Department of Radiation Oncology, Kasturba Medical College (Constituent unit of Manipal Academy of Higher Education), Mangalore, Karnataka, 575 001, India.
Department of Radiation Oncology, Medicover Cancer Institute, Nellore, Andhra Pradesh, 524002, India.
Phys Eng Sci Med. 2021 Jun;44(2):425-432. doi: 10.1007/s13246-021-00992-6. Epub 2021 Mar 26.
The aim of this study was to design and fabricate a thorax phantom to quantify the radiation doses to the region of the chest wall (with 3 ionization chambers), the organ at risk (OAR) (lung), and the surface using radiochromic films (EBT3) for three different 3D CRT treatment planning techniques. Anthropomorphic phantoms are one of the best tools for verifying the quality of the radiotherapy treatment plans generated by treatment planning systems since they can provide equivalent human tissue densities. Thirty acrylic plates were cut into ellipses 21 cm in height and 31 cm in width, and slots were created to insert lung equivalent cork material and bone equivalent Teflon material. Three treatment planning techniques were designed: (A) tangential pair beams, (B) tangential pair beams with wedges and (C) tangential beams followed by an anterior oblique beam. The percentage difference between the measured point doses and the calculated doses (measured with three CC13 ionization chambers) ranged from - 3.2 to 1.6%, with a mean deviation of - 1.04 ± 1.3%. The measured mean percentage doses on the target surface with EBT3 film were 90.3% and 95.1% of the prescribed dose with 5-mm and 10-mm boluses, respectively. Finally, the average absolute dose difference between the measured and calculated surface doses was within 10 cGy in all three planning techniques. The developed thorax phantom is suitable for point dose measurements using ionization chambers and for surface dose measurements using EBT3 Gafchromic films in post-mastectomy chest wall radiotherapy.
本研究旨在设计并制作一个胸部体模，以使用 EBT3 光致变色胶片（radiochromic films）量化胸部（使用 3 个电离室）、危及器官（organ at risk，OAR）（肺）和表面的剂量，共使用了三种不同的 3D-CRT 治疗计划技术。人体模型是验证治疗计划系统生成的放射治疗计划质量的最佳工具之一，因为它们可以提供等效的人体组织密度。将 30 个亚克力板切割成高度为 21cm、宽度为 31cm 的椭圆形，并创建插槽以插入肺等效软木材料和骨等效特氟隆材料。设计了三种治疗计划技术：（A）切线对射野，（B）切线对射野加楔形板，和（C）切线射野后加前斜野。测量点剂量与计算剂量（使用三个 CC13 电离室测量）之间的百分比差异在-3.2%至 1.6%之间，平均偏差为-1.04±1.3%。使用 EBT3 胶片测量的靶区表面的平均剂量百分比分别为 90.3%和 95.1%，分别使用 5mm 和 10mm 填充物。最后，三种计划技术中，测量和计算的表面剂量之间的平均绝对剂量差异均在 10cGy 以内。开发的胸部体模适用于使用电离室进行点剂量测量，以及在后乳腺癌胸壁放疗中使用 EBT3 Gafchromic 胶片进行表面剂量测量。
