Qi S, Liu R, Lian J, Hu A, Song H
UCLA School of Medicine, Los Angeles, CA.
Robert Boissoneault Oncology Inst., Ocala, FL.
Med Phys. 2012 Jun;39(6Part19):3837-3838. doi: 10.1118/1.4735663.
To compare prostate radiation planning using four VMAT techniques and IMRT on plan quality and dose delivery efficiency.
The four VMAT techniques are: 1) Monaco VMAT (Version 2.03.01, CMS Inc., MO); 2) RapidArc (Eclipse Version 10.0, Varian Medical System Inc., CA); 3) SmartArc (Pinnacle Version 9.0, Philips Radiation Oncology Systems, WI) and 4) helical TomoTherapy (TomoTherapy Version 3, Accuray Inc., CA). The IMRT planning employed 7-field fixed gantry on Pinnacle. Single full-arc plan using each technique was generated for five prostate cases. All plans were prescribed to 70 Gy (2.5 Gy/fx) to 95% PTV using 6 MV photon beams to achieve same PTV coverage and similar OAR sparing. The quality of dosimetric plans was evaluated using metrics: target coverage, heterogeneity index (HI), target/organ mean/max/min doses, EUD, dose-volume histogram, etc.
All VMAT plans are capable of delivering adequate target dose with equal or better OAR sparing than IMRT plans. The average mean PTV doses were 72.8, 73.1, 71.0 and 72.5 Gy with HIs of 1.10, 1.08, 1.03 and 1.05 for the Monaco, RadipArc, SmartArc and TomoTherapy plans respectively. In low dose range, TomoTherapy resulted in the highest V10 and V20 while V70 and V60 were generally lower compared to other plans. Generated on the same platform, the SmartArc plans were slightly more conformal (CI=1.04 vs 1.08) and less heterogeneous (HI=1.02 vs 1.04) with better OAR sparing compared to IMRT plans. The average required MUs were 817 (Monaco), 735 (RapidArc), 798 (SmartArc) and 4986(TomoTherapy), compared to 876 MUs for the IMRT plans.
All single-arc VMAT techniques under study improve normal tissue sparing with more efficient dose delivery compared to prostate IMRT plans. RapidArc plans require least MUs while SmartArc provided most homogenous plans. All VMAT plans demonstrate significantly reduced MUs to achieve comparable dosimetric plans compared to Tomotherapy.
比较使用四种容积调强弧形放疗（VMAT）技术和调强放疗（IMRT）进行前列腺放疗计划时的计划质量和剂量递送效率。
四种VMAT技术分别为：1）Monaco VMAT（版本2.03.01，CMS公司，密苏里州）；2）快速弧形放疗（Eclipse版本10.0，瓦里安医疗系统公司，加利福尼亚州）；3）智能弧形放疗（Pinnacle版本9.0，飞利浦放射肿瘤系统公司，威斯康星州）和4）螺旋断层放疗（TomoTherapy版本3，Accuray公司，加利福尼亚州）。IMRT计划在Pinnacle上采用7野固定机架。针对五例前列腺病例，使用每种技术生成单个全弧计划。所有计划均使用6兆伏光子束，规定给予95%计划靶体积（PTV）70 Gy（2.5 Gy/分次），以实现相同的PTV覆盖和类似的危及器官（OAR）保护。使用以下指标评估剂量学计划的质量：靶区覆盖、不均匀性指数（HI）、靶区/器官平均/最大/最小剂量、等效均匀剂量（EUD）、剂量体积直方图等。
与IMRT计划相比，所有VMAT计划都能够提供足够的靶区剂量，同时对OAR的保护相同或更好。Monaco、快速弧形放疗、智能弧形放疗和螺旋断层放疗计划的平均PTV平均剂量分别为72.8、73.1、71.0和72.5 Gy，HI分别为1.10、1.08、1.03和1.05。在低剂量范围内，螺旋断层放疗导致最高的V10和V20，而与其他计划相比，V70和V60通常较低。在同一平台上生成的智能弧形放疗计划与IMRT计划相比，稍更适形（适形指数CI = 1.04对1.08）且不均匀性更小（HI = 1.02对1.04），对OAR的保护更好。平均所需的机器跳数（MU）分别为817（Monaco）、735（快速弧形放疗）、798（智能弧形放疗）和4986（螺旋断层放疗），而IMRT计划为876 MU。
与前列腺IMRT计划相比，所研究的所有单弧VMAT技术均能改善对正常组织的保护，并提高剂量递送效率。快速弧形放疗计划所需的MU最少，而智能弧形放疗提供的计划最均匀。与断层放疗相比，所有VMAT计划在实现可比的剂量学计划时，MU均显著减少。
