JP2016128840A - Nuclear medicine diagnosis system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclear medicine diagnosis system capable of determining existence/absence and level of a cause of image quality deterioration in projection data collected by means of PET imaging in a short time.SOLUTION: The nuclear medicine diagnosis system includes: a ring-shaped detector; a simple image data generation section; and a display unit. The ring-shaped detector simultaneously measures gamma rays which are emitted from a subject given with a radioisotope. The simple image data generation section generates a simple image data in a real time without carrying out any reconfiguration processing on the basis of a part of information corresponding to a direction specified by an operator in the simultaneously measured data. The display unit displays the generated simple image data at real time.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a nuclear medicine diagnostic apparatus that images radioisotope distribution in a site to be examined by detecting γ-rays emitted from a subject to which a drug labeled with a radioisotope is administered. .

  Medical image diagnosis using an X-ray diagnostic apparatus, an MRI apparatus, an X-ray CT apparatus, a nuclear medicine imaging apparatus, etc. has made rapid progress along with the development of computer technology and has become indispensable in today's medical care. Yes.

  The above-described X-ray diagnostic apparatus and X-ray CT apparatus are intended for so-called morphological diagnosis in which diagnosis is performed by drawing the outline of an organ, tumor, or the like. On the other hand, the above-mentioned nuclear medicine imaging apparatus measures gamma rays emitted from a radioactive isotope or a labeled compound labeled with a radioisotope selectively taken into a living tissue from outside the body, and measures the measured gamma rays. The function distribution for the subject can be diagnosed by imaging the dose distribution.

  As nuclear medicine imaging devices, gamma cameras, single photon emission CT devices (SPECT (Single Photon Emission Computed Tomography) devices), positron emission CT devices (PET (Positron Emission Computed Tomography) devices), etc. are used in clinical settings. .

  The gamma camera is a flat detector in which γ rays emitted from the inside of a subject to which a drug labeled with a radioisotope (hereinafter referred to as a radioisotope) is administered are arranged facing the subject. Measure by. Thus, the gamma camera is a device that generates the radioisotope distribution projected on the flat detector as two-dimensional image data (gamma image data). The gamma camera specifies the incident direction of γ rays by a collimator attached to the front surface of the flat detector.

  The SPECT apparatus moves a flat detector similar to a gamma camera around a subject to which a radioisotope is administered. Alternatively, the SPECT apparatus arranges a plurality of flat detectors similar to a gamma camera around a subject to which a radioisotope is administered. As a result, the SPECT apparatus generates image data (SPECT image data) by performing reconstruction processing similar to that of the X-ray CT apparatus on the γ-ray information detected from a plurality of directions with respect to the subject.

  On the other hand, a PET apparatus receives a pair of γ rays emitted from a subject to which a radioisotope labeled with a nuclide emitting positrons (positrons) is emitted when the positrons combine with electrons and disappear. Detection is performed by a ring-shaped detector arranged around the specimen. The PET apparatus generates image data (PET image data) by reconstructing a pair of γ-ray information detected by a detector.

  In recent years, a so-called X-ray CT combined positron CT apparatus (hereinafter referred to as a PET-CT apparatus) in which an X-ray CT apparatus and a PET apparatus are integrated has also been developed. According to this PET-CT apparatus, it is possible to efficiently perform morphological diagnosis and functional diagnosis on the same subject. Furthermore, according to this PET-CT apparatus, attenuation correction data generated based on pixel values of X-ray CT image data when reconstructing projection data collected by PET imaging to generate PET image data By correcting the projection data using (attenuation map), good quality PET image data can be obtained.

JP 2009-47602 A

  In the collection of PET image data, projection data such as sinograms is generated based on information on the detection direction and detection position of γ rays emitted from the radioisotope administered to the subject, and the projection data is reconstructed. Thus, the PET image data is generated. Then, by displaying the obtained PET image data on a display unit or the like, the presence / absence in the projection data of the influence of body movement or the like that deteriorates the image quality of the PET image data (hereinafter referred to as an image quality deterioration factor) and the presence thereof. When there is an unacceptable image quality degradation factor that determines the degree, projection data has been collected again.

  However, in such a conventional method, it takes a long time to reconstruct the projection data. Therefore, when the projection data is collected again, it is necessary to administer the radioisotope to the subject again. In many cases, the subject has already left the laboratory when the presence of the image quality degradation factor is confirmed by observation of the PET image data. In such a case, the subject is requested to return to the hospital. There was a need. And the request | requirement of such re-administration of a radioisotope with respect to a subject and a return visit had the problem that not only the test | inspection efficiency will be reduced significantly but the burden of the subject increased.

  The problem to be solved by the present invention is to provide a nuclear medicine diagnostic apparatus capable of determining in a short time whether or not there is an image quality deterioration factor in projection data collected by PET imaging.

  The nuclear medicine diagnosis apparatus according to the embodiment includes a ring-shaped detector, a simple image data generation unit, and a display unit. The ring-shaped detector simultaneously measures gamma rays emitted from the subject administered with the radioisotope. The simple image data generation unit generates simple image data in real time without performing reconstruction processing based on a part of the information corresponding to the direction specified by the operator in the simultaneously measured data. To do. The display unit displays the generated simple image data in real time.

1 is a block diagram showing an overall configuration of a medical image diagnostic apparatus according to an embodiment. The block diagram which shows the specific structure of the X-ray CT imaging part with which the medical image diagnostic apparatus of this embodiment is provided. The block diagram which shows the specific structure of the PET imaging part with which the medical image diagnostic apparatus of this embodiment is provided. The figure which shows the specific structure of the detector module provided in the PET imaging part of this embodiment. The figure (1) which shows the detection direction and detection position of a gamma ray in simple PET imaging mode of this embodiment. FIG. 6B is a diagram (2) showing the detection direction and the detection position of γ rays in the simple PET imaging mode of the present embodiment. The figure for demonstrating the image data for evaluation produced | generated in the image data synthetic | combination part of this embodiment. The figure for demonstrating the X-ray CT frame part and PET frame part which are moved by the moving mechanism part of this embodiment. The flowchart which shows the production | generation procedure of PET image data in this embodiment. The block diagram which shows the whole structure of the medical image diagnostic apparatus in the modification of this embodiment. FIG. 6A is a diagram (1) for explaining a specific example of an image quality deterioration factor determined by image data for evaluation according to the present embodiment and its modification. FIG. 6B is a diagram (2) for explaining a specific example of the image quality deterioration factor determined by the evaluation image data of the present embodiment and its modification. The figure for demonstrating the modification of simple PET image data generation processing (1). FIG. 2 is a diagram (2) for explaining a modification of the simplified PET image data generation process.

  Embodiments of a medical image diagnostic apparatus will be described below with reference to the drawings.

  The medical image diagnostic apparatus according to the present embodiment described below first uses scanogram imaging mode projection data collected by X-ray imaging of a subject with an X-ray tube and an X-ray detector fixed at predetermined positions. Generate a scanogram based on it. Next, the medical image diagnostic apparatus generates projection data in the PET imaging mode based on the detection direction and detection position of γ rays emitted from the body of the subject to which the radioisotope is administered. Here, the medical image diagnostic apparatus generates the projection data in the PET imaging mode, and the X-ray imaging direction of the X-ray imaging extracted from the γ-ray detection result (specifically, the X-ray irradiation direction). Simple PET image data is generated based on the detected position of γ-rays detected from a direction substantially equal to the center direction). Then, the medical image diagnostic apparatus generates evaluation image data by superimposing the obtained simple PET image data on the above-described scanogram. Then, by observing the evaluation image data in which the observation point corresponding to the detected position of the γ-ray is displayed in real time on the display unit, the projection data in the PET imaging mode includes the influence of body movement or drug leakage as a factor of image quality deterioration. If it is confirmed that the medical image diagnosis device has not been detected, the medical image diagnostic apparatus reconstructs the projection data (projection data in the PET imaging mode) to generate diagnostic PET image data.

  In the following embodiment, a medical image that enables generation of scanogram as morphological image data based on projection data in scanogram imaging mode and generation of PET image data as functional image data based on projection data in PET imaging mode. A diagnostic device will be described. However, in the following embodiments, three-dimensional image data or a predetermined cross section generated based on projection data in the X-ray CT imaging mode obtained by rotating the X-ray tube and the X-ray detector around the subject at high speed. MPR image data or the like (for example, a coronal section) may be used as morphological image data.

(Device configuration)
The configuration of the medical image diagnostic apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the medical image diagnostic apparatus in the present embodiment, and FIGS. 2 and 3 are an X-ray CT imaging unit and a PET imaging unit provided in the medical image diagnostic apparatus of the present embodiment. It is a block diagram which shows the concrete structure of these.

  A medical image diagnostic apparatus 100 of this embodiment shown in FIG. 1 includes an X-ray CT imaging unit 1, a PET imaging unit 2, a morphological image data generation unit 3, a functional image data generation unit 4, and an image data synthesis unit 5. And a display unit 6. The X-ray CT imaging unit 1 collects projection data in the X-ray CT imaging mode from the subject 150. The X-ray CT imaging unit 1 according to the present embodiment uses the projection data generation unit 12 to detect X-rays emitted from the X-ray generation unit 11 of the rotating gantry fixed at a predetermined position and transmitted through the subject 150. Projection data for scanogram imaging mode is generated. The PET imaging unit 2 detects a pair of γ rays radiated from the body of the subject 150 to which the radioisotope is administered by the detector module 21 arranged around the subject 150, and the detection direction and Projection data in the PET imaging mode is generated based on the detection position. The morphological image data generation unit 3 generates a scanogram as morphological image data using the projection data in the scanogram imaging mode generated by the X-ray CT imaging unit 1. The functional image data generation unit 4 is simplified based on the detection position of γ rays detected from a direction substantially equal to the X-ray irradiation direction (specifically, the central direction of the X-ray irradiation direction) in the X-ray CT imaging unit 1. PET image data is generated. Furthermore, the functional image data generation unit 4 generates PET image data as functional image data based on the projection data in the PET imaging mode generated by the PET imaging unit 2. The image data synthesizing unit 5 generates evaluation image data for the purpose of evaluating the image quality deterioration factor of the projection data in the PET imaging mode by superimposing the simple PET image data on the scanogram. The display unit 6 displays the evaluation image data generated by the image data synthesis unit 5 and the PET image data generated by the functional image data generation unit 4.

  Further, the medical image diagnostic apparatus 100 includes a top board 7, a movement mechanism unit 8, an input unit 9, and a system control unit 10. The top plate 7 is installed on a bed (not shown), and the subject 150 is placed thereon. The moving mechanism unit 8 moves the X-ray CT gantry unit having the X-ray CT imaging unit 1 and the PET gantry unit (not shown) having the PET imaging unit 2 in the body axis direction (z direction in FIG. 1). Thus, the examination target part of the subject 150 is arranged in each imaging field. The input unit 9 inputs subject information, scanogram imaging mode, simple PET imaging mode and selection of PET imaging mode, input of setting of imaging conditions in these imaging modes, scanogram, simple PET image data, and PET image data. The generation conditions and display conditions are input and various command signals are input. The system control unit 10 comprehensively controls the above-described units included in the medical image diagnostic apparatus 100.

  Next, the configuration and function of each of the units included in the medical image diagnostic apparatus 100 will be described in more detail.

  The X-ray CT imaging unit 1 illustrated in FIG. 1 includes an X-ray generation unit 11, a projection data generation unit 12, a rotating gantry unit 13, and a fixed gantry unit 14 as illustrated in FIG. The X-ray generation unit 11 includes an X-ray tube 111, a high voltage generator 112, an X-ray restrictor 113, and a slip ring 114. The X-ray tube 111 irradiates the subject 150 with X-rays. The high voltage generator 112 generates a high voltage to be applied between the anode and the cathode of the X-ray tube 111. The X-ray diaphragm 113 sets an irradiation range of X-rays emitted from the X-ray tube 111. The slip ring 114 supplies a predetermined power to the rotating gantry 13.

  The X-ray tube 111 is a vacuum tube that generates X-rays, and emits X-rays by colliding electrons accelerated by a high voltage supplied from the high-voltage generator 112 with a tungsten target. On the other hand, the X-ray restrictor 113 is provided between the X-ray tube 111 and the subject 150, and has a function of narrowing the X-rays emitted from the X-ray tube 111 to a predetermined imaging region and the X-ray for the subject 150. And a function of setting the irradiation intensity distribution. For example, the X-ray restrictor 113 shapes the X-ray beam emitted from the X-ray tube 111 into a cone beam-shaped or fan-beam-shaped X-ray beam corresponding to the imaging region.

  Next, the projection data generation unit 12 includes an X-ray detector 121, a data collection unit 122, and a data transmission circuit 123. The X-ray detector 121 detects X-rays that have passed through the subject 150. The data acquisition unit 122 is a DAS (Data Acquisition System) unit, and performs current / voltage conversion and A / D conversion on the detection signals of a plurality of channels output from the X-ray detector 121. Hereinafter, the data collection unit 122 is referred to as a DAS unit 122. The data transmission circuit 123 performs parallel / serial conversion, electrical / optical / electrical conversion, and serial / parallel conversion on the output signal of the DAS unit 122.

  The X-ray detector 121 of the projection data generation unit 12 includes, for example, a plurality of X-ray detection elements (not shown) that are two-dimensionally arranged. Each of the X-ray detection elements is a scintillator that converts X-rays into light. And a photodiode that converts light into an electrical signal. These X-ray detection elements are attached to the rotating gantry 13 along an arc centered on the focal point of the X-ray tube 111.

  On the other hand, the DAS unit 122 performs current / voltage conversion and A / D conversion on the detection signal of the X-ray detector 121. The data transmission circuit 123 includes a parallel / serial converter, an electrical / optical / electrical converter, and a serial / parallel converter (not shown), and the detection signal output from the DAS unit 122 is sent to the rotary mount unit 13. It is converted into projection data of one channel in time series by the attached parallel / serial converter and supplied to the serial / parallel converter attached to the fixed base 14 by optical communication using the electrical / optical / electrical converter. Is done.

  Next, the projection data for one channel is converted into projection data for a plurality of channels by a serial / parallel converter and stored in the projection data storage unit 31 of the morphological image data generation unit 3 as projection data in the scanogram imaging mode.

  Note that the above-described data transmission method allows the signal transmission between the projection data generation unit 12 provided in the rotary gantry 13 and the morphological image data generation unit 3 provided outside the fixed gantry 14. For example, a device such as the slip ring described above may be used.

  In this case, the X-ray tube 111 and the X-ray diaphragm 113 of the X-ray generation unit 11 and the X-ray detector 121 and the DAS unit 122 of the projection data generation unit 12 face each other with the subject 150 interposed therebetween. Mounted on the rotary mount 13. Then, in the scanogram imaging mode, as shown in FIG. 2, the rotating gantry is arranged such that the X-ray tube 111 and the X-ray diaphragm 113 are arranged above the subject 150 and the X-ray detector 121 is arranged below. The part 13 is fixed at a predetermined position.

  Next, the PET imaging unit 2 in FIG. 1 includes a detector module 21 and a detection data processing unit 22 as shown in FIG. The detector module 21 is arranged concentrically around the subject 150 and detects a pair of gamma rays emitted from the body of the subject 150 to which the radioisotope is administered. The detection data processing unit 22 discriminates between detected γ-rays and noise, measures the detection time and detection position of γ-rays, and measures the detection direction based on the detection positions of a pair of γ-rays that are simultaneously measured, Further, projection data in the PET imaging mode is generated by accumulating the count value of γ rays in a predetermined period in correspondence with the γ ray detection position and the γ ray detection direction. Note that the line segment connecting the detection positions of a pair of γ-rays measured simultaneously is called a simultaneous measurement line (LOR: Line Of Response). A source of a pair of γ rays emitted from the body of the subject 150 is located on the LOR.

  A plurality of detector modules 21 (21-1 to 21-Nm) are arranged concentrically around the subject 150 placed in the imaging field of the PET imaging unit 2 while being placed on the top board 7. Is done. The γ rays emitted from the subject 150 are once converted into visible light by these detector modules 21 and then converted into an electrical signal (detection signal).

  FIG. 4 is a diagram illustrating a specific configuration of the detector module provided in the PET imaging unit of the present embodiment. As shown in FIG. 4, each of the detector modules 21-1 to 21 -Nm has a strip-shaped scintillator 211, a photomultiplier tube 212, and a light guide 213. The scintillator 211 detects γ rays emitted from the subject 150 and converts them to visible light. The photomultiplier tube 212 converts visible light converted by the scintillator 211 into an electric signal and amplifies the weak electric signal converted. The light guide 213 transmits visible light output from the scintillator 211 to the photomultiplier tube 212.

The scintillator 211 is made of a material such as bismuth germanide (BGO: (Bi ₄ Ge ₃ O ₁₂ )), thallium activated sodium iodide (NaI (Tl)), barium fluoride (BaF ₂ ), or the like. In particular, bismuth germanide having a high γ-ray photoelectric absorption per unit volume and barium fluoride having a fast response speed are suitable for the detector module 21 of the PET imaging unit 2.

The photomultiplier tube 212, for example, amplifies hundreds of photons into 10 ⁷ to 10 ¹⁰ electrons, collects the electrons at an anode as an output stage, and converts them into an electrical signal. Not equipped with photocathode and electron multiplier. For the photocathode, a multi-alkali material whose wavelength characteristic is substantially equal to the emission wavelength of the scintillator 211 or a bialkali material activated with oxygen or cesium is used, and the number of generated photoelectrons with respect to the number of incident photons is usually 20% to 30%. It is. On the other hand, the electron multiplier is composed of multi-stage electrodes arranged along an electron propagation path and an anode for collecting amplified electrons based on the secondary electron emission phenomenon. The tube voltage for amplification factor per stage in the case of 200V to 300V is about 5-fold, 10-stage approximately electrode is provided in order to obtain a ¹⁰⁷ amplification factor of the above.

  The light guide 213 is for optically coupling the scintillator 211 and the photomultiplier tube 212, and is light transmissive in order to efficiently transmit visible light output from the scintillator 211 to the photomultiplier tube 212. Excellent plastic material is used.

  Returning to FIG. 3, the detection data processing unit 22 of the PET imaging unit 2 includes Nm-channel data processing units 221-1 to 221-Nm connected to each of the detector modules 21-1 to 21-Nm. It has. The detection data processing unit 22 includes a detection direction measurement unit 222 that measures the detection direction of γ rays based on the detection position information of γ rays output from the data processing units 221-1 to 221-Nm. Further, the detection data processing unit 22 generates the projection data in the PET imaging mode by sequentially accumulating the count value of the detection signal in a predetermined period corresponding to the γ-ray detection position and the γ-ray detection direction. 223.

  Here, it is assumed that a pair of gamma rays emitted from the radioisotope S administered to the subject 150 is detected by the detector modules 21-a and 21-b, and the detector module 21- Only the data processing units 221-a and 221-b connected to a and 21-b are shown.

  Each of the data processing units 221-a and 221-b of the detection data processing unit 22 includes a signal synthesis unit 231, a signal discrimination unit 232, a waveform shaping unit 233, a detection time measurement unit 234, and a detection position measurement unit 235. It has. The signal combining unit 231 adds and combines the detection signals of a plurality of channels supplied from the photomultiplier tube 212 of the detector module 21-a or 21-b. The signal discriminating unit 232 discriminates the detection signal and noise caused by the γ-ray based on each peak value using the detection signal synthesized by the signal synthesis unit 231. The waveform shaping unit 233 shapes the combined detection signal output from the signal synthesis unit 231 into a rectangular wave. The detection time measuring unit 234 measures the detection time of the γ-ray corresponding to the detection signal discriminated by the signal discriminating unit 232 based on the front edge of the rectangular wave supplied from the waveform shaping unit 233. The detection position measurement unit 235 detects a plurality of channels supplied from the photomultiplier tube 212 of the detector module 21-a or 21-b with the detection position of the γ-ray corresponding to the detection signal discriminated by the signal discrimination unit 232. Measure based on the signal. For example, the detection position measurement unit 235 specifies the scintillator 211 that has emitted a plurality of photons derived from one γ-ray by performing center-of-gravity calculation using Anger logic, and the detected scintillator 211 The position is set as a γ-ray detection position. The specific configuration and function of each unit constituting the data processing unit 221 are described in Japanese Patent Application Laid-Open No. 2007-107995 and the like, and thus detailed description thereof is omitted.

  Next, the detection direction measurement unit 222 of the detection data processing unit 22 measures the detection time and detection position of γ rays supplied from the detection time measurement unit 234 provided in each of the data processing units 221-1 to 221-Nm. Based on the information on the detection position of the γ rays supplied from the unit 235, the detection direction of the γ rays emitted from the body of the subject 150 is measured. For example, the detection direction measuring unit 222 sets two detection positions where the difference in detection time is a predetermined time width as positions where a pair of γ rays emitted from the body of the subject 150 are detected substantially simultaneously. Then, for example, the detection direction measuring unit 222 measures a line segment connecting these two detection positions as LOR, and measures the LOR direction as the γ-ray detection direction.

  On the other hand, the projection data generation unit 223 generates PET imaging mode projection data based on the detection result of detecting γ rays emitted from the subject 150. The projection data generation unit 223 includes a storage circuit (not shown) having a cumulative calculation function, and stores the count value of the detection signal supplied from the detection direction measurement unit 222 in association with the above-described detection position and detection direction of the γ-ray. Save to circuit. For example, each time the detection of the γ rays by the detector module 21-a and the detector module 21-b is performed in a predetermined period, the count value of the detection signal is stored in the memory circuit corresponding to the detection position and the detection direction. Cumulative addition is performed at the address.

  Further, the detection data processing unit 22 detects the detection position of the γ-ray even when a pair of γ-rays is detected in another detector module 21 different from the detector module 21-a and the detector module 21-b. The detection direction is measured by the same method as described above, and the count value of the detection signal is cumulatively added at the address of the storage circuit corresponding to the detection position and detection direction of the γ-ray. That is, the count value of γ rays sequentially detected within a predetermined period is cumulatively added at the address of the storage circuit corresponding to the detection position and detection direction, thereby generating projection data in the PET imaging mode.

  Next, the morphological image data generation unit 3 illustrated in FIG. 1 includes a projection data storage unit 31, a scanogram generation unit 32, and a scanogram storage unit 33. Scanogram imaging collected by X-ray imaging performed by sequentially sliding and moving an X-ray CT gantry described later in the body axis direction (z direction) of the subject 150 with the rotating gantry 13 fixed at a predetermined position. The projection data of the mode is stored in the projection data storage unit 31 after the identification information of the imaging mode, the imaging position information (that is, the position information of the X-ray CT gantry), and the like are added as supplementary information.

  The scanogram generation unit 32 synthesizes the scanogram shooting mode projection data read from the projection data storage unit 31 based on the shooting mode identification information based on the shooting position information which is supplementary information. Thereby, the scanogram generator 32 generates a wide range of scanograms in the body axis direction. The obtained scanogram is temporarily stored in the scanogram storage unit 33. The scanogram generated at this time is similar to the fluoroscopic image data obtained by a normal X-ray diagnostic apparatus.

  On the other hand, the functional image data generation unit 4 includes a simple PET image data generation unit 41, a projection data storage unit 42, and a PET image data generation unit 43.

  The simple PET image data generation unit 41 generates simple PET image data based on information obtained by projecting the position of the generation source of γ rays emitted from the subject 150 to which the radioisotope is administered in a predetermined direction with respect to a predetermined projection plane. Generate. In the present embodiment, the shooting direction of the morphological image data is a predetermined direction, and the shooting cross section of the morphological image data is a predetermined projection plane. Then, the simplified PET image data generation unit 41 according to the present embodiment detects detected position information from the direction corresponding to the imaging direction of the morphological image data in the detected position information of γ rays emitted from the subject 150. Simple PET image data is generated based on the above. In other words, in the present embodiment, the simplified PET image data generation unit 41 detects from the direction corresponding to the direction perpendicular to the imaging section of the morphological image data in the detection position information of the γ rays emitted from the subject 150. Simple PET image data is generated based on the detected position information. Note that the imaging direction of the morphological image data is the center direction of the X-ray beam emitted from the X-ray generator 11 in a cone beam shape or a fan beam shape at the time of scanogram imaging. Hereinafter, the imaging direction of the morphological image data may be described as the center direction of the X-ray irradiation direction.

  The simple PET image data generation unit 41 generates simple PET image data based on the detected position information of γ rays detected in the process of collecting projection data in the PET imaging mode. In the present embodiment, the simplified PET image data generation unit 41 generates simplified PET image data based on the detected position information of γ rays detected from a predetermined direction in the process of collecting projection data in the PET imaging mode.

  The simplified PET image data generation unit 41 sequentially arranges measurement points whose luminance decreases with the passage of time from the detection time at the address of the data sheet corresponding to the position of the γ-ray generation source, thereby simplifying the PET image data. Is generated. The simplified PET image data generation unit 41 according to the present embodiment has a luminance as the time elapses from the detection time at the address of the data sheet corresponding to the detection position of the γ-ray detected from the imaging direction of the morphological image data which is a predetermined direction. Simplified PET image data is generated by sequentially arranging measurement points at which the attenuation decreases.

  For example, the simplified PET image data generation unit 41 includes a distribution data formation unit, an elapsed time measurement unit, and a lookup table (not shown), and the detection direction of the γ rays measured by the detection direction measurement unit 222 of the detection data processing unit 22 When the X-ray irradiation direction in the scanogram imaging mode is substantially equal to the center direction (for example, the y direction in FIG. 2), measurement points having a predetermined luminance are sequentially arranged at the address of the data sheet corresponding to the detected position of the γ-ray. To do. Thereby, the simple PET image data generation unit 41 generates simple PET image data in which the distribution state of the γ-ray generation source is projected on the projection plane orthogonal to the center direction of the X-ray irradiation direction described above.

  That is, when the detector module 21 of the PET imaging unit 2 detects γ-rays whose detection direction is substantially the same direction (y direction) as the center direction of the X-ray irradiation direction, the elapsed time measurement unit described above detects The elapsed time from the detection time of the γ ray measured by the detection time measuring unit 234 of the data processing unit 22 to the observation time is measured. Here, in the above-described lookup table, correspondence data between the elapsed time and the luminance value at the measurement point is stored in advance in units of imaging conditions in the PET imaging mode including administration drug information. The elapsed time measurement unit extracts a luminance value corresponding to the measurement result of the elapsed time from the lookup table.

  The distribution data forming unit arranges a plurality of measurement points having luminance values that change with time at the address of the data sheet corresponding to the detection position of the γ-ray, so that the luminance reaches the maximum value at the detection time. Simple PET image data composed of a plurality of measurement points that decrease with the passage of time is generated.

  5A and 5B are diagrams illustrating the detection direction and the detection position of γ rays in the simple PET imaging mode of the present embodiment. FIG. 5A shows the center direction of the X-ray irradiation direction in the scanogram imaging mode. FIG. 5B shows detection positions a1 to aN and b1 to bN when γ rays emitted from the body of the subject 150 are detected in a direction substantially equal to the central direction of the X-ray irradiation direction. However, in order to simplify the description, the center direction of the X-ray irradiation direction in FIG. 5A is the y direction. In FIG. 5B, only the γ-ray detection position in one cross section perpendicular to the body axis direction is described, and the description of the γ-ray detection positions in other cross sections perpendicular to the body axis direction is omitted. In the present embodiment, γ-ray detection positions in other multiple cross sections perpendicular to the body axis direction are also detected by the same method.

  In the example shown in FIG. 5A, the scanogram used as the morphological image data in the present embodiment is image data obtained by projecting the tissue morphology of the subject 150 in the y direction with respect to the zx plane. Therefore, as shown in FIG. 5B, since the LOR connecting the detection position a1 and the detection position b1 is substantially equal to the y direction, the position of the source S1 existing at any position on the LOR is represented by the zx plane. The positions projected in the y-direction are the z-coordinate and x-coordinate of the generation source S1, the z-coordinate and x-coordinate of the detection position a1, and the z-coordinate and x-coordinate of the detection position b1.

  5B is the z-coordinate and x-coordinate of the detection position a2 and the detection position b2, respectively, and the position of the generation source S3 shown in FIG. 5B. Are projected in the y direction with respect to the zx plane, and become the z coordinate and the x coordinate of the detection position a3 and the detection position b3, respectively. 5B is the z-coordinate and x-coordinate of the detection position a4 and the detection position b4, respectively, and the position of the generation source SN shown in FIG. 5B. Are projected in the y direction with respect to the zx plane, and become the z coordinate and the x coordinate of the detection position aN and the detection position bN, respectively.

  That is, if the LOR direction is a direction that substantially coincides with the direction perpendicular to the imaging section (imaging direction), the position where the position of the γ-ray generation source is projected onto the imaging section is the position of the source in the imaging direction. Can be obtained from the two pieces of detected position information used for determining the direction of the LOR. Note that the shooting direction and shooting section of the morphological image data can be arbitrarily changed by the operator as well as the y direction and zx section. For example, the simplified PET image data generation unit 41 converts the information of the detection position measured by the detection position measurement unit 235 into position information in an orthogonal coordinate system determined by the set imaging direction and imaging section, thereby obtaining γ The position where the position of the line generation source is projected onto the imaging section can be obtained. As described above, the simple PET image data generation unit 41 generates simple PET image data in which the position of the γ-ray generation source in the imaging section is depicted without performing reconstruction processing.

  Returning to FIG. 1, in the projection data storage unit 42 of the functional image data generation unit 4, the projection data generation unit 223 of the detection data processing unit 22 provided in the PET imaging unit 2 has a count value of a plurality of detection signals. Projection data in the PET imaging mode generated by accumulatively adding is temporarily stored. Then, the PET image data generation unit 43 generates PET image data using the projection data in the PET imaging mode. The PET image data generation unit 43 reconstructs the PET imaging mode projection data read from the projection data storage unit 42 to generate diagnostic PET image data.

  Next, the image data synthesizing unit 5 includes an addition synthesis processing unit (not shown), a wide range of scanograms in the body axis direction stored in the scanogram storage unit 33 of the morphological image data generation unit 3, and a functional image data generation unit A function of generating evaluation image data for the purpose of evaluating an image quality deterioration factor in projection data in the PET imaging mode by synthesizing simple PET image data generated in substantially real time in the 4 simple PET image data generation unit 41 have. In this case, the combination of the scanogram and the simplified PET image data is performed by imaging position information in the scanogram imaging mode (that is, position information of the X-ray CT frame) and imaging position information in the simple PET imaging mode (that is, the PET frame). Position information).

  FIG. 6 is a diagram for explaining the evaluation image data generated by the image data composition unit of the present embodiment. The image data 1000 shown in FIG. 6 is obtained by the scanogram generation unit 32 of the morphological image data generation unit 3 based on the projection data in the scanogram imaging mode collected by X-ray irradiation centered on the y direction indicated by the arrow in FIG. 5A. An extensive scanogram of the generated subject 150 is shown. Also, the image data 2000 shown in FIG. 6 is a simple PET image data generation unit 41 of the functional image data generation unit 4 based on the detection position of γ rays detected in the same direction as the center direction of the X-ray irradiation direction. Shows the simple PET image data generated. Further, the image data 3000 shown in FIG. 6 indicates the evaluation image data generated by the image data synthesis unit 5 by synthesizing the above-described simple PET image data and the scanogram, respectively.

  In the above-described evaluation image data shown on the display unit 6, for example, when each of the measurement points constituting the simple PET image data is distributed inside the examination target organ indicated by the broken line of the scanogram, It is determined that the influence of body movement when collecting projection data in the PET imaging mode is in an allowable range.

  Next, the display unit 6 in FIG. 1 includes a display data generation unit, a conversion processing unit, and a monitor (not shown). The display data generation unit converts the evaluation image data generated by the image data synthesis unit 5 and the PET image data generated by the PET image data generation unit 43 of the functional image data generation unit 4 into a predetermined display format for display. The data is generated, and the conversion processing unit performs conversion processing such as D / A conversion and TV format conversion on the display data generated by the display data generation unit and displays the data on the monitor. In the present embodiment, the display unit 6 displays, in real time, simple PET image data having a plurality of measurement points whose luminance decreases with time. Specifically, in the present embodiment, the display unit 6 displays the evaluation image data in real time.

  On the other hand, the moving mechanism unit 8 includes a gantry rotating unit, a gantry moving unit, and a moving mechanism control unit (not shown). The gantry rotating unit rotates the rotating gantry unit 13 of the X-ray CT imaging unit 1 on which the X-ray tube 111 and the X-ray detector 121 are mounted according to the gantry rotation control signal supplied from the moving mechanism control unit, and scanogram image data. It arrange | positions in the position suitable for the production | generation of.

  The gantry moving unit is a guide in which an X-ray CT gantry unit having an X-ray CT imaging unit 1 and a PET gantry unit having a PET imaging unit 2 are provided on a floor surface in accordance with a gantry movement control signal supplied from a moving mechanism control unit. The body 150 is moved in the body axis direction along the rail.

  The movement mechanism control unit supplies the gantry rotation control signal generated based on the imaging conditions of the scanogram imaging mode and the PET imaging mode supplied from the input unit 9 via the system control unit 10 to the gantry rotation unit, and controls the gantry movement control. The signal is supplied to the gantry moving part.

  FIG. 7 is a diagram for explaining an X-ray CT gantry and a PET gantry that are moved by the movement mechanism of the present embodiment. As shown in FIG. 7, a bed 161 having a top plate 7 on which the subject 150 is placed is installed on the floor surface 160 of the examination room, and a guide rail 162 is arranged in the body axis direction (z direction) of the top plate 7. It is installed. Then, the moving mechanism unit 8 includes an X-ray CT imaging unit such that the examination target region (examination target organ) of the subject 150 is arranged in the imaging field of the X-ray CT imaging unit 1 and the imaging field of the PET imaging unit 2. The X-ray CT gantry 163 having 1 and the PET gantry 164 having the PET imaging unit 2 are moved along the guide rail 162 in the body axis direction. Thereby, the photographing position in the scanogram photographing mode and the PET photographing mode is set.

  Next, the input unit 9 of FIG. 1 includes an input device such as a keyboard, a selection switch, a mouse, and a display panel, and forms an interactive interface when used in combination with the display unit 6. Then, input of object information, scanogram imaging mode, simple PET imaging mode and selection of PET imaging mode, setting of imaging conditions in these imaging modes, scanogram, simple PET image data, generation conditions of PET image data, and display conditions Setting, input of radioisotope information (administered drug information) to be administered to the subject 150, various X-ray CT imaging start instruction signal, PET imaging start instruction signal, and PET image data generation instruction signal An instruction signal is input using the above-described display panel or input device. In the present embodiment, the input unit 9 inputs an instruction signal (PET image data generation instruction signal) for generating PET image data based on the evaluation result of the simplified PET image data. Specifically, in the present embodiment, the input unit 9 inputs a PET image data generation instruction signal based on the evaluation result of the evaluation image data. More specifically, the input unit 9 receives a PET image data generation instruction signal from an operator who has observed the evaluation image data, and inputs the received PET image data generation instruction signal to the system control unit 10.

  On the other hand, the system control unit 10 includes a CPU and a storage circuit (not shown), and the input information, selection information, and setting information supplied from the input unit 9 are stored in the storage circuit. Then, the CPU comprehensively controls each unit provided in the medical image diagnostic apparatus 100 based on the information read from the storage circuit, and scanogram, simple PET image data, evaluation image data, and PET image data. Execute generation. For example, in accordance with the control of the system control unit 10 notified of the PET image data generation instruction signal from the input unit 6, the PET image data generation unit 43 reconstructs the projection data in the PET imaging mode, thereby converting the PET image data. Generate.

(PET image data generation procedure)
Next, a procedure for generating PET image data in this embodiment will be described with reference to the flowchart of FIG. FIG. 8 is a flowchart showing a procedure for generating PET image data in the present embodiment.

Prior to X-ray CT imaging and PET imaging of the subject 150, the operator of the medical image diagnostic apparatus 100 labels the subject 150 with positron emission nuclides such as ¹¹ C, ¹³ N, ¹⁵ O, and ¹⁸ F. The formed radioisotope (RI) is administered (step S1 in FIG. 8). Next, the operator performs initial setting (step S2 in FIG. 8). That is, the operator inputs the subject information at the input unit 9, the input of the administration drug information (that is, the type of radioisotope, the dose V0, the administration time t0, etc.), the imaging conditions in the scanogram imaging mode and the PET imaging mode. , Scanogram, simplified PET image data, evaluation image data, and PET image data generation conditions and display condition settings. These input information and setting information are stored in the storage circuit of the system control unit 10.

  Next, the operator places the subject 150 on the top board 7 and then inputs a gantry movement instruction signal at the input unit 9 so that the subject 150 is placed in the imaging field of the X-ray CT imaging unit 1. The X-ray CT gantry 163 is moved along the guide rail 162 in the body axis direction. When the movement of the X-ray CT gantry 163 is completed, the operator inputs an instruction signal (X-ray CT imaging start instruction signal) for starting X-ray CT imaging for the purpose of generating a scanogram. 9 (step S3 in FIG. 8).

  The system control unit 10 that has received this instruction signal causes the generation of projection data (first projection data) in the scanogram imaging mode (step S4 in FIG. 8). That is, the system control unit 10 controls each unit provided in the X-ray CT imaging unit 1 based on the imaging conditions in the scanogram imaging mode read from its own storage circuit, and the X-ray tube 111 and the X-ray detector 121. X-ray imaging is performed on the subject 150 that sequentially moves in the direction of the body axis while the rotating gantry 13 to which is attached is fixed at a predetermined position. The projection data of the scanogram imaging mode obtained at this time is the projection of the morphological image data generation unit 3 using the identification information of the imaging mode, the imaging position information (that is, the position information of the X-ray CT gantry unit 163) and the like as supplementary information. It is stored in the data storage unit 31.

  On the other hand, the scanogram generation unit 32 of the morphological image data generation unit 3 generates and stores a scanogram (step S5 in FIG. 8). That is, the scanogram generation unit 32 synthesizes the scanogram shooting mode projection data read from the projection data storage unit 31 based on the shooting mode identification information based on the shooting position information that is the accompanying information, and reduces noise or enhances the contour. A wide range of scanograms is generated in the body axis direction by performing a filtering process for the purpose as necessary. The obtained scanogram is stored in the scanogram storage unit 33.

  When the scanogram generation and storage are completed by the above-described procedure, the operator inputs the gantry movement instruction signal again in the input unit 9, and the examination target region of the subject 150 is placed in the imaging field of the PET imaging unit 2. In this manner, the PET gantry 164 is moved in the body axis direction along the guide rail 162. When the movement of the PET gantry unit 164 is completed, the operator inputs a simple PET image data and an instruction signal (PET imaging start instruction signal) for starting PET imaging for the purpose of generating PET image data. Input is performed in the unit 9 (step S6 in FIG. 8).

  Upon receiving this instruction signal, the system control unit 10 controls each unit provided in the PET imaging unit 2 based on the imaging conditions in the PET imaging mode read from its own storage circuit, and starts PET imaging for the subject 150. . Then, the projection data generation unit 223 provided in the data processing unit 221 of the PET imaging unit 2 stores the count value of the detection signal supplied from the detection direction measurement unit 222 in correspondence with the detection position and detection direction of the γ-ray. In addition, the PET imaging mode projection data (second projection data) is generated by sequentially accumulating count values of detection signals detected at the same detection position and detection direction within a predetermined time. The projection data (second projection data) is stored in the projection data storage unit 42 of the functional image data generation unit 4. (Step S7 in FIG. 8).

  On the other hand, the simplified PET image data generation unit 41 of the functional image data generation unit 4 has the same γ-ray detection direction measured by the detection direction measurement unit 222 as the center direction of the X-ray irradiation direction in the scanogram imaging mode. The distribution state of the γ-ray generation source on the projection plane orthogonal to the above-mentioned X-ray irradiation direction by sequentially arranging measurement points whose luminance decreases with time at the address of the data sheet corresponding to the detection position of the γ-ray Is generated (step S8 in FIG. 8).

  Next, the image data synthesizing unit 5 performs substantially real-time in a wide range scanogram in the body axis direction stored in the scanogram storage unit 33 of the morphological image data generation unit 3 and the simplified PET image data generation unit 41 of the functional image data generation unit 4. The image data for evaluation is generated by synthesizing with the simple PET image data generated in the above, and is displayed on the monitor of the display unit 6 (step S9 in FIG. 8).

  On the other hand, the operator of the medical image diagnostic apparatus 100 observing the evaluation image data displayed on the display unit 6, based on the evaluation image data, already collects projection data (second projection) in the PET imaging mode. The presence / absence of an image quality deterioration factor in the data) is determined (step S10 in FIG. 8). If it is determined that there is no image quality deterioration factor (No in step S10 in FIG. 8), a PET image data generation instruction signal is input through the input unit 9, and this instruction signal is received via the system control unit 10. The PET image data generation unit 43 of the functional image data generation unit 4 generates diagnostic PET image data by reconstructing the projection data in the PET imaging mode read from the projection data storage unit 42, and obtained. The PET image data is displayed on the monitor of the display unit 6 (step S11 in FIG. 8). Here, in step S11, the display unit 6 may display PET image data, or may display evaluation image data and PET image data.

  If it is determined that there is an unacceptable image quality degradation factor in the projection data in the PET imaging mode by observing the evaluation image data generated in step 9 (Yes in step S10 in FIG. 8). The operator inputs an instruction signal for collecting the projection data again at the input unit 9. Upon receiving this instruction signal, the system control unit 10 controls each unit of the PET imaging unit 2 and repeats steps S7 to S9 described above, thereby generating new projection data and generating evaluation image data. And display.

  In the above-described procedure, the radioisotope is administered to the subject 150 before the start of X-ray CT imaging, but may be performed when the X-ray CT imaging is completed. Further, when whole body PET imaging of the subject 150 is performed by the step and shoot method, in this embodiment, after step S11, the PET image data generated in step S11 partially overlaps with the examination target region. The PET gantry 164 is moved so that the site to be inspected is arranged in the imaging field of the PET imaging unit 2, and thereafter, the processing after step S <b> 7 is performed.

(Modification)
Next, a modification of the present embodiment will be described with reference to FIG. FIG. 9 is a block diagram illustrating an overall configuration of a medical image diagnostic apparatus according to a modification of the present embodiment.

  In the above-described embodiment, the medical image diagnostic apparatus capable of generating the scanogram as the morphological image data and the PET image data as the functional image data has been described. In this modification, only the above-described PET image data is generated. A medical image diagnostic apparatus that performs the above will be described.

  That is, in the medical image diagnostic apparatus according to this modification, first, the morphological image data of the subject 150 generated by another medical image diagnostic apparatus is stored in the morphological image data storage unit. Next, the medical image diagnostic apparatus of this modification generates projection data in the PET imaging mode based on the detection direction and detection position of γ rays emitted from the body of the subject 150 to which the radioisotope is administered, Simple PET image data is generated based on the detection position of the γ-ray detected from the imaging direction of the morphological image data extracted from the detection result of the γ-ray or the direction substantially equal to the direction perpendicular to the imaging section. Then, the medical image diagnostic apparatus according to the present modification generates evaluation image data by superimposing the obtained simple PET image data on the above-described morphological image data read from the morphological image data storage unit. The medical image diagnostic apparatus according to this modification does not include an unacceptable image quality deterioration factor in the projection data in the PET imaging mode by observing the evaluation image data in which the detection position of the γ-ray is displayed in real time on the display unit. Is confirmed, the projection data is reconstructed to generate diagnostic PET image data.

  In the block diagram of FIG. 9 showing the overall configuration of the medical image diagnostic apparatus according to this modification, units having the same configuration and function as the unit of the medical image diagnostic apparatus 100 shown in FIG. Detailed description is omitted.

  That is, the medical image diagnostic apparatus 200 of this modification shown in FIG. 9 includes a PET imaging unit 2, a morphological image data storage unit 50, a functional image data generation unit 4, an image data synthesis unit 5a, and a display unit 6. It has. The PET imaging unit 2 detects a pair of γ-rays emitted from the body of the subject 150 to which the radioisotope is administered by the detector module 21 arranged around the subject, and based on the detection direction and the detection position. Projection data in the PET imaging mode is generated. In the morphological image data storage unit 50, morphological image data collected by another medical image processing apparatus or the like installed separately is stored in advance. The functional image data generation unit 4 generates simple PET image data based on the detection position of the γ-ray detected from a direction substantially equal to the imaging direction of the morphological image data or the direction perpendicular to the imaging cross section, and further PET imaging PET image data as functional image data is generated based on the projection data in the PET imaging mode generated in the unit 2. The image data synthesis unit 5a generates evaluation image data for the purpose of evaluating the image quality deterioration factor in the projection data in the PET imaging mode by superimposing the simple PET image data on the morphological image data. The display unit 6 displays the evaluation image data generated by the image data synthesis unit 5 a and the PET image data generated by the functional image data generation unit 4.

  Furthermore, the medical image diagnostic apparatus 200 moves the subject 7 by moving the top plate 7 on which the subject 150 is placed and the PET gantry (not shown) having the PET imaging unit 2 in the body axis direction (z direction in FIG. 9). The moving mechanism unit 8a arranges 150 inspection target parts in the imaging field of the PET imaging unit 2. Further, the medical image diagnostic apparatus 200 inputs subject information, selects a simple PET imaging mode and a PET imaging mode, sets imaging conditions in these imaging modes, simple PET image data, evaluation image data, and PET image data. An input unit 9a for setting generation conditions and display conditions, inputting various command signals, and the like, and a system control unit 10a for comprehensively controlling each unit of the medical image diagnostic apparatus 200 are provided.

  The morphological image data storage unit 50 includes, for example, a scanogram generated by an X-ray CT apparatus or an MRI apparatus, MPR (Multi Planar Reconstruction) image data in a coronal section of the subject 150, and further by an X-ray diagnostic apparatus. The generated fluoroscopic image data and the like are stored in advance with the shooting position information as supplementary information.

  On the other hand, the image data synthesizing unit 5a has an addition synthesis processing unit (not shown), and includes a wide range of morphological image data in the body axis direction stored in the morphological image data storage unit 50, and a simplified PET of the functional image data generating unit 4. The image data generation unit 41 has a function of generating evaluation image data for the purpose of evaluating the image quality deterioration factor of the projection data in the PET imaging mode by combining the simple PET image data generated in substantially real time. ing. In this case, the combination of the morphological image data and the simple PET image data is performed based on the photographing position information added to each image data.

  Next, the moving mechanism unit 8a includes a gantry moving unit and a moving mechanism control unit (not shown). The gantry moving unit moves the PET gantry unit having the PET imaging unit 2 in the body axis direction of the subject 150 along the guide rail provided on the floor according to the gantry movement control signal supplied from the moving mechanism control unit. . On the other hand, the movement mechanism control unit supplies the gantry movement control signal generated based on the imaging condition of the PET imaging mode supplied from the input unit 9a via the system control unit 10a to the gantry moving unit.

  The input unit 9 a includes an input device such as a keyboard, a selection switch, and a mouse, and a display panel, and forms an interactive interface when used in combination with the display unit 6. Then, input of subject information, selection of simple PET imaging mode and PET imaging mode, setting of imaging conditions in these imaging modes, setting of generation conditions and display conditions of simple PET image data and PET image data, Input of radioisotope information (administered drug information) to be administered, and input of various instruction signals including a PET imaging start instruction signal and a PET image data generation instruction signal, etc. Done with.

  On the other hand, the system control unit 10a includes a CPU and a storage circuit (not shown), and the input information, selection information, and setting information supplied from the input unit 9a are stored in the storage circuit. Then, the CPU comprehensively controls each unit provided in the medical image diagnostic apparatus 200 based on the information read from the storage circuit, and generates simple PET image data, evaluation image data, and PET image data. Is executed.

  Note that the PET image data generation procedure in this modification is the same as the procedure in steps S6 to S10 shown in FIG.

  Next, a specific example of the image quality deterioration factor determined by the evaluation image data of the above-described embodiment and its modification will be described with reference to FIGS. 10A and 10B. FIG. 10A and FIG. 10B are diagrams for explaining specific examples of image quality deterioration factors determined by the image data for evaluation according to the embodiment and its modifications.

  FIG. 10A shows evaluation image data when a significant image quality deterioration factor due to body movement of the subject 150 occurs in the projection data in the PET imaging mode. In this case, the simple PET image data shows this. A part of the plurality of measurement points is displayed outside the inspection target organ indicated in the morphological image data such as a scanogram. Accordingly, the operator can determine whether or not to re-collect projection data based on the position and number of measurement points indicated in the vicinity of the organ to be examined in the simple PET image data.

  On the other hand, FIG. 10B shows image data for evaluation in the case where the image quality deterioration factor due to the drug leakage at the drug injection portion occurs in the projection data in the PET imaging mode when the radioisotope is administered to the subject 150. Yes, in this case, many measurement points indicating the generation source of γ rays are displayed in the vicinity of the drug injection portion of the subject's upper limb indicated in the morphological image data. When many γ glands resulting from such drug leaks are detected at sites other than the organ to be examined, these become factors of image quality deterioration, making it difficult to obtain good PET image data. In such a case, the operator can determine whether or not to re-collect the projection data based on the position, number, occurrence frequency, and the like of the measurement points indicated in the part other than the examination target organ in the evaluation image data. It becomes possible.

  According to the present embodiment and the modification thereof described above, the projection data is generated based on the detection information of the γ rays emitted from the subject to which the radioisotope is administered, and the projection data is reconstructed. When generating PET image data, it is possible to determine in a short time whether or not there is an image quality deterioration factor in the projection data by using simple PET image data generated based on γ rays detected from a predetermined direction.

  In particular, by combining and displaying morphological image data such as a scanogram collected from the subject and the simplified PET image data, the influence of the body motion of the subject that occurred during the collection of projection data and the administration of radioisotopes It is possible to accurately and easily grasp the effects of drug leakage at the time.

  Further, in the simple PET image data, since the measurement point whose luminance has the maximum value at the detection time and decreases with time is displayed in real time, the temporal deterioration of the image quality caused by the above-described body movement, drug leakage, etc. Changes can be captured in real time.

  That is, according to the present embodiment and its modification, when generating PET image data based on the projection data in the PET imaging mode, simplified PET generated based on the detected position information of γ rays detected from a predetermined direction. By observing the image data in real time, it is possible to determine the presence and extent of various image quality deterioration factors in the projection data. According to the present embodiment and its modification, when there is an unacceptable image quality degradation factor in the projection data, recollection of the projection data for the subject is performed without waiting for the generation of the PET image data. be able to.

  For this reason, it is always possible to generate good PET image data, and diagnostic accuracy is improved. In addition, when image quality degradation factors occur, re-collection of projection data is immediately implemented, so that re-administration of radioisotopes and re-visiting are unnecessary, which not only greatly improves examination efficiency, but The burden can be reduced.

  As mentioned above, although embodiment of this indication and its modification were described, this indication is not limited to the above-mentioned embodiment and its modification, and it can change and implement it further. For example, in the above-described embodiment, medical data that enables generation of scanogram as morphological image data based on projection data in scanogram imaging mode and generation of PET image data as functional image data based on projection data in PET imaging mode The diagnostic imaging device was described. However, in the above-described embodiment, three-dimensional image data generated based on the projection data in the X-ray CT imaging mode obtained by rotating the X-ray tube 111 and the X-ray detector 121 around the subject 150 at high speed. Alternatively, two-dimensional image data in a predetermined section (for example, a coronal section) may be used as the morphological image data. The two-dimensional image data in this case is MPR (Multi Planar Reconstruction) image data or MIP (Maximum Intensity Projection) based on three-dimensional data (volume data) obtained by reconstructing projection data in the X-ray CT imaging mode. It may be image data.

  Further, in the above-described embodiment, the X-ray CT imaging unit 1 and PET are used to move the X-ray CT imaging unit 1 and PET by moving the X-ray CT frame unit 163 and the PET frame unit 164 along the guide rail 162 in the body axis direction. The case where it is arranged in the photographing field of the photographing unit 2 has been described. However, in the above-described embodiment, the inspection target region may be arranged with respect to the above-described imaging field by moving the top plate 7 on which the subject 150 is placed in the body axis direction.

  Further, in the above-described embodiment and its modification, the image quality deterioration factor in the projection data in the PET imaging mode is evaluated using the evaluation image data generated by combining the morphological image data such as the scanogram and the simple PET image data. Although the case has been described, the above-described image quality deterioration factor may be evaluated using simple PET image data. For example, as illustrated in FIG. 10B, in the simplified PET image data in the case where a drug leakage has occurred, a large number of measurement points are depicted at a site away from the site estimated as the examination target organ. Therefore, in the case where it is determined whether or not there is a drug leak as an image quality deterioration factor, the above-described embodiment and its modification may display simple PET image data as evaluation image data. In such a case, the PET image data is generated based on the evaluation result of the simple PET image data.

  Furthermore, in the above-described embodiment and its modification, simplified PET is performed using detection position information in which the LOR direction is the predetermined direction as information obtained by projecting the position of the γ-ray generation source in a predetermined direction with respect to the predetermined projection plane. The case of generating image data has been described. However, the simplified PET image data may be generated by a modification described below. 11 and 12 are diagrams for explaining a modification of the simplified PET image data generation process.

  As described above, the PET apparatus sets projection data for reconstructing PET image data, with two detection positions having a detection time difference having a predetermined time width as positions where a pair of γ rays are detected substantially simultaneously. Is generated. On the other hand, in recent years, a TOF (Time Of Flight) -PET apparatus that estimates the position of the generation source of γ rays on the LOR using a time difference between detection times has been put into practical use. That is, as shown in FIG. 11, the TOF-PET apparatus can estimate the probability distribution D1 in which the γ-ray generation source exists at each position of the LOR using the detection time difference. Therefore, when the medical image diagnostic apparatus 100 or the medical image diagnostic apparatus 200 is a TOF-PET apparatus, the simplified PET image data generation unit 41 estimates the γ-ray estimated based on the detected position information and detection time information of γ-ray. Simple PET image data is generated using the position of the generation source.

  For example, as illustrated in FIG. 11, the simplified PET image data generation unit 41 obtains a probability distribution D2 obtained by projecting the probability distribution D1 in the LOR in the y direction with respect to the zx plane that is the imaging section. Then, for example, the simple PET image data generation unit 41 generates simple PET image data by setting the position at the peak of the probability distribution D2 as the measurement point described above.

  In the modification using the TOF function, any direction of the LOR can be used for simple PET image data. For example, in a modification using the TOF function, simple PET image data can be generated using all LORs that are sequentially specified within a predetermined time. As a result, in the modified example using the TOF function, it is possible to accurately evaluate the presence or absence and the degree of the image quality deterioration factor. However, in this modified example, in order to perform the process of estimating the position of the γ-ray generation source using the detection time difference, compared to the method using LOR in a predetermined direction, real time in the generation and display of simple PET image data The characteristics are slightly reduced.

  Therefore, when the TOF function is used, the simplified PET image data generation unit 41 may limit the LOR used for generating the simplified PET image data. For example, when the predetermined direction is the y direction, the simple PET image data generation unit 41 may limit the LOR used for generating the simple PET image data to the LOR included in the xy plane. Further, for example, the simplified PET image data generation unit 41 limits the LOR used for generating the simplified PET image data to an LOR that is included in the xy plane and whose direction is a predetermined range on the xy plane. You may do it. For example, as illustrated in FIG. 12, the simple PET image data generation unit 41 may limit the LOR used for generating the simple PET image data to an LOR whose direction is substantially equal to the x direction. The simple PET image data generation unit 41 may generate simple PET image data by using both the method using the TOF function and the method using the LOR in the direction substantially equal to the predetermined direction described above.

  Note that a part of the medical image diagnostic apparatus 100 according to the embodiment of the present disclosure and the medical image diagnostic apparatus 200 according to the modified example can also be realized by using a computer as hardware. For example, the system control unit 10 (10a) and the like included in the medical image diagnostic apparatus 100 (200) described above can realize various functions by causing a processor such as a CPU mounted on a computer to execute a predetermined control program. it can. In this case, the system control unit 10 (10a) or the like may install the above-described control program in a computer in advance, or may be stored in a storage medium readable by the computer or distributed via a network. It may be installed on other computers.

  As described above, according to the embodiment and the modification, it is possible to determine in a short time whether or not there is an image quality deterioration factor in the projection data collected by PET imaging.

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

DESCRIPTION OF SYMBOLS 1 ... X-ray CT imaging | photography part 11 ... X-ray generation part 12 ... Projection data generation part 2 ... PET imaging part 21 ... Detector module 22 ... Detection data processing part 3 ... Form image data generation part 31 ... Projection data storage part 32 ... Scanogram generation unit 33 ... Scanogram storage unit 4 ... Functional image data generation unit 41 ... Simple PET image data generation unit 42 ... Projection data storage unit 43 ... PET image data generation unit 5, 5a ... Image data synthesis unit 6 ... Display unit 7 ... Top plate 8, 8a ... Moving mechanism unit 9, 9a ... Input unit 10, 10a ... System control unit 50 ... Morphological image data storage unit 100, 200 ... Medical image diagnostic apparatus

Claims (1)

A ring-shaped detector that simultaneously measures gamma rays emitted from a subject administered with a radioisotope,
A simple image data generation unit that generates simple image data in real time without performing a reconstruction process based on a part of information corresponding to a direction designated by an operator of the simultaneously measured data; ,
A display unit for displaying the generated simple image data in real time;
A nuclear medicine diagnostic apparatus.

Images