JPH0457986B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention is a single photon emission
Concerning improvement of CT equipment (emission type computerized tomography equipment using single photon radionuclides).

(b) Prior art As is well known, a single photon emission CT system uses a radiation detector to image a single tomographic plane of a subject to which a radioactive isotope of a single photon-emitting nuclide has been administered. The radiation emitted from the single photon-emitting radioisotope contained in the object is made incident on the radiation detector through the collimator, data on the number of incident radiation is obtained, and this data is By processing with a computer, the radioisotope concentration distribution image in the tomographic plane of the object is reconstructed as a tomographic image.

A single photon emission CT device of a type called a ring type is constructed as shown in FIGS. 1 and 2. In FIG. 1, a large number of radiation detectors 1 are arranged and fixed in a ring shape, and a collimator 2 is placed in a rotating ring shape inside the detectors.
A subject 3 is placed inside this morimeter 2.

As shown in FIG. 2, a large number of sets of radiation detectors 1 and ring-shaped collimators 2 are arranged in three layers in a direction perpendicular to the tomographic plane of the subject 3.

Each of these ring-shaped collimators 2 is arranged so that the direction of collimation faces different tomographic planes in the plane perpendicular to the tomographic plane (parallel to the plane of the paper in Fig. 2). For example, as shown in FIG. 1, the directions of the radiation transmitting holes are determined so that the directions differ slightly within the plane (parallel to the plane). When the direction of the radiation transmitting hole is determined as shown in FIG. It swings so as to cover the entire subject 3 within the plane. This ring type collimator 2 is
It is designed to be rotationally driven by an appropriate rotational drive mechanism (not shown). In this way, the ring-shaped collimator 2 rotates 180 degrees to collect the necessary data, and in this case there are three layers, so
Tomographic images in three different tomographic planes are reconstructed.

Other types are constructed as shown in FIG.

When viewed from the side, it looks the same as in Figure 2.

A parallel plate-shaped collimator 2 and a radiation detector 1 are arranged linearly on each side of a square surrounding the subject 3, so that the collimator 2 and the radiation detector 1 rotate around the subject 3 as a unit. The necessary data can be collected by rotating them 1/4 turn.

In addition, as shown in Fig. 1, a ring-shaped collimator 2 is integrated into a ring-shaped structure and rotates as a whole.
Instead of using a collimator, there is also a type that uses a collimator that is fixed in the form of a ring as a whole and is configured by swinging each of a number of thin radiation-shielding plates so that the direction of each radiation-transmitting hole swings. .

By the way, with these single photon emission CT devices, the data collected is
The radiation is emitted from a single photon-emitting radioisotope inside the body, passes through the internal composition of the subject 3, reaches the body surface, and exits the body. It is affected by the absorption of radiation that occurs. Therefore, there is a drawback that quantitative evaluation of the obtained tomographic image is difficult.

(c) Purpose This invention improves the accuracy of quantitative measurement of data regarding the concentration distribution of single photon-emitting radioisotopes by correcting the effects of radiation absorption in the body. The purpose of the present invention is to provide a single photon emission CT device with high performance.

(d) Configuration This invention is a single photon emission device.
In a CT apparatus, a large number of radiation detectors are arranged around a subject on a predetermined tomographic plane of the subject, and a single photon-emitting radioactive substance is arranged inside the radiation detector array and is contained in the subject. an image data collection collimator that regulates the direction of incidence of radiation emitted from an isotope on the radiation detector within the tomographic plane; A collimator for collecting correction data is arranged inside the array, and a collimator for collecting correction data is arranged inside the detector array at a position opposite to the collimator for collecting correction data with the object in between. The present invention is characterized in that it includes a radiation source that can be regarded as a point source, and a rotation mechanism that rotates the correction data collection collimator and the radiation source together around the subject.

(E) Embodiment FIGS. 4 and 5 show an embodiment in which the present invention is applied to the single photon emission CT apparatus shown in FIGS. 1 and 2. In FIGS. 4 and 5, instead of the collimator 2 (see FIGS. 1 and 2) for obtaining a concentration distribution image of a single photon-emitting radioisotope within the subject 3, The fabricated collimator 5 and the lead shield 4 containing the radiation source 7 are placed inside the ring of the radiation detector 1. This lead shield 4
The collimator 5 and the collimator 5 are held by a frame 6 so as to rotate together. The lead shield 4 is used to prevent radiation from the radiation source 7 from traveling in directions other than the collimator 5. Radiation emitted from the radiation source 7 passes through the subject 3, passes through the collimator 5, and enters the radiation detector 1. The radiation detector 1 provides an output corresponding to the amount of radiation attenuation caused by the subject 3, so the radiation detector 1
Data regarding radiation absorption in the subject 3 will be detected from this point. By rotating the frame 6, data from all directions is collected, and by processing this data for image composition using a computer, a distribution of radiation absorption coefficients can be obtained, similar to the third generation CT apparatus. This distribution image is obtained for three tomographic planes that are the same as the tomographic plane from which the concentration distribution image of the single photon-emitting radioisotope is to be obtained.

After collecting data for absorption correction in this way, remove the lead shield 4 housing the radiation source 7 and the collimator 5 along with the frame 6, and replace it with a normal collimator 2 as shown in FIGS. 1 and 2. Attach to. The collimator 2 is then rotated to collect data. Since this data is influenced by radiation absorption within the body of the subject 3 as described above, it is corrected using the radiation absorption coefficient distribution data described above to remove that influence. In this way, it is possible to obtain a quantitatively accurate tomographic image of the concentration distribution of the single photon-emitting radioisotope, which is free from the influence of radiation absorption within the body of the subject 3.

In this case, the tomographic plane on which data was collected to reconstruct the tomographic image of the radioisotope concentration distribution and the tomographic plane on which the radiation absorption distribution data for correction were collected are the same tomographic plane of the same subject 3. It should be noted that since the correction data is corrected, correction data relating to the object to be corrected can be obtained, and correction can be performed with extremely high precision in accordance with the actual object 3.

FIG. 6 shows an embodiment applied to the single photon emission CT device shown in FIG. A lead shield 4 containing a source 7 and a collimator 5 are arranged.

In this case, the lead shield 4 housing the radiation source 7 and the collimator 5 are rotated together with the radiation detector 1 to obtain data regarding the distribution of the radiation absorption coefficient of the subject 3.
The data related to the concentration distribution image of radioactive isotopes in the area are corrected. In this case as well, since the tomographic planes from which both data are collected are the same tomographic plane of the same subject 3, as in the above embodiment, accurate correction can be performed.

Note that when applying to other types of single photon emission CT equipment, the collimator is replaced in the same way as in the above embodiment, and the radiation source is arranged to obtain data on the distribution of the radiation absorption coefficient of the subject. The data can be used for correction.

(F) Effect Single photon emission according to this invention
With a CT device, absorption correction data can be collected in a short time with a simple configuration in which the collimator is replaced and the collimator and the radiation source are rotated together around the subject. By using this absorption correction data, it is possible to very accurately remove the effects of radiation absorption within the subject's body, and quantitatively measure the tomographic image of the concentration distribution of single photon-emitting radioisotopes within the subject. Accuracy can be improved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the conventional example viewed from the front, Figure 2 is a schematic sectional view of the conventional example viewed from the side, and Figure 3 is a schematic cross-sectional view of the conventional example viewed from the side.
The figure is a schematic diagram of another conventional example seen from the front, FIG. 4 is a schematic diagram of an embodiment of the present invention seen from the front, and FIG.
The figure is a schematic sectional view of the same embodiment seen from the side, and FIG. 6 is a schematic diagram of another embodiment seen from the front. 1... Radiation detector, 2, 5... Collimator,
3...Subject, 4...Lead shield, 6...Frame, 7...Radiation source.

Claims (1)

[Claims] 1 A large number of radiation detectors are arranged around the subject on a predetermined tomographic plane of the subject, and radioisotopes that emit single photons contained in the subject are arranged inside the radiation detector array. an image data collection collimator that regulates the direction of incidence of emitted radiation on the radiation detector within the tomographic plane; A collimator for collecting correction data disposed in and inside the detector array,
a radiation source that can be substantially regarded as a point source on the tomographic plane, the radiation source being disposed at a position facing the correction data collection collimator across the subject;
A single photon emission CT apparatus comprising: a rotation mechanism that rotates the correction data collection collimator and the radiation source together around the subject.