基于LaBr_(3)(Ce)晶体耦合SiPM阵列的可变角分辨率伽玛相机的设计与研制

Design and development of a variable angular resolution gamma camera based on LaBr_(3)(Ce)crystal-coupled SiPM array

编码孔径成像技术由于探测效率高、信噪比高、角分辨率好、成像质量稳定可靠等优点而广泛应用于核安全、核设施的去污及退役的测量、核医学等领域。建立通过改变编码准直器和探测器之间距离进而实现可变角分辨的伽玛成像系统。整个成像系统主要由编码准直器、位置灵敏探测(position sensitive detector,PSD)、数据采集卡以及图像重建系统组成。该成像系统的编码准直器采用修正均匀冗余阵列(modified uniformly redundant array,MURA)编码方式,为了保障对较高能量射线的探测能力,编码准直器的材料采用含钨量90%的钨铜合金,PSD通过LaBr_(3)(Ce)晶体耦合SiPM阵列组成,重建算法采用的是直接互卷积算法,快速高效。测试结果显示,整个位置灵敏探测器的平均能量分辨率为4.96%(662 keV);该辐射成像系统可以准确地对Am-241、Cs-137、Co-60进行清晰成像,并通过改变编码准直器和探测器之间的距离成功分辨出两个Cs-137点源的位置。

Coded aperture imaging technology is widely used in nuclear safety,nuclear facility decontamination and decommissioning measurement as well as nuclear medicine due to its advantages of high detection efficiency,high signal-to-noise ratio,good angular resolution,and stable and reliable imaging quality.Aiming at the problems of the fixed imaging field of view and angular resolution of the traditional coded aperture gamma imaging system,a gamma imaging system with variable angular resolution is proposed by changing the distance between the coded collimator and the detector.The imaging system is mainly composed of coded collimator,position sensitive detector(PSD),data acquisition card and image reconstruction system.The coded collimator of the imaging system adopts the Modified Uniformly Redundant Array(MURA)coded method.In order to ensure the detection ability of higher energy rays,the material of the coding collimator adopts tungsten copper alloy with 90%tungsten content.The PSD is composed of LaBr_(3)(Ce)crystal coupled SiPM array,and the reconstruction algorithm adopts the direct convolution algorithm which is fast and efficient.The test results show that the average energy resolution of the PSD is 4.96%(662 keV).The radiation imaging system can accurately locate Am-241,Cs-137,and Co-60 clearly,and can successfully distinguish the positions of two Cs-137 point sources by changing the distance between the coded collimator and the detector.