Department of Medical Physics, Institute of Oncology Ljubljana, Zaloška cesta 2, Ljubljana 1000, Slovenia.
Phys Med Biol. 2018 Sep 6;63(17):175013. doi: 10.1088/1361-6560/aad9c1.
The main objective of multichannel radiochromic film dosimetry methods is to correct, or at least mitigate, spatial heterogeneities in the film-scanner response, especially variations in the active layer thickness. To this end, films can also be scanned prior to irradiation. In this study, the abilities of various single channel and multichannel methods to reduce spatial heterogeneities, with and without scanning before irradiation, were tested. Red, green and blue single channel models, two additive channel independent perturbation (CHIP) models and two multiplicative CHIP models were compared with the Multigaussian method. The Multigaussian method is a new approach to multichannel dosimetry, based on experimental findings. It assumes that the probability density function of the response vector formed by the pixel values of the different color channels, including irradiated and non-irradiated scans, follows a multivariate Gaussian distribution. The Multigaussian method provided more accurate doses than the other models under comparison, especially when incorporating the information of the film prior to irradiation. The relative dose differences between reference doses measured with MatriXX and film doses were examined. After applying inter-scan and lateral corrections, the lowest mean absolute errors were 0.8% and 1.0% for the Multigaussian method with and without the information of the scan before irradiation, respectively. Followed by the uniform multiplicative CHIP and red single channel models, using pixel values and net optical density, respectively, both with 1.1%.
多通道放射色迹胶片剂量测定方法的主要目标是校正，或至少减轻胶片扫描仪响应中的空间不均匀性，特别是活性层厚度的变化。为此，也可以在辐照之前扫描胶片。在这项研究中，测试了各种单通道和多通道方法在辐照前后扫描时减少空间不均匀性的能力。与多高斯方法相比，比较了红、绿、蓝单通道模型、两个加性通道独立扰动（CHIP）模型和两个乘法 CHIP 模型。多高斯方法是一种新的多通道剂量测定方法，基于实验结果。它假设，由不同颜色通道的像素值形成的响应向量的概率密度函数，包括辐照和未辐照的扫描，遵循多元高斯分布。与比较中的其他模型相比，多高斯方法提供了更准确的剂量，尤其是在包含辐照前胶片信息的情况下。检查了用 MatriXX 测量的参考剂量与胶片剂量之间的相对剂量差异。在应用扫描间和横向校正后，对于多高斯方法，在包含和不包含辐照前扫描信息的情况下，最低平均绝对误差分别为 0.8%和 1.0%。其次是均匀乘法 CHIP 和红单通道模型，分别使用像素值和净光密度，误差均为 1.1%。
