基于MURA编码孔径准直器核辐射成像系统设计

Design of nuclear imaging system based on MURA coded aperture collimator

具有位置分辨能力的辐射成像系统在许多领域如天文观测、放射源检测与监控、核能开发和生物医学等都有广泛的应用。设计了一套适用于远场成像的便携式新型辐射成像系统。系统采用由LaBr3晶体与H8500平面型位置灵敏光电倍增管组成的位置灵敏探测器,满足高分辨率的设计要求。同时为了获得更高的射线探测效率,准直器采用由钨铜合金制作的修正均匀冗余阵列(MURA)嵌套编码板。图像重建算法采用最大似然期望最大化(MLEM)统计迭代算法,能够有效地抑制系统统计噪声。测试结果表明,该辐射成像系统能够对远场放射源进行清晰成像,能够很好地满足分辨率与视场角的设计要求。

Background： Location nuclear imaging systems have been used in many fields, such as astronomical observation, radioactive source monitoring, nuclear development, biomedicine, etc. Purpose： It puts forward much higher requirements of monitoring and control of safety of nuclear facilities and radioactive sources. In this paper, a new portable nuclear imaging system is designed, which can be used in far field imaging. Methods： It uses high resolution detector which consists of LaBr3 crystal and H8500 position sensitive photomultiplier to meet the design requirements of high resolution. In order to acquire the higher radiation collection efficiency, we choose modified uniformly redundant arrays （MURA） as system collimator. It uses the maximum likelihood-expectation maximization （MLEM） algorithms in reconstruction procedure. Results： The test results show that the imaging system can image the far field radioactive source clearly. The field-of-view of our system can achieve the design goal：±10°-±20°, and its resolution can be variable among 0.923°-2.038°. Conclusions： It can meet the design requirements of resolution and FOV very well. This radiation imaging system can achieve miniaturization and portability radiation imaging robot which is suited for the long-range control.