JPH03586B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention belongs to the technical field of tomography devices,
By rotating and scanning a radiation detector, whose spatial resolution decreases at least in inverse proportion to the distance to the subject, around the subject's body axis, radiation emitted by radioactive elements distributed within the subject is detected, and the detected data is The present invention relates to a radiation tomography apparatus that reconstructs a tomographic image of a subject.

Technical background of the invention and its problems A radiation tomography apparatus, such as a gamma ray tomography apparatus, uses, for example, an Anger type gamma camera as shown in FIG. 1 as a radiation detector 1 (hereinafter also simply referred to as a detector). This is rotated in steps or continuously around the subject 2, and the detector 1 detects and collects gamma rays emitted from within the subject 2 in all directions on the rotating surface, and processes all the obtained detection data. This method reconstructs a tomographic image of the subject.

However, a detector usually has the characteristic that its spatial resolution and detection sensitivity decrease significantly as the distance from the subject increases. Therefore, in a tomographic image of the subject obtained by rotating and scanning a circumference of a radius R centered on the body axis with the detector 1, the central part becomes unclear.
It could not be used as appropriate medical information for diagnosis.

Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and provides a radiation tomography apparatus capable of obtaining clear and good tomographic images even though the detector has the above-mentioned characteristics. The purpose is to

Summary of the invention The summary of the invention for achieving the above object is as follows:
A measurement position detection means is provided to detect the distance between the subject and the detector, and the detector is brought close to the subject when measuring radiation, and after radiation measurement, the detector is moved sufficiently away from the subject. The feature is that the detector is rotated to the next measurement angle, and the tomographic image of the subject is reconstructed based on the detection data obtained by the detector that rotates and scans around the subject by repeating the following two operations: This is a radiographic tomography device.

Embodiment of the Invention Next, an embodiment of the invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention, and FIG. 3 is an explanatory diagram showing rotational scanning by the detector in this invention.

As shown in FIG. 2, a radiation tomography apparatus, such as a gamma ray tomography apparatus, mainly includes a gamma ray detector 4, a data collection processing section 5, a rotational movement means 6 for the gamma ray detector, and a rotation angle detection section 7 for the gamma ray detector. , gamma ray detector measurement position detection unit 8,
The gamma ray detector includes a rotation radius detector 9, a linear movement means 10 in the rotation radius direction of the gamma ray detector, and a control means 11 for controlling movement of the gamma ray detector.

The gamma ray detector 4 includes, for example, a collimator,
It is equipped with at least a scintillator, a light guide, and a photomultiplier tube, and is placed at a predetermined position relative to the subject 2 by a gamma ray detector rotational movement means 6 and a gamma ray detector linear movement means 10, which will be described later. is configured to detect gamma rays from radioisotopes (RI) in

The data collection processing unit 5 collects detection data per unit time output from the gamma ray detector 4 placed at a predetermined position with respect to the subject 2, and processes the collected data by a computer using, for example, a convolution method. , which reconstructs a tomographic image of the subject 2.

The gamma ray detector rotational movement means 6 (hereinafter also simply referred to as rotational movement means) has, for example, a fixed pedestal equipped with a fixed pedestal and the gamma ray detector 4 and supported by the fixed pedestal. The gamma ray detector 4 is rotated around the body axis of the subject 2 by rotating the fixed frame in a vertical plane using a source.

Rotation angle detection section 7 of gamma ray detector 4 (hereinafter referred to as
It is also simply referred to as an angle detection section. ) is a device that detects the rotation angle of the gamma ray detector 4, for example,
It can be constructed as appropriate using an encoder, potentiometer, or the like.

The measurement position detection unit 8 (hereinafter also simply referred to as measurement position detection unit) of the gamma ray detector detects the position of the gamma ray detector 4 at a constant distance from the subject 2 along the radial direction of the rotational trajectory of the gamma ray detector 4. It is a device for detecting the presence of an object, and can be suitably configured using, for example, a proximity switch.

The rotation radius detection unit 9 of the gamma ray detector (hereinafter also simply referred to as the rotation radius detection unit) is a device that detects that the gamma ray detector 4 is located on a rotation orbit, and uses, for example, a lead screw, etc. It can be configured as appropriate.

The linear movement means 10 in the rotational radius direction of the gamma ray detector (hereinafter also referred to as simple linear movement means) is as follows:
It is a device for moving the gamma ray detector 4 along the radial direction of the rotating orbit. For example, the gamma ray detector 4 can be appropriately configured to be mounted on a rotating mount so that it can reciprocate along the radial direction of the rotating orbit. can.

Control means 11 for controlling movement of the gamma ray detector
(hereinafter also simply referred to as control means) inputs detection signals from the rotation angle detection section 7, measurement position detection section 8, and rotation radius detection section 9, and brings the gamma ray detector close to the subject when measuring gamma rays. After measuring gamma rays, the gamma ray detector is separated from the subject, and a drive signal and a stop signal are sent to the rotational movement means 6 and the linear movement means 10 so that the gamma ray detector is rotated by a predetermined angle after the gamma ray detector is separated from the subject at a certain distance. It is configured to output data regarding the position of the gamma ray detector 4 at the time of gamma ray measurement to the data collection processing section 5.

Next, the operation of the above configuration will be described.

As shown in FIG. 3, the initial state is a state in which the gamma ray detector 4 is located above the subject 2 on the rotating orbit.

First, the linear movement means 10 is driven by a drive signal output from the control means 11, and the gamma ray detector 4 is lowered toward the subject 2 along the radial direction. When the descending gamma ray detector 4 reaches a certain distance from the subject 2, the control means 11 outputs a stop signal to the linear movement means 10 according to the detection signal output by the measurement position detection section 8, and the gamma ray detector 4
stop moving. Next, gamma ray detector 4
detects and measures RI within the subject 2, and outputs the detected data to the data processing section 5.

When the measurement at that position is completed, the control means 11
The drive signal output from the linear moving means 1
0 is driven, and the gamma ray detector 4 rises along the radial direction in the direction of arrow 3A in FIG. When the gamma ray detector 4 rises and reaches the rotational orbit, the control means 11 inputs the detection signal output from the rotation radius detection section 9 and outputs a stop signal to the linear movement means 10, and the gamma ray detector 4 stop moving.

Next, the rotational movement means 6 is operated by a drive signal from the control means 11, and the gamma ray detector 4 is moved to the third position.
Rotationally moves in the direction of arrow 3B in the figure. When the rotating gamma ray detector 4 reaches a position at a predetermined rotation angle α with respect to the initial position, the angle detection unit 7
The control means 11 outputs a stop signal to the rotational movement means 6 by inputting the detection signal output from the gamma ray detector 4, and stops the rotational movement of the gamma ray detector 4.

By repeating the above operations, the gamma ray detector 4
is rotated and scanned around the body axis of the subject 2,
The data collection processing unit collects data on the proximity position of the gamma ray detector 4 and the subject 2 during RI measurement, data on the rotation angle of the gamma ray detector 4, and all detection data detected and measured by the gamma ray detector 4. 5, and the data collection processing unit 5
Based on these data, a tomographic image of the subject 2 is reconstructed by a convolution method or the like.

As is clear from the above configuration and operation, when the gamma ray detector 4 is fixed and moved, the gamma ray detector 4 is moved away from the subject 2, so the safety of the subject 2 is ensured without colliding with the subject 2. can do. When measuring RI, since the gamma ray detector 4 is brought close to the subject 2, the RI can be detected and measured with detector characteristics of high resolution and high sensitivity. Moreover, gamma ray detector 4
When approaching the subject 2, the gamma ray detector 4 detects that it has reached a certain distance from the subject 2 and stops the linear movement of the gamma ray detector 4 toward the subject 2. , the safety of the subject 2 can be ensured without the gamma ray detector 4 coming too close to the subject 2 and crushing the subject 2.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the embodiment described above, and can be implemented with various modifications within the scope of the gist of the invention.

Effects of the Invention According to the present invention, the following effects can be achieved. In other words, even though the spatial resolution and detection sensitivity of radiation detectors decrease in inverse proportion to the distance from the subject, the safety of the subject can be maintained up to the distance where high resolution and high detection sensitivity can be achieved. At the same time, since the radiation detector is brought close to the subject for each measurement, a clear tomographic image can always be reconstructed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing rotational scanning by a radiation detector in a conventional radiation tomography apparatus, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a rotational scanning by a radiation detector in the present invention. FIG. 4... Gamma ray detector, 5... Data collection processing section, 6... Rotation movement means, 7... Rotation angle detection section, 8... Measurement position detection section, 9... Rotation radius detection section, 10... Straight line Movement means, 11... control means.

Claims (1)

[Claims] 1 By rotating and scanning a radiation detector, whose spatial resolution decreases in inverse proportion to the distance to the subject, around the subject's body axis, radiation emitted by radioactive elements distributed within the subject is detected, and the radiation detected by the subject is detected. In a radiation tomography apparatus that reconstructs a tomographic image of A radiation tomography apparatus comprising: a control means for bringing a detector close to a subject and for moving the radiation detector away from the subject during rotational movement.