Li Z, Liu C, Palta J R
Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, USA.
Int J Radiat Oncol Biol Phys. 1998 Apr 1;41(1):239-44. doi: 10.1016/s0360-3016(98)00014-5.
To present a comparison of optimized dose distributions for a set of high-dose-rate (HDR) vaginal cylinders calculated by a commercial treatment-planning system with benchmark calculations using Monte-Carlo-calculated dosimetry data.
Optimized dose distributions using both an isotropic and an anisotropic dose calculation model were obtained for a set of HDR vaginal cylinders. Mathematical optimization techniques available in the computer treatment-planning system were used to calculate dwell times and positions. These dose distributions were compared with benchmark calculations with TG43 formalism and using Monte-Carlo-calculated data. The same dwell times and positions were used for a quantitative comparison of dose calculated with three dose models.
The isotropic dose calculation model can result in discrepancies as high as 50%. The anisotropic dose calculation model compared better with benchmark calculations. The differences were more significant at the apex of the vaginal cylinder, which is typically used as the prescription point.
Dose calculation models available in a computer treatment-planning system must be evaluated carefully to ensure their correct application. It should also be noted that when optimized dose distribution at a distance from the cylinder surface is calculated using an accurate dose calculation model, the vaginal mucosa dose becomes significantly higher, and therefore should be carefully monitored.
比较商业治疗计划系统计算的一组高剂量率（HDR）阴道施源器的优化剂量分布与使用蒙特卡罗计算剂量学数据的基准计算结果。
对于一组HDR阴道施源器，使用各向同性和各向异性剂量计算模型获得优化剂量分布。利用计算机治疗计划系统中可用的数学优化技术计算驻留时间和位置。将这些剂量分布与采用TG43形式并使用蒙特卡罗计算数据的基准计算结果进行比较。使用相同的驻留时间和位置对三种剂量模型计算的剂量进行定量比较。
各向同性剂量计算模型可能导致高达50%的差异。各向异性剂量计算模型与基准计算结果的比较更好。在阴道施源器的顶端差异更为显著，该位置通常用作处方点。
必须仔细评估计算机治疗计划系统中可用的剂量计算模型，以确保其正确应用。还应注意，当使用精确剂量计算模型计算距施源器表面一定距离处的优化剂量分布时，阴道黏膜剂量会显著更高，因此应仔细监测。
