Introduction
Given tissue inhomogeneity and lack of backscatter media, superficial brachytherapy necessitates more accurate dosimetry than TG-43 formalism. However, the introduction of modern model-based dose calculation algorithms into clinical practice should be carefully evaluated. The aim of this work was to compare dose distributions calculated with TG-43 and advanced collapsed cone engine (ACE) algorithms for individual multi-catheter moulds, and investigate the impact of target size and the lack of bolus to differences between plans.

Material and methods
Eleven treatment plans for individual mould multi-catheter high-dose-rate brachytherapy (IMM HDR) were selected for retrospective analysis. All treatment plans were initially calculated with TG-43 formula and re-calculated using ACE algorithm. Plan re-calculation with ACE was repeated for each plan in order to assess the impact of bolus. To evaluate differences between TG-43 and ACE dose distributions, dose-volume histogram (DVH) parameters for each ROI were compared. Dmax (maximal point dose), D0.1cc, and D2cc were calculated for each risk’s organ (OARs) and for external contour. For clinical target volume (CTV), D98, D90, D50, CTV coverage (CTV-V100), and dose delivered to reference point were compared between the plans.

Results
A significantly lower values (p < 0.05) of CTV parameters were observed for treatment plans calculated with ACE algorithm comparing to TG-43. Further analysis showed that differences between CTV-V100 for ACE and TG-43 plans depended on CTV volume. Dosimetric parameters for OARs were significantly lower in ACE plans than those of TG-43. Only D2cc for external and D0.1cc for both eye lenses in ACE plans were insignificantly different comparing to TG-43 plans.

Conclusions
Results show that differences between dosimetric parameters are statistically significant. However, their clinical relevance is still undetermined. Careful re-evaluation of the clinical results based on long-term research on TG-43 is necessary to safely introduce modern algorithms to clinical practice.



中文翻译：

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浅部近距离放射治疗中的高级剂量计算算法——组织不均匀性对治疗计划剂量测定的影响

简介
鉴于组织不均匀性和缺乏反向散射介质，表面近距离放射治疗需要比 TG-43 形式更准确的剂量测定。然而，应仔细评估将现代基于模型的剂量计算算法引入临床实践。这项工作的目的是比较使用 TG-43 和先进的塌陷锥形引擎 (ACE) 算法计算的单个多导管模具的剂量分布，并研究目标尺寸和缺乏丸剂对计划之间差异的影响。

材料与方法
选择了 11 种针对个体霉菌多导管高剂量率近距离放射治疗 (IMM HDR) 的治疗方案进行回顾性分析。所有治疗计划最初都使用 TG-43 公式计算，然后使用 ACE 算法重新计算。对每个计划重复使用 ACE 重新计算计划，以评估推注的影响。为了评估 TG-43 和 ACE 剂量分布之间的差异，比较了每个 ROI 的剂量体积直方图 (DVH) 参数。计算每个风险器官 (OAR) 和外部轮廓的 Dmax（最大点剂量）、D0.1cc 和 D2cc。对于临床目标体积 (CTV)、D98、D90、D50、CTV 覆盖率 (CTV-V100) 和递送至参考点的剂量在计划之间进行比较。

结果
与 TG-43 相比，使用 ACE 算法计算的治疗计划的 CTV 参数值显着降低 (p < 0.05)。进一步的分析表明，ACE 和 TG-43 计划的 CTV-V100 之间的差异取决于 CTV 体积。ACE 计划中 OAR 的剂量学参数明显低于 TG-43。与 TG-43 计划相比，ACE 计划中的外部镜片只有 D2cc 和两个眼睛镜片的 D0.1cc 差别不大。

结论
结果表明，剂量学参数之间的差异具有统计学意义。然而，它们的临床相关性仍未确定。基于对 TG-43 的长期研究，仔细重新评估临床结果对于将现代算法安全地引入临床实践是必要的。