JP5355101B2 - PET apparatus and PET-CT apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PET (Positron Emission Tomography) device and a PET-CT device capable of collecting &gamma;-rays from a desired portion with excellent sensitivity, while restricting incidence of unnecessary &gamma;-rays. <P>SOLUTION: This PET device includes a detector 30 for detecting &gamma;-rays emitted from a radioactive isotope administered into a subject M, and a septa 40 arranged on the &gamma;-ray incidence side of the detector 30. The septa 40 includes: a first collimator part 41 used as a 2D image collection domain by restricting an incidence direction to the detector 30 of &gamma;-rays by a shielding plate 44; a second collimator part 42 separated as long as a prescribed distance along a body axis direction of the subject M relative to the first collimator part 41, and used as a 2D image collection domain by restricting an incidence direction to the detector 30 of &gamma;-rays by the shielding plate 44; a 3D image collection domain part 43 provided between the first collimator part 41 and the second collimator part 42; a data collection part 61 for collecting projection data acquired from the detector 30; and an image reconstitution part 62 for reconstituting an image based on the projection data. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a PET apparatus and a PET-CT apparatus that are nuclear medicine diagnostic apparatuses, and more particularly to an apparatus that efficiently collects data by reducing incidence of unnecessary gamma rays.

  A PET (Positron Emission Tomography) apparatus and a PET-CT apparatus are nuclear medicine diagnostic apparatuses that use a positron-emitting radionuclide, detect annihilation gamma rays thereof, and photograph a distribution image of the nuclide. For example, when a drug labeled with a positron-emitting radionuclide (hereinafter referred to as “RI”) is administered to a subject, it accumulates in a specific organ (heart, liver, etc.). At that time, the gamma rays emitted to the outside of the subject are detected by a detector arranged outside the subject and data is collected. Since annihilation gamma rays are emitted in the opposite direction of 180 °, it is detected that they are simultaneously incident on a pair of detectors, and data indicating that a nuclide exists on a line connecting the pair of detectors is obtained. By processing data collected by such coincidence with a predetermined algorithm, it is possible to reconstruct a nuclide concentration distribution image in a predetermined cross section.

  A scintillation detector or the like is used as a detector for detecting gamma rays outside the subject. Such detectors are arranged so as to surround the subject, and multiple rows are arranged in the body axis direction. The gamma rays from the nuclides located in the detector plane are emitted in parallel to the plane and detected by being incident on one of the detectors arranged in a ring shape. The data on the plane (slice plane) is collected, and the reconstructed image is a density distribution image of the nuclide on the slice plane. Usually, this detector ring is formed in a plurality of layers so that data acquisition and image reconstruction can be performed not only on one slice plane but also on a plurality of slice planes stacked in a certain range.

  By the way, in a PET apparatus that detects gamma rays using a multilayer detector ring in this way, a two-dimensional collection apparatus that performs coincidence counting only within a two-dimensional plane for each layer, and straddling between each layer ( That is, it is performed by appropriately selecting a three-dimensional collection device to be performed (within a three-dimensional volume).

  In the two-dimensional collection apparatus as shown in FIG. 4, one in which a shielding plate 110 is provided between slices is known so that gamma rays from other layers do not enter the detector 100 (for example, Patent Document 1, Patent Document 1). 2). In FIG. 4, M represents the subject, H represents the heart, and L represents the liver. With such a configuration, it is possible to limit gamma rays entering the detector by blocking gamma rays incident obliquely, thereby reducing the number of signals, occurrence of accidental coincidence coefficient components, and the like. For this reason, it is possible to collect data with little noise and high quantitativeness.

On the other hand, in the three-dimensional acquisition apparatus as shown in FIG. 5, a device in which a shielding plate 120 is provided at the end of the visual field is known so that gamma rays from other than the image acquisition area do not enter the detector 100.
JP 09-033659 A JP 2003-307570 A

  The above-described PET apparatus and PET-CT apparatus have the following problems. That is, in the two-dimensional collection device, the sensitivity is remarkably lowered by the amount of not using incident data from an oblique direction.

  On the other hand, in the three-dimensional acquisition device, sensitivity is increased because incident data from an oblique direction is used, but unnecessary gamma ray incidence in the field of view cannot be blocked. For example, when collecting image data of the heart H, gamma rays from the adjacent liver L are incident, and a high-accuracy image cannot be obtained.

  Therefore, an object of the present invention is to provide a PET apparatus and a PET-CT apparatus that limit the incidence of unnecessary gamma rays and can collect gamma rays from a desired site with high sensitivity.

  In order to solve the above problems and achieve the object, the PET apparatus and the PET-CT apparatus of the present invention are configured as follows.

A detector for detecting gamma rays emitted from the radioisotope administered into the subject, a septum disposed on the gamma ray incident side of the detector, and a control device connected to the detector, The sceptor limits the incident direction of the gamma rays to the detector by a plurality of shielding plates arranged along the direction orthogonal to the body axis of the subject while being separated from each other in the body axis direction of the subject. By doing so, the first collimator unit serving as a 2D image acquisition region and the first collimator unit are separated from each other by a predetermined distance along the body axis direction of the subject and separated from each other in the body axis direction of the subject. and then while the second collimator portion serving as 2D image acquisition area at limiting the incident direction to the detector of the gamma rays by a plurality of shielding plates disposed along the direction orthogonal to the body axis of the subject The first collimator Wherein provided between the second collimator unit, mutually to the first collimator unit and the body axis direction of the second said body axis direction of spacing by the subject is greater than the distance between the shield plate collimator unit and And a 3D image acquisition region unit having a pair of shielding plates arranged along a direction orthogonal to the body axis of the subject while being separated from each other , and the control device obtains projection data obtained from the detector A data collection unit that collects images and an image reconstruction unit that reconstructs an image based on the projection data.

  According to the present invention, it is possible to limit the incidence of unnecessary gamma rays and to collect gamma rays from a desired site with high sensitivity.

  FIG. 1 is an explanatory diagram showing a configuration of a PET apparatus 10 according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a use state in the PET apparatus 10, and FIG. 3 is an explanatory diagram showing an image reconstruction process. . Since the PET-CT apparatus is a form of the PET apparatus 10, only the PET apparatus 10 will be described here.

  The PET apparatus 10 includes a gantry 20 installed on the floor, a couch device 50 having a top plate on which the subject 20 installed near the gantry 20 is placed, and the couch 20 and the couch device 50. And a connected control device 60. In FIG. 3, the longitudinal direction of the top plate (body axis direction of the subject 20) is the Z direction, the direction orthogonal to the Z direction is the Y direction, and the direction orthogonal to the Z direction and the Y direction is the X direction.

  The gantry 20 is provided with a tunnel portion 21, and a detector 30 is disposed so as to surround the tunnel portion 21. A detector 30 is arranged. The detector 30 is configured by two-dimensionally arranging a number of gamma ray detectors on a cylindrical side surface. Each gamma ray detector is composed of a combination of a scintillator and a photomultiplier tube.

  On the gamma ray input surface side of the detector 30, a septa 40, which is a member on a plate that shields gamma rays, is provided. The septa 40 includes a first collimator unit (2D image collection region) 41 and a second collimator unit (2D image collection region) 42 that is spaced apart from the first collimator unit 41 in the body axis direction. Between the unit 41 and the second collimator unit 42, a 3D image collection region unit 43 is provided. Therefore, the projection data obtained through the 2D image collection region which is the first collimator unit 41 and the second collimator unit 42 and the projection data obtained through the 3D image collection region 43 are input to the detector 30. Is done.

  In the first collimator unit 41 and the second collimator unit 42, a shielding plate 44 is provided in parallel in a direction perpendicular to the body axis. That is, both ends of the 3D image collection region 43 in the body axis direction correspond to the shielding plates 44 of the first collimator unit 41 and the second collimator unit 42.

  The couch device 50 includes a couch 51 fixed to the floor, and a couch top plate 52 provided on the couch 51 and inserted into the tunnel portion 21 of the gantry 20. The bed top plate 52 is moved in a direction penetrating the tunnel portion 21, and a subject (subject) M is laid thereon.

  The control device 60 cooperates with the data collection unit 61 that accumulates the signals detected by the detector 30, the image reconstruction unit 62 that reconstructs the data accumulated in the data collection unit 61 as an image, and these. And a control unit 63.

  The PET apparatus 10 configured as described above creates an image as follows. Here, the heart H is the target organ. First, a drug RI labeled with a positron-emitting radionuclide is administered to the subject M. Next, the subject M is laid on the couch top 52. Then, the couch device 50 is driven, and the couch top plate 52 is moved to a position where the 3D image collection area 43 faces the measurement target, for example, the heart H.

  Next, data collection is started. In a portion corresponding to the first collimator unit 41 and the second collimator unit 42, the control device 60 collects data in the 2D acquisition mode. From the radionuclide of the subject 20, a pair (two) of γ rays are emitted in opposite directions when positron annihilation occurs. The emitted gamma rays are collimated by the shielding plate 44, and only the gamma rays emitted from the slice plane enter each layer (each slice plane) of the detector 30, and data collection is performed in the 2D acquisition mode. In other words, in the 2D acquisition mode, the body axis direction is simultaneously incident on the same position (the same slice plane), but the coincidence processing is performed so as to detect a pair of gamma rays, and the body axis direction is different (different slice planes). ) Do not count the simultaneous incidence of gamma rays.

  On the other hand, in the portion corresponding to the 3D image collection area unit 43, data is collected in the 3D collection mode. The gamma rays emitted from the subject M are not collimated by the shielding plate 44, and the gamma rays are also incident in an oblique direction across the layers of the multilayer slice, and data collection in the 3D acquisition mode is performed. . In other words, the simultaneous counting process is performed so as to detect a pair of gamma rays that are simultaneously incident, including positions with different body axis directions (different slice planes).

  The control device 60 is supplied with projection data from the detector 30 and image data indicating the imaging position. The image data is added with information on the collection mode determined by the imaging position, and the data is identified in the state of being collected in the 2D collection mode or in the 3D collection mode (ST10). It is stored in the collection unit 61 (ST10).

  When the data collection is completed, the image data collected in the 2D collection mode is reconstructed by a method such as a filter back projection method or an OS-EM method, and a tomographic image (PET image) is created. In this reconstruction processing, only gamma ray incidence in the same slice plane is considered, and processing is performed so as not to consider gamma ray incidence in an oblique direction across different slices (ST11). Next, the images collected in the 3D acquisition mode are rearranged into data for each slice by the FORE method or the like (ST12), and reconstruction is performed using the image data. In this reconstruction process, a process considering the incidence of gamma rays is also performed in an oblique direction across different slices (ST13).

  Next, since the sensitivity differs between the 2D image and the 3D image, sensitivity correction is performed (ST14), the images are combined (ST15), and output as one image data (ST16).

  As described above, according to the PET apparatus 10 according to the present embodiment, when the diagnosis of the heart H is performed, sufficient gamma rays entering from the liver L can be restricted and sufficient sensitivity can be ensured. An image can be obtained. In addition to the heart H, as with conventional 2D images, it is possible to reduce signal counting and the occurrence of accidental coincidence coefficient components and to collect data with little noise and high quantitativeness. It becomes.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

Explanatory drawing which shows the structure of the PET apparatus which concerns on one embodiment of this invention. Explanatory drawing which shows the positional relationship in the PET apparatus. Explanatory drawing which shows the production | generation procedure of the image data in the PET apparatus. Explanatory drawing which shows the basic principle of the two-dimensional collection apparatus of PET apparatus. Explanatory drawing which shows the basic principle of the three-dimensional collection apparatus of PET apparatus.

  DESCRIPTION OF SYMBOLS 10 ... PET apparatus, 20 ... Mount, 30 ... Detector, 40 ... Scepter, 41 ... 1st collimator part (2D image collection area), 42 ... 2nd collimator part (2D image collection area), 43 ... 3D image collection area , 44 ... shielding plate, 50 ... couch device, 60 ... control device, 61 ... data collection unit, 62 ... image reconstruction unit.

Claims (4)

A detector for detecting gamma rays emitted from a radioisotope administered into the subject;
A scepter disposed on the gamma ray incident side of the detector ;
A control device connected to the detector,
The sceptor limits the incident direction of the gamma rays to the detector by a plurality of shielding plates arranged along the direction orthogonal to the body axis of the subject while being separated from each other in the body axis direction of the subject. A first collimator unit to be a 2D image collection region
The first collimator unit is separated by a predetermined distance along the body axis direction of the subject , and is separated from each other in the body axis direction of the subject, along the direction orthogonal to the body axis of the subject. A second collimator section serving as a 2D image collection region by limiting the incident direction of the gamma rays to the detector by a plurality of shielding plates arranged
The body axis of the subject is provided between the first collimator unit and the second collimator unit and is larger than the interval between the first collimator unit and the second collimator unit in the body axis direction of the shielding plate. A 3D image acquisition region unit having a set of shielding plates arranged along a direction orthogonal to the body axis of the subject while being spaced apart from each other in the direction ,
The control device includes a data collection unit that collects projection data obtained from the detector;
A PET apparatus comprising: an image reconstruction unit configured to reconstruct an image based on the projection data.   The image reconstruction unit adjusts and combines the sensitivity of the projection data obtained through the 2D image collection area and the projection data obtained through the 3D image collection area. The PET apparatus as described. A detector for detecting gamma rays emitted from a radioisotope administered into the subject;
A scepter disposed on the gamma ray incident side of the detector ;
A control device connected to the detector,
The sceptor limits the incident direction of the gamma rays to the detector by a plurality of shielding plates arranged along the direction orthogonal to the body axis of the subject while being separated from each other in the body axis direction of the subject. A first collimator unit to be a 2D image collection region
The first collimator unit is separated by a predetermined distance along the body axis direction of the subject , and is separated from each other in the body axis direction of the subject, along the direction orthogonal to the body axis of the subject. A second collimator section serving as a 2D image collection region by limiting the incident direction of the gamma rays to the detector by a plurality of shielding plates arranged
The object is provided between the first collimator and the second collimator unit, and is spaced from the subject by an interval greater than the interval in the body axis direction of the shielding plate of each of the first collimator unit and the second collimator unit. A 3D image acquisition region unit having a set of shielding plates arranged along a direction orthogonal to the body axis of the subject while being separated from each other in the body axis direction ,
The control device includes a data collection unit that collects projection data obtained from the detector;
A PET-CT apparatus comprising: an image reconstruction unit that reconstructs an image based on the projection data.   The image reconstruction unit adjusts and combines the sensitivity of the projection data obtained through the 2D image collection area and the projection data obtained through the 3D image collection area. The PET-CT apparatus as described.

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