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Radiochromic film based transit dosimetry for verification of dose delivery with intensity modulated radiotherapy
Author(s) -
Chung Kwangzoo,
Yoon Myonggeun,
Son Jaeman,
Yong Park Sung,
Lee Kiho,
Shin Dongho,
Kyung Lim Young,
Byeong Lee Se
Publication year - 2013
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 - 10.1118/1.4788658
Subject(s) - imaging phantom , dosimetry , quality assurance , nuclear medicine , ionization chamber , intensity (physics) , medicine , materials science , optics , physics , ion , external quality assessment , pathology , quantum mechanics , ionization
Purpose: To evaluate the transit dose based patient specific quality assurance (QA) of intensity modulated radiation therapy (IMRT) for verification of the accuracy of dose delivered to the patient.Methods: Five IMRT plans were selected and utilized to irradiate a homogeneous plastic water phantom and an inhomogeneous anthropomorphic phantom. The transit dose distribution was measured with radiochromic film and was compared with the computed dose map on the same plane using a gamma index with a 3% dose and a 3 mm distance‐to‐dose agreement tolerance limit.Results: While the average gamma index for comparisons of dose distributions was less than one for 98.9% of all pixels from the transit dose with the homogeneous phantom, the passing rate was reduced to 95.0% for the transit dose with the inhomogeneous phantom. Transit doses due to a 5 mm setup error may cause up to a 50% failure rate of the gamma index.Conclusions: Transit dose based IMRT QA may be superior to the traditional QA method since the former can show whether the inhomogeneity correction algorithm from TPS is accurate. In addition, transit dose based IMRT QA can be used to verify the accuracy of the dose delivered to the patient during treatment by revealing significant increases in the failure rate of the gamma index resulting from errors in patient positioning during treatment.