-ray CT scanner, reconstructs the CT image for each phase and amplitude, and plans a radiation treatment for each phase and amplitude. Formulate. However, since this method sorts projection data into a plurality of phase and amplitude sections, the amount of projection data in each section is a fraction of the number of sections, and as a result, the image quality of the reconstructed CT image may deteriorate. is there. On the other hand, in order to maintain the image quality of the CT image, the X-ray irradiation amount must be increased, and the exposure amount may increase. In addition, this method may require several times the time required for formulating a radiation treatment plan.

International Commission on Radiation Units and Measurements Report 50, 62, [online], searched on June 1, 2012, Internet <URL: http://www.icru.org/>

  The problem to be solved by the present invention is to provide a PET-CT apparatus and an image processing apparatus capable of providing appropriate information for designating a target volume to a radiation treatment planner.

  The PET-CT apparatus according to the embodiment includes an image reconstruction unit, an image generation unit, and a display control unit. The image reconstruction unit reconstructs a breath-hold CT image from projection data collected under breath holding by an X-ray CT scanner, and reconstructs a free-breath PET image from projection data collected under free breath by a PET scanner To do. The image generation unit generates a deconvolved free-breathing PET image by deconvolutioning the free-breathing PET image with a spatial resolution of the PET. The display control unit displays the breath-holding CT image and the deconvolved free-breathing PET image on the display unit.

FIG. 1 is a diagram illustrating a configuration of a PET-CT apparatus according to the present embodiment. FIG. 2 is a diagram showing a PET scanner and an X-ray CT scanner in the present embodiment. FIG. 3 is a diagram showing the configuration of the PET scanner in the present embodiment. FIG. 4 is a diagram showing a configuration of the console device in the present embodiment. FIG. 5 is a diagram showing the concept of the target volume in the present embodiment. FIG. 6 is a diagram for explaining generation of a treatment plan image in the present embodiment. FIG. 7 is a diagram illustrating an example of a PET image in the present embodiment. FIG. 8 is a flowchart showing a processing procedure in the present embodiment.

  Hereinafter, a PET-CT apparatus and an image processing apparatus according to embodiments will be described with reference to the drawings. In the following embodiments, CT images and PET images collected by a PET-CT apparatus are used to support radiation treatment planning.

  FIG. 1 is a diagram illustrating a configuration of a PET-CT apparatus 100 according to the present embodiment. As shown in FIG. 1, the PET-CT apparatus 100 according to the present embodiment includes a PET scanner 200, an X-ray CT scanner 300, a bed 400, and a console apparatus 500. As shown in FIG. 1, the bed 400 includes a top 401 on which the subject 402 is placed, and the subject 402 is moved into the imaging port of the PET-CT apparatus 100 under the control of the console device 500. Let Note that the subject 402 is not included in the PET-CT apparatus 100.

  The PET scanner 200 detects annihilation gamma rays emitted from the subject 402 and generates count information based on the detection result. Specifically, first, a radiopharmaceutical labeled with a positron emitting nuclide is administered to the subject 402. Then, the positron emitting nuclide selectively taken into the living tissue in the subject 402 emits positrons, and the emitted positrons combine with the electrons and disappear. At this time, the positron emits a pair of annihilation gamma rays in almost opposite directions. On the other hand, the PET scanner 200 detects annihilation gamma rays using a detector 210 arranged in a ring shape around the subject 402, and generates count information based on the detection result.

  FIG. 2 is a diagram illustrating the PET scanner 200 and the X-ray CT scanner 300 in the present embodiment, and FIG. 3 is a diagram illustrating the configuration of the PET scanner 200 in the present embodiment. As shown in FIGS. 2 and 3, in the PET scanner 200, a plurality of detectors 210 are arranged in the X-axis direction, and a plurality of detectors 210 are arranged around the subject 402 in a ring shape.

  For example, the detector 210 is a photon counting type, anger type detector, and includes a scintillator, a photomultiplier tube (PMT (Photomultiplier Tube)), and a light guide. The scintillator converts annihilation gamma rays emitted from the subject 402 into scintillation light, and outputs the converted scintillation light. The scintillator is formed by scintillator crystals such as NaI (Sodium Iodide), BGO (Bismuth Germanate), LYSO (Lutetium Yttrium Oxyorthosilicate), LSO (Lutetium Oxyorthosilicate), and LGSO (Lutetium Gadolinium Oxyorthosilicate). . The photomultiplier tube multiplies the scintillation light output from the scintillator and converts it into an electrical signal. The light guide transmits scintillation light output from the scintillator to the photomultiplier tube. The light guide is formed of, for example, a plastic material having excellent light transmittance.

  The photomultiplier tube has 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 is an outlet for electrons. 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.

  As described above, the detector 210 converts the annihilation gamma rays emitted from the subject 402 into scintillation light by the scintillator, and converts the converted scintillation light into an electric signal by the photomultiplier tube. Detect annihilation gamma rays emitted.

  The radiopharmaceutical is, for example, 18F-labeled deoxyglucose labeled with 18F (fluorine). The count information includes a detection position indicating the position of the detector 210 that detected the annihilation gamma ray, an energy value of the annihilation gamma ray incident on the detector 210, and a detection time when the detector 210 detected the annihilation gamma ray.

  The X-ray CT scanner 300 detects X-rays transmitted through the subject 402 and generates projection data based on the detection result. Specifically, as shown in FIG. 2, the X-ray CT scanner 300 includes an X-ray tube 301 that emits X-rays and an X-ray detector 302 that detects X-rays emitted by the X-ray tube 301. Have. While rotating around the body axis of the subject 402, the X-ray tube 301 irradiates the subject 402 with X-rays, and the X-ray detector 302 detects X-rays transmitted through the subject 402. The X-ray CT scanner 300 performs projection processing, AD (Analog Digital) conversion processing, and the like on the X-rays detected by the X-ray detector 302 to generate projection data.

  FIG. 4 is a diagram showing a configuration of the console device 500 in the present embodiment. The console device 500 generates coincidence counting information using the counting information generated by the PET scanner 200, and reconstructs a PET image based on the generated coincidence counting information. Further, the console device 500 reconstructs an X-ray CT image based on the projection data generated by the X-ray CT scanner 300.

  Specifically, as illustrated in FIG. 4, the console device 500 includes an input / output unit 510 and a control unit 520. Also. The console device 500 includes a buffer 531, a coincidence count information storage unit 532, a count information collection unit 533, a coincidence count information generation unit 534, and a PET image reconstruction unit 535. In addition, the console device 500 includes an X-ray projection data storage unit 541 and an X-ray CT image reconstruction unit 542. In the present embodiment, the case where the reconstruction of the PET image and the reconstruction of the X-ray CT image are physically performed in one console apparatus will be described. However, the reconstruction of the PET image and the X-ray CT image are described. The reconfiguration may be performed in a separate console device.

  The input / output unit 510 receives various instructions from the user of the PET-CT apparatus 100 and transmits the received various instructions to the control unit 520. The input / output unit 510 receives information from the control unit 520 and outputs the received information. For example, the input / output unit 510 is an input unit such as a keyboard, a mouse, or a microphone, or an output unit (also referred to as a display unit) such as a monitor or a speaker.

  The control unit 520 controls imaging by the PET-CT apparatus 100 by controlling the PET scanner 200 and the X-ray CT scanner 300. In addition, the control unit 520 controls the PET image reconstruction process and the X-ray CT image reconstruction process in the console device 500. In addition, the control unit 520 outputs a PET image, an X-ray CT image, a treatment plan image described later, and the like to the monitor of the input / output unit 510. The control unit 520 is an electronic circuit such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a central processing unit (CPU), or a micro processing unit (MPU). Details of each unit included in the control unit 520 will be described later.

  The buffer 531 stores the count information stored by the count information collection unit 533. Further, the coincidence count information storage unit 532 stores the coincidence count information stored by the coincidence count information generation unit 534. The buffer 531 and the coincidence counting information storage unit 532 are, for example, a semiconductor memory device such as a RAM (Random Access Memory) and a flash memory (Flash Memory), a hard disk, and an optical disk.

  The count information collection unit 533 sequentially receives count information generated by the PET scanner 200 and stores the received count information in the buffer 531. The counting information collection unit 533 may be installed in the PET scanner 200. Here, the relationship between the annihilation gamma rays detected by the detector 210 and the pair of annihilation gamma rays emitted from the subject 402 will be described. For example, when a pair of annihilation gamma rays is emitted, the detector 210 detects only one of the pair of annihilation gamma rays, and the other annihilation gamma ray is detected by the other detector 210. A line connecting two detection positions obtained by simultaneously counting a pair of annihilation gamma rays is referred to as LOR (Line of Response).

  The coincidence count information generation unit 534 generates a time series list (also referred to as “Coincidence List”) of coincidence count information using the count information collected by the count information collection unit 533. Specifically, the coincidence count information generation unit 534 searches the count information stored in the buffer 531 for a set of count information obtained by counting a pair of annihilation gamma rays substantially simultaneously based on the count information detection time. The coincidence count information generation unit 534 generates coincidence count information for each set of retrieved count information, and stores the coincidence count information in the coincidence count information storage unit 532 while arranging the generated coincidence count information approximately in time series.

  For example, the coincidence count information generation unit 534 generates coincidence count information based on the set coincidence count information generation condition. A time window width is specified as the coincidence counting information generation condition. For example, the coincidence information generation unit 534 generates coincidence information based on the time window width “several nanoseconds”. Note that the coincidence information generation unit 534 may generate coincidence information using the energy window width together with the time window width.

  The PET image reconstruction unit 535 reconstructs a PET image. Specifically, the PET image reconstruction unit 535 reads out a time series list of coincidence counting information stored in the coincidence counting information storage unit 532 as projection data, and reconstructs a PET image using the read projection data. .

  The X-ray projection data storage unit 541 stores the projection data transmitted from the X-ray CT scanner 300. The X-ray CT image reconstruction unit 542 reconstructs an X-ray CT image by performing a back projection process on the projection data stored in the X-ray projection data storage unit 541 by, for example, an FBP (Filtered Back Projection) method.

  The PET-CT apparatus 100 described above provides a support tool for accepting designation of a target volume from a treatment planner using a CT image and a PET image. Such processing is executed by the control unit 520 of the console device 500 in the present embodiment. Specifically, the control unit 520 includes an image collection unit 520a, a treatment plan image generation unit 520b, a display control unit 520c, and a treatment plan reception unit 520d.

  The image acquisition unit 520a controls projection data for reconstructing a PET image and projection data for reconstructing a CT image by controlling the PET scanner 200, the X-ray CT scanner 300, and other units. collect. For example, the image acquisition unit 520a first controls the X-ray CT scanner 300, and collects projection data for reconstructing a 3D CT image while holding the breath of the subject 402 (with the breath stopped). To do. In the following, this collection is referred to as a “breath-hold 3DCT scan”. Subsequently, the image collection unit 520a moves the top plate 401 and controls the PET scanner 200 to collect projection data for reconstructing a 3D PET image while holding the breath of the subject 402. Hereinafter, this collection is referred to as a “breath-hold 3D PET scan”. Next, the image collection unit 520a controls the PET scanner 200 to collect projection data for reconstructing a 3D PET image under free breathing (a state in which the subject 402 is freely breathed). In the following, this collection is referred to as a “free breathing 3DPET scan”. Note that it is desirable that the breath-holding 3DCT scan and the breath-holding 3DPET scan have the same breath-holding state as much as possible. In addition, the breath holding and free breathing control of the subject 402 may be performed using a known technique such as a voice guide. The order of scanning is not limited to this, and any order may be used. For example, while collecting projection data under free breathing, projection data corresponding to under breath holding may be collected. .

  The X-ray CT image reconstruction unit 542 described above reconstructs a CT image from the projection data collected by the breath-holding 3DCT scan. Hereinafter, this CT image is referred to as “BH-CT image” or “BH-CT”. “BH” means Breathe Hold. Further, the above-described PET image reconstruction unit 535 reconstructs a PET image from the projection data collected by the breath-holding 3D PET scan. Hereinafter, this PET image is referred to as “BH-PET image” or “BH-PET”. In addition, the PET image reconstruction unit 535 reconstructs a PET image from projection data collected by a free-breathing 3D PET scan. Hereinafter, this PET image is referred to as “FB-PET image” or “FB-PET”. “FB” means Free Breathe.

  The treatment plan image generation unit 520b receives the designation of the target volume using the CT image reconstructed by the X-ray CT image reconstruction unit 542 and the PET image reconstructed by the PET image reconstruction unit 535. An image for treatment planning is generated.

  FIG. 5 is a diagram showing the concept of the target volume in the present embodiment. Target volumes include GTV, CTV, ITV, and PTV. First, GTV is also referred to as “gross tumor volume” and refers to a tumor range that can be recognized from the image with the naked eye (or with a technique equivalent to the naked eye). CTV is also referred to as “clinical target volume”, and refers to a range in which GTV includes minute lesions (for example, cancer cells infiltrated between cells) that cannot be recognized from the image with the naked eye. In addition, ITV refers to a range in which the CTV further includes, as an internal margin (IM), effects due to movements of internal organs such as breathing, swallowing, heartbeat, and peristalsis. PTV is also referred to as “planned target volume”, and refers to a range in which ITV further considers a setup error (SM (Setup Margin), for example, an instrument error, top droop, etc.) in irradiation. In general, there is a relationship of GTV ≦ CTV ≦ ITV <PTV.

  FIG. 6 is a diagram for explaining generation of a treatment plan image in the present embodiment, and FIG. 7 is a diagram illustrating an example of a PET image in the present embodiment. In FIG. 6, a portion enclosed by “CT” includes a conceptual diagram of a respiratory waveform indicating breath holding (BH) and a conceptual diagram of a BH-CT image collected under breath holding. In FIG. 6, a part enclosed by “PET” includes a conceptual diagram of a respiratory waveform indicating breath holding (BH) and free breathing (FB), a BH-PET image collected under breath holding, and free breathing. A conceptual diagram of the FB-PET image collected below, a treatment plan image generated from the BH-PET image, and a treatment plan image generated from the FB-PET image are shown. Further, a conceptual diagram of a profile is shown below each treatment plan image. FIG. 7 shows tumor images (two shaded circles) on the BH-PET image and the FB-PET image. As shown in FIG. 7, the tumor image on the FB-PET image is wider than the tumor image on the BH-PET image due to respiratory movement. In this case, by deconvolution of the tumor region on the FB-PET image with the tumor region on the BH-PET image, it is possible to know where the tumor stays and distributes with respiratory movement. Can do.

  In the present embodiment, the treatment planner is not presented with the BH-PET image or the FB-PET image itself to accept the designation of the target volume, but from the BH-PET image or the FB-PET image. By specifying the target volume by generating an image and presenting the treatment planning image. This treatment planning image is generated by paying attention to the fact that the PET image is drawn in a state where the PET image is usually expanded by the spatial resolution of PET. That is, as will be described later, the treatment plan image generation unit 520b generates a treatment plan image by deconvolution of each PET image with a PET spatial resolution. Hereinafter, the relationship between each image and the target volume will be described using an expression expressing the relationship.

First, the relationship between the BH-CT image and GTV will be described. As shown in FIG. 6, in the BH-CT image, a tumor that can be recognized by the naked eye (or by a technique equivalent to the naked eye) is indicated by a circle filled with black. Here, it can be considered that the spatial resolution of CT is sufficiently higher than the spatial resolution of PET. For this reason, in this embodiment, regarding the BH-CT image, the BH-CT image itself is handled as a treatment planning image. That is, the outline of the tumor depicted in the BH-CT image itself is handled as equivalent to GTV (see formula (1)).

  Next, the relationship between the BH-PET image and CTV will be described. For example, since accumulation of 18F-labeled deoxyglucose is depicted in the PET image, this is considered to be equivalent to, for example, that cancer cells infiltrating between cells are depicted. In the BH-PET image shown in FIG. 6, a circle surrounded by a dotted line corresponds to the tumor depicted in the BH-PET image. Here, in the PET image, the CTV is drawn in a state where the spatial resolution of the PET is convoluted. In other words, in the PET image, the CTV is drawn in a state of being wider than the true CTV by the amount of the spatial resolution of the PET. In FIG. 6, “SpRes” means Spatial Resolution. In addition, the crosses surrounded by circles mean convolution.

For this reason, the treatment plan image generation unit 520b generates a treatment plan image by deconvolution of the BH-PET image with the spatial resolution of the PET (see formula (2)). As shown in FIG. 6, the treatment plan image (left) depicts a tumor that is shrunk by the spatial resolution of PET (a circle surrounded by a solid line inside a circle surrounded by a dotted line in FIG. 6). It can be said that the tumor depicted in this treatment planning image is closer to the true CTV than the tumor depicted in the BH-PET image. In FIG. 6, a circle surrounded by a dotted line on the treatment plan image is expressed for convenience of explanation. Further, “/” means deconvolution.

  Next, the relationship between the FB-PET image and ITV will be described. In the FB-PET image shown in FIG. 6, a circle surrounded by a dotted line corresponds to the tumor depicted in the FB-PET image. Here, in the PET image, the ITV is drawn in a state where the spatial resolution of the PET is convoluted. In other words, in the PET image, the ITV is drawn in a state that is wider than the true ITV by the amount of the spatial resolution of the PET.

For this reason, the treatment plan image generation unit 520b generates a treatment plan image by deconvolution of the FB-PET image with the spatial resolution of the PET (see Expression (3)). As shown in FIG. 6, the treatment plan image (right) depicts a tumor that is shrunk by the spatial resolution of PET (a circle surrounded by a solid line inside a circle surrounded by a dotted line in FIG. 6). It can be said that the tumor depicted in this treatment planning image is closer to the true ITV than the tumor depicted in the FB-PET image. In FIG. 6, a circle surrounded by a dotted line on the treatment plan image is expressed for convenience of explanation.

In the following, the other relationship between each image and the target volume will be briefly described. First, an FB-PET image obtained by deconvolution with a BH-PET image is an integral kernel (hereinafter referred to as an ITV) that generates ITV from CTV. (Refer to equation (4)).

Also, the CTV convolved with the IM kernel shown in equation (4) corresponds to ITV (see equation (5)). In this case, for example, one of the ITV derived from the equation (3) and the ITV derived from the equation (5) can be used for the other check.

Further, ITV plus a setting error in irradiation corresponds to PTV (see equation (6)). In addition, since the setting error in irradiation is a value depending on, for example, equipment used in a hospital, for example, a value set in advance as a known value is used. The known value is, for example, a value provided by a device vendor or a value measured by a hospital technician.

  Returning to FIG. 4, the display control unit 520c generates the BH-CT image itself reconstructed by the X-ray CT image reconstruction unit 542, or the treatment plan image generation unit 520b from the BH-PET image or the FB-PET image. The treated treatment plan image is displayed on the input / output unit 510. For example, the display control unit 520c displays the BH-CT image illustrated in FIG. 6 and the two treatment plan images illustrated in FIG.

  The treatment plan receiving unit 520d receives the designation of the target volume on the treatment plan image displayed on the input / output unit 510. For example, the treatment plan receiving unit 520d receives a GTV designation for a BH-CT image from a treatment planner. That is, for example, the treatment planner outlines the tumor depicted on the BH-CT image by operating the mouse while browsing the BH-CT image displayed on the monitor. The treatment plan receiving unit 520d receives the contour input by the treatment planner as the GTV designation.

  Further, for example, the treatment plan receiving unit 520d receives the designation of the CTV for the treatment plan image generated from the BH-PET image from the treatment planner. In other words, for example, the treatment planner performs contouring of the tumor drawn on the treatment plan image by operating the mouse while browsing the treatment plan image displayed on the monitor. Here, if it is considered to perform contouring on the BH-PET image itself, in this case, the treatment planner will take into account that the image is drawn in a state expanded by the spatial resolution of the PET. Even then, the CTV is designated based on an ambiguous assumption without being based on the basis. On the other hand, in the present embodiment, an image obtained by adjusting the spatial resolution of PET by calculation is displayed, so that the treatment planner can designate a CTV based on a certain degree of basis.

  Similarly, for example, the treatment plan receiving unit 520d receives an ITV designation for a treatment plan image generated from an FB-PET image from a treatment planner. In other words, for example, the treatment planner performs contouring of the tumor drawn on the treatment plan image by operating the mouse while browsing the treatment plan image displayed on the monitor. Similar to the designation of CTV, in this embodiment, an image in which the amount of spatial resolution of PET is adjusted by calculation is displayed, so that the treatment planner can designate ITV based on a certain degree of basis.

By the way, in this embodiment, the BH-PET image and the FB-PET image have been subjected to attenuation correction using a CT image. That is, the PET image reconstruction unit 535 performs attenuation correction of the BH-PET image using the BH-CT image (see formula (7)), and uses the FB-CT image that is a CT image under free breathing to perform FB. -Attenuation correction of the PET image is performed (see equation (8)). “Mu” means Mu-map.

However, as described above, in this embodiment, an FB-CT image that is a CT image under free breathing is not collected. Therefore, the PET image reconstruction unit 535 derives an FB-CT image by convolving the IM derived in Equation (4) with the BH-CT image (see Equation (9)). Note that “*” means convolution.

Specifically, attenuation correction of the FB-PET image using the FB-CT image is performed by the iterative process of (10).

  First, in the processes “0” and “1”, the PET image reconstruction unit 535 uses the BH-CT image for the first attenuation correction, and uses the first FB-PET image (FB-PET (0)). Reconfigure. Subsequently, in process “2”, the PET image reconstruction unit 535 derives an IM kernel by deconvolution of the first FB-PET image with the BH-PET image, and in process “3”, the BH-CT A first FB-CT image is obtained by convolving the IM kernel with the image.

  Then, when “1” is substituted into the variable “i” for counting repetition in the process “4”, the PET image reconstruction unit 535 is derived in the process “3” in the processes “5” and “6”. The first FB-CT image is used for the second attenuation correction, and the second FB-PET image is reconstructed. Subsequently, in process “7”, the PET image reconstruction unit 535 derives an IM kernel by deconvolution of the second FB-PET image with the BH-PET image, and in process “8”, the BH-CT A second FB-CT image is obtained by convolving the IM kernel with the image.

  The PET image reconstruction unit 535 compares the first FB-CT image and the second FB-CT image, and repeats the above processing until it converges (for example, repeats 2 to 3 times). An image is derived, and attenuation correction of the FB-PET image is performed using the derived FB-CT image. Note that such an FB-CT image is not an actually collected free breathing CT image, and may be referred to as, for example, a breathing average CT image, for example.

  FIG. 8 is a flowchart showing a processing procedure in the present embodiment. As shown in FIG. 8, first, the image acquisition unit 520a controls the PET scanner 200, the X-ray CT scanner 300, and other units, and performs a breath holding 3DCT scan, a breath holding 3DPET scan, and a free breathing 3DPET scan (step) S1-S3).

  Then, the X-ray CT image reconstruction unit 542 and the PET image reconstruction unit 535 reconstruct a BH-CT image, a BH-PET image, and an FB-PET image using the projection data collected in steps S1 to S3. In addition, the treatment plan image generation unit 520b generates a treatment plan image (step S4).

  Thereafter, the display control unit 520c inputs the treatment plan image generated in step S4, the reconstructed image such as the BH-CT image, the BH-PET image, and the FB-PET image, and the tumor position distribution image as necessary. It outputs to the output part 510 (step S5). Here, the tumor position distribution image is an image showing where the tumors are staying distributed. For example, as shown in FIG. 6, the tumor position distribution image may be a diagram in which a profile of CTV or ITV is superimposed on a profile (a waveform indicated by a dotted line in FIG. 6) analyzed from a PET image. For example, in the CTV and ITV profiles, the range of actual respiratory movement may be indicated using arrows.

  As described above, according to the present embodiment, it is possible to provide appropriate information for designating the target volume to the radiation therapy planner. That is, according to the present embodiment, the collection of CT images is only the collection performed under breath hold, so that the exposure dose can be reduced while maintaining the image quality of the CT images. In addition, since it is not a method of allocating projection data to a plurality of phases and amplitude categories, PET acquisition time and radiation treatment plan formulation time are short.

  For example, according to the present embodiment, the size and movement of a tumor are analyzed and output by a scan flow of breath holding 3DCT scan, breath holding 3DPET scan, free breathing 3DPET scan, image reconstruction, and image analysis, and radiation therapy is performed. Information for planning can be collected appropriately. As a result, a simpler and more reliable radiation treatment plan is possible.

  In addition, embodiment is not restricted to embodiment mentioned above, It can implement with another different various form.

  For example, in the above-described embodiment, the example in which the treatment planner is provided with the treatment plan image generated from the BH-CT image and each of the BH-PET image and the FB-PET image has been described. It is not limited to this. The PET-CT apparatus 100 may select and provide necessary information as information for designating the target volume to the treatment planner.

  For example, in the above-described embodiment, the method of displaying the treatment plan image generated from the BH-PET image and receiving the designation of the CTV has been described. However, the present invention is not limited to this. For example, CTV may be obtained by performing a separate biopsy with reference to GTV. In this case, the image collection unit 520a can omit the breath holding 3DPET scan.

  In the above-described embodiment, an example in which the PET-CT apparatus 100 includes the treatment plan image generation unit 520b, the display control unit 520c, and the treatment plan reception unit 520d has been described. However, the embodiment is limited to this. It is not a thing. For example, instead of the PET-CT apparatus 100, the image processing apparatus may include a treatment plan image generation unit 520b, a display control unit 520c, and a treatment plan reception unit 520d, and execute the various processes described above. In this case, for example, the image processing apparatus stores the PET image and CT image reconstructed by the PET-CT apparatus 100 in the storage unit, and executes the various processes described above using these images stored in the storage unit. do it. Further, for example, the image processing apparatus may receive projection data from the PET-CT apparatus 100, reconstruct the PET image and the CT image in the apparatus itself, and execute the various processes described above. Here, the image processing device is, for example, a workstation, an image storage device (image server) of PACS (Picture Archiving and Communication System), a viewer, or various devices of an electronic medical record system.

  Moreover, the PET-CT apparatus 100 and the image processing apparatus do not necessarily assume a radiation treatment plan, and may execute the above-described attenuation correction. In this case, for example, the PET-CT apparatus 100 and the image processing apparatus include a storage unit and an image reconstruction unit. The storage unit includes a breath-hold CT image reconstructed from projection data collected under breath holding by an X-ray CT scanner, and a free-breathing PET reconstructed from projection data collected under free breath by a PET scanner. Store the image. Further, the image reconstruction unit performs attenuation correction of the free breathing PET image using the breath-holding CT image.

  For example, the image reconstruction unit reconstructs the first free-breathing PET image using the breath-holding CT image for the first attenuation correction, and deconvolves the first free-breathing PET image with the breath-holding PET image. To derive a first IM respiratory kernel, convolve the first IM integral kernel with the breath-holding CT image to obtain a first free breathing CT image, and use the first free breathing CT image as a second attenuation correction. To reconstruct the second free breathing PET image and deconvolve the second free breathing PET image with the breath-holding PET image to derive a second IM integral kernel, The process of obtaining the second free breathing CT image by convolving the IM integration kernel is repeated until convergence, and the free breathing PET image with the attenuation corrected is derived.

  In the above-described embodiment, an example in which a 3D image is a processing target has been described. However, the embodiment is not limited thereto, and the same applies to a case where a 2D image is a processing target. can do.

  According to the PET-CT apparatus and the image processing apparatus of at least one embodiment described above, appropriate information for designating a target volume can be provided to a radiation treatment planner.

  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 scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 100 PET-CT apparatus 500 Console apparatus 520 Control part 520a Image collection part 520b Treatment plan image generation part 520c Display control part 520d Treatment plan reception part

Claims (8)

Respiratory CT images are reconstructed from projection data collected under breath holding by an X-ray CT (Computed Tomography) scanner, and free breathing PET is obtained from projection data collected under free breathing by a PET (Positron Emission computed Tomography) scanner. An image reconstruction unit for reconstructing an image;
An image generation unit that generates a deconvolved free-breathing PET image by deconvolutioning the free-breathing PET image with a spatial resolution of the PET;
A PET-CT apparatus comprising: a display control unit that displays the breath-holding CT image and the deconvolved free-breathing PET image on a display unit. The image reconstruction unit further reconstructs a breath-hold PET image from projection data collected under a breath-hold by a PET scanner,
The image generation unit further generates a deconvolved breath-holding PET image by deconvolutioning the breath-holding PET image with a spatial resolution of the PET,
The PET-CT apparatus according to claim 1, wherein the display control unit further displays the deconvolved breath-holding PET image.   The PET-CT apparatus according to claim 1, further comprising a treatment plan receiving unit that receives designation of a target volume of a radiation treatment plan on the image displayed on the display unit.   The treatment plan receiving unit receives an ITV (Internal Target Volume) designation on the deconvolved free-breathing PET image, and accepts a CTV (Clinical Target Volume) designation on the deconvolved breath-holding PET image The PET-CT apparatus according to claim 3.   The PET-CT apparatus according to claim 1, wherein the image reconstruction unit performs attenuation correction of the free-breathing PET image using the breath-holding CT image. The image reconstruction unit
Reconstructing a first free breathing PET image using the breath-hold CT image for a first attenuation correction;
Deriving a first IM (Internal Margin) integral kernel by deconvolution of the first free-breathing PET image with the breath-holding PET image;
A first free breath CT image is obtained by convolving the first IM integral kernel with the breath-hold CT image;
Reconstructing a second free breathing PET image using the first free breathing CT image for a second attenuation correction;
Deconvolution of the second free-breathing PET image with the breath-holding PET image to derive a second IM integral kernel;
By convolving the second IM integration kernel with the breath-holding CT image, the processing for obtaining the second free-breathing CT image is repeated until convergence, and a free-breathing PET image with attenuation corrected is derived. The PET-CT apparatus according to claim 5. Stores breath-hold CT images reconstructed from projection data collected under breath hold by an X-ray CT scanner and free-breath PET images reconstructed from projection data collected under free breath by a PET scanner A storage unit;
An image reconstruction unit that performs attenuation correction of the free-breathing PET image using the breath-holding CT image,
The image reconstruction unit
Reconstructing a first free breathing PET image using the breath-hold CT image for a first attenuation correction;
Deconvolution of the first free breathing PET image with the breath-holding PET image to derive a first IM integral kernel;
A first free breath CT image is obtained by convolving the first IM integral kernel with the breath-hold CT image;
Reconstructing a second free breathing PET image using the first free breathing CT image for a second attenuation correction;
Deriving a second IM by deconvolution of the second free-breathing PET image with the breath-holding PET image;
By convolving the second IM integration kernel with the breath-holding CT image, the processing for obtaining the second free-breathing CT image is repeated until convergence, and a free-breathing PET image with attenuation corrected is derived. PET-CT device. Stores breath-hold CT images reconstructed from projection data collected under breath hold by an X-ray CT scanner and free-breath PET images reconstructed from projection data collected under free breath by a PET scanner A storage unit;
An image generation unit that generates a deconvolved free-breathing PET image by deconvolutioning the free-breathing PET image with a spatial resolution of the PET;
An image processing apparatus comprising: a display control unit configured to display the breath-holding CT image and the deconvolved free-breathing PET image on a display unit.

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