同位素Tl-201的单光子发射CT影像的康普顿散射校正

给出一种基于康普顿散射理论的Tl-201 SPECT影像的散射校正方法,此方法仅考虑一次散射和二次散射的影响.计算中将散射介质分成散射小元,然后积分求出每一小元内所有电子的散射光子数,一个电子的散射几率由Klein-Nishina公式确定,散射光子被分配至散射小元中心对应的探测器接收孔位置.辐射源的奇点问题也通过这种积分方法解决.误差主要来自于计算中有限的散射元体积和受限制的散射介质,但计算的线源响应函数和散射比与Monte Carlo计算结果相符,计算时间缩短40倍.

COMPENSATION FOR COMPTON SCATTER EFFECTS IN Tl-201 SPECT

A method based on the Compton scatter theory is derived to compensate the effects of single and double scattering in Tl-201 SPECT.The scatter medium is divided into small volume elements and the scatter counts contributed by such a volume element are obtained by integrating the number of photons scattered by all electrons within the element.The scatter probability from an electron is determined by the Klein-Nishina formula.The counts are then assigned to the detector bin that is the projection point of the center of the element.In this way the singularity in calculating the scatter counts near a point source is eliminated.The main approximation is the finite volume of the element and the limited range of scatter medium included in the calculation.In spite of the approximation,the calculated scatter line source response function and scatter-to-primary ratio agree reasonably with those from Monte Carlo simulation and the computation time is shortened 40 times.