Rehman Jalil Ur, Isa Muhammad, Ahmad Nisar, Nasar Gulfam, Asghar H M Noor Ul Huda Khan, Gilani Zaheer Abbas, Chow James C L, Afzal Muhammad, Ibbott Geoffrey S
Department of Physics, Balochistan University of Information Technology, Engineering and Management Sciences, Quetta, Pakistan.
Department of Physics, The Islamia University of Bahawalpur, Bahawalpur, Pakistan.
J Med Phys. 2018 Apr-Jun;43(2):129-135. doi: 10.4103/jmp.JMP_106_17.
This analysis estimated secondary cancer risks after volumetric modulated arc therapy (VMAT) and compared those risks to the risks associated with other modalities of head-and-neck (H&N) radiotherapy. Images of H&N anthropomorphic phantom were acquired with a computed tomography scanner and exported via digital imaging and communications in medicine (DICOM) standards to a treatment planning system. Treatment plans were performed using a VMAT dual-arc technique, a nine-field intensity-modulated radiation therapy (IMRT) technique, and a four-field three-dimensional conformal therapy (3DCRT) technique. The prescription dose was 66.0 Gy for all three techniques, but to accommodate the range of dosimeter responses, we delivered a single dose of 6.60 Gy to the isocenter. The lifetime risk for secondary cancers was estimated according to National Council on Radiation Protection and Measurements (NCRP) Report 116. VMAT delivered the lowest maximum doses to esophagus (23 Gy), and normal brain (40 Gy). In comparison, maximum doses for 3DCRT were 74% and 40%, higher than those for VMAT for the esophagus, and normal brain, respectively. The normal tissue complication probability and equivalent uniform dose for the brain (2.1%, 0.9%, 0.8% and 3.8 Gy, 2.6 Gy, 2.3 Gy) and esophagus (4.2%, 0.7%, 0.4% and 3.7 Gy, 2.2 Gy, 1.8 Gy) were calculated for the 3DCRT, IMRT and VMAT respectively. Fractional esophagus OAR volumes receiving more than 20 Gy were 3.6% for VMAT, 23.6% for IMRT, and 100% for 3DCRT. The calculations for mean doses, NTCP, EUD and OAR volumes suggest that the risk of secondary cancer induction after VMAT is lower than after IMRT and 3DCRT.
本分析估计了容积调强弧形放疗（VMAT）后的继发癌风险，并将这些风险与头颈部（H&N）放疗的其他方式相关风险进行了比较。使用计算机断层扫描仪获取H&N人体模型的图像，并通过医学数字成像和通信（DICOM）标准将其导出到治疗计划系统。使用VMAT双弧技术、九野调强放射治疗（IMRT）技术和四野三维适形治疗（3DCRT）技术进行治疗计划。三种技术的处方剂量均为66.0 Gy，但为了适应剂量计响应范围，我们向等中心单次给予6.60 Gy剂量。根据美国国家辐射防护与测量委员会（NCRP）第116号报告估计继发癌的终生风险。VMAT对食管（23 Gy）和正常脑（40 Gy）的最大剂量最低。相比之下，3DCRT对食管和正常脑的最大剂量分别比VMAT高74%和40%。分别计算了3DCRT、IMRT和VMAT对脑（2.1%、0.9%、0.8%和3.8 Gy、2.6 Gy、2.3 Gy）和食管（4.2%、0.7%、0.4%和3.7 Gy、2.2 Gy、1.8 Gy）的正常组织并发症概率和等效均匀剂量。接受超过20 Gy的食管危及器官（OAR）体积分数，VMAT为3.6%，IMRT为23.6%，3DCRT为100%。平均剂量、正常组织并发症概率（NTCP）、等效均匀剂量（EUD）和OAR体积的计算表明，VMAT后诱发继发癌的风险低于IMRT和3DCRT。
