Performance of a new star-bar phantom designed for MTF calculations in x-ray imaging systems.

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.

Optimizing the recalibration process in radiochromic film dosimetry.

Intra-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.

Monte Carlo uncertainty analysis of dose estimates in radiochromic film dosimetry with single-channel and multichannel algorithms.

Purpose: 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.

On the re-calibration process in radiochromic film dosimetry.

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.

The incidence of the different sources of noise on the uncertainty in radiochromic film dosimetry using single channel and multichannel methods.

The 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.

Characterization of noise and digitizer response variability in radiochromic film dosimetry. Impact on treatment verification.

Purpose: 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.

Technical Note: Statistical dependences between channels in radiochromic film readings. Implications in multichannel dosimetry.

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.

Technical Note: MTF determination from a star bar pattern image.

Purpose: 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.