JPS625192A - Ring type spect apparatus - Google Patents

Abstract

PURPOSE:To obtain a high natural spatial resolution and detection efficiency while achieving a reduction in the cost of the equipment as a whole, by using a charge split type SWPC. CONSTITUTION:A hexagonal SWPC1 has a hexagonal chamber 2 and an inert gas with a high atomic number and a quenching gas is sealed up thereinto at a high atmospheric pressure. One wire 3 is supported with an insulator strut 4 in the chamber 2 and a high voltage is applied to the wire 3 to turn outer walls 21 and 22 to a ground potential. Radiation from the RI in a person 6 to be inspected is made incident into the chamber 2 through a number of parallel slots of a hexagonal collimator 5 in the SWPC1 to obtain 1-dimensional positional information of the incident radiation along the length of the wire 3. Then, a subtractor 33, an adder 34 and a divider 35 are used to obtain a position signal and an energy signal thereby assuring an accurate discrimination of position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a nuclear medicine diagnostic device, and in particular to a ring type S
P E CT (Single Photon Emi
ssionComputed Tomograph7)
Regarding equipment.

BACKGROUND ART In a conventional ring-type SPECT device, a large number of scintillators are arranged in a ring shape around the circumference, and the light emission from each scintillator is detected by a photomultiplier tube optically coupled to each scintillator. There is. Then, the direction of incidence of the incident radiation is determined by a rotating turbofan-shaped collimator, etc., and projection data regarding the count of the incident radiation is collected.Based on this projection data, the computer administers the radiation to the subject and accumulates it in a specific organ. R doing
An image representing the concentration distribution of I (radioisotope) is reconstructed.

Problems to be Solved by the Invention Conventional ring-type SPECT devices use a combination of a scintillator and a photomultiplier tube as a radiation detector as described above, so their specific spatial resolution depends on the size of the scintillator and the photomultiplier tube. 10m limited by the diameter of the doubler tube
There is also the problem that only a spatial resolution of about mFWHM can be obtained, and that the sensitivity is reduced by the dead space between the detectors. Furthermore, the combination of a large number of scintillators and photomultiplier tubes is expensive, and a large number of electronic circuits such as single channel analyzers connected after the photomultiplier tubes are also required, leading to increased costs.

It is an object of the present invention to provide a ring-type SPECT device that improves the inherent resolution, maintains sensitivity at the same level as conventional devices, reduces costs, and has high stability.

Means for Solving the Problems In the ring-type SPECT device according to the present invention, a ring-shaped charge-splitting type single-wire position detection proportional counter (hereinafter abbreviated as 5WPC) in a circular or polygonal shape is used. This ring-shaped charge splitting type 5WPC has an inert gas with a high atomic number and a small amount of quenching gas sealed at high pressure in a ring-shaped chamber, and 7 nodes are arranged along the ring-shaped chamber. It consists of a single wire arranged in a ring shape.

When the working radiation enters the ring-shaped chamber, it causes an ionization phenomenon, and the electrons are collected in a single wire that forms the anode. These electrons flow toward both ends of the wire, but since the wire has resistance in the length direction, the output at both ends of the wire corresponds to the incident position of the radiation. Therefore, it is possible to obtain one-dimensional positional information on which position of the ring shape the radiation is incident on.

Embodiment In FIGS. 1 and 2, the hexagonal SWP C1 has a hexagonal chamber 2, and in this hexagonal chamber 2, an inert gas with a high atomic number (for example, Xe, etc.) and a quenching gas, such as CCHa, are contained. ) is enclosed in high pressure. Inside this hexagonal chamber 2, one wire 3 is supported by an insulator support 4 and is arranged in a hexagonal shape along this hexagonal chamber 2. A high voltage is applied to this wire 3, while the hexagonal outer wall 21 of the chamber 2,
The inner wall 22 is at ground potential, so that the wire 3 functions as an anode, and the chamber outer wall 21 and inner wall 22 function as a cathode.

A hexagonal collimator 5 is placed inside this hexagonal swpct. This hexagonal collimator 5 has a large number of parallel holes on each side in a direction perpendicular to that side.
Radiation from the RI in the head of the patient enters the chamber 2 through this hole. The radiation whose incident angle has been sieved in this way enters the chamber 2 and ionizes the Xe atoms.
Pairs of electrons and ions are generated, and the electrons drift toward the anode due to the electric field between the seven node cathodes, and when they reach the area of strong electric field near the anode, they cause an electron avalanche.
It is collected in wire 3 of the anode. At this time, the electrons flow in the opposite direction toward both ends A and B of the wire 3. Since this wire 3 has resistance in its length direction, the outputs a and b after passing through the integrators 31 and 32 become one-dimensional position information of the incident radiation in the length direction of the wire 3. Therefore, outputs a and b are led to a subtracter 33 and an adder 34, respectively,
By creating (a-b) and (a + b) and sending these to the divider 35, it is possible to obtain a position signal of (a-b)/(a+b). Further, the sum signal (a+b) becomes an energy signal corresponding to the energy of the incident radiation. By appropriately processing both signals, it is possible to perform accurate position discrimination.

When using this hexagon 5WPC1, hexagon 5WPC
1 together with the collimator 5 by 60° (=360'/6), projection data in each direction within a plane perpendicular to the body axis of the subject 6 can be collected.

Generally, when using a gas detector as a radiation detector, the most important issue is detection efficiency, but by sealing an inert gas with a high atomic number (such as Xe) into high pressure,
This can be improved by increasing the probability that γ-rays cause the photoelectric effect. That is, when Xe gas is sealed at 20° C. and 20 atm, the distance between the outer wall 21 and the inner wall 22 of the chamber is a practical thickness of 10 cm.
It is possible to achieve a detection efficiency comparable to that of a system using a conventional NaI scintillator for K e V gamma rays.

FIG. 3 shows another embodiment using a circular 5WPC7. Inside the circular chamber 8, one wire 9 is connected to the outer wall 81 of the chamber.
They are stretched by a large number of support wires 91 via insulators 92, and are arranged in a pseudo-circle. A high voltage is applied to this wire 9 while the circular outer wall 81 of the chamber 8
．． The inner wall 82 is at ground potential, the wire 9 functions as an anode, and the chamber outer wall 81 and inner wall 82 function as a cathode.
Inside, an inert gas with a high atomic number and a quenching gas are sealed at high pressure. A turbofan-like collimator IO is arranged inside this circular 5WPC7. By rotating this turbofan-shaped collimator 10 as shown by the arrow, the direction of incidence of radiation incident on each position is changed. In other words, the direction of incidence can be determined by the rotational position of the collimator 10.

In the case of FIG. 3, only the collimator IO needs to be rotated, and the circular 5WPC7 and the like have the advantage that no mechanical movement is required. That is, by rotating the collimator 10, projection data in each direction within a plane perpendicular to the body axis of the subject 6 can be collected.

If the circular 5WPCs 7 in FIG. 3 are stacked in many layers in the axial direction of the subject 6 as shown in FIG. 4, images of many slices at different positions in the axial direction of the subject 6 can be obtained. can be obtained at the same time. Also in the case of the embodiments of FIGS. 1 and 2,
Although not shown, hexagons swpc t may be similarly overlapped.

In the several embodiments described above, if the 7-node wire is divided into several parts in the ring direction and position information is obtained independently from each part, it is possible to cope with high counting rates.

Effects of the Invention According to the present invention, since a ring-shaped charge-splitting type 5WPC is used, it is possible to achieve high intrinsic spatial resolution and detection efficiency comparable to conventional ones, and the cost of the charge-splitting type SWPC is reduced by a scintillator and a photoelectron multiplier. Since it is much cheaper than a combination of tubes and requires a simpler electronic circuit, the cost of the entire device can be significantly reduced. Furthermore, increasing the number of different slices in the direction of the subject's body axis is easy because it is only necessary to overlap ring-shaped charge splitting SWPCs. Furthermore, since a high-pressure gas detector is used, stability is also high.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a partially cutaway perspective view of the same embodiment, Fig. 3 is a sectional view of another embodiment, and Fig. 4 is a body axial direction. FIG. 1...Hexagonal 5WPC2...Hexagonal chamber 3.9
...Wire 4...Insulator support 5.10...
・Collimator 6... Subject 7... Circular 5WPC8
...Circular chamber holder 20 hand Itomori Keiji Seisho (self-proposal) March 29, 1985 1. Indication of the incident 1985 Patent Application No. 142728 2. Name of the invention Ring-type SPECT device 3. Amendment Relationship with the case of the person who filed the patent application Address of the patent applicant: 37 Roots Funa-Omachi, Nijo-shita, Kawaramachi-dori, Nakagyo-ku, Kyoto City
No. 8 Name (199) Shimadzu Corporation Representative: Yoko Jika 4, Agent address: 504 Burke Avenue Apartment, 1-20-1 Sendagaya, Shibuya-ku, Tokyo. 6. Contents of correction (1) "Using an rNaI scintillator" in the second line of page 7 of the specification is corrected to "Using an rNaI scintillator (thickness 10 mm or more)". that's all

Claims (1)

[Claims] (1) An inert gas with a high atomic number and a small amount of quenching gas are sealed at high pressure in a ring-shaped chamber, and a single wire serving as an anode is placed along the ring-shaped chamber. Ring type S with a charge split type single wire position detection proportional counter arranged in the shape
PECT device.