康普顿相机图像重建中的快速滤波反投影算法

提出一个由CZT像素探测器与NaI闪烁体阵列组成的康普顿相机,计算探测器系统的几何参数、散射体探测器的能量分辨率及多普勒展宽等因素对相机空间分辨率的影响.相机的总体角分辨率为5.1°~5.6°,主要影响因素为探测器系统的几何参数.首先用解析方法研究图像重建中的滤波反投影算法,不考虑展宽影响时点源重建图像的角分辨率可达1.7°,考虑展宽影响时角分辨率可达4.2°;然后利用Geant4程序进行模拟,用实际应用方法对模拟数据进行重建,不考虑展宽影响时的角分辨率为1.7°,考虑展宽影响时角分辨率可达5.1°.采用滤波反投影算法进行图像重建时,在OpenCL框架下利用GPU实现并行加速,加速比为79倍.

A Fast Filtered-Back-Projection Algorithm for Image Reconstruction of Compton Camera

A Compton camera consisting of a CZT pixel detector and a NaI scintillator array was proposed. Factors that affect angular resolution of the camera, including geometry of detectors, energy resolution and Doppler effect of CZT detector, were analyzed. Overall angular resolution was between 5.1° and 5.6° and geometry of detectors was confirmed as main factor that limits angular resolution of the camera. A filtered-back projection algorithm was analytically deduced. The angular resolution was 1.7° as broadening was omitted, and 4.2° as broadening was considered. Geant4 simulations were performed and the data were reconstructed with a practical method of filtered-back projection algorithm. Angular resolution was 1.7° as broadening was omitted and 5.1° as practical broadening factors of Compton camera was considered. Parallel acceleration with GPU in the framework of OpenCL was applied in the reconstruction and the acceleration ratio was 79.