Medical Physics & Informatics Lab., Department of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan.
J Appl Clin Med Phys. 2011 Nov 15;12(4):3587. doi: 10.1120/jacmp.v12i4.3587.
The purpose of this study was to evaluate and quantify the planning performance of SmartArc-based volumetric-modulated arc radiotherapy (VMAT) versus fixed-beam intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) using a sequential mode treatment plan. The plan quality and performance of dual arc-VMAT (DA-VMAT) using the Pinnacle3 Smart-Arc system (clinical version 9.0; Philips, Fitchburg, WI, USA) were evaluated and compared with those of seven-field (7F)-IMRT in 18 consecutive NPC patients. Analysis parameters included the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), maximum and mean dose, normal tissue complication probability (NTCP) for the specified organs at risk (OARs), and comprehensive quality index (CQI) for an overall evaluation in the 11 OARs. Treatment delivery time, monitor units per fraction (MU/fr), and Gamma(3 mm, 3%) evaluations were also analyzed. DA-VMAT achieved similar target coverage and slightly better homogeneity than conventional 7F-IMRT with a similar CI and HI. NTCP values were only significantly lower in the left parotid gland (for xerostomia) for DA-VMAT plans. The mean value of CQI at 0.98 ± 0.02 indicated a 2% benefit in sparing OARs by DA-VMAT. The MU/fr used and average delivery times appeared to show improved efficiencies in DA-VMAT. Each technique demonstrated high accuracy in dose delivery in terms of a high-quality assurance (QA) passing rate (> 98%) of the Gamma(3 mm, 3%) criterion. The major difference between DA-VMAT and 7F-IMRT using a sequential mode for treating NPC cases appears to be improved efficiency, resulting in a faster delivery time and the use of fewer MU/fr.
本研究旨在通过序贯模式治疗计划，评估并量化基于 SmartArc 的容积调强弧形放疗（VMAT）与固定束强度调制放疗（IMRT）治疗鼻咽癌（NPC）的计划性能。我们评估并比较了使用 Pinnacle3 Smart-Arc 系统（临床版 9.0；飞利浦，美国威斯康星州菲特堡）的双弧-VMAT（DA-VMAT）与七野（7F）-IMRT 计划质量和性能，共有 18 例连续 NPC 患者参与。分析参数包括计划靶区（PTV）的适形指数（CI）和均匀性指数（HI）、最大和平均剂量、指定危及器官（OAR）的正常组织并发症概率（NTCP），以及 11 个 OAR 整体评估的综合质量指数（CQI）。还分析了治疗传输时间、每分次的监测单位数（MU/fr）和 Gamma（3mm，3%）评估。DA-VMAT 实现了与传统 7F-IMRT 相似的靶区覆盖和稍好的均匀性，CI 和 HI 相似。仅在左侧腮腺（口干）的 NTCP 值在 DA-VMAT 计划中明显更低。0.98±0.02 的平均 CQI 值表明，DA-VMAT 可使 OAR 受照剂量减少 2%。MU/fr 的使用和平均传输时间似乎显示出 DA-VMAT 的效率提高。两种技术在剂量传递方面都表现出了很高的精度，Gamma（3mm，3%）标准的高质量保证（QA）通过率均>98%。在使用序贯模式治疗 NPC 病例时，DA-VMAT 和 7F-IMRT 的主要区别似乎在于效率提高，从而使传输时间更快，MU/fr 使用更少。
