Purpose: A new phantom, designed and manufactured for modulation transfer function (MTF) calculations is presented in this work. The phantom has a star-bar pattern and is manufactured in stainless steel. Modulation transfer function determinations are carried out with the new phantom and with an edge phantom to compare their performance and to compare them with previous theoretical predictions.
View Article and Find Full Text PDFIntra-lot, inter-scan and other variabilities in radiochromic film dosimetry may have a severe impact on absolute dosimetry with this dosimeter. In the literature, several dosimetry protocols may be found characterized by different calibration functions and different film response variables. Also, the re-calibration methods found in the literature correct and minimize the impact of the variabilities in the absolute dose estimates.
View Article and Find Full Text PDFPurpose: To provide a multi-stage model to calculate uncertainty in radiochromic film dosimetry with Monte-Carlo techniques. This new approach is applied to single-channel and multichannel algorithms.
Material And Methods: Two lots of Gafchromic EBT3 are exposed in two different Varian linacs.
Purpose: The accuracy and precision of the dose estimates obtained with radiochromic film dosimetry are investigated in a clinical environment. The improvement in the accuracy of dose estimates reached with corrective methods is analyzed. Two novel re-calibration algorithms for radiochromic film dosimetry are presented.
View Article and Find Full Text PDFThe influence of the various sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Pieces of an RCF were each irradiated to different uniform doses, ranging from 0 to 1092 cGy.
View Article and Find Full Text PDFPurpose: To study how noise and scanner response variability affect radiochromic film dosimetry.
Methods: Five treatment plans were analyzed in this work with two different multichannel protocols: the multichannel algorithm of Mayer et al. and the efficient protocol of Lewis et al.
Purpose: This note studies the statistical relationships between color channels in radiochromic film readings with flatbed scanners. The same relationships are studied for noise. Finally, their implications for multichannel film dosimetry are discussed.
View Article and Find Full Text PDFPurpose: A procedure to obtain the MTF of an image system from a star bar pattern image is presented. The results obtained are compared to the standard analysis of an edge image (as described in the norm IEC 62220-1).
Methods: The images used are artificially generated following a procedure that simulates sampling, blurring, and noise present in a real phantom image.