JP6104960B2 - Nuclear medicine imaging equipment - Google Patents

Description

  Embodiments described herein relate generally to a nuclear medicine imaging apparatus.

  Conventionally, as a nuclear medicine imaging apparatus, a positron emission computed tomography apparatus (hereinafter referred to as a PET (Positron Emission computed Tomography) apparatus) is known. The PET device generates a functional image of, for example, a human body tissue. Specifically, in imaging with a PET apparatus, a drug labeled with a positron emitting nuclide is first administered to a subject. Then, the positron emitting nuclide selectively taken into the biological tissue in the subject emits positron, and the emitted positron is combined with the electron and disappears. At this time, the positron emits a pair of gamma rays in substantially opposite directions. On the other hand, the PET apparatus detects gamma rays using a detector arranged in a ring shape around the subject, and generates coincidence count information (Coincidence List) from the detection result. Then, the PET apparatus performs reconstruction by back projection processing using the generated coincidence information, and generates a PET image.

  Here, in recent years, PET apparatuses having a TOF (Time Of Flight) function have appeared. A PET apparatus that does not have a TOF function performs reconfiguration on the assumption that positrons exist with equal probability on an LOR (Line Of Response) that connects a pair of detectors that detect a pair of gamma rays. On the other hand, the PET apparatus having the TOF function calculates the spatial position of the positron on the LOR by using a detection time difference in which gamma rays are detected by a set of detectors. Then, the PET apparatus having the TOF function performs reconstruction by back projection processing in consideration of the calculated spatial position, and generates a PET image.

Edited by Japan Imaging and Medical Systems Association, “Medical Imaging / Radiological Equipment Handbook”, Meiko Art Printing Co., Ltd. 2001, P.190-191

  However, the conventional technique has a problem that it takes a long time to generate a PET image as a result of a long time required for reconstruction by back projection processing. For example, in the related art, several minutes are required until a PET image is generated after photographing by the PET apparatus. For this reason, it is required to shorten the generation time of the PET image.

The nuclear medicine imaging apparatus according to the embodiment includes a blur width storage unit, an estimation unit, an image generation unit, a display control unit, and an image reconstruction unit . The blur width storage means stores the blur width of the image determined according to the time resolution of the detector that detects the radiation. The estimation means uses the spatial position of the pair of detectors that have detected the pair of radiations emitted from the positrons, and the set of detection times at which the pair of detectors have detected the pair of radiations. A spatial position of the positron is estimated on a line connecting a set of detectors. The image generation means stores the blur width storage means centered on the spatial position estimated by the estimation means so that the spatial resolution corresponding to the temporal resolution is reflected on a line connecting the set of detectors. Pixel values are assigned to the pixels corresponding to the blurred width, and images are sequentially generated without performing reconstruction processing. The display control means sequentially displays on the display unit each time the image generation means generates the image. The image reconstruction unit performs reconstruction by back projection processing. Such a nuclear medicine imaging apparatus selects whether to generate an image by the image generation means or to generate an image by the image reconstruction means according to the time resolution of the detector, and to select an image by the selected means. Generate.

FIG. 1 is a block diagram illustrating the configuration of the PET apparatus according to the first embodiment. FIG. 2 is a diagram for explaining the detector module according to the first embodiment. FIG. 3 is a diagram for explaining the data storage unit according to the first embodiment. FIG. 4 is a diagram illustrating an example of count information stored in the count information storage unit according to the first embodiment. FIG. 5 is a diagram illustrating an example of coincidence counting information stored in the coincidence counting information storage unit according to the first embodiment. FIG. 6 is a diagram illustrating an example of the spatial position information stored in the spatial position information storage unit according to the first embodiment. FIG. 7 is a diagram illustrating an example of the blur width of an image stored in the blur width storage unit according to the first embodiment. FIG. 8 is a diagram for explaining the image generation unit according to the first embodiment. FIG. 9 is a diagram for explaining the assignment of positron spatial positions and pixel values. FIG. 10 is a diagram for explaining the relationship between the time resolution and the blur width. FIG. 11 is a diagram for explaining the display of the generated PET image. FIG. 12 is a flowchart showing a processing procedure for displaying a PET image in real time. FIG. 13 is a flowchart illustrating a processing procedure for displaying a PET image after imaging.

  Hereinafter, a PET apparatus 100 according to Examples 1 and 2 will be described as an example of a nuclear medicine imaging apparatus according to an embodiment.

  The PET apparatus 100 according to the first embodiment does not generate a PET image by performing reconstruction by back projection processing, but a detector based on the positron spatial position estimated on LOR (Line Of Response). A PET image is generated by assigning pixel values to pixels corresponding to the blur width determined according to the time resolution. For this reason, according to the PET apparatus 100 according to the first embodiment, the generation time of the PET image can be shortened, and the PET image can be displayed in real time during imaging. Such a function is realized centering on processing by the image generation unit 26 described later.

[Configuration of PET apparatus 100 according to Embodiment 1]
The configuration of the PET apparatus 100 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a block diagram illustrating the configuration of the PET apparatus 100 according to the first embodiment. As illustrated in FIG. 1, the PET device 100 according to the first embodiment includes a gantry device 10 and a console device 20.

  The gantry device 10 detects a pair of gamma rays emitted from positrons, and collects count information based on the detection result. As illustrated in FIG. 1, the gantry device 10 includes a top plate 11, a bed 12, a bed driving unit 13, a detector module 14, and a counting information collection unit 15. The gantry device 10 has a cavity serving as a photographing port as illustrated in FIG.

  The top plate 11 is a bed on which the subject P lies, and is placed on the bed 12. The bed driving unit 13 moves the bed 12 under the control of a bed control unit 23 described later. For example, the bed driving unit 13 moves the subject P into the imaging port of the gantry device 10 by moving the bed 12.

  The detector module 14 detects gamma rays emitted from the subject P. As illustrated in FIG. 1, a plurality of detector modules 14 are arranged in the gantry device 10 so as to surround the subject P in a ring shape.

  FIG. 2 is a diagram for explaining the detector module 14 according to the first embodiment. As illustrated in FIG. 2A, the detector module 14 is a photon counting type, anger type detector, and is also referred to as a scintillator 141 and a photomultiplier tube (PMT). 142) and a light guide 143. 2B shows a state where the detector module 14 is observed from the direction of the arrow illustrated in FIG.

  The scintillator 141 converts gamma rays emitted from the subject P and incident into visible light, and outputs the converted visible light (hereinafter, scintillation light). The scintillator 141 is formed of, for example, a scintillator crystal such as NaI (sodium iodide) or BGO (bismuth acid germanate), and is two-dimensionally arranged as illustrated in FIG. The photomultiplier tube 142 multiplies the scintillation light output from the scintillator 141 and converts it into an electrical signal. As illustrated in FIG. 2A, a plurality of photomultiplier tubes 142 are arranged. The light guide 143 transmits the scintillation light output from the scintillator 141 to the photomultiplier tube 142. The light guide 143 is formed of, for example, a plastic material having excellent light transmittance.

  The photomultiplier tube 142 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 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. In such an example, the gain factor of the photomultiplier tube 142 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.

  As described above, the detector module 14 converts the gamma rays emitted from the subject P into scintillation light by the scintillator 141, and converts the converted scintillation light into an electrical signal by the photomultiplier tube 142. Detects gamma rays emitted from.

  Returning to FIG. 1, the count information collection unit 15 collects count information based on the detection result by the detector module 14. Specifically, the counting information collection unit 15 detects the position of the gamma ray incident on the detector module 14, the energy value of the gamma ray at the time of incidence on the detector module 14, and the detection of the gamma ray incident on the detector module 14. Time is collected for each detector module 14, and the collected count information is transmitted to the console device 20.

  First, the count information collection unit 15 performs an anger type position calculation process in order to collect the detection position from the detection result by the detector module 14. Specifically, the counting information collection unit 15 specifies the photomultiplier tube 142 that converts the scintillation light output from the scintillator 141 into an electrical signal at the same timing. Then, the counting information collection unit 15 calculates the position of the center of gravity using the energy value of the gamma ray corresponding to the position of each specified photomultiplier tube 142 and the intensity of the electric signal. A scintillator number (P) indicating the position is determined. When the photomultiplier tube 142 is a position detection type photomultiplier tube, the photomultiplier tube 142 may collect the detection position.

Further, the counting information collection unit 15 determines the energy value (E) of the gamma rays incident on the detector module 14 by integrating the intensity of the electric signal output by each photomultiplier tube 142. The counting information collection unit 15 collects the detection time (T) when the gamma ray is detected by the detector module 14. For example, the count information collection unit 15 collects the detection time (T) with an accuracy of 10 ⁻¹² seconds (picoseconds). Note that the detection time (T) may be an absolute time, or may be an elapsed time from the start of imaging, for example.

  Thus, the count information collection unit 15 collects the scintillator number (P), the energy value (E), and the detection time (T) as the count information.

  Here, as will be described later, the PET apparatus 100 according to the first embodiment generates a PET image in real time and displays the generated PET image in real time during imaging of the PET image. For this reason, the count information collection unit 15 immediately transmits the collected count information to the console device 20 every time the count information is collected during shooting.

  The console device 20 receives an operation of the PET device 100 by an operator, controls the imaging of the PET image, and generates a PET image using the count information collected by the gantry device 10. Specifically, as illustrated in FIG. 1, the console device 20 includes an input unit 21, a display unit 22, a bed control unit 23, a data storage unit 24, a coincidence count information generation unit 25, and image generation. Unit 26 and system control unit 27. Each part of the console device 20 is connected via an internal bus.

  The input unit 21 is a mouse, a keyboard, or the like used for inputting various instructions and various settings by the operator of the PET apparatus 100, and transfers the various instructions and various settings that are input to the system control unit 27. The display unit 22 is a monitor or the like that is referred to by an operator, and displays a PET image and receives a GUI (Graphical User Interface) for receiving various instructions and various settings from the operator under the control of the system control unit 27. ) Is displayed. The couch control unit 23 controls the couch driving unit 13.

  The data storage unit 24 stores various data used in the PET apparatus 100. FIG. 3 is a diagram for explaining the data storage unit 24 according to the first embodiment. As illustrated in FIG. 3, the data storage unit 24 includes a count information storage unit 24a, a coincidence count information storage unit 24b, a spatial position information storage unit 24c, a blur width storage unit 24d, and a PET image storage unit 24e. Have The data storage unit 24 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory, a hard disk, an optical disk, or the like.

  The count information storage unit 24 a stores count information for each detector module 14 collected by the count information collection unit 15. Specifically, the count information storage unit 24 a stores the count information for each detector module 14 transmitted from the count information collection unit 15. The count information stored in the count information storage unit 24 a is used for processing by the coincidence count information generation unit 25. Note that the count information stored in the count information storage unit 24a may be deleted after being used for processing by the coincidence count information generation unit 25, or may be stored for a predetermined period.

  Here, as described above, the PET apparatus 100 according to the first embodiment generates a PET image in real time during imaging of the PET image, and displays the generated PET image in real time. Each time the count information is collected during shooting, the collected count information is immediately transmitted to the console device 20. For this reason, the count information storage unit 24 a sequentially stores the count information sequentially transmitted from the count information collection unit 15.

  FIG. 4 is a diagram illustrating an example of count information stored in the count information storage unit 24a according to the first embodiment. As illustrated in FIG. 4, the count information storage unit 24 a associates a scintillator number (P), an energy value (E), and a detection time (T) with a module ID that identifies the detector module 14. Remember. 4 illustrates a state in which the count information storage unit 24a stores all the count information collected in the shooting, but the count information storage unit 24a is sequentially added from the count information collection unit 15 as described above. Since the transmitted count information is sequentially stored, the count information illustrated in FIG. 4 is stored sequentially.

  The coincidence information storage unit 24b stores the coincidence information generated by the coincidence information generation unit 25. Specifically, the coincidence counting information storage unit 24b stores the coincidence counting information by being stored by the coincidence counting information generation unit 25. The coincidence counting information stored in the coincidence counting information storage unit 24 b is used for processing by the image generation unit 26. Note that the coincidence counting information stored in the coincidence counting information storage unit 24b may be deleted after being used for processing by the image generation unit 26, or may be stored for a predetermined period.

  Here, as described above, the count information sequentially collected by the count information collection unit 15 is sequentially stored by the count information storage unit 24a. For this reason, as will be described later, the coincidence count information generation unit 25 also sequentially generates coincidence count information, and the coincidence count information storage unit 24b sequentially stores the coincidence count information sequentially stored by the coincidence count information generation unit 25. Remember.

  FIG. 5 is a diagram illustrating an example of coincidence counting information stored in the coincidence counting information storage unit 24b according to the first embodiment. As illustrated in FIG. 5, the coincidence information storage unit 24 b includes a coincidence No. indicating the order in which the coincidence information is generated in time series. Is stored in association with the count information.

  The spatial position information storage unit 24 c stores positron spatial position information estimated by a spatial position estimation unit 26 a described later. Specifically, the spatial position information storage unit 24c stores the spatial position information of positrons by being stored by the spatial position estimation unit 26a. The spatial position information stored in the spatial position information storage unit 24c is used for processing by a pixel value assignment unit 26b and a designated image generation unit 26d described later. In the first embodiment, in principle, the spatial position information stored in the spatial position information storage unit 24c is stored for a certain period in order to correspond to later imaging.

  Here, as described above, the coincidence counting information sequentially generated by the coincidence counting information generation unit 25 is sequentially stored by the coincidence counting information storage unit 24b. Therefore, as described later, the spatial position estimation unit 26a also sequentially estimates the spatial position, and the spatial position information storage unit 24c sequentially stores the spatial position information sequentially stored by the spatial position estimation unit 26a.

  FIG. 6 is a diagram illustrating an example of the spatial position information stored in the spatial position information storage unit 24c according to the first embodiment. As illustrated in FIG. 6, the spatial position information storage unit 24 c includes a count No. indicating the order in which the coincidence count information is generated in time series. The spatial position of the positron and the detection time are stored in association with. The spatial position of the positron is indicated by a combination of the x coordinate, the y coordinate, and the z coordinate, for example, as illustrated in FIG.

  The blur width storage unit 24d stores a blur width of an image used for generating a PET image. Specifically, the blur width storage unit 24d stores the blur width of an image in advance by being input by an operator of the PET apparatus 100. The blur width of the image stored in the blur width storage unit 24d is used for processing by the pixel value allocation unit 26b described later.

  FIG. 7 is a diagram illustrating an example of the blur width of an image stored in the blur width storage unit 24d according to the first embodiment. As illustrated in FIG. 7, the blur width storage unit 24 d stores the blur width of the image in association with the time resolution of the detector module 14.

  Here, as described above, a plurality of detector modules 14 are arranged in the gantry device 10. For this reason, it is considered that the time resolution does not match between the detector modules 14. In this regard, in the first embodiment, it is assumed that the time resolution is consistent among all the detector modules 14 by performing timing calibration by a known technique before imaging.

  The PET image storage unit 24e stores a PET image generated by a pixel value allocation unit 26b and a designated image generation unit 26d described later. Specifically, the PET image storage unit 24e stores the PET image by being stored by the pixel value assignment unit 26b or the designated image generation unit 26d. Further, the PET image stored in the PET image storage unit 24 e is displayed on the display unit 22 by the system control unit 27.

  Returning to FIG. 1, the coincidence counting information generating unit 25 generates coincidence counting information using the counting information collected by the counting information collecting unit 15. Specifically, the coincidence count information generation unit 25 sequentially reads the count information sequentially stored in the count information storage unit 24a, and a pair of gamma rays emitted from the positron is simultaneously counted based on the energy value and the detection time. The combination of counted information is searched. Further, the coincidence count information generation unit 25 generates a combination of the retrieved count information as coincidence count information, and sequentially stores the generated coincidence count information in the coincidence count information storage unit 24b.

  For example, the coincidence count information generation unit 25 generates coincidence count information based on the coincidence count information generation condition input by the operator. An energy window width and a time window width are specified as the coincidence information generation condition. For example, the coincidence counting information generating unit 25 generates coincidence counting information based on the energy window width “350 keV to 550 keV” and the time window width “600 picoseconds”.

  For example, the coincidence count information generation unit 25 refers to the count information storage unit 24a and refers to the energy value (E) and the detection time (T) illustrated in FIG. The coincidence counting information generation unit 25 then counts the difference in the detection time (T) within the time window width “600 picoseconds” and the energy value (E) within the energy window width “350 keV to 550 keV”. A combination of information is searched between the detector modules 14. Then, when the coincidence information generation unit 25 searches for a combination of “P11, E11, T11” and “P22, E22, T22” as a combination that satisfies the coincidence generation condition, the coincidence information generation unit 25 generates the coincidence information, As illustrated, it is stored in the coincidence information storage unit 24b.

  In addition to the energy window width and the time window width, the operator can perform random correction to exclude accidental coincidence and scattering to exclude the generation of scattered gamma ray counting information as coincidence counting information. Parameters for performing correction, sensitivity correction for correcting the difference in sensitivity between the detector modules 14, and attenuation correction for correcting the energy value of gamma rays attenuated inside the subject P are also included. It can be incorporated in the coincidence information generation condition.

  Returning to FIG. 1, the image generation unit 26 will be described. As described in the beginning, the PET apparatus 100 according to the first embodiment does not generate a PET image by performing reconstruction by back projection processing, but focuses on the spatial position of the positron estimated on the LOR. A PET image is generated by assigning pixel values to pixels corresponding to the blur width determined according to the time resolution of the detector module 14. Such a function is realized centering on processing by the image generation unit 26.

  FIG. 8 is a diagram for explaining the image generation unit 26 according to the first embodiment. As illustrated in FIG. 8, the image generation unit 26 includes a spatial position estimation unit 26a, a pixel value assignment unit 26b, an image designation reception unit 26c, and a designation image generation unit 26d.

  The spatial position estimation unit 26a estimates the spatial position of the positron on the LOR that connects the pair of detector modules 14 that detect a pair of gamma rays emitted from the positron. Specifically, the spatial position estimation unit 26a sequentially reads the coincidence count information sequentially stored in the coincidence count information storage unit 24b, and sets the spatial position of the set of detector modules 14 specified by the scintillator number and the set. The spatial position of the positron is estimated using the detection time of. Here, the spatial position estimation unit 26a has a TOF function, calculates a detection time difference from a set of detection times, and estimates the spatial position of the positron based on the calculated time difference. In addition, when the spatial position is estimated, the spatial position estimation unit 26a generates spatial position information, and sequentially stores the generated spatial position information in the spatial position information storage unit 24c.

  FIG. 9 is a diagram for explaining the assignment of positron spatial positions and pixel values. As illustrated in FIG. 9A, a pair of gamma rays emitted from the positron is detected by a set of detector modules 14. LOR is a line a that connects a pair of detector modules 14 that detect a pair of gamma rays. The spatial position estimation unit 26a calculates a detection time difference from a set of detection times, and estimates the spatial position b of the positron based on the calculated time difference. The spatial position b of the positron is indicated by a combination of the x coordinate, the y coordinate, and the z coordinate, for example, as illustrated in FIG.

  The spatial position estimation unit 26a according to the first embodiment uses a count No. indicating the order in which the coincidence count information is generated in time series as the spatial position information. And a combination of the positron spatial position and the detection time. The spatial position estimating unit 26a reads the coincidence No. read from the coincidence counting information storage unit 24b. For the count number included in the spatial position information. And In addition, the spatial position estimation unit 26a uses, for example, the earlier detection time or the average value of the set of detection times among the set of detection times read from the coincidence information storage unit 24b as the spatial position information. Included detection time. Note that the spatial position estimation unit 26a may use both sets of detection times as detection times included in the spatial position information.

  Returning to FIG. 8, the pixel value assigning unit 26b assigns pixel values to the pixels corresponding to the blur width stored in the blur width storage unit 24d, with the positron spatial position estimated by the spatial position estimating unit 26a as the center. A PET image is generated. Thus, the spatial resolution corresponding to the time resolution of the detector module 14 is reflected on the LOR connecting the pair of detector modules 14.

  Specifically, the pixel value assignment unit 26b sequentially reads the spatial position information sequentially stored in the spatial position information storage unit 24c. In addition, the pixel value assigning unit 26b refers to the blur width storage unit 24d and acquires the blur width stored in association with the time resolution of the detector module 14. Then, the pixel value assigning unit 26b generates a PET image by assigning pixel values to the pixels corresponding to the acquired blur width around the spatial position included in the spatial position information, and the generated PET image is stored in the PET image storage unit. 24e is sequentially stored.

  FIG. 10 is a diagram for explaining the relationship between the time resolution and the blur width. If the PET apparatus does not have the TOF function, the PET apparatus assumes that positrons exist on the LOR with equal probability. This is illustrated by a straight line a illustrated in FIG. On the other hand, if the PET apparatus has a TOF function and the time resolution is infinitely good, the PET apparatus should be able to estimate that a positron exists at one point on the LOR. This is illustrated by a bar graph b illustrated in FIG. Indicates that the existence probability is 1.0.

  In this regard, when the temporal resolution is good to some extent, the PET apparatus 100 according to the first embodiment has a detector module 14 centered on the spatial position c of the positron estimated on the LOR as shown in FIG. A PET image is generated by assigning pixel values to pixels corresponding to the blur width determined according to the time resolution. Here, the blur width is, for example, a full-width at half maximum (hereinafter referred to as FWHM (Full Width at Half Maximum)) when the blur distribution of the image is a mountain-shaped function d as illustrated in FIG. Note that the integral value of the existence probability is 1.0.

  As illustrated using FIG. 7, the blur width storage unit 24 d according to the first embodiment stores the blur width of the image in advance in association with the time resolution of the detector module 14. Further, as described above, in the first embodiment, the average time resolution between all the detector modules 14 is measured to obtain the system time resolution by performing timing adjustment by a known technique before imaging. For example, assuming that the system time resolution is “200 picoseconds”, the time resolution of all coincidence measurements is “200 picoseconds”.

  Then, the pixel value assigning unit 26b refers to the blur width storage unit 24d, and for example, stores the blur width (FWHM) “60 mm” stored in association with the time resolution (FWHM) “200 picoseconds” of the detector module 14. To get. Then, the pixel value assigning unit 26b indicates that there is a pixel value in the voxel corresponding to the acquired blur width “60 mm” around the spatial position indicated by the combination of the x coordinate, the y coordinate, and the x coordinate. By assigning “points”, a PET image is generated.

  For example, as illustrated in FIGS. 9B and 9C, pixel values are assigned to the shape of an elliptical sphere so that the LOR direction has a blur width around the estimated spatial position. Further, as illustrated in FIGS. 9B and 9C, the pixel values are assigned so that the luminance at the spatial position is high (dark) and the luminance is low (thin) as the distance from the spatial position increases. Such processing can be performed in a short time unlike reconstruction by back projection processing.

  Returning to FIG. 8, the image designation accepting unit 26 c accepts the condition designation of the generated PET image. Specifically, the image designation accepting unit 26c accepts at least one of detection time and spatial coordinates as a condition designation for the generated PET image from the operator of the PET apparatus 100. The image designation receiving unit 26c transmits the received condition designation to the designated image generating unit 26d.

  The designated image generating unit 26d generates a PET image based on the condition designation received by the image designation receiving unit 26c. Specifically, when the designated image generating unit 26d receives the condition designation from the image designation receiving unit 26c, the designated image generating unit 26d refers to the spatial position information storage unit 24c using the received condition designation, and the spatial position necessary for generating the PET image. Get information. Then, the designated image generation unit 26d generates a PET image using the acquired spatial position information.

For example, when the designated image generation unit 26d receives the detection time “t _{x to} t _y ” as the condition designation, the designated image generation unit 26d refers to the spatial position information storage unit 24c, and the spatial position whose detection time is within “t _{x to} t _y ” Get information only. Then, the designated image generation unit 26d generates a PET image by the same method as the pixel value assignment unit 26b. That is, the designated image generation unit 26d refers to the blur width storage unit 24d and acquires the blur width stored in association with the time resolution of the detector module 14. Then, the designated image generation unit 26d generates a PET image by allocating pixel values to the pixels corresponding to the acquired blur width around the spatial position included in the spatial position information, and the generated PET image is stored in the PET image storage unit. 24e. Similarly, when the spatial coordinates are designated as the condition designation, the designated image generation unit 26d refers to the spatial position information storage unit 24c and acquires only the spatial position information of the corresponding spatial coordinates.

  As described above, in the PET apparatus 100 according to the first embodiment, the image designation receiving unit 26c accepts the condition designation of the PET image to be generated after shooting, for example, and the designated image generating unit 26d is based on the accepted condition designation. A new PET image is generated.

  In other words, the PET image generated by the pixel value assigning unit 26b is displayed in real time during shooting, but the PET image generated by the designated image generating unit 26d is mainly displayed after shooting. Is. For example, it is assumed that after imaging, a doctor designates only a time width of interest, only an image area of interest, or a time width of interest and an image area. Then, the designated image generation unit 26d generates a PET image corresponding to this.

  For example, it is assumed that a certain shooting is performed for one hour, and the spatial position information stored in the spatial position information storage unit 24c is for one hour. At this time, it is assumed that the doctor wants to observe only the PET image in a certain time zone after examining the examination time of the medicine, the time activity curve, etc. In this regard, the spatial position information storage unit 24c according to the first embodiment stores all the spatial positions of positrons estimated during imaging and the inspection time in association with each other. For this reason, even when a doctor later thinks that he wants to observe only a PET image in a certain time zone, the PET apparatus 100 according to the first embodiment flexibly extracts the spatial position information corresponding to the corresponding time zone. A desired PET image can be generated afterwards. The same applies when an image area is designated as well as a time zone.

  The system control unit 27 performs overall control of the PET apparatus 100 by controlling the gantry device 10 and the console device 20. For example, the system control unit 27 controls imaging in the PET apparatus 100. Further, for example, the system control unit 27 controls the counting information collecting process by the counting information collecting unit 15 and the coincidence counting information generating process by the coincidence counting information generating unit 25. For example, the system control unit 27 controls image generation processing by the image generation unit 26.

  For example, the system control unit 27 controls the display processing of the PET image stored in the data storage unit 24. For example, every time a PET image is sequentially stored in the data storage unit 24 by the pixel value assignment unit 26b, the system control unit 27 sequentially reads out and displays the PET image on the display unit 22. Thus, the PET image is displayed in real time while the PET image is captured. For example, when the designated image generation unit 26 d stores a PET image in the data storage unit 24, the system control unit 27 reads the PET image and displays it on the display unit 22.

  FIG. 11 is a diagram for explaining the display of the generated PET image. For example, the system control unit 27 receives designation of the display direction of the PET image (for example, two-dimensional directions of axial, coronal, and sagittal) from the operator of the PET apparatus 100, and the pixel value assignment unit 26b and the like according to the received display direction The PET image generated by the designated image generation unit 26d is displayed on the display unit 22. For example, when the system control unit 27 receives a designation to display in all display directions of axial, coronal, and sagittal, as illustrated in FIG. 11, the axial, coronal, and sagittal PET images are displayed within one screen. Display all.

  Each unit such as the coincidence counting information generation unit 25, the image generation unit 26, and the system control unit 27 includes an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), or a central processing unit (CPU). And an electronic circuit such as MPU (Micro Processing Unit).

[Processing Procedure by PET Apparatus 100 According to Example 1]
Subsequently, a processing procedure performed by the PET apparatus 100 according to the first embodiment will be described with reference to FIGS. 12 and 13. FIG. 12 is a flowchart showing a processing procedure for displaying a PET image in real time. FIG. 13 is a flowchart illustrating a processing procedure for displaying a PET image after imaging.

  As illustrated in FIG. 12, in the PET apparatus 100 according to the first embodiment, when imaging is started (Yes at Step S101), the count information collection unit 15 sequentially collects count information (Step S102), and simultaneously The counting information generation unit 25 sequentially generates coincidence counting information (step S103).

  Then, the spatial position estimation unit 26a sequentially estimates the spatial position of the positron (step S104), and the pixel value allocation unit 26b focuses on the spatial position of the positron estimated by the spatial position estimation unit 26a. By assigning pixel values to the pixels corresponding to the blur width stored in 24d, PET images are sequentially generated (step S105).

  Subsequently, the system control unit 27 sequentially displays the PET images sequentially generated by the pixel value assignment unit 26b on the display unit 22 (step S106). The series of processing in steps S102 to S106 is repeated until the photographing is completed, and the PET image can be displayed in real time during the photographing.

  Next, as illustrated in FIG. 13, in the PET apparatus 100 according to the first embodiment, after the imaging, when the image designation receiving unit 26c receives the designation of the time width (Yes in Step S201), the designated image generating unit 26d. However, the spatial position information of the corresponding time width is acquired (step S202).

  Then, the designated image generation unit 26d generates a PET image by allocating pixel values to pixels corresponding to the blur width stored in the blur width storage unit 24d around the spatial position included in the acquired spatial position information. (Step S203). Subsequently, the system control unit 27 displays the PET image generated by the designated image generation unit 26d on the display unit 22 (step S204).

[Effect of Example 1]
As described above, the PET apparatus 100 according to the first embodiment includes the blur width storage unit 24d. The blur width storage unit 24d stores the blur width of the image determined according to the time resolution of the detector module 14 that detects gamma rays. The PET apparatus 100 includes a spatial position estimation unit 26a and a pixel value assignment unit 26b. The spatial position estimation unit 26 a detects the spatial position of the pair of detector modules 14 that detected the pair of gamma rays emitted from the positrons, and the pair of detections that detected the pair of gamma rays by the pair of detector modules 14. The time is used to estimate the spatial position of the positron on the LOR connecting the set of detector modules 14. Further, the pixel value assigning unit 26b is centered on the spatial position estimated by the spatial position estimating unit 26a so that the spatial resolution corresponding to the temporal resolution is reflected on the LOR connecting the set of detector modules 14. An image is generated by assigning pixel values to pixels corresponding to the blur width stored in the blur width storage unit 24d. Further, the PET apparatus 100 according to the first embodiment displays a PET image on the display unit 22 in a two-dimensional direction designated in advance.

  For this reason, according to the first embodiment, it is possible to reduce the generation time of the PET image. For example, it is possible to display a PET image in real time in parallel with imaging, and for example, it is possible to display a PET image while performing treatment.

  The PET apparatus 100 according to the first embodiment includes a spatial position information storage unit 24c. The spatial position information storage unit 24c detects the spatial position of the positron estimated by the spatial position estimation unit 26a and the positron is a detector. The detection time detected by the module 14 is stored in association with each other. The PET apparatus 100 includes an image designation receiving unit 26c and a designated image generating unit 26d. The image designation accepting unit 26c accepts at least one of the spatial position and the detection time as the condition designation of the PET image to be generated. The designated image generation unit 26d refers to the spatial position information storage unit 24c using the condition designation received by the image designation reception unit 26c, acquires the spatial position necessary for generating the PET image, and uses the acquired spatial position. At the center, an image is generated by assigning pixel values to pixels corresponding to the blur width stored by the blur width storage unit 24d.

  For this reason, according to the first embodiment, for example, even when a doctor wants to observe only a PET image in a certain time zone (or image region), the corresponding time zone (or image region) is considered. ) Can be extracted flexibly and a desired PET image can be generated afterwards. The flexibility here is different from that depending on the time interval collected at the time of shooting, as in the case of conventional dynamic imaging. That is, the time zone and the image area can be arbitrarily designated.

  It should be noted that the disclosed technique may be implemented in various different forms other than the above-described embodiments.

  First, in the first embodiment, it is assumed that the time resolution is the same among all the detector modules 14 by performing timing adjustment by a known technique before photographing, but the disclosed technique is not limited to this. . For example, when the time resolution differs for each detector module 14, the image generation unit 26 may generate an image using a blur width corresponding to the time resolution for each detector module 14.

  For example, the PET apparatus 100 adjusts the timing before imaging, measures each time resolution of each detector module 14, and stores it in the storage unit. Then, the pixel value assigning unit 26b refers to the storage unit for each of the pair of detector modules 14 and obtains each time resolution. For example, the pixel value assigning unit 26b stores the blur width using a value (or an average value) having a lower time resolution. Reference is made to part 24d. Subsequently, the pixel value assigning unit 26b acquires a blur width, and generates a PET image by assigning pixel values to pixels corresponding to the acquired blur width, with the spatial position included in the spatial position information as a center.

  In the first embodiment, the PET apparatus 100 includes only the image generation unit 26 and does not perform reconstruction by back projection processing. However, the disclosed technique is not limited thereto. For example, the PET apparatus 100 further includes an image reconstruction unit that performs reconstruction by backprojection processing. For example, the image generation unit 26 generates an image or the image reconstruction unit reconstructs an image according to time resolution. You may choose to configure. For example, when the time resolution cannot achieve 200 picoseconds, the PET apparatus 100 may select the reconstruction by the image reconstruction unit.

  Moreover, in the said Example 1, although FIG. 1 was illustrated as a structure of the PET apparatus 100, the technique of an indication is not restricted to this. For example, the counting information collection unit 15 may be provided on the console device 20 side, and conversely, the coincidence counting information generation unit 25 may be provided on the gantry device 10 side. Various data stored in the data storage unit 24 may be provided on the gantry device 10 side or may be provided on the console device 20 side.

DESCRIPTION OF SYMBOLS 100 PET apparatus 26 Image generation part 26a Spatial position estimation part 26b Pixel value allocation part 26c Image designation | designated reception part 26d Designated image generation part

Claims (5)

A blur width storing means for storing a blur width of an image determined according to a time resolution of a detector for detecting radiation;
Using the spatial position of a set of detectors that have detected a pair of radiation emitted from a positron and a set of detection times at which the pair of detectors has been detected by the set of detectors, the set of detections A guessing means for guessing the spatial position of the positron on the line connecting the vessels;
The blur width stored by the blur width storage means centered on the spatial position estimated by the estimation means so that the spatial resolution corresponding to the temporal resolution is reflected on the line connecting the set of detectors. Image generation means for assigning pixel values to the pixels and sequentially generating images without performing reconstruction processing;
Display control means for sequentially displaying on the display unit each time the image is generated by the image generation means;
Image reconstruction means for performing reconstruction by back projection processing,
According to the time resolution of the detector, it is selected whether to generate an image by the image generation means or to generate an image by the image reconstruction means, and an image is generated by the selected means. Nuclear medicine imaging device. Spatial position storage means for storing the spatial position of the positron estimated by the estimation means and the detection time at which the positron was detected by the detector in association with each other;
As a condition designation of an image to be generated, designation accepting means for accepting at least one of a spatial position and a detection time;
The spatial position storage means is referred to using the condition designation received by the designation reception means, the spatial position necessary for image generation is acquired, and the acquired blur position is stored by the blur width storage means. The nuclear medicine imaging apparatus according to claim 1, further comprising: designated image generation means for generating an image by allocating pixel values to pixels corresponding to the blurred width. The display control means receives the display direction of the image from the operator, the display direction of the image received and wherein the to be displayed on the display unit, a nuclear medicine imaging apparatus according to claim 1 or 2. Wherein the display control unit, one screen axial image in, and wherein the displaying the coronal image and a sagittal image on the display unit, a nuclear medicine imaging apparatus according to any one of claims 1-3. The image generation means sequentially generates the image in real time,
The display control means may for displaying the image successively generated on the display unit in real time, nuclear medicine imaging apparatus according to any one of claims 1-4.

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