  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. A
new approach to multichannel dosimetry, based on experimental findings, i.e.,
the Multigaussian method, is introduced. The Multigaussian method 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.
