Maharaj Kapil Dev, Goodall Simon, Sabet Mahsheed, Dass Joshua, Ibrahim Mounir, Mahmood Talat, Rowshanfarzad Pejman
School of Physics, Mathematics and Computing, The University of Western Australia, 35 Stirling Highway, Mailbag M013, Crawley, WA, 6009, Australia.
GenesisCare, Wembley, WA, Australia.
Phys Eng Sci Med. 2025 Mar 18. doi: 10.1007/s13246-025-01530-4.
Radiotherapy is an essential component of cancer treatment, but healthy tissues can be exposed to out-of-field doses, potentially causing adverse effects and secondary cancers. This study investigates peripheral doses outside the electron beam applicator in an Elekta Versa HD linear accelerator. Peripheral doses outside an electron applicator were measured using 6, 9, and 12 MeV beams at their respective maximum dose depths while maintaining a 100 cm source-to-surface distance. Measurements employed EBT3 films within Plastic Water DT phantoms. The influence of field size on penumbra width and peripheral doses were examined using various cutouts (6 × 6 cm², 10 × 10 cm², and a 5 cm diameter circle) within a 10 × 10 cm² applicator, with gantry and collimator angles set to 0 degrees. Additionally, the impact of collimator angles on penumbra width and peripheral doses was explored, enhancing the understanding of dose distribution. Measured profiles were also compared with those calculated using Monaco treatment planning system. Findings showed that both penumbra width and peripheral dose values increased with energy across different field sizes and collimator angles. Root Mean Square Deviation (RMSD) analysis indicated deviations of 1.8 mm for penumbra and 1.1% for peripheral doses between measured profiles and Treatment Planning System (TPS) predictions for all field sizes. Peripheral doses remained below 5% of the maximum dose at distances ranging from 10 to 15 mm away from the field edges, indicating acceptable tolerance levels (ICRU report 24). However, further dose reduction may be possible with additional shielding to keep doses as low as reasonably achievable. This study highlights the critical importance of considering peripheral doses in radiotherapy, emphasizing the need to evaluate the impact on healthy tissues outside the primary treatment area to ensure patient safety and mitigate long-term treatment-related side effects. The findings underscore the necessity of implementing appropriate measures to minimize peripheral doses.
放射治疗是癌症治疗的重要组成部分，但健康组织可能会受到射野外剂量的照射，这有可能导致不良反应和继发性癌症。本研究调查了医科达Versa HD直线加速器中电子束施源器外的周边剂量。在保持源皮距为100 cm的情况下，使用6、9和12 MeV的电子束在各自的最大剂量深度测量电子施源器外的周边剂量。测量采用塑料水DT模体中的EBT3胶片。在10×10 cm²的施源器内，使用各种限光筒（6×6 cm²、10×10 cm²和直径5 cm的圆形），将机架和准直器角度设置为0度，研究射野大小对半值层宽度和周边剂量的影响。此外，还探讨了准直器角度对半值层宽度和周边剂量的影响，以加深对剂量分布的理解。还将测量的剂量分布与使用Monaco治疗计划系统计算的剂量分布进行了比较。结果表明，在不同的射野大小和准直器角度下，半值层宽度和周边剂量值均随能量增加而增加。均方根偏差（RMSD）分析表明，对于所有射野大小，测量的剂量分布与治疗计划系统（TPS）预测之间的半值层偏差为1.8 mm，周边剂量偏差为1.1%。在距射野边缘10至15 mm的距离处，周边剂量仍低于最大剂量的5%，表明耐受水平可接受（ICRU报告24）。然而，通过额外的屏蔽措施进一步降低剂量是可能的，以使剂量尽可能低至合理可行的水平。本研究强调了在放射治疗中考虑周边剂量的至关重要性，强调需要评估对主要治疗区域外健康组织的影响，以确保患者安全并减轻长期治疗相关的副作用。研究结果强调了采取适当措施将周边剂量降至最低的必要性。
