Colodro Juan Fernando Mata, Berná Alfredo Serna, Puchades Vicente Puchades, Amores David Ramos, Baños Miguel Alcaraz
Department of Medical Physics and Radiation Protection, Santa Lucia University Hospital, Cartagena, Murcia, Spain.
Department of Medical Physic Radiology and Physical Medicine, Faculty of Medicine/Dentistry, University of Murcia, Murcia, Spain.
J Med Phys. 2017 Jul-Sep;42(3):133-139. doi: 10.4103/jmp.JMP_130_16.
The aim of this work is to verify the use of radiochromic film in the quality assurance (QA) of volumetric-modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT) plans and compare the results with those obtained using an ion chamber array.
QA was performed for 14 plans using a two-dimensional-array seven29 and EBT3 film. Dose values per session ranged between 7.5 Gy and 18 Gy. The multichannel method was used to obtain a dose map for film.
The results obtained were compared with treatment planning system calculated profiles through gamma analysis. Passing criteria were 3%/3 mm, 2%/2 mm and 3%/1.5 mm with maximum and local dose (LD) normalization. Mean gamma passing rate (GPR) (percentage of points presenting a gamma function value of <1) was obtained and compared. Calibration curves were obtained for each color channel within the dose range 0-16 Gy. Mean GPR values for film were >98.9% for all criteria when normalizing per maximum dose. When using LD, normalization was >92.7%. GPR values for the array were lower for all criteria; this difference being statistically significant when normalizing at LD, reaching 12% for the 3%/1.5 mm criterion.
Both detectors provide satisfactory results for the QA of plans for VMAT lung SBRT. The film provided greater mean GPR values, afforded greater spatial resolution and was more efficient overall.
本研究的目的是验证放射变色胶片在容积调强弧形放疗（VMAT）肺部立体定向体部放疗（SBRT）计划质量保证（QA）中的应用，并将结果与使用电离室阵列获得的结果进行比较。
使用二维阵列seven29和EBT3胶片对14个计划进行质量保证。每次治疗的剂量值在7.5 Gy至18 Gy之间。采用多通道方法获取胶片的剂量分布图。
通过伽马分析将获得的结果与治疗计划系统计算的轮廓进行比较。通过标准为3%/3 mm、2%/2 mm和3%/1.5 mm，采用最大剂量和局部剂量（LD）归一化。获得平均伽马通过率（GPR）（伽马函数值<1的点的百分比）并进行比较。在0-16 Gy剂量范围内为每个颜色通道获得校准曲线。按最大剂量归一化时，胶片的平均GPR值在所有标准下均>98.9%。使用LD归一化时，>92.7%。阵列的GPR值在所有标准下均较低；在LD归一化时，这种差异具有统计学意义，对于3%/1.5 mm标准达到12%。
两种探测器在VMAT肺部SBRT计划的质量保证中均提供了令人满意的结果。胶片提供了更高的平均GPR值，具有更高的空间分辨率，总体上更有效。
