目的/目标
小现场测量提出了挑战。尽管许多高分辨率探测器都是市售的,小场剂量测定的EPID仍未充分开发。本研究旨在评估EPID在小场测量中的性能,并得出量身定制的校正因子,以进行精确的小场剂量测定验证。
材料/方法
六个高分辨率辐射探测器,包括W2和W1塑料闪烁体,边缘检测器,微硅,使用了microDiamond和EPID。输出因素,深度剂量和剖面,测量了各种束能量(6MV-FF,6MV-FFF,10MV-FF,和10MV-FFF)和使用VarianTruebeam线性加速器的场大小(10x10cm2,5x5cm2,4x4cm2,3x3cm2,2x2cm2,1x1cm2,0.5x0.5cm2)。在测量期间,将适当深度的丙烯酸板放置在EPID上,而3D水箱与五点探测器一起使用。将EPID测量数据与W2塑料闪烁体和其他高分辨率检测器的测量结果进行比较。分析包括产出因子的百分比偏差,PDD和配置文件的百分比差异,FWHM,平坦区域的最大差异,半影,和1Dγ进行了分析。在STATA16.2中,以W2闪烁体为参考,使用指数函数和分数多项式拟合对输出因子和深度剂量比进行拟合,并得到相应的公式。使用两台Truebeam机器验证了所建立的校正因子。
结果
在所有场大小和能量上比较EPID和W2-PSD时,产出因子的偏差在1%到15%之间。深度剂量,超过dmax的百分比差异在1%到19%之间。对于配置文件,在100%-80%区域观察到最大4%。使用两个独立的EPID验证了校正因子公式,并在3%内紧密匹配。

结论
EPID可以有效地作为小场剂量学验证工具,并具有适当的校正因子。
Purpose/Objective. Small-field measurement poses challenges. Although many high-resolution detectors are commercially available, the
EPID for small-field dosimetry remains underexplored. This study aimed to evaluate the performance of
EPID for small-field measurements and to derive tailored correction factors for precise small-field dosimetry verification.Material/Methods. Six high-resolution radiation detectors, including W2 and W1 plastic scintillators, Edge-detector, microSilicon, microDiamond and
EPID were utilized. The output factors, depth doses and profiles, were measured for various beam energies (6 MV-FF, 6 MV-FFF, 10 MV-FF, and 10 MV-FFF) and field sizes (10 × 10 cm2, 5 × 5 cm2, 4 × 4 cm2, 3 × 3 cm2, 2 × 2 cm2, 1 × 1 cm2, 0.5 × 0.5 cm2) using a Varian Truebeam linear accelerator. During measurements, acrylic plates of appropriate depth were placed on the
EPID, while a 3D water tank was used with five-point detectors. EPID measured data were compared with W2 plastic scintillator and measurements from other high-resolution detectors. The analysis included percentage deviations in output factors, differences in percentage for PDD and for the profiles, FWHM, maximum difference in the flat region, penumbra, and 1D gamma were analyzed. The output factor and depth dose ratios were fitted using exponential functions and fractional polynomial fitting in STATA 16.2, with W2 scintillator as reference, and corresponding formulae were obtained. The established correction factors were validated using two Truebeam machines.Results. When comparing
EPID and W2-PSD across all field-sizes and energies, the deviation for output factors ranged from 1% to 15%. Depth doses, the percentage difference beyond dmax ranged from 1% to 19%. For profiles, maximum of 4% was observed in the 100%-80% region. The correction factor formulae were validated with two independent EPIDs and closely matched within 3%.Conclusion. EPID can effectively serve as small-field dosimetry verification tool with appropriate correction factors.