Radiation Oncology Department, Oncology Institute of Southern Switzerland, Bellinzona, Switzerland.
Radiat Oncol. 2010 Nov 15;5:106. doi: 10.1186/1748-717X-5-106.
A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer.
Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV_WAR) and 45 Gy to the pelvis and pelvic nodes (PTV_Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V90% > 95%, for PTV_Pelvis: Dmax < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds.
IMRT and RapidArc resulted comparable for target coverage. For PTV_WAR, V90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV_Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U5-95% = D5%-D95%/Dmean). U5-95% for PTV_WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV_Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAIIMRT6 = 97.3 ± 2.6%, GAIIMRT15 = 94.4 ± 2.1%, GAIRA6 = 98.7 ± 1.0% and GAIRA15 = 95.7 ± 3.7%.
RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT.
本研究旨在评估卵巢癌全腹部放疗（WAR）后容积调强弧形治疗（RapidArc，RA）和固定野调强放疗（IMRT）的剂量学特征。
为 5 名患者分别优化了 IMRT 和 RA 计划，处方全腹部 25 Gy（PTV_WAR）和骨盆及盆腔淋巴结 45 Gy（PTV_Pelvis），采用同步整合推量（SIB）技术。使用 6 MV（RA6、IMRT6）和 15 MV（RA15、IMRT15）光子进行了计划研究。目标是：对于两个 PTV，V90%>95%；对于 PTV_Pelvis，Dmax<105%；对于危及器官，需要最大限度地保护。MU 和治疗时间衡量了治疗效率。使用 3%和 3mm 阈值的伽马一致性指数（GAI）对治疗前质量保证进行评分。
IMRT 和 RapidArc 对靶区覆盖的结果相当。对于 PTV_WAR，V90%分别为 99.8±0.2%和 93.4±7.3%（IMRT6 和 IMRT15），98.4±1.7%和 98.6±0.9%（RA6 和 RA15）。对于 PTV_Pelvis，靶区覆盖得到了改善。RapidArc 使剂量均匀性略有改善（均匀度定义为 U5-95%=D5%-D95%/Dmean）。PTV_WAR 的 U5-95%分别为 0.34±0.05 和 0.32±0.06（IMRT6 和 IMRT15），0.30±0.03 和 0.26±0.04（RA6 和 RA15）；对于 PTV_Pelvis，所有技术的结果均相等为 0.1。对于危及器官，不同技术之间存在细微差异。MU 分别为 3130±221（IMRT6）、2841±318（IMRT15）、538±29（RA6）、635±139（RA15）；平均测量治疗时间分别为 18.0±0.8 和 17.4±2.2 分钟（IMRT6 和 IMRT15）和 4.8±0.2 分钟（RA6 和 RA15）。GAIIMRT6=97.3±2.6%，GAIIMRT15=94.4±2.1%，GAIRA6=98.7±1.0%，GAIRA15=95.7±3.7%。
RapidArc 为 WAR 治疗提供了一种解决方案，与 IMRT 相比，它具有良好的剂量学特征，并且具有显著的逻辑改进。
