Singh Pawan Kumar, Verma Rohit, Tripathi Deepak, Singh Sukhvir, Bhushan Manindra, Kumar Lalit, Barik Soumitra, Gairola Munish
Department of Physics, Amity Institute of Applied Sciences, Amity University (AUUP), Noida, India.
Department of Radiation Oncology, Vardhman Mahavir Medical College and Safdarjung Hospital, Delhi, India.
J Med Phys. 2024 Apr-Jun;49(2):270-278. doi: 10.4103/jmp.jmp_182_23. Epub 2024 Jun 25.
The metal present in the implant creates artifacts during the treatment simulation, which impacts the treatment planning and delivery of the prescribed dose to the target and sparing normal tissues. This retrospective study evaluated the uncertainties in the planning and delivery of doses for prosthesis cases with dedicated phantom.
In this retrospective study, 11 patients with a hip prosthesis having cervix carcinoma were selected. Two treatment plans were generated on treatment planning system (TPS) for each case. Plan_No_Res was without any beam restriction, and Plan_exit_only was the plan with restricted beam entry through the metallic implant. An indigenous phantom was utilized to verify the accuracy of the treatment. In the phantom, some groves were present, which could be filled by implants that mimic the patient's geometries, like left, right and bilateral femur implants. The delivered doses were recorded using optically stimulated luminescence dosimeters (OSLDs), which were placed at different positions in the phantom. The plans were further calculated using megavoltage computed tomography (MVCT) scans acquired during treatment.
The patient data showed no significant dose changes between the two planning methods. The treatment time increases from 412.18 ± 86.65 to 427.36 ± 104.80 with = 0.03 for Plan_No_Res and Plan_exit_only, respectively. The difference between planned and delivered doses of various points across phantom geometries was within ± 9.5% in each case as left, right, and bilateral implant. The variations between OSLDs and MVCT calculated doses were also within ± 10.8%.
The study showed the competency of tomotherapy planning for hip prosthesis cases. The phantom measurements demonstrate the errors in dosimetry near the implant material, suggesting the need for precise methods to deal with artifact-related issues.
植入物中的金属在治疗模拟过程中会产生伪影，这会影响治疗计划以及向靶区输送规定剂量并保护正常组织。这项回顾性研究评估了使用专用体模的假体病例在剂量计划和输送方面的不确定性。
在这项回顾性研究中，选取了11例患有宫颈癌的髋关节假体患者。为每个病例在治疗计划系统（TPS）上生成两个治疗计划。Plan_No_Res没有任何射束限制，而Plan_exit_only是通过金属植入物限制射束入射的计划。使用一个自制体模来验证治疗的准确性。在体模中，有一些凹槽，可以用模拟患者几何形状的植入物填充，如左、右和双侧股骨植入物。使用光激励发光剂量计（OSLD）记录输送的剂量，这些剂量计放置在体模的不同位置。使用治疗期间采集的兆伏级计算机断层扫描（MVCT）对计划进行进一步计算。
患者数据显示两种计划方法之间的剂量没有显著变化。Plan_No_Res和Plan_exit_only的治疗时间分别从412.18±86.65增加到427.36±104.80，P = 0.03。在每种情况下，如左、右和双侧植入物，体模不同几何形状各点的计划剂量与输送剂量之间的差异在±9.5%以内。OSLD和MVCT计算剂量之间的差异也在±10.8%以内。
该研究表明了断层放射治疗计划在髋关节假体病例中的适用性。体模测量显示了植入物材料附近剂量测定中的误差，表明需要精确方法来处理与伪影相关的问题。
