JPH06105294B2 - Multi-slice ring ECT device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-slice ring ECT apparatus for taking a tomographic image of the distribution of RI (radioisotope) administered to a human body in multiple layers.

2. Description of the Related Art In a conventional ring ECT device, a large number of detectors each having one scintillator and one photomultiplier tube (hereinafter abbreviated as PMT) are arranged in a circle (or a polygon). . Therefore, when this is multi-sliced, it is usual to stack the above circular array of detectors in multiple layers.

Problems to be Solved by the Invention However, stacking a large number of detectors arranged in a circle (or a polygon) in a further multilayer structure requires a great number of scintillators and PMTs, which is very expensive. It will be The position of the slice plane is determined by the position of each layer of the detector circular array stacked in multiple layers, so if you want to obtain an image of a specific tomographic plane of the subject, one layer of the detector circular array is located at that position. Accurate positioning of the subject relative to the detector circular array is required to match the positions of.

This invention requires less scintillator and PMT,
An object of the present invention is to provide a multi-slice ring ECT device that can be manufactured at low cost and that requires a simple slice surface positioning operation.

Means for Solving the Problems A multi-slice ring ECT device according to the present invention is provided with a cylindrical light guide and a large number inside the cylindrical light guide so that the longitudinal direction is the axial direction of the cylindrical light guide. A long and narrow rod-shaped scintillator to be arranged, and a plurality of PMTs, which are two-dimensionally arranged on the outer surface of the cylindrical light guide, one PMT covering a plurality of scintillators, and bipolar outputs of the PMTs. Includes a number of adders corresponding to the number of scintillator boundaries, the output polarities of which are inverted when light is emitted at one side of the boundary of the scintillator and when light is emitted at the other side of the scintillator. It has a slice plane direction position calculation circuit and an Anger type body axis direction position calculation circuit.

Action The slice plane direction position calculation circuit determines which scintillator emitted light, 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 Anger method, the slice plane is arbitrarily selected.

Since one PMT covers a plurality of rod-shaped scintillators, the number thereof may be small. Further, since the scintillator also has a rod shape that is long in the body axis direction, the number can be reduced. Therefore, it becomes 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. The rod-shaped scintillator 11 is made of, for example, NaI crystal enclosed in an aluminum case, and its longitudinal direction is oriented in the axial direction of the cylindrical light guide 12. The outer surface of this cylindrical light guide 12 has many
The PMT13s are arranged two-dimensionally. Each PMT 13 covers several rod-shaped scintillators 11 (four in this embodiment, as shown in FIG. 3). Although not shown, a collimator is arranged inside the cylindrical array of the scintillator 11.

Position discrimination in the slice plane direction (direction parallel to the paper surface of FIG. 1, circumferential direction), that is, discrimination of which scintillator 11 emits light is performed by a circuit as shown in FIG. The scintillator 11 is # 1, # 2, # 3, # in the slice plane direction.
4, ..., and their boundaries are m, n, p, ..., PM
It is assumed that T13 are arranged in the slice plane direction as A, B, C, .... The outputs of the respective PMTs 13 of A, B, C, ... Are designated as A, B, C, ... And these bipolar outputs are input through adders 31, 32, 33 ,. If the output of the adder 31 emits light on the boundary m, it becomes 0 volt, when it emits light above (in FIG. 3), it becomes positive, and when it emits light below, it becomes negative. So that the output of the adder 32 is 0 volts when light is emitted on the boundary n, positive when light is emitted above it, and negative when light is emitted below it. The weighting resistors 21 to 27 are arranged so that the output of the adder 33 becomes 0 volt when light emission occurs on the boundary p, becomes positive when light emission occurs above the boundary p, and becomes negative when light emission occurs at the lower side. Determine each value. The comparators 41, 42, 43, ... Determine whether the output of the adder 31 is positive or negative. When the output is positive, "0" is output from the non-inverting output terminal and "1" is output from the inverting output terminal. , Respectively, and when negative, outputs "1" from the non-inverting output terminal.
Is output from the inverting output terminal. The non-inverting output terminal and the inverting output terminal of the adjacent ones of the comparators 41, 42, 43, ... Are connected to the respective inputs of the AND circuits 51, 52 ,. Input to the flip-flops 61, 62, ...

In this circuit, as many adders 31, 32, ... And comparators 41, 42, ... Are required as the number of boundaries of the rod-shaped scintillator 11, and the light emitting position is the place where the sign of the output signal of the adders 31, 32 ,. In other words, it is fundamental to distinguish from the radiation incident position.

For example, if γ-rays are incident on the scintillator 11 of # 2 and light is emitted from the scintillator 11 of # 2, the adder
The output of 31 is negative, the output of adder 32 is negative, and the output of adder 33 is positive. Therefore, it is possible to identify that light is emitted below the boundary n and above the boundary p, that is, that γ-rays are incident on the # 2 scintillator 11. Specifically, the comparator
An output occurs only from the AND signal 52 to which the "1" signal generated at the non-inverting output terminal of 42 and the "1" signal generated at the inverting output terminal of the comparator 43 are input, and as a result, only from the flip-flop 62. Signal is generated and the # 2 scintillator
It is determined in 11 that light emission has occurred.

On the other hand, the position discrimination in the body axis direction (direction perpendicular to the paper surface of FIG. 1, axial direction of the cylindrical array of scintillators 11), that is, the discrimination in which position in the longitudinal direction of one scintillator 11 the light emission occurs is more The known Anger method is used. For example, assuming that the PMTs 13 are arranged in three columns in the body axis direction as shown in FIG. 2, the sum of the output of energy signals of the PMTs 13 in each column, that is, the leftmost column, the central column, and the rightmost column (in FIG. 2). Where P, Q, and R respectively, the position in the body axis direction is obtained by (P−R) / (P + Q + R).

From the above, position signals in the slice plane direction and body axis direction are obtained, the position information of the collimator is added to this, and image processing is performed to reconstruct a tomographic image on the slice plane at an arbitrary position within the effective visual field. Composed. Therefore,
The slice plane that you want to obtain an image can be roughly set so that it lies within the effective visual field in the body axis direction (width in the axial direction of the cylindrical array of the scintillator 11), so the position of the slice plane is set precisely before measurement. There is no need to do it.

Although the rod-shaped scintillators 11 are arranged in a cylindrical shape in the above, they can be applied as a detector of a gamma camera if arranged in a plane.

EFFECTS OF THE INVENTION According to the multi-slice ring ECT device of the present invention, when it is desired to obtain the same effective field of view, as compared with the case of using a detector that is a combination of one scintillator and one PMT,
Since the number of scintillators and PMTs can be greatly reduced, a multi-slice ring ECT device can be manufactured at a low price. Moreover, since a tomographic image on an arbitrary slice plane can be obtained, strictness is not required when positioning the subject, which is easy.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention seen from the front, FIG. 2 is a partially cutaway side view of the embodiment, and FIG. 3 is a slice plane direction position discriminating circuit of the embodiment. It is a block diagram. 11 …… Rod scintillator 12 …… Cylindrical light guide 13 …… PMT 21 to 27 …… Weighting resistor 31 to 33 …… Adder 41 to 43 …… Comparator 51,52 …… AND circuit 61,62 …… Flip-flop

Claims (1)

[Claims] 1. A cylindrical light guide, a plurality of elongated rod-shaped scintillators arranged inside the cylindrical light guide so that the longitudinal direction is the axial direction of the cylindrical light guide, and the cylindrical light. By multiplying the photomultiplier tubes, which are arranged two-dimensionally on the outer surface of the guide, one scintillator by one, and the bipolar outputs of the photomultiplier tubes by weighted addition, A slice plane direction position calculation circuit including an adder of a number corresponding to the number of scintillator boundaries, the output polarity of which is inverted when light is emitted on one side of a certain boundary of the scintillator and when light is emitted on the other side of the boundary. , A multi-slice ring ECT device having an Anger type body axis direction position calculation circuit.