Department of Fundamental Electricity and Instrumentation, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Belgium.
Phys Med Biol. 2010 Nov 7;55(21):6515-32. doi: 10.1088/0031-9155/55/21/012. Epub 2010 Oct 19.
This paper presents a study of possible models to describe the relation between the scintillation light point-of-origin and the measured photo detector pixel signals in monolithic scintillation crystals. From these models the X, Y and depth of interaction (DOI) coordinates can be estimated simultaneously by nonlinear least-square fitting. The method depends only on the information embedded in the signals of individual events, and therefore does not need any prior position training or calibration. Three possible distributions of the light sources were evaluated: an exact solid-angle-based distribution, an approximate solid-angle distribution and an extended approximate solid-angle-based distribution which includes internal reflection at side and bottom surfaces. The performance of the general model using these three distributions was studied using Monte Carlo simulated data of a 20 x 20 x 10 mm lutetium oxyorthosilicate (Lu₂SiO₅ or LSO) block read out by 2 Hamamatsu S8550 avalanche photo diode arrays. The approximate solid-angle-based model had the best compromise between resolution and simplicity. This model was also evaluated using experimental data by positioning a narrow 1.2 mm full width at half maximum (FWHM) beam of 511 keV photons at known positions on the 20 x 20 x 10 mm LSO block. An average intrinsic resolution in the X-direction of 1.4 mm FWHM was obtained for positions covering the complete block. The intrinsic DOI resolution was estimated at 2.6 mm FWHM.
本文研究了在整体闪烁晶体中描述闪烁光点起源与测量光电探测器像素信号之间关系的可能模型。通过这些模型，可以通过非线性最小二乘拟合同时估计 X、Y 和相互作用深度（DOI）坐标。该方法仅依赖于单个事件信号中嵌入的信息，因此不需要任何先前的位置训练或校准。评估了三种可能的光源分布：基于精确立体角的分布、近似立体角分布和包括侧面和底面内部反射的扩展近似立体角分布。使用模拟的 20x20x10mm 硅酸镥（Lu₂SiO₅ 或 LSO）闪烁体块的 2 个 Hamamatsu S8550 雪崩光电二极管（APD）阵列读取的蒙特卡罗模拟数据研究了使用这三种分布的通用模型的性能。基于近似立体角的模型在分辨率和简单性之间具有最佳折衷。该模型还使用实验数据进行了评估，通过将 511keV 光子的 1.2mm 全宽半最大值（FWHM）窄束定位在 20x20x10mm LSO 块上的已知位置。对于覆盖整个块的位置，获得了 X 方向的平均固有分辨率为 1.4mm FWHM。固有 DOI 分辨率估计为 2.6mm FWHM。
