摘要:
介绍了一种正电子发射断层成像术实时查找表电路.该电路接收符合电路输出的位置信号和能量信号,用查表的方法完成重心法中的除法运算,然后再第二次查表得到该丫光子所入射到的晶格的离散化坐标值和能量阈值,并完成能量甄别以剔除部分散射事件.此外,该电路还结合了呼吸门控和心电门控功能.查找表存储在flash器件中,由CPLD控制读写.本设计的特点是利用硬件电路来完成查找表功能,效率更高,每次事件的查表寻址的延迟时间小于100 ns,并且可以在线更新查找表的内容,使用方便.另外,还说明了用CPLD来读写NOR flash的方法,以及该电路与系统中其它模块间的数据通信方法.
Abstract:
A new design of look-up-table(LUT)electronics for a small animal positron emission tomography(PET)system is proposed.Position and energy signals for a coincidence event are generated in a coincidence circuit board and sent to the LUT board,in which the centroid of this event is calculated by the LUT approach.The centroid is used as an index of the crystal element.Corresponding coordinates and energy threshold of this crystal are obtained from the other tables,and the scattered events are rejected.Interfaces for receiving respiratory and electrocardiac gate signals are designed for future use.All the look-up tables are stored in NOR flash memory which is controlled by a Complex Programmable Logic Device.The LUT board communicates with PC through Ethernet board.The advantage of this specific hardware design is that the LUT operation can be performed in a more efficient way,with a＜100 ns time delay.The paper also describes the operation of the flash-memory with a CPLD,and the data flow between this LUT and other modules in our PET system.
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