JPH065282B2 - Output sensitivity adjustment method for scintillation camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an output sensitivity adjusting method for a scintillation camera having a signal processing function for energy correction so that the output sensitivity from each photomultiplier tube is averaged.

[Technical background of the invention and its problems]

The general structure of a scintillation camera is shown in FIG. In FIG. 4, reference numeral 1 is a scintillator that emits scintillation light when a gamma ray emitted from a subject to which a radioisotope (hereinafter referred to as RI) is injected, and 2 is scintillation light that is optically coupled to the scintillator 1. Is a photomultiplier tube (hereinafter referred to as a photomultiplier) for converting into an electric signal. A plurality of photomultipliers 2 are arranged, and these compose a detector together with a collimator, a light guide and the like (not shown). The signal from the detector (photomal output signal) is passed through the preamplifier 3 and then taken into the X and Y axis calculation circuit 4 to calculate the position information of the scintillation light, and the variable resistor 5, the summing amplifier 6 and the pulse height analysis circuit. 7, the crest value information of the added signal is calculated, and an image showing a distribution image of RI is displayed on the display system 8 based on the position information and the crest value information.

In the above configuration, the number of the photomultipliers 2 is finite, and due to variations in the optical coupling between the scintillator 1 and the photomultiplier 2, the detection sensitivity of the output of the addition amplifier 6 varies depending on the position of the incident gamma ray. Therefore, the value of the variable resistor 5 for gain adjustment corresponding to the preamplifier 3 of each Photomaru 2 is adjusted, and the output level of each Photomaru 2 is corrected so that the detection sensitivity does not differ depending on the position of the incident gamma ray. Usually, such correction is called energy correction.

In the energy correction described above, if a certain variable resistor 5 is adjusted, the gains of the other preamplifiers adjacent to it also change, so that it becomes necessary to readjust it again. That is, a satisfactory adjustment result cannot be obtained by a series of one-time adjustments, and several asymptotic adjustments are required, which is very cumbersome and takes a lot of time.

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object thereof is to provide a method for adjusting the output sensitivity of a scintillation camera in which the output sensitivity can be made constant without requiring a gain adjustment that is cumbersome and requires man-hours. is there.

[Outline of Invention]

In order to achieve such an object, the adjustment method according to the present invention is such that resistance value data of a variable resistor for gain adjustment is obtained in advance from a plurality of adjusted scintillation cameras,
In a scintillation camera having a signal processing function of energy correction so that the output sensitivity from each photomultiplier tube is averaged, the resistance value of the variable resistor is fixed based on the resistance value data. To do.

Example of Invention

An embodiment of an output sensitivity adjusting method of a scintillation camera according to the present invention will be described below with reference to FIG. 1 showing a work procedure and FIGS. 2 and 3 showing a scintillation camera to which the embodiment is applied. In FIG. 2, the same parts as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 2 and FIG. 3, the fixed resistor 9, the summing amplifier 6, and the luminance signal accompanying the wave height analysis from the wave height analysis circuit 7 and the position signal from the X and Y axis calculation circuit 4 are the image processing device 1.
At 0, energy correction processing as shown in FIG. 3 is performed, and an image showing a distribution image of RI is displayed on the display system 8 by the corrected data.

In FIG. 3 (a), the solid line shows the characteristic of the output sensitivity before the correction, and the number of the installed Photomaru 2 is finite,
An uneven-output characteristic is produced. The image processing apparatus 10 performs the weighting process shown in FIG. 3B on each output of the photomultiplier 2 to obtain a substantially averaged output sensitivity characteristic as indicated by the broken line in FIG. 3A.

A method of adjusting the output sensitivity for the scintillation camera shown in FIGS. 2 and 3 will be specifically described with reference to FIG.

First, a plurality of scintillation cameras (units A and B) which do not include the image processing device 10 shown in FIG. 4 as the process S1, that is, a model in which the resistance value of the variable resistor 5 needs to be adjusted and whose resistance value has been adjusted. , ~, No. N), the resistance value data is collected, a representative value is determined by a statistical method such as an average value method or a least squares method as a process S2, and this determined value is shown as a process S3 in FIG. It is used when adjusting a scintillation camera which is an adjustment target and has the image processing apparatus 10 shown. In step S3, the representative value obtained in step S2 is determined as the value of the fixed resistor 9 in step S32 through step S31, and the fixed resistance value is obtained. In this case, if a fixed resistance value is used, the gain of each preamplifier changes corresponding to the reason described in the prior art. Therefore, the output sensitivity needs to be readjusted, but in S33, the image processing apparatus 10 can perform the signal weighting processing as shown in FIG. 3, and the fixed resistance is set to a range in which the sensitivity can be made uniform by the signal weighting processing. If the value is set, the adjustment amount is corrected in S34.

As described above, according to this embodiment, the operational effects as listed below are provided.

 The adjustment man-hours at the time of product shipment adjustment can be saved.

 The maintenance adjustment man-hours after shipment can be reduced.

The preamplifier 3 may be replaced when a variation in sensitivity occurs (at the time of failure), but even in this case, the variation in the characteristics of the preamplifier 3 after the replacement can be corrected, so that the replacement preamplifier 3 can be selected. It does not take time and effort.

〔The invention's effect〕

As described above, according to the present invention, the resistance value data of the variable resistors for gain adjustment is previously obtained from a plurality of adjusted scintillation cameras, and the output sensitivity from each photomultiplier tube is averaged. In a scintillation camera equipped with a signal processing function for energy correction, by fixing the resistance value of the variable resistor based on the resistance value data, it is not necessary to perform gain adjustment that is cumbersome and requires man-hours, and output sensitivity It is possible to provide a method for adjusting the output sensitivity of a scintillation camera that can be made uniform.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an output sensitivity adjusting method of a scintillation camera according to the present invention, FIGS. 2 and 3 are diagrams for explaining a scintillation camera to which the present invention is applied, and FIG. 4 respectively. FIG. 4 is a block diagram showing a scintillation camera that performs energy correction by adjusting a variable resistor. 1 ... Scintillator, 2 ... Photomultiplier tube (photomar), 3
... Preamplifier, 4 ... X, Y-axis position calculation circuit, variable resistor, 6 ... Summing amplifier, 7 ... Wave height analysis circuit, 8 ... Display system,
9 ... Fixed resistance value, 10 ... Image processing device.

Claims (1)

[Claims] 1. A gamma ray of the same energy having a variable resistor for gain adjustment for adjusting the output sensitivity of each of a plurality of photomultiplier tubes optically coupled to a scintillator that emits scintillation light by incident gamma rays. In order to make the output sensitivities from the photomultiplier tubes substantially uniform when is incident, the resistance value data is obtained in advance from a plurality of scintillation cameras in which the variable resistors are set to a predetermined resistance value. In a scintillation camera equipped with a signal processing function for energy correction so that the output sensitivities from the respective photomultiplier tubes are averaged, the resistance value of the variable resistor should be fixed based on the resistance value data. A characteristic method for adjusting the output sensitivity of a scintillation camera.