基于FPGA的PET快速符合系统设计
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摘要
符合探测是PET成像技术的本质,其设计好坏直接影响着整个系统的性能。针对PET系统的多通道、高速、大数据处理的特性,首先引入基于视野的自适应时间窗,并将其窗值预存在FPGA RAM中以供符合查找,这在一定程度上降低了PET系统随机散射的概率,保证了符合数据的有效性;其次针对系统对后端处理速度的需求,结合FPGA并行处理的优点,在子板FPGA中提出利用并行全比较排序算法对模块时间数据进行一次排序,待数据汇总到母板FPGA中时进一步利用FIFIO缓存,完成所有子板数据的二次排序;最后为了保证数据不被丢失,提出基于多时间片的并行处理的架构,将多个时间片内的数据缓存进行乒乓处理,达到系统对实时性的要求。最终经测试表明,这种基于FPGA的以空间换时间符合策略满足人体PET成像装置对后端处理速度及实时性的要求。
Coincidence detection is the essence of PET imaging system,and its design directly affects the performance of the whole system. Focusing on the characteristics of multi-channel,high-speed and bulk data handling in PET systems,the paper first introduced the adaptive time window based on field of view and pre-stored their values in FPGA RAM for table look-up,which could reduce the random scattering probability of PET system and ensure the validity of coincidence data. Secondly,to meet the processing speed requirements of the system on back-end circuit,the first sorting was performed in childboard FPGA using comparsion sort algorithm based on the advantages of parallel processing of FPGA. And the second sorting was excuted in motherboard FPGA when all the data was cached to FIFO.Lastly,the time slice-based parallel processing architecture was proposed to ensure that system data was not lost. Multiple time-slice data was stored for "ping-pong structure" post-processing to obtain the system real-time performance. Finally,this FPGA-based coincidence strategy trading space for time was proven to fulfill the back-end processing speed and real-time requirements of human PET system through tests.
Coincidence detection is the essence of PET imaging system,and its design directly affects the performance of the whole system. Focusing on the characteristics of multi-channel,high-speed and bulk data handling in PET systems,the paper first introduced the adaptive time window based on field of view and pre-stored their values in FPGA RAM for table look-up,which could reduce the random scattering probability of PET system and ensure the validity of coincidence data. Secondly,to meet the processing speed requirements of the system on back-end circuit,the first sorting was performed in childboard FPGA using comparsion sort algorithm based on the advantages of parallel processing of FPGA. And the second sorting was excuted in motherboard FPGA when all the data was cached to FIFO.Lastly,the time slice-based parallel processing architecture was proposed to ensure that system data was not lost. Multiple time-slice data was stored for "ping-pong structure" post-processing to obtain the system real-time performance. Finally,this FPGA-based coincidence strategy trading space for time was proven to fulfill the back-end processing speed and real-time requirements of human PET system through tests.
引文
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[17]刘星.TOF-PET系统模拟[D].兰州:兰州大学,2014.
[2]Jones T,Townsend D.History and future technical innovation in positron emission tomography[J].Journal of Medical Imaging,2017,4(1):011013.
[3]Vandenberghe S,Mikhaylova E,D’Hoe E,et al.Recent developments in time-of-flight PET[J].Ejnmmi Physics,2016,3(1):3.
[4]刘伟,陈源宝,龙岸文,等.全数字化小动物PET符合探测系统的设计与研究[J].中华核医学与分子影像杂志,2013,33(3):223-225.
[5]朱雪洲.用于TOF-PET的SiPM阵列探测器读出电路研究[D].北京:清华大学,2016.
[6]刘苇.基于MVT的多通道闪烁脉冲数字化系统的设计与实现[D].武汉:华中科技大学,2015.
[7]王文博.基于FPGA的TOF PET符合判选研究[D].长春:中国科学院长春光学精密机械与物理研究所,2012.
[8]訾立强,郭宝增,于雪莲,等.基于FPGA的高速数据采集系统设计[J].电子设计工程,2014(23):74-76.
[9]Gebhardt P,Weissler B,Zinke M,et al.FPGA-based singles and coincidences processing pipeline for integrated digital PET/MR detectors[C]//Nuclear Science Symposium and Medical Imaging Conference.IEEE,2013:2479-2482.
[10]Mei X,Xi D,Zeng C,et al.A 72-channel FPGA-only MVT digitizer board and a micro-system for coincidence detection/imaging[C]//Nuclear Science Symposium and Medical Imaging Conference.IEEE,2014:1-4.
[11]胡二猛,钱承山,张永宏,等.基于FPGA的硬件排序系统设计[J].电子技术应用,2015,41(12):39-41.
[12]钱孝桃,刘超.基于FPGA的串并集合排序在雷达系统中的应用[J].电子设计工程,2015,23(23):136-137.
[13]师廷伟,金长江.基于FPGA的并行全比较排序算法[J].数字技术与应用,2013(10):126-127.
[14]王博,安军社.基于FPGA的中值滤波系统设计及仿真测试[J].电子设计工程,2016,24(19):167-170.
[15]邵高峰.符合窗对Trans-PET系统性能及图像质量的影响研究[D].武汉:华中科技大学,2016.
[16]王璐瑶.应用适应性PET--Trans-PET系统设计和实现[D].武汉:华中科技大学,2015.
[17]刘星.TOF-PET系统模拟[D].兰州:兰州大学,2014.