闪烁脉冲时间信息实时处理单元设计

Real Time Processing Module for Scintillation Pulse Timing Information

多阈值采样法是以闪烁脉冲特征模型为先验知识,通过预设多个阈值电压,对脉冲上升沿数字化得到的时间-阈值采样点进行最小均方误差拟合以精确获取脉冲起始时间。高计数率是目前PET仪器发展的一个热点方向,这就要求采用多阈值方法提取时间信息的数据获取系统具有快速高效处理脉冲以减少系统死时间的能力。论文提出了一种基于FPGA的闪烁脉冲上升沿拟合算法,通过数据预处理技术、流水线设计结构和并行处理简化算法复杂度,实现实时闪烁脉冲时间信息快速获取。仿真和实验结果表明,在FPGA上实现该算法的处理速度和精度均达到设计要求,可以满足在高计数率环境下对闪烁脉冲进行实时处理的需求。

The multi-voltage threshold（MVT） method utilizes the characterizing model of scintillation pulse as a priori knowledge.It digitizes the pulse＇s leading edge with a set of predefined threshold voltages,and then accurately computes the pulse arrival time by fitting the time-threshold samples with least mean square error algorithm.Nowadays,high count rate has became an attractive feature in PET system development.The data acquisition system using MVT method to obtain timing information should have enough processing power to reduce the system dead time.In this paper,an FPGA-based pulse leading edge fitting algorithm is proposed.Technologies of data pre-processing,pipeline structure and parallel processing are employed to reduce the algorithm complexity and to realize the real-time acquisition of scintillation pulse timing information.The simulation and experimental results show that the algorithm＇s processing efficiency and accuracy have meet the design requirement and are enough for real-time pulse processing in high count rate situation.