Bidmead A M, Garton A J, Childs P J
Physics Department, Royal Marsden Hospital, London, UK.
Phys Med Biol. 1995 Mar;40(3):393-411. doi: 10.1088/0031-9155/40/3/005.
The measurement of beam data for dynamic wedge dosimetry requires the integration of radiation dose at points across the radiation field during the dose delivery. The different measurement techniques required when using a linear diode array to measure beam profiles and when using ionization chambers to measure depth doses and effective wedge factors are described. The segmented treatment tables (STTS), which specify the delivered dose as a function of jaw position, are used by the control algorithm to deliver dynamic wedge fields. The reproducibility achieved using STTS is very consistent (and the stability of the accelerators is very good) so there is no significant variation in effective wedge factor or profile shape. There is a unique set of 132 STTS for each energy and design of treatment machine, which encompasses all the dynamic wedge data. There are significant discontinuities of up to 14% in wedge factors at certain field sizes. This means that wedge factors have to be measured at small increments (0.5 cm) in field size, as it is the width of the dynamic wedge field that determines the STT used. Considerable care must be taken when implementing these data on a current generation treatment planning computer.
动态楔形野剂量测定中射束数据的测量需要在剂量输送过程中对辐射野内各点的辐射剂量进行积分。描述了使用线性二极管阵列测量射束轮廓以及使用电离室测量深度剂量和有效楔形因子时所需的不同测量技术。控制算法使用分段治疗表（STT），该表将输送剂量指定为牙钳位置的函数，以输送动态楔形野。使用STT实现的再现性非常一致（并且加速器的稳定性非常好），因此有效楔形因子或轮廓形状没有显著变化。对于每台治疗机的每种能量和设计，都有一组独特的132个STT，其中包含所有动态楔形数据。在某些射野尺寸下，楔形因子存在高达14%的显著不连续性。这意味着必须在射野尺寸上以小增量（0.5厘米）测量楔形因子，因为动态楔形野的宽度决定了所使用的STT。在当前一代治疗计划计算机上实施这些数据时必须格外小心。
