基于平板型闪烁晶体成像探测器位置刻度系统

Position Calibration System for Imaging Detector Based on Flat Plate Scintillation Crystal

对于通过准直方式成像的γ相机,因其闪烁体、位置灵敏光电倍增管(PSPMT)光阴极均具有一定的厚度,以及通过重心法计算位置的方式等原因,造成了γ相机在不对所成图像进行修正的情况下,这些γ图像向中心压缩,即出现边沿压缩效应。为减少和修正边沿压缩效应,本文设计了一套刻度系统。该系统采用逐点扫描探测器表面的办法,获得平板型探测器有效区域内所扫点位置与探测器响应位置的原始信息,得到进入探测器的光子的真实位置与γ相机电路输出信息之间的关系映射,形成用于还原每个进入γ相机有效区域内γ光子的实际位置的查找表,从而有效解决了γ相机成像时无法避免的边沿压缩效应造成的图像畸变。该系统在刻度过程中无需人工干预,自动生成位置查找表,为γ相机小孔成像的图像还原或编码孔成像的图像重建提供了必要条件。

The routine collimation imagingγcamera would produce the gamma image with shrinkage effect if not corrected,due to such factors as scintillator thickness,PSPMT photo cathode thickness and centroid method for calculating photo position.For this reason,a newly developed calibration system was presented in this paper,and the experimental verification was carried out.The system can scan the surface of plate scintillator detector in a point-by-point way so as to obtain the initial informations of both the scanning point position within the effective zone and the response position of the plate scintillator detector.In this way,the information on the realistic position of gamma photo entering the detector and its mirror image shaped from the output circuitcan be obtained,so that the position lookup table can be created to restore the realistic position of each photo entering the effective zone ofγcamera.As a result,the image distortion arising from gamma imaging that would be unable to be avoided can be effectively reduced.The calibration system is able to create automatically aposition lookup table,without manual operation.This provides the necessary conditions for the restoration of pinhole image or/and the reconstruction of aperture-coded image by using gamma camera.