Distefano Gail, Lee Jonny, Jafari Shakardokht, Gouldstone Clare, Baker Colin, Mayles Helen, Clark Catharine H
Department of Medical Physics, Royal Surrey County Hospital NHS Trust, Guildford, UK.
Clatterbridge Cancer Centre, Liverpool, UK.
Radiother Oncol. 2017 Mar;122(3):406-410. doi: 10.1016/j.radonc.2016.12.016. Epub 2017 Jan 20.
A UK national dosimetry audit was carried out to assess the accuracy of Stereotactic Ablative Body Radiotherapy (SABR) lung treatment delivery.
This mail-based audit used an anthropomorphic thorax phantom containing nine alanine pellets positioned in the lung region for dosimetry, as well as EBT3 film in the axial plane for isodose comparison. Centres used their local planning protocol/technique, creating 27 SABR plans. A range of delivery techniques including conformal, volumetric modulated arc therapy (VMAT) and Cyberknife (CK) were used with six different calculation algorithms (collapsed cone, superposition, pencil-beam (PB), AAA, Acuros and Monte Carlo).
The mean difference between measured and calculated dose (excluding PB results) was 0.4±1.4% for alanine and 1.4±3.4% for film. PB differences were -6.1% and -12.9% respectively. The median of the absolute maximum isodose-to-isodose distances was 3mm (-6mm to 7mm) and 5mm (-10mm to +19mm) for the 100% and 50% isodose lines respectively.
Alanine and film is an effective combination for verifying dosimetric and geometric accuracy. There were some differences across dose algorithms, and geometric accuracy was better for VMAT and CK compared with conformal techniques. The alanine dosimetry results showed that planned and delivered doses were within ±3.0% for 25/27 SABR plans.
开展了一项英国全国剂量测定审核，以评估立体定向体部放疗（SABR）肺部治疗的剂量传递准确性。
这项基于邮件的审核使用了一个包含九个置于肺部区域用于剂量测定的丙氨酸小球的人体胸部模型，以及轴向平面的EBT3胶片用于等剂量线比较。各中心采用其当地的计划方案/技术，制定了27个SABR计划。使用了一系列包括适形放疗、容积调强弧形放疗（VMAT）和射波刀（CK）在内的传递技术，以及六种不同的计算算法（坍缩圆锥算法、叠加算法、笔形束算法（PB）、AAA算法、Acuros算法和蒙特卡罗算法）。
测量剂量与计算剂量之间的平均差异（不包括PB结果），丙氨酸测量结果为0.4±1.4%，胶片测量结果为1.4±3.4%。PB差异分别为-6.1%和-12.9%。100%等剂量线和50%等剂量线的绝对最大等剂量线间距的中位数分别为3毫米（-6毫米至7毫米）和5毫米（-10毫米至+19毫米）。
丙氨酸和胶片是验证剂量测定和几何精度的有效组合。不同剂量算法之间存在一些差异，与适形技术相比，VMAT和CK的几何精度更好。丙氨酸剂量测定结果显示，27个SABR计划中有25个计划的计划剂量与实际交付剂量在±3.0%以内。
