JP2002341035A - Spect device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically and safely determine the optimum track of a radiation detector when rotating the detector around a subject to collect data. SOLUTION: An optical beam is radiated from a projection part 21 to the subject 21, and made incident on a light receiving part 22 arranged opposite to the projector 21 with the subject 31 between to obtain data corresponding to the optical beam interrupted by the subject 31 and the optical beam not interrupted thereby from the light receiving part 22. The subject profile in the circumferential direction of the subject 31 is reconfigured from these data, the optimum track of a gamma camera 12 is calculated from the profile, and the gamma camera 12 is rotated so as to automatically move along the track.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SPECT (Single Photon / Non-Photon Spectroscopy) for rotating a radiation detector to capture a concentration distribution image of a single photon emitting nuclide as a tomographic image.
Emission computer tomography) device.

[0002]

2. Description of the Related Art When a radioisotope (RI) of a single-photon emitting radionuclide is distributed in a subject, a SPECT apparatus detects gamma rays emitted from the radioisotope to detect the nuclide in the subject. This is for taking a distribution image. For example, when a drug labeled with a single photon emitting radionuclide is administered to a human body as a subject, the drug accumulates in a specific organ. At that time, gamma rays emitted outside the human body are detected by a detector arranged outside the human body. If the incident position is detected while regulating the direction of the gamma ray incident on the detector with a collimator, and radiation events are counted for each position, the data (projection data) that projects the RI concentration distribution in the direction regulated by the collimator can be obtained. Obtainable. By collecting such projection data from multiple directions and performing a reconstruction operation using an algorithm such as a back projection method, a RI density distribution image (tomographic image) in a section similar to a slice of a human body is reconstructed. can do.

In this SPECT apparatus, a gamma ray detector is rotated to collect projection data from multiple directions. A gamma camera is usually used as the gamma ray detector. This gamma ray detector can collect data with higher resolution when it is closer to the subject. Therefore, the gamma ray detector is rotated on a trajectory close to the human body within a range where the gamma ray detector does not collide with the human body or the examination table. Conventionally, in order to determine the closest approach trajectory, once, the gamma ray detector is once rotated around the human body, and at that time, the operator manually adjusts the distance to the human body so that the detector approaches the human body as much as possible I have. Thus, the closest approach trajectory is obtained and stored, and data collection is performed by controlling the gamma ray detector to move on the trajectory.

[0004]

However, it is inefficient to manually obtain the closest approach trajectory as in the prior art.

In view of the above, it is an object of the present invention to provide an improved SPECT apparatus capable of automatically and safely finding the closest trajectory of a radiation detector to a subject.

[0006]

In order to achieve the above object, in a SPECT apparatus according to the present invention, a radiation detector rotated around a subject and a light beam having high directivity are irradiated to the subject. And a light receiver disposed opposite to the light emitter with the object interposed therebetween, and data obtained from the light receiver, which is related to the blocking / non-blocking of the irradiation light by the object, in the direction around the object. An arithmetic unit for reconstructing the contour of the subject and a rotation controller for calculating the trajectory of the radiation detector from the contour and rotating the radiation detector around the subject so as to move on the trajectory are provided. It has become.

[0007] A light beam having high directivity from the projector (note that
Here, “light” has a broad sense and includes infrared rays, etc.) toward the subject, and this light beam is made incident on a light receiver that is disposed opposite to the projector with the subject interposed therebetween. Since the light beam is blocked by the subject, data relating to blocking / non-blocking of the light can be obtained from the light receiving device, and the contour of the subject in the peripheral direction of the subject can be reconstructed from this data. That is, it is possible to detect the external shape of the subject using the light beam and calculate the optimum trajectory of the radiation detector in accordance with the detected external shape. Therefore, the radiation detector can be rotated so as to automatically move along the trajectory.

[0008]

Next, embodiments of the present invention will be described in detail with reference to the drawings. The SPECT apparatus according to the present invention is configured as shown in FIG. In FIG. 1, a gantry 11 has a gamma camera 1
2, the gamma camera 12 is rotated as shown by an arrow around a subject (patient) 31 disposed in a tunnel-shaped examination space.
The subject 31 is lying on an examination table (examination bed) 32 as shown in FIG. The gamma camera 12 is for detecting gamma rays from the single photon emitting RI attached to the drug administered into the subject 31. Although not shown in FIG. Is provided.

The gamma camera 12 is rotated one revolution around the subject 31 under the control of the rotation control device 15 as shown in FIG. 3, and the data collection device 13 collects projection data from 360 ° directions. Is performed, the projection data is processed by the image reconstruction device 14 using an algorithm such as a back projection method, and the body axis of the subject 31 (FIGS. 1 and 2)
A tomographic image in a cross section (XY plane) perpendicular to the Z axis is reconstructed. In this example, two gamma cameras 12 are arranged at 180 ° intervals, and 360
Two gamma cameras 12 to collect projection data
Need only be rotated 180 ° together.

In such a SPECT apparatus, according to the present invention, the light projecting unit 21 and the light receiving unit 22 are arranged to face each other with the subject 31 interposed therebetween. In this example, the light projecting unit 21 includes a large number of light emitting elements arranged on a ring-shaped rotating frame 26 that rotates on the XY plane, and the light receiving unit 22 includes a large number of light emitting elements arranged on the same rotating frame 26. Of light receiving elements. The light beam from each projector element has high directivity and is arranged to be incident on the corresponding light receiving element. Here, two sets of the light projecting unit 21 and the light receiving unit 22 are provided, and they are arranged on the rotating frame 26 at intervals of 90 °.
Data for 80 ° can be obtained.

The lower part of the abdomen of the subject 31 (position A in FIG. 2)
Image (SPE) in the range from to the top (position B in FIG. 2)
When imaging a CT image), the subject 3 is detected within the range AB.
1 must be determined. Therefore, the light emitting unit 2
1. Every time the light receiving unit 22 rotates 90 °, the entire position of the gantry 11 is shifted in the Z direction as shown by the arrow in FIG.

The light beam emitted from the light projecting unit 21 is cut off by the subject 31 and the inspection table 32, and only the light beam not cut off by these light enters the light receiving unit 22. Assuming that a signal of, for example, "1" is obtained from the light receiving element to which the light beam has entered, and a signal of, for example, "0" can be obtained from the light receiving element to which no light beam has entered, as shown in FIG. Note that data in which signals of 1 and 0 are arranged in correspondence with the position is obtained.

As shown in FIG. 3, such data obtained from the light receiving section 22 is output to the data collection device 2 for each angle.
3 collected. The rotation control device 15 controls the rotation of the rotating frame 26 and outputs a signal indicating the angle of the rotating frame 26, that is, the irradiation angle of the light beam. The angle signal is sent to the data collection device 23, and data from the light receiving unit 22 is collected for each angle.

When the light projecting unit 21 and the light receiving unit 22 rotate at a certain position in the Z direction and data of 180 ° is collected at that position, the contour reconstructing device 24 processes the data of 180 °. By doing so, the contour of the subject 31 including the examination table 32 is reconstructed at that position. As shown in FIG. 4, the trajectory of the light beam reaching the light receiving unit 22 is filled with “1”, and the superposition (addition) for each angle is performed for 180 °. An area that has not been obtained, that is, an area remaining as “0” is obtained. This region represents a region including the subject 31 and the examination table 32, and the outer edge thereof represents a contour. Based on such a principle, the contour 41 as shown in FIG.

Since a large number of contours 41 are obtained in the range from the position A to the position B, the largest one of the contours 41 is extracted and sent to the trajectory calculator 25, and the gamma camera 12 is moved to the subject 31. The trajectory 42 (FIG. 5) for rotation in the range AB is calculated. The trajectory 42 is determined as an optimal trajectory in which the gamma camera 12 moves closest to the subject 31 and the examination table 32 in the range AB without AB collision.

The data of the optimum trajectory 42 thus obtained is sent to the rotation control device 15, and the rotation control device 15 controls the movement trajectory of the gamma camera 12 so that the gamma camera 12 rotates through the optimum trajectory 42. As a result, the gamma camera 12 is configured such that the subject 31 and the examination table 3
SPECT data can be collected by moving on the trajectory closest to them, without colliding with the target 2, and a tomographic image with excellent image quality can be captured.

The above description relates to one embodiment, and it goes without saying that the specific configuration and the like can be variously changed without departing from the spirit of the present invention. For example, a configuration in which a number of elements are arranged as the configuration of the light projecting unit 21 and the light receiving unit 22 is used. It is also possible to configure so that the element and the single photodetector element are scanned in the direction perpendicular to the projection direction while facing each other to obtain data on light blocking / non-blocking at each position in the direction perpendicular to the projection direction. It is possible. Further, in the above description, the gantry 11 is shifted in the Z direction as shown by the arrow in FIG. 2 in order to obtain data by the light beam in the range AB of the subject 31.
2, the inspection table 32 may be moved in the direction opposite to the arrow in FIG.

[0018]

As described above, the SPE of the present invention
According to the CT device, the contour of the subject can be obtained by the light beam without actually bringing the radiation detector close to the subject, and the radiation detector automatically moves on the optimum trajectory calculated from the contour. Since the radiation detector can be rotated around the subject, there is no danger of the radiation detector colliding with the subject (human body), safety is enhanced, and the burden on the operator is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of a SPECT apparatus according to an embodiment of the present invention as viewed from the front.

FIG. 2 is a schematic diagram of the embodiment viewed from a side.

FIG. 3 is an exemplary block diagram showing a data processing system according to the embodiment;

FIG. 4 is an explanatory diagram for explaining data using a light beam and contour reconstruction performed using the data.

FIG. 5 is a schematic diagram showing a contour and a trajectory obtained on a predetermined section of the subject.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Gantry 12 Gamma camera 13 SPECT data acquisition device 14 Image reconstruction device 15 Rotation control device 21 Light projection unit 22 Light reception unit 23 Optical data acquisition device 24 Contour reconstruction device 25 Orbit calculator 26 Rotating frame 31 Subject 32 Examination table 41 Contour 42 orbit

Claims (1)

[Claims] 1. A radiation detector rotated around a subject, a projector for irradiating the subject with a highly directional light beam, a light receiver opposed to the projector with the subject interposed therebetween, An arithmetic unit that reconstructs a subject contour in a subject peripheral direction by processing data on blocking / non-blocking of irradiation light by the subject, obtained from the light receiver,
A SPECT apparatus comprising: a rotation controller that calculates a trajectory of the radiation detector from the contour and rotates the radiation detector around the subject so as to move on the trajectory.