正电子发射断层成像系统中数字化多通道时间数字转换研究

Multi-channel Digitized Time-to-Digital Converter of Positron Emission Tomography System

利用现场可编程门阵列(FPGA)内部延迟链,对正电子发射断层成像(PET)系统中高精度时间数字转换(TDC)进行研究。采用粗时间和精细时间相结合的方式测量时间,粗时间利用时钟计数器实现,精细时间利用FPGA延迟链实现。测试时间测量的微分非线性和积分非线性,并在双探头PET实验平台上通过时间符合,对系统总体时间分辨进行测试。实验结果表明,TDC时间分辨达79.3ps,微分非线性为-0.2LSB/0.2LSB,积分非线性为-0.2LSB/0.3LSB,双探头PET实验系统总体时间分辨达2.1ns,可满足PET系统对时间测量的要求。

High precision time-to-digital converter（TDC） in positron emission tomography（PET） system was studied with the delay chains in field-programmable-gate-array（FPGA）.Time measurement includes two parts,coarse time measurement implemented by a clock-driven counter,fine time measurement by delay chains in FPGA.Differential nonlinearity（DNL） and integral nonlinearity（INL） were tested,and also,total time resolution of the double-detector PET experimental platform was measured by time coincidence.The results demonstrate that the time resolution of TDC reaches 79.3 ps,and the DNL is between-0.2 LSB and 0.2 LSB,the INL is between-0.2 LSB and 0.3 LSB,the total time resolution of the double-detector PET experimental platform reaches 2.1 ns.Performance of the TDC,implemented in FPGA,can meet the demand of time measurement in PET system.