The Christie Hospital, Manchester, UK.
Clin Oncol (R Coll Radiol). 2013 Apr;25(4):265-71. doi: 10.1016/j.clon.2012.11.005. Epub 2012 Dec 5.
This paper details the considerations and calculations made by this centre for the implementation of the biologically equivalent dose in 2 Gy fractions (EQD2) radiobiology calculations recommended by the Gynaecological Groupe Européen de Curiethérapie - European Society for Therapeutic Radiology and Oncology, in converting our cervix, body of uterus and vaginal vault low dose rate (LDR) treatment prescription schedules for caesium-137 to equivalent pulsed dose rate (PDR) protocols using iridium-192.
The assumptions made in order to calculate the EQD2 for both the LDR and the corresponding PDR schedules are detailed. The source geometries and prescription points are discussed for all standard treatment schedules. The prescription point for vaginal vault treatments has been altered to a 5 mm depth rather than the applicator surface, and the prescribed dose for all applicator sizes has been normalised at this depth.
The calculated PDR schedules are presented, with corresponding target and organ at risk values given for LDR and PDR versions of standard treatment schedules. A standard 32.5 Gy point A cervix prescription used in Manchester with LDR has been converted to 2 × 19 Gy for PDR.
PDR schedules have been calculated to correspond with our established LDR treatments in terms of EQD2 dose to the target. There is a theoretical improvement in the therapeutic ratio due to a reduction in the calculated EQD2 to organs at risk.
本文详细介绍了该中心在将妇科肿瘤欧洲放射治疗和肿瘤学协会推荐的等效生物剂量 2Gy 分数（EQD2）放射生物学计算应用于我们的宫颈、子宫体和阴道穹窿低剂量率（LDR）铯-137 治疗方案转换为等效脉冲剂量率（PDR）方案时所考虑的因素和计算方法，使用的是铱-192。
详细说明了为 LDR 和相应的 PDR 方案计算 EQD2 时所做的假设。讨论了所有标准治疗方案的源几何形状和处方点。阴道穹窿治疗的处方点已更改为 5 毫米深度而不是施源器表面，并且所有施源器尺寸的规定剂量已在该深度归一化。
给出了计算得到的 PDR 方案，并给出了 LDR 和 PDR 版本的标准治疗方案的靶区和危及器官的相应靶区和危及器官值。曼彻斯特使用 LDR 的标准 32.5Gy 点 A 宫颈处方已转换为 PDR 的 2×19Gy。
根据靶区的 EQD2 剂量，已计算出与我们既定的 LDR 治疗相对应的 PDR 方案。由于计算出的 EQD2 对危及器官的减少，治疗比得到了理论上的改善。
