JPS61155884A - Gamma camera detector - Google Patents

Abstract

PURPOSE:To correct a photomultiplier tube without moving a detector body by operating an opening/closing device with an external signal. CONSTITUTION:When the gain drift of the photomultiplier tube 9 is corrected by a gamma camera detector which obtains a two-dimensional distribution of radioisotope, one opening/closing device facing one photomultiplier tube 9 to be corrected is closed with a signal group 11 to cut off light from a scintillator 4 and a light emitting element 6 is turned on with a signal 10 to obtain a reference signal. This reference signal is passed through a light guide 7, scatteringly reflected by the opening/closing device 8 made of liquid crystal, and incident on the photodetection surface of the photomultiplier tube 9 to be corrected. At this time, almost no light enters the photomultiplier tube 9 from the scintillator 4. The shape of the opening/closing device 8 made of liquid crystal is devised to equalize reference light incident on respective photomultiplier tubes 9. Then, the output value of a photomultiplier tube 9 on which the reference signal is inputted is calculated and compared with a reference value to control the gain, thereby correcting its gain drift.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a gamma camera detector that obtains a two-dimensional distribution of radioisotopes administered into the body, and further relates to a gamma camera detector having a function of correcting gain drift of a photomultiplier tube. Regarding camera detectors.

[Technical background of the invention and its problems] When photomultiplier tubes used in gamma camera detectors are used for long periods of time, they tend to drift due to the influence of the earth's magnetism, making it difficult to accurately detect radioisotopes. It becomes difficult to obtain a two-dimensional distribution.

Therefore, it is necessary to correct it.

When correcting the gain drift of a photomultiplier tube, it is necessary to apply reference light at a certain period and change the gain of the photomultiplier tube so that its output becomes a constant value.

Conventionally, this reference light has been provided either by incorporating a light emitting element between the photomultipliers W or by using a special photomultiplier tube incorporating a light emitting element.

However, in the former case, there was a problem that the structure was complicated, and in the latter case, there was a problem that the price was high because special parts were used.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides a gamma camera detector that has a simple structure and has a function of correcting the gain drift of a photomultiplier tube without moving the gamma camera body. The purpose is to

[Summary of the invention! ! ] In order to achieve the above object, the present invention provides a light guide equipped with a light emitting element that emits reference light between a photomultiplier tube and a scintillator, and an opening/closing system that transmits or blocks light from the scintillator or diffusely reflects the reference light. It is characterized by providing means.

[Embodiments of the invention] Next, one embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, gamma rays 1 are generated from a radioisotope administered into the body.

The gamma camera detector 2 has a collimator 3, on which is placed a scintillator 4 that emits light when gamma rays 1 are incident thereon. Furthermore, a light guide 7 having a glass 5 and a light emitting element 6 that emits reference light around it is placed on the top. Built into the light guide 7 is an opening/closing means 8 made of liquid crystal that can be switched between transparent and opaque in response to an external signal. A plurality of hexagonally densely arranged photomultiplier tubes 9 are provided above the light guide 7.

The aforementioned opening/closing means 8 is provided facing the light receiving surface of the photomultiplier tube 9. Note that the signal 10 is a control signal that causes the light emitting element 6 to emit or extinguish light. Further, the signal group 11 is a control signal group for opening and closing the plurality of opening/closing means 8 one by one or together.

Next, the operation of the gamma camera detector 2 according to the present invention configured as described above will be explained.

First, the operation of the normal gamma camera detector 2 will be described. First, the opening/closing means 8 is held in an open state, that is, a transparent state, by the signal group 11, and the light emitting element 6 is extinguished by the signal 10. In this state, gamma rays 1 generated from the radioisotope administered into the body enter the scintillator 4 via the collimator 3. Here, the scintillator 4 causes scintillation and emits light. This light is glass 5
After passing through the light guide 7, the light passes through the opening/closing means 8 and enters the photomultiplier tube 9, and the position is calculated based on the output signal of the photomultiplier tube 9 to determine the incident position of the gamma ray.

Next, when correcting the gain drift of the photomultiplier tube 9 after a certain period of time has elapsed, first, one of the opening/closing means 8 facing one of the photomultiplier tubes 9 to be corrected is set to the closed state using the signal group 11. It is set in an opaque state to block light from the scintillator 4, and causes the light emitting element 6 to emit light in response to the signal 10, thereby causing the reference signal to emit light. The reference signal from the light emitting element 6 passes through the light guide 7, is diffusely reflected by the opening/closing means 8 made of liquid crystal, and enters the light receiving surface of the photomultiplier tube 9 to be corrected. At this time, almost no light from the scintillator 4 enters the photomultiplier tube 9 provided opposite the opening/closing means 8 which is in the closed state. By devising the shape of the liquid crystal opening/closing means 8, the reference light entering each photomultiplier tube 9 can be made equal. The output value of the photomultiplier tube 9 into which the reference signal is input is determined and compared with the reference value to control the gain and correct the gain drift. When the gain drift correction for one photomultiplier tube 9 is completed, the signal group 11 is controlled to correct another photomultiplier tube 9 next.

In this way, the photoelectron image fuze 9 can be corrected sequentially.

Alternatively, it is possible to control the signal group 11 to open and close all the switching devices 8 at the same time to correct all the photomultiplier tubes 9 at the same time, or it is also possible to correct each of the photomultiplier tubes in units of a fixed number.

[Effects of the Invention] As described above, according to the present invention, the photomultiplier tube can be corrected without moving the gamma camera detector main body by opening and closing the opening/closing device in response to an external signal.

Furthermore, by incorporating the opening/closing device into the light guide, a conventional gamma camera detector can be used as is.

In addition, if a switching device is provided facing each photomultiplier tube,
Correction can be performed for each photomultiplier tube one by one or for a certain number of photomultiplier tubes, and if necessary, all photomultiplier tubes can be corrected at the same time.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a gamma camera detector according to the present invention, and FIG. 2 is a sectional view taken along line I-M in FIG. 1... Gamma ray, 2... Gamma camera detector, 3...
...Collimator, 4...Scintillator, 5...Glass, 6...Light emitting element, 7...Light guide, 8...Opening/closing means, 9...
...Photomultiplier tube. Agent: Patent attorney Kensuke Norichika (and 1 other person) Figure 2

Claims (4)

[Claims] (1) Consisting of a collimator, a scintillator that emits gamma rays, and a photomultiplier tube that faces this scintillator and receives light from the scintillator, and a reference light is provided between the photomultiplier tube and the scintillator. A gamma camera detector comprising a light guide equipped with a light emitting element that emits light and an opening/closing means that transmits or blocks light from a scintillator. (2) The gamma camera detector according to claim 1, wherein the opening/closing means is a liquid crystal. (3) The gamma camera detector according to claim 1, wherein the opening/closing means is incorporated within the light guide. (4) The gamma camera detector according to claim 1, wherein the opening/closing means is provided for each predetermined number of photomultiplier tubes.