Rajadurai E, Saravana Kumar A, Govindarajan K N, Pandu Bharath, Jacob Saro
Department of Medical Physics, PSG Institute of Medical Sciences Research and Hospitals, Coimbatore, Tamil Nadu, India.
Department of Radiotherapy, Bangalore Baptist Hospital, Bengaluru, Karnataka, India.
J Med Phys. 2025 Jan-Mar;50(1):75-85. doi: 10.4103/jmp.jmp_155_24. Epub 2025 Feb 24.
This study aims to methodically explore and evaluate the effectiveness of volumetric-modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) with both flattened and unflattened 6MV beams for treating pharyngeal carcinomas.
Twenty patients who had previously undergone treatment for advanced pharyngeal cancer were randomly chosen. They were replanned using a fixed nine-field dynamic IMRT and VMAT with RapidArc using both 6MV flattened and unflattened beams. A total of 80 similar treatment plans were generated for the TrueBeam SVC setup. These plans were assessed for target coverage, maximum and mean doses to the organs at risk, monitor unit (MU), beam-on time, dose to healthy tissue, and other indicators of dose quality.
Target coverage was nearly identical across all the techniques. VMAT (6FF and 6FFF) achieved equivalent or superior target coverage while plans give better sparing of mean doses of parotid glands, esophagus, larynx, and maximum dose of the spinal cord while maintaining equivalent maximum dose of the brainstem. The MUs required for VMAT plans were about 4-5 times less than that of IMRT plans, additionally, the 6MV plan shows 20%-30% lesser MU than 6FFF plans in both techniques.
VMAT-6FFF shows fewer hot spots in the planning target volume (PTV) high-risk volume and equivalent or higher hot spots in the PTV intermediate-risk and PTV low-risk volumes. In terms of treatment time, VMAT 6FF has fewer MUs than VMAT 6 FFF. Hence, it shows that VMAT 6FF has less treatment time.
本研究旨在系统地探索和评估容积调强弧形放疗（VMAT）和调强放疗（IMRT）在使用均整和非均整6MV射束治疗鼻咽癌方面的有效性。
随机选择20例先前接受过晚期鼻咽癌治疗的患者。使用固定的九野动态IMRT和使用均整和非均整6MV射束的RapidArc进行VMAT对他们重新进行计划。针对TrueBeam SVC设置共生成了80个相似的治疗计划。对这些计划进行靶区覆盖、危及器官的最大剂量和平均剂量、监测单位（MU）、照射时间、健康组织剂量以及其他剂量质量指标的评估。
所有技术的靶区覆盖情况几乎相同。VMAT（6FF和6FFF）实现了等效或更好的靶区覆盖，同时计划在保持脑干最大剂量等效的情况下，对腮腺、食管、喉的平均剂量和脊髓的最大剂量有更好的 sparing。VMAT计划所需的MU比IMRT计划少约4 - 5倍，此外，在两种技术中，6MV计划的MU比6FFF计划少20% - 30%。
VMAT - 6FFF在计划靶区（PTV）高风险体积中的热点较少，在PTV中风险和PTV低风险体积中的热点等效或更多。在治疗时间方面，VMAT 6FF的MU比VMAT 6FFF少。因此，表明VMAT 6FF的治疗时间更短。
