JPS625193A - Radiation type tomograph - Google Patents

Abstract

PURPOSE:To enable an accurate absorption correction, a simple and short-time data collection and a reduction in the burden on an object to be inspected, by obtaining a transmission data on the basis of the difference between outputs from two gamma rays detectors of a camera. CONSTITUTION:A rotary plate 1a is turned and gamma rays are detected with detectors 2 and 11 at four angles of rotation with the position of the gamma rays detector 11 to collect data. In this case, the detector 2 detects gamma rays from an RI in an object 3 to be detected and emission data alone is taken in. The detector 11 detects gamma rays from the RI in the object 3 being detected and gammarays transmitted through the object 3 being detected from a flood source 4 and emission data and transmission data are taken in. Then, the difference is computed between the sum data and the output of the detector 2 to obtain a correct transmission data.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention includes a scintillation camera, an image data processing device, and a rotating plate device, and a gamma ray detector of the scintillation camera provided on the rotating plate. , relates to a radiation tomography apparatus that captures data at appropriate locations while rotating around a subject to whom a radioisotope has been administered, and reconstructs an image based on the captured emission data to obtain a tomographic image.

[Background of the invention]

In this type of device (also called an emission CT device (ECT)), gamma rays are generated from radioisotopes (hereinafter referred to as RI) deep within the subject.

Since it is absorbed inside the subject before reaching the detector, the reconstructed image value at the center of the tomographic image becomes lower than the true value.

For this reason, images have traditionally been reconstructed after performing absorption correction on the captured emission data, but conventional absorption correction is performed based on assumed values of the absorption coefficients of each part of the object. Therefore, it cannot be done accurately.

Therefore, an apparatus was devised that once collects transmission data, calculates the actual absorption coefficient from that data, and then collects emission data, performs absorption correction, and reconstructs an image. That is, as shown in FIGS. 4 and 5, 1
A gamma ray detector 2 and a subject 3 of a scintillation camera provided on an annular rotating plate 1a driven by a rotating plate device 1.
A flood source (a γ-ray source formed in a plate shape and configured to emit γ-rays of uniform intensity from each part of the plate surface) 4 is removably attached to a position on the rotary plate 1a facing each other across the plate. It is made by arranging it. As can be seen from FIG. 5, the subject 3 has its body axis aligned with the rotation center axis x of the rotating body 1a
- It is positioned toward the X direction.

In such an apparatus, the gamma rays 5 emitted from the flood source 4 and transmitted through the subject 3 are first collected by rotating the rotary plate 1a, for example, in the direction of arrow A in the figure, as in the case of collecting normal emission data. The detector 2 detects and collects transmission data. Thereafter, the seven rad sources 4 are removed from the rotary plate 1a, and the subject 3 is removed.
RI is administered, and while rotating the rotary plate 1a, the above R
The gamma rays from I are detected by the detector 2 to collect emission data. Then, absorption correction is performed on this emission data using the absorption coefficient actually obtained from the transmission data.

The image was reconstructed.

According to the above-mentioned device, the absorption coefficient is actually determined from the transmission data collected using the flood source 4,
Accurate absorption correction can be performed because absorption correction is performed in this way. However, it is necessary to drive the rotary plate device 1 twice to collect transmission data and emission data, and in the middle of the process, a flood source is detected. Since the removal work and RI administration described in step 4 are performed, it takes a lot of time and effort to collect data, and there are problems in that the operability is low and the burden on the subject is large.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems.In addition to being able to perform accurate absorption correction, data collection can be done easily and in a short time, improving operability and reducing the burden on the subject. The purpose of the present invention is to provide a radiation tomography device that can perform measurement.

[Summary of the invention]

The device of the present invention is provided with a second gamma ray detector at a position on a rotary plate separated by a predetermined rotation angle from the gamma ray detector of a scintillation camera, and a rotary plate facing the second gamma ray detector with a subject in between. A flood source is disposed at the upper position, and the transmission data is obtained by calculating the difference between the data from the two gamma ray detectors, thereby achieving the above object.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a front view showing essential parts of an embodiment of a radiation tomography apparatus according to the present invention, and FIG. 2 is a side view of the same. la, 3 and xx are the same as in FIGS. 4 and 5, respectively. 2 and 4 similarly indicate a gamma ray detector (hereinafter referred to as the first gamma ray detector) and a flood source of the scintillation camera, but in the present invention, their arrangement positional relationship is the same as that shown in FIGS. 4 and 5, as will be described later. Different from the illustration.

Reference numeral 11 denotes a gamma ray detector (second gamma ray detector) provided separately from the first gamma ray detector 2; They are arranged at positions on the rotary plate la that are 90 degrees apart in the direction of arrow A. The flood source 4 is disposed on a rotary plate la facing the second gamma ray detector 11 with the subject 3 in between.

In such a configuration, data collection is performed as follows. That is, while rotating the rotary plate 1a, for example, in the direction of arrow A in FIG.
This is performed by detecting gamma rays using the detectors 2 and 11 at four rotational angle portions of 180° and 270°. In this case, the first γ-ray detector 2 detects γ from the RI within the subject 3.
This means that only the lines are detected, that is, only the emission data is captured.

In addition, the second γ-ray detector 11 detects γ from the RI within the subject 3.
Both the γ-rays 12 and the γ-rays emitted from the flood source 4 and transmitted through the subject 3 are detected, that is, the sum data of emission data and transmission data is captured. Therefore, by calculating the difference between the sum data and the emission data captured by the first gamma ray detector 2, accurate transmission data can be obtained. Equivalent absorption coefficients are determined.

This will be explained below based on FIG. FIG. 3 is a block diagram showing an example of the essential parts of the above-mentioned device of the present invention.
and 11 are the same as in FIGS. 1 and 2, respectively. 21 is a first image memory that stores emission data taken in by the first γ-ray detector 2; 22 is a second γ-ray detector 1;
This is a second image memory that stores sum data of the emission data and transmission data captured in step 1.

These image memories 21 and 22 are 0°, 90°, 180', and 2, depending on the data acquisition location and the number thereof.
It is divided into four sections of 70°, and the data captured by the gamma ray detector 2°11 is sequentially stored in each corresponding section. Here, the sections of the image memories 21 and 22 are arranged at an angle of 270 degrees from the top of the figure.

00.90° and 180°, while the latter is O',
90°.

The reason why the angles are 180° and 270° is because the first γ-ray detector 2 is spaced 90' from the second γ-ray detector 11 in the opposite direction to the rotational direction of the rotating plate 1a, as shown in FIG. This is because it is set up as follows.

The first to fourth subtracters 23 to 26 are connected to the image memory 2.
Difference data is obtained by subtracting data stored in 1.22 for each same acquisition point (rotation angle part), and the obtained difference data, that is, transmission data, is
The image is stored in the corresponding section of the image memory 27. The image data processing device 28 calculates an absorption coefficient from the transmission data stored in the third image memory 27, performs absorption correction on the emission data stored in the first image memory 21, and then performs an image reconstruction calculation. I do.

According to the above configuration, transmission data is obtained by calculating the difference between the sum data of the emission data and transmission data captured by the second γ-ray detector 11 and the emission data captured by the first γ-ray detector 2, Since the absorption coefficient is determined in this way, the same absorption coefficient as determined by the apparatus shown in FIGS. 4 and 5 can be determined, and accurate absorption correction can be performed. Moreover, since the emission data and transmission data can be obtained with one drive operation (labor) of the rotary plate device 1, data collection can be done easily and in a short time.

In the above-described embodiment, a case has been described in which data is captured at four locations separated by 90°, but the present invention is not limited to this. When increasing or decreasing the number of data capture locations, each image memory 21.22.2
7 sections and the number of subtractors 23 to 26 may be increased or decreased, respectively.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform accurate absorption correction, and data collection can be performed easily and in a short time, improving operability and reducing the burden on the subject. .

[Brief explanation of the drawing]

FIG. 1 is a front view showing essential parts of an embodiment of the device of the present invention, FIG. 2 is a side view, FIG. 3 is a block diagram, and FIG.
The figure is a front view showing the main parts of the conventional device, and FIG. 5 is a side view. DESCRIPTION OF SYMBOLS 1... Rotating plate device, 1a... Rotating plate, 2... γ-ray detector of scintillation camera (first γ-ray detector),
3... Subject, 4... Flood source, 11...
2nd γ-ray detector, 21.22.27... Image memory, 23-26... Subtractor, 28... Image data processing device. Patent applicant Hitachi Medeico Co., Ltd. Agent Patent attorney Tadashi Akimoto Figure 1 B00 211 Figure 5/a /

Claims (1)

[Claims] It is equipped with a scintillation camera, an image data processing device, and a rotary plate device, and the gamma ray detector of the scintillation camera provided on the rotary plate is rotated around the subject to whom the radioisotope has been administered, and is placed at appropriate locations. In a radial tomography system that captures data with a camera, performs absorption correction on the captured emission data using transmission data obtained using a flood source, and reconstructs the image to obtain a tomographic image, the γ of the scintillation camera is A second gamma ray detector is provided on the rotary plate at a predetermined rotation angle away from the ray detector, and the flood detector is provided on the rotary plate at a position facing the second gamma ray detector with the object in between. A radiation tomography apparatus, characterized in that the transmission data is obtained by calculating a difference between data from the two gamma ray detectors.