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Enhanced epidermal dose caused by localized electron contamination from lead cutouts used in kilovoltage radiotherapy
Author(s) -
Lye J. E.,
Butler D. J.,
Webb D. V.
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3458722
Subject(s) - contamination , electromagnetic shielding , materials science , monte carlo method , lead (geology) , nuclear medicine , dosimetry , cathode ray , electron , physics , medicine , composite material , geology , nuclear physics , ecology , statistics , mathematics , geomorphology , biology
Purpose: To investigate and quantify electron contamination from the lead cutouts used in kilovoltage x‐ray radiotherapy. Methods: The lead cutouts were modeled with the Monte Carlo EGSnrc user codes DOSXYZnrc and DOSRZnrc for x‐ray beams ranging from 50 to 300kV p . The results from the model were confirmed with Gafchromic film measurements. The model and measurements investigated the dose distribution with and without gladwrap™ shielding under the lead, and dose distributions with round, square, and serrated edge cutouts. Results: Large dose enhancement near the edges of the lead was observed due to electron contamination. At the epidermal/dermal border, there is double the dose at the edge of the lead compared to the central dose due to electron contamination for a 150kV pbeam and three times the dose for a 300kV pbeam. gladwrap™ shielding effectively removes the contaminant dose enhancement using ten and four layers for 300 and 150kV pbeams, respectively. Conclusions: The contaminant dose enhancement is undesirable as it could cause unnecessary erythema and hyperpigmentation at the border of the treated and untreated skin and lead to a poorer cosmetic outcome. The contamination is easily removed by gladwrap™ shielding placed under or around the lead cutout.