Nicolini Giorgia, Clivio Alessandro, Fogliata Antonella, Vanetti Eugenio, Cozzi Luca
Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland.
Radiat Oncol. 2009 Jul 24;4:27. doi: 10.1186/1748-717X-4-27.
A study was performed comparing dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) on patients with bilateral breast carcinoma.
Plans for IMRT and RA, were optimised for 10 patients prescribing 50 Gy to the breast (PTVII, 2.0 Gy/fraction) and 60 Gy to the tumour bed (PTVI, 2.4 Gy/fraction). Objectives were: for PTVs V(90%)>95%, D(max)<107%; Mean lung dose MLD<15 Gy, V(20Gy)<22%; heart involvement was to be minimised. The MU and delivery time measured treatment efficiency. Pre-treatment dosimetry was performed using EPID and a 2D-array based methods.
For PTVII minus PTVI, V(90%) was 97.8 +/- 3.4% for RA and 94.0 +/- 3.5% for IMRT (findings are reported as mean +/- 1 standard deviation); D(5%)-D(95%) (homogeneity) was 7.3 +/- 1.4 Gy (RA) and 11.0 +/- 1.1 Gy (IMRT). Conformity index (V(95%)/V(PTVII)) was 1.10 +/- 0.06 (RA) and 1.14 +/- 0.09 (IMRT). MLD was <9.5 Gy for all cases on each lung, V(20Gy) was 9.7 +/- 1.3% (RA) and 12.8 +/- 2.5% (IMRT) on left lung, similar for right lung. Mean dose to heart was 6.0 +/- 2.7 Gy (RA) and 7.4 +/- 2.5 Gy (IMRT). MU resulted in 796 +/- 121 (RA) and 1398 +/- 301 (IMRT); the average measured treatment time was 3.0 +/- 0.1 minutes (RA) and 11.5 +/- 2.0 (IMRT). From pre-treatment dosimetry, % of field area with gamma <1 resulted 98.8 +/- 1.3% and 99.1 +/- 1.5% for RA and IMRT respectively with EPID and 99.1 +/- 1.8% and 99.5 +/- 1.3% with 2D-array (DeltaD = 3% and DTA = 3 mm).
RapidArc showed dosimetric improvements with respect to IMRT, delivery parameters confirmed its logistical advantages, pre-treatment dosimetry proved its reliability.
开展一项研究，比较容积调强弧形放疗（RapidArc，RA）与固定野调强放疗（IMRT）对双侧乳腺癌患者的剂量学特征。
为10例患者优化IMRT和RA计划，处方剂量为乳腺50 Gy（PTVII，2.0 Gy/分次）和瘤床60 Gy（PTVI，2.4 Gy/分次）。目标为：PTV的V(90%)>95%，D(max)<107%；平均肺剂量MLD<15 Gy，V(20 Gy)<22%；尽量减少心脏受照。用MU和照射时间衡量治疗效率。使用电子射野影像装置（EPID）和基于二维阵列的方法进行治疗前剂量测定。
对于PTVII减去PTVI，RA的V(90%)为97.8±3.4%，IMRT为94.0±3.5%（结果报告为均值±1标准差）；D(5%) - D(95%)（均匀性）为7.3±1.4 Gy（RA）和11.0±1.1 Gy（IMRT）。适形指数（V(95%)/V(PTVII)）为1.10±0.06（RA）和1.14±0.09（IMRT）。每侧肺的所有病例MLD均<9.5 Gy，左肺的V(20 Gy)为9.7±1.3%（RA）和12.8±2.5%（IMRT），右肺情况类似。心脏平均剂量为6.0±2.7 Gy（RA）和7.4±2.5 Gy（IMRT）。MU方面，RA为796±121，IMRT为1398±301；平均测量治疗时间为3.0±0.1分钟（RA）和
