Diagnostic system

The present invention relates to a diagnostic system including a nuclear medicine diagnostic device and an X-ray CT device, and particularly relates to a technique for eliminating a positional deviation between data for X-ray CT and nuclear medicine.

As the above-mentioned nuclear medicine diagnostic device, that is, an ECT (Emission Computed Tomography) device, a PET (Positron Emission Tomography) device will be described as an example. The PET device will reconstruct the tomographic image of the subject only when it detects multiple γ-rays generated by the disappearance of protons (Positrons), that is, positrons, and simultaneously detects γ-rays with multiple detectors. It is configured.

With this PET device, various biological functions can be quantitatively measured by measuring the process of drug accumulation in the target tissue over time after administering the radiopharmaceutical to the subject. Therefore, the tomographic image obtained by the PET device has functional information.

However, the above-mentioned tomographic image lacks morphological information such as position information. Therefore, a diagnosis that combines a PET device and an X-ray CT device and superimposes a tomographic image obtained by the X-ray CT device and a tomographic image obtained by the PET device to obtain two types of information, functional information and morphological information. The system has been used in recent years.

Since the X-ray CT device and the PET device are not installed at the same position but are installed close to each other, in reality, both projection data obtained by each device and both are installed. Positional deviation occurs between tomographic images. Therefore, position information is extracted between the data for CT and PET equipment, and at least one of the two tomographic images is moved based on the position shift between the extracted data to eliminate the position shift. ing.

Since morphological information is scarce for PET data, when extracting position information, the same γ-ray source as the radiopharmaceutical is provided outside the subject in the PET device, and the subject is irradiated from the γ-ray source. Absorption correction data (also called "transmission data") obtained based on transmitted γ-rays is used.

That is, the position information of the projection data for CT and the position information of the absorption correction data are extracted. On the other hand, the projection data for PET is absorbed and corrected based on the absorption correction data. Since the absorption correction data has morphological information as well as the CT data, the PET data (projection data and tomographic image) obtained after the correction has morphological information. At least one of the corrected PET data (projection data and tomographic image) and CT data (projection data and tomographic image) having this morphological information is extracted and the projection data and absorption correction for CT. The position shift is eliminated by moving the data based on the position shift (see, for example, Patent Document 1).

Note that there is no positional deviation between the projection data for PET and the absorption correction data because each data can be obtained by transmitting γ-rays through substantially the same position in the PET device. Therefore, the positional deviation between the projection data for CT and the absorption correction data is equivalent to the positional deviation between the data for CT and PET. In Patent Document 1, a SPECT (Single Photon Emission CT) device is taken as an example for explanation.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 10-137231 (pages 4-6, Fig. 2-4)</text></patcit>

<p> However, in the case of such a diagnostic system, imaging by X-ray CT and imaging by a PET device are not performed at the same time, and one of the imaging is performed first and the other imaging is performed later. Therefore, the subject moves during such imaging, and the positional deviation between the CT and PET data changes over time, so that the morphological information of each data can be obtained accurately. Can not.</p><p> In addition, one of the causes of the positional deviation is the deflection of the top plate on which the subject is placed. Therefore, it is conceivable to install a top plate with increased strength in order to eliminate the deflection of the top plate, or to install a top plate that moves while being bent. However, if the strength of the top plate is increased, the absorption of γ-rays by the top plate increases, which causes a decrease in the sensitivity of γ-rays. Further, in the case of a top plate that moves while being bent, a special top plate must be prepared, and the device itself becomes large-scale. In addition, the subject may move even if the top plate is not bent, and the purpose of accurately obtaining the morphological information of the data cannot be achieved.</p><p> The present invention has been made in view of such circumstances, and an object of the present invention is to provide a diagnostic system capable of accurately obtaining morphological information of each data for X-ray CT and nuclear medicine.</p>

<p> As a result of diligent research to solve the above problems, the inventor obtained the following findings.</p><p> That is, when the subject is a human or an animal, biological functions such as the heart and blood vessels always move, so the subject inevitably moves. Therefore, we decided to change the way of thinking and extract the position information based on the object that does not change with time with respect to the position, instead of extracting the position information based on the data with time change represented by the subject. I came up with it. For example, even if the top plate has a deflection, when the subject is placed on the top plate, the top plate immediately bends due to the weight of the subject, but the deflection is maintained after a predetermined time. That is, after a predetermined time has passed, the top plate does not change with time. In this way, if the top plate that does not change with time with respect to the position is irradiated with radiation or X-rays and the position information is extracted based on the data obtained by the irradiation, the position deviation can be eliminated accurately. At the same time, we obtained the knowledge that the morphological information of each data can be obtained with high accuracy.</p><p> The present invention based on such findings has the following configuration.</p><p> That is, the invention according to claim 1 obtains projection data based on the radiation generated from the subject to which the radiopharmaceutical is administered, and reconstructs the projection data to obtain a tomographic image of the subject for nuclear medicine. Obtain projection data based on the nuclear medicine diagnostic equipment and X-rays emitted from the outside of the subject and transmitted through the subject, and reconstruct the projection data to obtain a tomographic image for X-ray CT of the subject. A diagnostic system configured to include a line CT device, which is a position information extracting means for extracting position information of projection data for X-ray CT and position information of absorption correction data having morphological information, and morphological information. Based on the absorption correction data having the above, the absorption correction means for correcting the projection data for nuclear medicine having the functional information, and the projection data / absorption correction for the X-ray CT extracted by the position information extraction means. Based on the positional deviation between the data, at least one of the projection data for X-ray CT and the projection data for nuclear medicine corrected by the absorption correction means is moved, or the tomographic image for X-ray CT and the above. Projection for X-ray CT and nuclear medicine with reference to an object that does not change over time with respect to position, with a moving means to move at least one of the tomographic images for nuclear medicine after correction by absorption correction means It is characterized in that the data and the absorption correction data are obtained, and the projection data and the absorption correction data for nuclear medicine are obtained for each radiation transmitted through substantially the same position of the object.</p><p> [Action / Effect] According to the invention described in claim 1, projection data and absorption correction data for X-ray CT and nuclear medicine are obtained based on an object whose position does not change with time, and the data thereof are obtained. Projection data and absorption correction data for nuclear medicine are obtained for each radiation transmitted through substantially the same position of the object. Therefore, even if the radiography by the X-ray CT device and the radiography by the nuclear medicine diagnostic device are not simultaneous but at intervals in time, there is a positional deviation between the projection data and the absorption correction data for nuclear medicine in the above-mentioned object. It does not occur, and there is no change over time in the positional deviation between the projection data for X-ray CT and the absorption correction data in the object. From this, even if there is a time interval between radiographs, the positional deviation between data such as X-ray CT / nuclear medicine projection data and tomographic images on the object is the projection for X-ray CT on the object. It is equivalent to the positional deviation between the data and the absorption correction data.</p><p> The data for nuclear medicine (projection data and tomographic image) before correction has functional information but lacks morphological information, and the data for X-ray CT and absorption correction data have morphological information. Therefore, in order to eliminate the positional deviation between the data for X-ray CT and the data for nuclear medicine, absorption correction data is used instead of the data for nuclear medicine. That is, the position information extracting means extracts the position information of the projection data for X-ray CT and the position information of the absorption correction data, and the absorption correction means corrects the projection data for nuclear medicine based on the absorption correction data. .. As a result, the corrected data such as projection data and tomographic image for nuclear medicine also have morphological information. In addition, the moving means is nuclear medicine after correction by the projection data for X-ray CT and the absorption correction means based on the positional deviation between the projection data for X-ray CT and the absorption correction data extracted by the position information extraction means. Move at least one of the projected data for X-ray CT, or move at least one of the tomographic image for X-ray CT and the tomographic image for nuclear medicine corrected by absorption correction means. By moving in this way, it is possible to eliminate the positional deviation between the projection data for X-ray CT and the absorption correction data in the object, and the position between the data for X-ray CT and nuclear medicine in the object. The deviation can be eliminated. Therefore, even if the subject changes with time, for example, due to body movement, the positional deviation can be accurately eliminated based on the object to be imaged together with the subject regardless of the subject, and for X-ray CT. -It is possible to accurately obtain morphological information of each data for nuclear medicine.</p><p> An example of the above-mentioned absorption correction data is obtained based on the radiation transmitted from the radiation source and transmitted through the subject by equipping the nuclear medicine diagnostic device with the same radiation source as the radiopharmaceutical. The invention according to claim 2). In this way, the position of the object through which the radiation generated from the radiopharmaceutical is transmitted to obtain the projection data for nuclear medicine, and the position of the object through which the radiation emitted from the radiation source is transmitted to obtain the absorption correction data. Is almost the same.</p><p> An example of the above-mentioned invention is to superimpose and output tomographic images for X-ray CT and nuclear medicine whose positional deviation has been eliminated by the above-mentioned moving means (the invention according to claim 3). The superimposed tomographic image obtains two types of information, functional information and morphological information.</p>

<p> According to the diagnostic system according to the present invention, projection data and absorption correction data for X-ray CT and nuclear medicine are obtained based on an object whose position does not change with time, and the position of the object is substantially the same. Since the projection data and absorption correction data for nuclear medicine are obtained for each radiation transmitted through the above-mentioned objects, there is no positional deviation between the projection data for nuclear medicine and the absorption correction data in the above-mentioned object. There is no change over time in the positional deviation between the projection data for X-ray CT and the absorption correction data. From this, even if there is a time interval between radiographs, the positional deviation between data such as X-ray CT / nuclear medicine projection data and tomographic images on the object is the projection for X-ray CT on the object. It is equivalent to the positional deviation between the data and the absorption correction data. Therefore, in order to eliminate the positional deviation between the data for X-ray CT and nuclear medicine, the absorption correction data is used instead of the data for nuclear medicine to extract the position information and correct the projection data for nuclear medicine. , Move data for X-ray CT and nuclear medicine based on misalignment. By moving in this way, it is possible to eliminate the positional deviation between the projection data for X-ray CT and the absorption correction data in the object, and the position between the data for X-ray CT and nuclear medicine in the object. The deviation can be eliminated. As a result, it is possible to accurately obtain morphological information of each data for X-ray CT and nuclear medicine.</p>

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic perspective view of a diagnostic system according to an embodiment, and FIG. 2 is a side view and a block diagram of the example system. In this embodiment, a PET (Positron Emission Tomography) device will be described as an example of a nuclear medicine device.

As shown in FIG. 1, the present embodiment system is roughly divided into a PET device 1, an X-ray CT device 2, and a top plate 3. The PET device 1 and the X-ray CT device 2 are arranged in close proximity to each other. As shown in FIG. 2, the top plate 3 is configured to place the subject M, move up and down, and move in parallel along the body axis Z of the subject M. With this configuration, the subject M placed on the top plate 3 passes through the opening 11a of the gantry 11 of the PET device 1 and the opening 21a of the gantry 21 of the X-ray CT device 2.

In addition, the present embodiment system includes a top plate drive unit 4, a stacking unit 5, a controller 6, an input unit 7, and an output unit 8. The top plate driving unit 4 is a mechanism for driving the top plate 3 so as to perform the above-mentioned movement, and is composed of a motor or the like (not shown). The superimposing unit 5 includes a position information extracting unit 5a and a moving unit 5b, and is composed of a tomographic image for PET obtained by the PET device 1 and a CT image obtained by the X-ray CT device 2. The position information extraction unit 5a extracts each position information from the tomographic image, and the moving unit 5b moves each image based on the extraction result so as to eliminate the position deviation and superimposes both images. The tomographic image for PET corresponds to the tomographic image for nuclear medicine in the present invention, and the tomographic image for CT corresponds to the tomographic image for X-ray CT in the present invention. Further, the position information extraction unit 5a corresponds to the position information extraction means in the present invention, and the moving unit 5b corresponds to the moving means in the present invention.

The controller 6 comprehensively controls each processing unit that constitutes the PET device 1, each processing unit that constitutes the X-ray CT device 2, the top plate drive unit 4, the stacking unit 5, and the like. For convenience of illustration, in FIG. 2, the connector connected to the controller 6 is a top plate drive unit 4, a stacking unit 5, an input unit 7, an output unit 8, a gantry drive unit 24 in the X-ray CT device 2 described later, and the like. Although only the high voltage generating unit 25 and the collimator driving unit 26 are shown, the processing units constituting the PET device 1 and the X-ray CT device 2 to be controlled are also connected to the controller 6 via the connector. Please note. The controller 6 is composed of a central processing unit (CPU) and the like. The controller 6 also performs the flowchart of FIG. 3 described later.

The input unit 7 sends the data and commands input by the operator to the controller 6. The input unit 7 is composed of a pointing device represented by a mouse, a keyboard, a joystick, a trackball, a touch panel, and the like. The output unit 8 is composed of a display unit represented by a monitor or the like, a printer, or the like.

The PET device 1 includes a gantry 11 having an opening 11a, a plurality of scintillator blocks 12 arranged close to each other, and a plurality of photomultipliers 13. The scintillator block 12 and the photomultiplier 13 are arranged in a ring shape so as to surround the body axis Z of the subject M, and are embedded in the gantry 11. The photomultiplier 13 is arranged outside the scintillator block 12. As a specific arrangement of the scintillator blocks 12, for example, two scintillator blocks 12 are arranged in a direction parallel to the body axis Z of the subject M, and a large number of scintillator blocks 12 are arranged around the body axis Z of the subject M. The form of lining up can be mentioned. The scintillator block 12 and the photomultiplier 13 constitute a γ-ray detector.

Further, the PET device 1 includes a line source 14 and a line source drive unit 15. The line source 14 is a radioactive agent to be administered to the subject M, that is, a radiation source that irradiates the same radiation (γ-ray in this example) as the radioisotope (RI), and is arranged outside the subject M. Has been done. The line source driving unit 15 is a mechanism that drives the line source 14 so as to rotate around the body axis Z of the subject M independently of the gantry 11, and is composed of a motor or the like (not shown). There is. The line source 14 corresponds to the radiation source in the present invention.

In addition, the PET device 1 includes a PET projection data derivation unit 16, an absorption correction data derivation unit 17, an absorption correction unit 18, and a PET reconstruction unit 19. These are realized by the controller 6 executing a program stored in a storage medium (not shown) composed of a ROM (Read-only Memory) or the like or an instruction input by the input unit 7, and processed by these. The data is written to a storage medium (not shown) represented by RAM (Random-Access Memory) and stored, and if necessary, read from the storage medium to obtain PET projection data (also called "emission data"). In this case, data is sent in the order of PET projection data derivation unit 16, absorption correction unit 18, PET reconstruction unit 19, and when obtaining absorption correction data (transmission data), absorption correction data derivation unit 17, absorption correction unit 17, Data is sent in the order of 18, PET reconstruction unit 19. The projection data for PET corresponds to the projection data for nuclear medicine in the present invention.

The scintillator block 12 converts the γ-rays generated from the subject M to which the radiopharmaceutical is administered into light, and the photomultiplier 13 photoelectrically converts the converted light and outputs it as an electric signal. The electric signal is sent to the PET projection data derivation unit 16 as image information (pixels).

Specifically, when a radiopharmaceutical is administered to subject M, a plurality of γ-rays are generated due to the disappearance of the positron-releasing RI positron. The PET projection data derivation unit 16 checks the position of the scintillator block 12 and the incident timing of the γ-rays, and only when the γ-rays are simultaneously incident on the two scintillator blocks 12 located opposite to each other across the subject M. The sent image information is judged to be appropriate data. When γ-rays are incident on only one scintillator 12, the PET projection data derivation unit 14 treats them as noise instead of γ-rays generated by the disappearance of the positron, and determines that the image information sent at that time is also noise. Is rejected.

The image information sent to the PET projection data derivation unit 16 is sent to the absorption correction unit 18 as projection data for PET. The projection data for PET sent to the absorption correction unit 18 is made to act on the absorption correction data (transmission data) sent from the absorption correction data derivation unit 17 to the absorption correction unit 18, and the γ in the body of the subject M is γ. Correct the projection data for PET in consideration of line absorption. The absorption correction unit 18 corresponds to the absorption correction means in the present invention.

The line source 14 irradiates the subject M with γ-rays while rotating around the body axis Z of the subject M, and the scintillator block 12 illuminates the irradiated γ-rays in the correction data derivation unit 17. The converted light is photoelectrically converted by the photomultiplier 13 and output to an electric signal. The electric signal is sent to the absorption correction data derivation unit 17 as image information (pixels).

Absorption correction data is obtained based on the image information sent to the absorption correction data derivation unit 17. The absorption correction data derivation unit 17 uses an operation that expresses the relationship between the absorption coefficient of γ-rays or X-rays and energy to obtain projection data for CT, that is, distribution data of the X-ray absorption coefficient of the γ-ray absorption coefficient. It is converted into distribution data, and the distribution data of the γ-ray absorption coefficient is obtained as absorption correction data. The derived absorption correction data is sent to the absorption correction unit 18 described above.

The corrected projection data for PET is sent to the PET reconstruction unit 19. The PET reconstruction unit 19 reconstructs the projection data to obtain a tomographic image for PET in consideration of the absorption of γ-rays in the body of the subject M. In this way, by providing the absorption correction unit 18 and the PET reconstruction unit 19, the projection data for PET is corrected based on the absorption correction data, and the tomographic image for PET is corrected. The corrected tomographic image for PET is sent to the superimposition portion 5.

The X-ray CT apparatus 2 includes a gantry 21 having an opening 21a, an X-ray tube 22, and an X-ray detector 23. The X-ray tube 22 and the X-ray detector 23 are arranged so as to face each other with the subject M in between, and are embedded in the gantry 21. A large number of detection elements constituting the X-ray detector 3 are arranged in a fan shape around the body axis Z of the subject M.

In addition, the X-ray CT apparatus 2 includes a gantry drive unit 24, a high voltage generation unit 25, a collimator drive unit 26, and a CT reconstruction unit 27. The CT reconstruction unit 27 is realized by the controller 6 executing a program stored in a storage medium (not shown) composed of a ROM (Read-only Memory) or the like or an instruction input by the input unit 7. The data processed by these is written to a storage medium (not shown) represented by RAM (Random-Access Memory) and stored, and if necessary, read from the storage medium and reconstructed by X-ray. When the detector 23 sends the data to the CT reconstruction unit 27 and extracts the position information of the projection data for CT, the X-ray detector 23 sends the data from the X-ray detector 23 to the position information extraction unit 5a of the superimposition unit 5.

The gantry drive unit 24 is a mechanism that drives the X-ray tube 22 and the X-ray tube detector 23 so as to rotate around the body axis Z of the subject M in the gantry 21 while maintaining the opposite relationship with each other. , It is composed of a motor and the like (not shown).

The high voltage generator 25 generates the tube voltage and tube current of the X-ray tube 22. The collimator drive unit 26 is a mechanism that sets the X-ray field of view and drives the collimator (not shown) close to the X-ray tube 22 to move in the horizontal direction, such as a motor (not shown). It is composed of.

In the case of the indirect conversion type X-ray detector 23, the scintillator (not shown) in the X-ray detector 23 converts the X-rays irradiated from the X-ray tube 22 and transmitted through the subject M into light. , The converted light is photoelectrically converted by a light-sensitive film (not shown) and output as an electric signal. In the case of the direct conversion type X-ray detector 23, the radiation sensitive film (not shown) directly converts the X-ray into an electric signal and outputs it. The electric signal is sent as image information (pixels) to the CT reconstruction unit 27 or the position information extraction unit 5a. The image information sent to the CT reconstruction unit 27 and the position information extraction unit 5a is transmitted as projection data for CT.

The image information (projection data for CT) sent to the CT reconstruction unit 27 is reconstructed to obtain a tomographic image for CT. This tomographic image for CT is sent to the moving part 5b of the superimposing part 5.

The position information extraction unit 5a and the movement unit 5b in the superposition unit 5 output a program stored in a storage medium (not shown) composed of a ROM (Read-only Memory) or the like or an instruction input by the input unit 7. It is realized by executing the controller 6, and the data processed by these is written to and stored in a storage medium (not shown) represented by RAM (Random-Access Memory) or the like, and read from the storage medium as needed. , Send to output unit 8.

The position information extraction unit 5a extracts the position information of the tomographic image for PET and also extracts the position information of the tomographic image for CT. The tomographic image for PET originally lacks morphological information such as position information, but the absorption correction data has morphological information like the tomographic image for CT, and is for PET based on the absorption correction data. By correcting the tomographic image, the corrected tomographic image for PET has morphological information. Based on the extraction result of each tomographic image, the positional deviation between the two images is detected. In order to eliminate this positional deviation, the moving portion 5b moves at least one of the tomographic images for PET and CT and superimposes both images.

Next, the flow of a series of diagnoses in the present embodiment system will be described with reference to the flowchart of FIG. 3, and specific methods for extracting position information and eliminating the position deviation will be described in FIGS. 4 and 5. This will be described with reference to the figure. FIG. 4 is an explanatory view of the state of deflection when the subject M is placed on the top plate 3, and FIG. 5 is an explanatory view showing each tomographic image seen from the body axis Z side. , "Transmission" in Fig. 5 represents the absorption correction data on the tomographic image, and "Emission" in Fig. 5 represents the tomographic image for PET.

Step S1 (Placement of subject) Subject M is administered with a radiopharmaceutical, that is, a radioisotope (RI). After administration of the drug, wait for the accumulation of the drug in the cancer, that is, the distribution of the drug in the tumor. This accumulation time is, for example, about 40 to 60 minutes after administration of the drug. The subject M in which the drug is accumulated in the cancer is placed on the top plate 3.

When the subject M is placed on the top plate 3, as shown in FIG. 4, the top plate 3 bends due to the weight of the subject M, but the deflection is maintained after a predetermined time. That is, after a predetermined time has passed, the top plate 3 does not change with time and maintains the state of the solid line shown in FIG. For convenience of illustration, the subject M is not shown in FIG.

The surface of the tomographic image for CT obtained by the X-ray CT device 2 is the slice surface S of the CT shown in FIG.₁It becomes the face of. The surface of the tomographic image for PET obtained by the PET device 1 is the slice surface S of PET shown in FIG.₂Will be. CT slice surface S₁Is the irradiation surface connecting the X-ray tube 22 and the X-ray detector 23, and the PET slice surface S₂Is an irradiation surface that is irradiated to the subject M from the line source 14 in the case of a transmission, and in the case of an emission, the γ-rays generated from the subject M are simultaneously incident on two scintillator blocks 12 located opposite to each other. It becomes the incident surface when it is used (see Fig. 1).

Top plate 3 before bending and CT slice surface S after bending₁As shown in Fig. 4, the positional deviation from the top plate 3 in₁At the same time, the top plate 3 before bending and the slice surface S of PET after bending₂As shown in Fig. 4, the positional deviation from the top plate 3 in₂And. CT slice surface S after bending₁Top plate 3 and PET slice surface S in₂As shown in Fig. 4, the positional deviation from the top plate 3 in₃Then t₃Is (t₂-t₁). That is, between the projection data and tomographic image (emission data) and absorption correction data (transmission) for PET obtained by the PET device 1 and the projection data and tomographic image for CT obtained by the X-ray CT device 2. In "(t₂-t₁) , The position shift occurs.

When the subject M is a human or an animal, biological functions such as the heart and blood vessels always move, so the subject M always moves between the radiographs taken by the X-ray CT device 2 and the pictures taken by the PET device 1. To do. Therefore, based on the above-mentioned object that does not change with time, such as the top plate 3, projection data and absorption correction data for CT and PET, which will be described later, are obtained.

Step S2 (CT scan) The operator inputs an instruction to the input unit 7 and sends it to the controller 6, and the controller 6 executes the instruction, or the controller 6 executes the program stored in the storage medium (not shown). , Control the CT scan (scanning) by operating the motor of the top plate drive unit 4. Specifically, the top plate 3 moves in a direction parallel to the body axis Z of the subject M while the subject M is placed on it according to the movement of the top plate drive unit 4, and the movement of the gantry drive unit 24 Therefore, when the X-ray tube 22 and the X-ray detector 23 rotate around the body axis of the subject M, the imaging cross section (slice surface) of the subject M changes and the whole body of the subject M is scanned. If necessary, the controller 6 may operate the motor of the collimator drive unit 26 or the like to set the X-ray illumination field of view within a predetermined range.

Step S3 (Derivation of projection data for CT) In this way, the data obtained by performing the CT whole body scan is detected by the X-ray detector 23, and the position information of the CT reconstruction unit 27 and the overlay unit 5 is extracted. Send to part 5a.

As data, the slice surface S of CT₁In addition to the subject M in, the CT slice surface S₁The top plate 3 in the above is detected by the X-ray detector 23. The tomographic image for CT at this time is as shown by the dotted line in FIG. 5, and the symbol D is the slice plane S of CT.₁The tomographic image of the subject M in FIG. 5 (CT (subject) in FIG.₁The tomographic image of the top plate 3 in (Fig. 5 is "CT (top plate)") is shown.

Step S4 (PET scan) The controller 6 operates the motor of the top plate drive unit 4 to scan the subject M, and scintillator block 12 and the photo multi are γ-rays generated from the subject M to which the radiopharmaceutical is administered. Detect with pliers 13. In this way, the data obtained by performing the PET scan is sent to the PET projection data derivation unit 16. Then, the PET projection data derivation unit 16 obtains the projection data (emission data) for PET.

Step S5 (Derivation of projection data for PET) As data, the slice surface S of PET₂The subject M in the above is detected by the scintillator block 12 and the photomultiplier 13. The tomographic image for PET at this time is as shown by the solid line in FIG. 5, and the symbol A is the slice plane S of PET.₂A tomographic image of subject M in (Fig. 5 shows "PET (emission, subject)").

Step S6 (Line source scan) The controller 6 operates the motor of the line source drive unit 15, etc., and while the line source 14 scans the subject M, the scintillator block blocks the γ-rays emitted from the line source 14. Detect with 12 and photo multiplier 13. In this way, the data obtained by scanning the line source 14 is sent to the absorption correction data 17. Then, the absorption correction data (transmission data) is obtained from the absorption correction data 17.

Step S7 (Derivation of absorption correction data) Absorption correction data (transmission data) and projection data for PET (emission data) are obtained for each γ-ray that has passed through approximately the same position of the top plate 3 that is the target. Therefore, the PET scan in step S4 taken to obtain the emission data and the line source scan in step S6 taken to obtain the transmission data have the same PET slice surface S.₂Will be. As data, the slice surface S of PET₂In addition to the subject M in, PET slice surface S₂The top plate 3 in the above is detected by the scintillator block 12 and the photomultiplier 13. When the absorption correction data at this time is represented on the tomographic image, it is as shown by the solid line in FIG. 5, and the symbol C is the slice plane S of PET.₂The tomographic image of the subject M in the above (PET (transmission, subject) in FIG. 5) is shown, and the symbol B is the slice plane S of the PET.₂The tomographic image of the top plate 3 in (Fig. 5 shows "PET (transmission, top plate)".

Step S8 (Correction of tomographic image for PET) In step S5, the projection data for PET obtained by the PET projection data derivation unit 16 (PET (emission, subject) A in FIG. 5) is absorbed in step S7. The absorption correction unit 18 corrects the tomographic image for PET by applying the absorption correction data (PET (transmission, subject) C in FIG. 5) obtained by the correction data derivation unit 17.

Step S9 (Extraction of position information) The position information extraction unit 5a in the superposition unit 5 is the PET slice surface S of the tomographic images for PET.₂The position information of the tomographic image of the top plate 3 (PET (transmission, top plate) B in Fig. 5), which is the object in the above, is extracted, and the CT slice surface S of the tomographic images for CT is extracted.₁The position information of the tomographic image of the top plate 3 (CT (top plate) E in Fig. 5) is extracted. Since the top plate 3 does not change over time, the positional deviation between the data for the X-ray CT device 1 and PET is the positional deviation between PET (transmission, top plate) B and CT (top plate) E, that is, (t).₂-t₁).

Step S10 (Movement / Superimposition of Images) The moving part 5b in the superimposing part 5 is a tomographic image for PET after correction, that is, PET (emission, subject) so as to eliminate the positional deviation extracted in step S9. Specimen) A and the tomographic image for CT, that is, CT (subject) D and CT (top plate) E are moved and both images are superimposed. Both the superimposed images are output to the output unit 8. In this embodiment, for example, the output is displayed on a monitor. In addition, step S9 and step S10 may be performed while displaying the output on the output unit 8 of a monitor or the like.

In this way, the diagnosis in the present embodiment system is performed in a series of steps S1 to S10.

According to the present embodiment system having the above configuration, the projection data and the absorption correction data for CT and PET are obtained with reference to the top plate 3 which is an object whose position does not change with time, and the projection data and the absorption correction data are obtained. Approximately the same position of the top plate 3 (in this embodiment, the PET slice surface S in FIG. 4)₂Projection data for PET (PET (emission, subject) A in Fig. 5) and absorption correction data (PET (transmission, top plate) B, PET in Fig. 5) (Transmission, subject) C ). Therefore, even if the imaging by the X-ray CT apparatus 2 and the imaging by the PET apparatus 1 are not simultaneous but at intervals in time, there is a positional deviation between the projection data for PET and the absorption correction data on the above-mentioned top plate 3. It does not occur, and on the top plate 3, between the projection data for CT (CT (top plate) E in Fig. 5) and absorption correction data (PET (transmission, top plate) B in Fig. 5). There is no change over time in the positional deviation. From this, even if there is a time interval between shootings, there is a positional shift between data such as CT / PET projection data and tomographic images on the top plate 3, which is the object.₃(= t₂-t₁) Is the positional deviation between the projection data and absorption correction data for CT on the top plate 3.₃(= t₂-t₁) Is equivalent.

The PET data (projection data and tomographic image) before correction has functional information but lacks morphological information, and the CT data and absorption correction data have morphological information. Therefore, in order to eliminate the positional deviation between the CT and PET data, absorption correction data is used instead of the PET data. That is, the position information extraction unit 5a extracts the position information of the projection data for CT and the position information of the absorption correction data, and the absorption correction unit 18 corrects the projection data for PET based on the absorption correction data. As a result, the corrected data such as the projection data for PET and the tomographic image also have morphological information. Further, the moving unit 5b is used for the tomographic image for CT and the PET after correction by the absorption correction unit 18 based on the positional deviation between the projection data for CT and the absorption correction data extracted by the position information extraction unit 5a. Move at least one of the tomographic images. By moving in this way, it is possible to eliminate the positional deviation between the projection data and absorption correction data for CT on the top plate 3, and also eliminate the positional deviation between the CT and PET data on the top plate 3. can do. Therefore, even if the subject M changes with time due to body movement, for example, the positional deviation should be accurately eliminated based on the top plate 3 which is the object to be photographed together with the subject M regardless of the subject M. At the same time, it is possible to accurately obtain the morphological information of each data for CT and PET.

In this embodiment, a line radiation source 14 for irradiating the same γ-ray source as the radiopharmaceutical is provided outside the subject M in the PET device 1, and γ-rays irradiated from the line source 14 and transmitted through the subject. Absorption correction data is obtained based on. In this way, the position of the top plate 3 through which the γ-rays generated from the radioactive agent are transmitted to obtain the projection data for PET and the γ-rays emitted from the line source 14 to obtain the absorption correction data are transmitted. PET slice surface S that is approximately the same as the position of the top plate 3, that is, the imaging cross section is the same.₂Will be.

Further, in this embodiment, the tomographic images for CT and PET that are not displaced from each other by the moving unit 5b are superimposed and output to, for example, the output unit 8, so that the superimposed tomographic images can be used as functional information and. Obtain two types of morphological information. Note that the tomographic images that are superimposed and output may be stored in a storage medium (not shown) without being limited to the output to the output unit 8.

The present invention is not limited to the above embodiment, and can be modified and implemented as follows.

(1) In the above-described embodiment, as shown in FIG. 3, a series of diagnoses were performed in the order of CT imaging (steps S2, S3), emission imaging (steps S4, S5), and transmission imaging (steps S6, S7). However, as shown in Fig. 6, CT imaging (steps T2, T3), transmission imaging (steps T4, T5), emission imaging (steps T6, T7), and as shown in Fig. 7, emission imaging (steps). U2, U3), transmission imaging (steps U4, U5), CT imaging (steps U7, U8), and as shown in Fig. 8, transmission imaging (steps V2, V3), emission imaging (steps V4, V5). , CT imaging (steps V7, V8) may be performed in this order.

(2) In the above-described embodiment, the top plate 3 has been taken as an example as an object having no change with time with respect to the position, but the present invention is not particularly limited as long as there is no change with time with respect to the position. For example, each data may be obtained by using a positioning wire or the like arranged along the top plate as an object and using the wire as a reference. Further, each data may be obtained by using a marker or the like as an object and using the marker as a reference.

(3) In the above-described embodiment, the absorption correction data is obtained based on the γ-rays irradiated from the line source 14 and transmitted through the subject, but the absorption correction data is not limited to this. For example, in the projection data for CT obtained from the X-ray CT apparatus 2, the distribution data of the X-ray absorption coefficient is converted into the distribution data of the γ-ray absorption coefficient, and the distribution data of the γ-ray absorption coefficient is obtained as absorption correction data. You may. When the absorption correction data converted from the CT projection data is used for absorption correction, the morphological information is scarce for the PET projection data that is the target of the absorption correction, so the PET projection data is obtained. It is premised that the position of the object through which the γ-rays generated from the radiopharmaceutical are transmitted and the position of the object through which the X-rays are transmitted in order to obtain the projection data for CT are substantially the same. In the case of the embodiment, when the PET device 1 and the X-ray CT device 2 are so close to each other that the deflection of the top plate 3 can be ignored, the position of the top plate 3 through which X-rays and γ-rays pass is substantially the same. Then, the absorption correction data converted from the projection data for CT can be used in the absorption correction.

(4) In the above-described embodiment, the tomographic images for CT and PET after the most configuration are moved to eliminate the positional deviation based on the positional deviation, but the target of the movement is not limited to the tomographic image and the CT. The position shift may be eliminated by moving the projection data for use and PET.

(5) In the above-described embodiment, the PET apparatus is taken as an example, but the present invention is a SPECT (Single Photon Emission CT) apparatus that detects a single γ-ray and reconstructs a tomographic image of a subject. It can also be applied to.

(6) In the above-described embodiment, the scintillator block 12 and the photomultiplier 13 are stationary types that detect γ-rays while remaining stationary, but the scintillator block 12 and the photomultiplier 13 rotate around the subject M. However, it may be a rotary type that detects γ-rays.

(7) In the above-described embodiment, a nuclear medicine device represented by a PET device, a SPECT device, or the like is arranged adjacent to the X-ray CT device 2 at the positions shown in FIGS. 1 and 2, that is, FIG. 2. Although it was arranged adjacent to the left side of the X-ray CT apparatus 2 when viewed from the paper surface of, it was arranged on the opposite side of FIGS. 1 and 2, that is, adjacent to the right side of the X-ray CT apparatus 2 from the paper surface of FIG. It may be arranged.

<figref num="1">It is a schematic perspective view of the diagnostic system which concerns on Example.</figref><figref num="2">It is a side view and a block diagram of the Example system.</figref><figref num="3">It is a flowchart which showed the flow of a series of diagnosis in an Example system.</figref><figref num="4">It is explanatory drawing which looked at the state of bending when the subject was placed on the top plate.</figref><figref num="5">It is explanatory drawing which shows each tomographic image seen from the body axis side.</figref><figref num="6">It is a flowchart which showed the flow of a series of diagnosis which concerns on a modification.</figref><figref num="7">It is a flowchart which showed the flow of a series of diagnosis which concerns on a modification.</figref><figref num="8">It is a flowchart which showed the flow of a series of diagnosis which concerns on a modification.</figref>

Code description

1 ... PET device 2 ... X-ray CT device 3 ... Top plate 5a ... Position information extraction unit 5b ... Moving unit 14 ... Line source 18 ... Absorption correction unit M. .. Subject