Author/Editor		Méndez Carot, Ignasi; Polšak, Aljoša; Hudej, Rihard; Casar, Božidar
Title		The Multigaussian method
Type		članek
Vol. and No.		Letnik 63, št. 17
Publication year		2018
Volume		str. [1-5]
ISSN		0031-9155 - Physics in medicine and biology
Language		eng
Abstract		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%.
Keywords		dozimetrija radiokromska filmska dozimetrija radioterapija medicinska fizika dosimetry radiochromic film dosimetry medical physics radiotherapy