JPS6361174A - Multislice ring ect apparatus - Google Patents

Abstract

PURPOSE:To achieve cost reduction, by a method wherein a plurality of bar- shaped scintillators are covered with one photomultiplier tube (PMT) and formed into a long bar shape in a body axis direction and a position operation circuit is provided in a slice surface direction and the body axis direction. CONSTITUTION:A large number of PMTs 13 are two-dimensionally arranged to the outside surface of a cylindrical light guide 12 and constituted so that each of them covers a plurality of bar-shaped scintillators 11. In the positional discrimination in a slice surface direction, that is, in the discrimination of the scintillator 11 generating the emission of light, for example, when it is assumed that gamma-rays are incident on the #2 scintillator 11 to generate the emission of light from the #2 scintillator 11, the outputs of adders 31-32 respectively become negative, negative and positive. Herein, it can be discriminated that the emission of light is generated below a boundary (n) and above boundary P. Concretely '1' signals respectively generated at the non-reversal and reversal output terminals of comparators 42, 43 are inputted. Output is generated only from an AND circuit 52 and, as a result, output is generated only from FF62. In the positional discrimination in a body axis direction, an Anger system is used as is conventional.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a multi-slice ring ECT device that takes tomographic images of the distribution of RI (radioisotope) administered to a human body over multiple layers.

Prior art A conventional ring ECT device has one scintillator and one scintillator.
A large number of detectors each consisting of a combination of photomultiplier tubes (hereinafter abbreviated as PMT) are arranged in a circular (or polygonal) configuration. Therefore, when making this into a multi-slice, the circular array of the detectors described above is usually stacked in multiple layers.

Problems to be Solved by the Invention However, if a large number of detectors are arranged in a circular (or polygonal) manner and then stacked in multiple layers, a large number of scintillators and PMTs are required, which is very expensive. Become something. In addition, the position of the slice plane is determined by the position of each layer of the circular array of detectors arranged in multiple layers, so if you want to obtain an image of a specific tomographic plane of the subject, place one of the circular arrays of detectors at that position. Accurate positioning of the subject relative to the circular array of detectors is required to match the position of the layers.

It is an object of the present invention to provide a multi-slice ring ECT device that requires a small number of scintillators and PMTs, can be manufactured at low cost, and requires only rough positioning of the slice plane.

Means for Solving the Problems The multi-slice ring ECT device according to the present invention includes a cylindrical light guide and an inner side of the cylindrical light guide.
A large number of slender bar-shaped scintillators are arranged so that the longitudinal direction is the axial direction of the cylindrical light guide, and scintillators are arranged two-dimensionally on the outer surface of the cylindrical light guide, each of which has a plurality of scintillators. A large number of PMTs covering the scintillator and the bipolar outputs of the PMTs are weighted and added together, so that the output polarity is reversed when light is emitted on one side of a certain boundary of the scintillator and when light is emitted on the other side. The present invention has a slice plane direction position calculation circuit including a number of adders corresponding to the number of scintillator boundaries, and an Anger type body axis direction position calculation circuit.

The active slice plane direction position calculation circuit determines in which scintillator light emission occurs, that is, the radiation incident position in the slice plane direction.

Further, since the position calculation in the body axis direction (slice thickness direction) is performed by the Unger method, the selection of the slice plane is arbitrary.

One PMT covers multiple rod-shaped scintillators, so the number of scintillators can be small, and the scintillators can also be
Since they are long rod-shaped in the direction of the body axis, the number can be reduced. Therefore, it is inexpensive.

Embodiment As shown in FIGS. 1 and 2, a large number of elongated rod-shaped scintillators 11 are arranged inside a cylindrical light guide 12. This rod-shaped scintillator 11 is made of, for example, a NaI crystal sealed in an aluminum case, and its longitudinal direction is oriented in the axial direction of the cylindrical light guide 12. A large number of PMTs 13 are two-dimensionally arranged on the outer surface of this cylindrical light guide 12.

Each PMT 13 covers several rod-shaped scintillators 11 (in this embodiment, four as shown in FIG. 3). Although not shown, a collimator is arranged inside the cylindrical array of scintillators 11.

Slice plane direction (direction parallel to the plane of the paper in Figure 1).

Position discrimination (in the circumferential direction), that is, discrimination as to which scintillator 11 emits light, is performed by a circuit as shown in FIG. The scintillator 11 is #1 and #2 in the slice plane direction.
, #3, #4,... and their boundary is m
*n, P*..., and the PMTs 13 are arranged as A, B, C1... in the slice plane direction. The outputs of each PMT 13 of A, B, C1... are designated as A, B, C1..., and these bipolar outputs are sent to adders 31.3z, 3 via weighting resistors 21 to 27.
3. Input in... Suppose that the output of the adder 31 becomes positive when light emission occurs on the boundary m, and becomes positive when light emission occurs above 0 port (in Fig. 3), and becomes negative when light emission occurs below it. In addition, the output of the adder 32 is set so that when light emission occurs on the boundary n, the output of the adder 32 becomes positive when light emission occurs above the boundary n, and becomes negative when light emission occurs below it. The weighting resistors 21 to 21 are set so that the output becomes positive when light emission occurs on the boundary p, positive when light emission occurs above it, and negative when light emission occurs below it.
Define each of the 27 items. And comparator 41.42
．． 43, . . . determine whether the output of the adder 31 is positive or negative, and when it is positive, rQ
'' and rlJ are output from the inverted output terminal, and when negative, ``1'' is output from the non-inverted output terminal, and ``0'' is output from the inverted output terminal. The non-inverting output terminal and the inverting output terminal of the adjacent comparators 41, 42, 43, .
are connected to the respective inputs of the AND circuits 51, 52, .
The outputs of... are respectively connected to flip-flops 61, 62...
・Enter in.

In this circuit, the number of adders 31, 32, . . .
, . . . are necessary, and the point where the sign of the output signal of the adders 31, 32, .

For example, if gamma rays are incident on the #2 scintillator 11 and light emission occurs in the #2 scintillator 11, the output of the adder 31 is negative, the output of the adder 32 is negative, and the output of the adder 32 is negative.
The output of 3 becomes positive. Therefore, it can be determined that light emission has occurred below the boundary n and above the boundary P, that is, that the γ rays have entered the #2 scintillator 11. Specifically, the “l” signal generated at the non-inverting output terminal of the comparator 42 and the “1” signal generated at the inverting output terminal of the comparator 43
An output is generated only from the AND circuit 52 to which the signal is input, and as a result, a signal is generated only from the flip-flop 62, and it is determined that light emission has occurred in the #2 scintillator 11.

On the other hand, position discrimination in the body axis direction (direction perpendicular to the paper plane of FIG. 1, axial direction of the cylindrical array of scintillators 11), that is, discrimination of the position in the longitudinal direction of one scintillator 11 at which light emission has occurred, has been conventionally performed. The known Unger method is used. For example, suppose that the PMTs 13 are arranged in three rows in the body axis direction as shown in FIG.
The output sums of the 13 energy signals are P and Q, respectively.

If it is R, (P-R)/(P+Q+R) The position in the body axis direction can be determined by

Through the above steps, position signals in the slice plane direction and body axis direction are obtained, and by adding the collimator position information to this and performing image processing, a tomographic image on the slice plane at any position within the effective field of view is reconstructed. configured. therefore,
It is only necessary to set the slice plane roughly so that the slice plane for which you want to obtain an image falls within the effective field of view in the body axis direction (the width in the axial direction of the cylindrical array of scintillators 11), so the position of the slice plane can be precisely set before measurement. There is no need to do so.

In addition, although the rod-shaped scintillators 11 are arranged in a cylindrical shape in the above, if they are arranged in a planar shape, they can be applied as a detector for a gamma camera.

Effects of the Invention According to the multi-slice ring ECTIII of the present invention, the number of scintillators and PMTs can be reduced compared to the case where a detector with a combination of one scintillator and one PMT is used to obtain the same effective field of view. can be significantly reduced, so a multi-slice ring ECT device can be manufactured at low cost. Furthermore, since a tomographic image can be obtained on any slice plane, precision is not required when positioning the subject, and it is easy.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of an embodiment of the present invention, FIG. 2 is a partially cutaway side view of the same embodiment, and FIG. 3 is a slice plane direction position discrimination circuit of the same embodiment. It is a block diagram. 11... Rod-shaped scintillator 12... Cylindrical light guide 13... PMT 21-27... Weighting resistors 31-33... Adders 41-43... Comparators 51, 52... AND circuit

Claims (1)

[Claims] (1) A cylindrical light guide, a large number of elongated bar-shaped scintillators arranged inside the cylindrical light guide with the longitudinal direction thereof being in the axial direction of the cylindrical light guide, and A large number of photomultiplier tubes are arranged two-dimensionally on the outer surface, each covering a plurality of scintillators, and the bipolar outputs of the photomultiplier tubes are weighted and added to form the scintillator. A slice surface direction position calculation circuit including a number of adders corresponding to the number of scintillator boundaries, whose output polarity is inverted when light is emitted on one side of a certain boundary and when light is emitted on the other side; A multi-slice ring ECT device having a body axial position calculation circuit according to the method.