Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR, China.
Department of Clinical Oncology, The Chinese University of Hong Kong, Hong Kong SAR, China.
J Appl Clin Med Phys. 2022 Aug;23(8):e13698. doi: 10.1002/acm2.13698. Epub 2022 Jun 14.
To evaluate the effect of material assignment in nasal cavity on dose calculation for the volumetric modulated arc therapy (VMAT) of nasopharyngeal carcinoma (NPC) using Acuros XB (AXB) algorithm.
The VMAT plans of 30 patients with NPC were calculated using AXB with material auto-assignment of nasal cavity to lung and reassignment to air respectively. The doses to the planning target volumes (PTVs) overlapping with nasal cavity with material auto-assignment of lung (AXB_Lung) were compared to the values obtained when nasal cavity was reassigned to air (AXB_Air) under the dose-to-medium (D ) reporting mode of AXB.
For dose calculated under AXB_Lung, the D , D , and D of the PTV _Air Cavity (PTV of prescription dose 69.96 Gy overlapping with nasal cavity) were on average 16.1%, 1.6%, and 8.6% larger than that calculated under AXB_Air, respectively. Up to 19.5% difference in D , 3% difference in D , and 11.2% difference in D were observed in the worst cases for PTV . Similar trend was observed for the PTV _Air Cavity, in which the D , D , and D calculated under AXB_Lung were on average 14.7%, 2.5%, and 10.2% larger than that calculated under AXB_Air, respectively. In the worst cases, the difference observed in D , D , and D could be up to 17.7%, 4.5%, and 12.7%, respectively.
Significant dose difference calculated by AXB between the material assignment of lung and air in nasal cavity for NPC cases might imply the possibility of underdosage to the PTVs that overlap with inhomogeneity. Therefore, attention should be put to ensure that accurate material assignment for dose calculation under AXB such that optimal dosage was given for tumor control.
评估 Acuros XB（AXB）算法在鼻咽癌调强弧形治疗（VMAT）中鼻腔材料分配对剂量计算的影响。
分别使用 AXB 对 30 例鼻咽癌患者的 VMAT 计划进行计算，鼻腔材料自动分配为肺和空气。比较鼻腔材料自动分配为肺（AXB_Lung）时与重新分配为空气（AXB_Air）时重叠鼻腔的计划靶区（PTV）的剂量，在 AXB 的剂量到介质（D）报告模式下。
对于在 AXB_Lung 下计算的剂量，PTV _Air Cavity（与鼻腔重叠的处方剂量为 69.96 Gy 的 PTV）的 D 、 D 、和 D 平均比在 AXB_Air 下计算的分别大 16.1%、1.6%和 8.6%。在最差情况下，D 、 D 、和 D 之间观察到高达 19.5%的差异。在 PTV _Air Cavity 中观察到类似的趋势，在 AXB_Lung 下计算的 D 、 D 、和 D 平均比在 AXB_Air 下计算的分别大 14.7%、2.5%和 10.2%。在最差情况下，D 、 D 、和 D 之间的差异可达 17.7%、4.5%和 12.7%。
在鼻咽癌病例中，AXB 计算的鼻腔肺和空气之间的材料分配之间存在显著的剂量差异，这可能意味着与不均匀性重叠的 PTV 存在剂量不足的可能性。因此，应注意确保 AXB 下的剂量计算进行准确的材料分配，以使肿瘤控制获得最佳剂量。
