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首页> 美国卫生研究院文献>Journal of Applied Clinical Medical Physics >Gafchromic EBT3 film dosimetry in electron beams — energy dependence and improved film read‐out
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Gafchromic EBT3 film dosimetry in electron beams — energy dependence and improved film read‐out

机译：电子束中的全色EBT3薄膜剂量学—能量依赖性和改进的薄膜读出

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For megavoltage photon radiation, the fundamental dosimetry characteristics of Gafchromic EBT3 film were determined in  60Co gamma ray beam with addition of experimental and Monte Carlo (MC)‐simulated energy dependence of the film for 6 MV photon beam and 6 MeV, 9 MeV, 12 MeV, and 16 MeV electron beams in water phantom. For the film read‐out, two phase correction of scanner sensitivity was applied: a matrix correction for scanning area and dose‐dependent correction by iterative procedure. With these corrections, the uniformity of response can be improved to be within ±50 pixel values (PVs). To improve the read‐out accuracy, a procedure with flipped film orientations was established. With the method, scanner uniformity can be improved further and dust particles, scratches and/or dirt on scanner glass can be detected and eliminated. Responses from red and green channels were averaged for read‐out, which decreased the effect of noise present in values from separate channels. Since the signal level with the blue channel is considerably lower than with other channels, the signal variation due to different perturbation effects increases the noise level so that the blue channel is not recommended to be used for dose determination. However, the blue channel can be used for the detection of emulsion thickness variations for film quality evaluations with unexposed films. With electron beams ranging from 6 MeV to 16 MeV and at reference measurement conditions in water, the energy dependence of the EBT3 film is uniform within 0.5%, with uncertainties close to 1.6% (k = 2). Including 6 MV photon beam and the electron beams mentioned, the energy dependence is within 1.1%. No notable differences were found between the experimental and MC‐simulated responses, indicating negligible change in intrinsic energy dependence of the EBT3 film for 6 MV photon beam and 6 MeV–16 MeV electron beams. Based on the dosimetric characteristics of the EBT3 film, the read‐out procedure established, the nearly uniform energy dependence found and the estimated uncertainties, the EBT3 film was concluded to be a suitable 2D dosimeter for measuring electron or mixed photon/electron dose distributions in water phantom. Uncertainties of 3.7% (k = 2) for absolute and 2.3% (k = 2) for relative dose were estimated.PACS numbers: 87.53.Bn, 87.55.K‐, 87.55.Qr
机译：对于兆伏光子辐射，在 60 Coγ射线束中确定了Gafchromic EBT3膜的基本剂量特性，并添加了实验和蒙特卡罗（MC）模拟的膜对6 MV光子束的能量依赖性水模体中的6 MeV，9 MeV，12 MeV和16 MeV电子束。对于胶片读出，应用了扫描仪灵敏度的两阶段校正：用于扫描区域的矩阵校正和通过迭代程序进行的剂量依赖性校正。通过这些校正，可以将响应的均匀性提高到±50像素值（PVs）之内。为了提高读出精度，建立了胶片翻转方向的程序。利用该方法，可以进一步提高扫描仪的均匀性，并且可以检测并消除扫描仪玻璃上的灰尘颗粒，划痕和/或灰尘。对红色和绿色通道的响应进行平均以进行读出，这减少了来自单独通道的值中存在的噪声的影响。由于带有蓝色通道的信号电平明显低于其他通道，因此由于不同的干扰效应而导致的信号变化会增加噪声电平，因此不建议将蓝色通道用于剂量确定。但是，蓝色通道可用于检测乳剂厚度变化，以评估未曝光胶片的胶片质量。当电子束的范围从6 MeV到16 MeV，并且在水中处于参考测量条件下时，EBT3膜的能量依赖性在0.5％内均匀一致，不确定性接近1.6％（k = 2）。包括上述6 MV光子束和电子束，能量依赖性在1.1％以内。在实验和MC模拟的响应之间没有发现显着差异，表明对于6 MV光子束和6 MeV–16 MeV电子束，EBT3膜的内在能量依赖性变化可忽略不计。根据EBT3膜的剂量特性，建立的读出程序，发现几乎均匀的能量依赖性和估计的不确定性，得出结论，EBT3膜是用于测量电子或电子中混合的光子/电子剂量分布的合适二维剂量计。水幻影。估计绝对剂量的不确定度为3.7％（k = 2），相对剂量的不确定度为2.3％（k = 2）.PACS编号：87.53.Bn，87.55.K-，87.55.Qr

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