医科达加速器的剂量监测与控制系统

Dose monitoring and control system of Elekta linear accelerator

从机器物理和电子工程双重角度,系统全面地解析医科达直线加速器的剂量监测与控制系统全貌。剖析电离室的构造特征以及与构造特征相对应的故障发生机理,阐释漏电与短路的区别,极板间灰尘引起尖端放电打火导致极板穿孔与裂纹,极板的耐辐射性与辐照老化导致的裂纹。总结电离室漏电、短路、开路、穿孔与裂纹5种因素的原因与故障现象。提出并说明等效灵敏体积的概念,阐释剂量监测与控制的本质是保持配对收集极板之间的电离电流相等。阐释剂量均匀性的保证机制和能量稳定机制,阐述完整的剂量学质量控制调整方法和该系统的维护维修方法。

The dose monitoring and control system of Elekta linear accelerator were analyzed systematically from twofold view of machine physics and electronics engineering.The structure characteristics of ionization chamber and corresponding malfunction mechanisms were dissected and the differences between leakage and short circuit were also discussed.The discharge at sharp points result from dust between pole plates led to small hole or cracks of plate,moreover,the capability of resistant radiation and radiation aging of plates also resulted in cracks.Here,we summarized the causes of leakage,short circuit,open circuit,small hole and crack and the corresponding malfunctions,proposed and explained the concept of equivalent sensitive volume,and revealed that the essence of dose monitoring and control was to maintain the equal ionization current between paired plates.Finally,the maintain mechanism of profile uniformity and energy stabilization,and the adjustment methods for dosimetric quality control and troubleshooting were expounded.