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Clinical reference dosimetry: Comparison between AAPM TG‐21 and TG‐51 protocols
Author(s) -
Ding G. X.,
Cygler J. E.,
Kwok C. B.
Publication year - 2000
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 - 10.1118/1.598999
Subject(s) - dosimetry , absorbed dose , calibration , nist , ionization chamber , nuclear medicine , primary standard , materials science , ionization , physics , medicine , computer science , ion , quantum mechanics , natural language processing
We compare the results of absorbed dose determined at reference conditions according to the AAPM TG‐21 dose calibration protocol and the new AAPM TG‐51 protocol. The AAPM TG‐21 protocol for absorbed dose calibration is based on ionization chambers having exposure calibration factors for60 Co gamma rays, N x . The new AAPM TG‐51 dosimetry protocol for absorbed dose calibration is based on ionization chambers having60 Co absorbed dose‐to‐water calibration factor, N D , w60 Co . This study shows that the dose changes are within 1% for a cobalt beam, 0.5% for photon energies of 6 and 18 MV, and 2%–3% for electron beams with energies of 6 to 20 MeV. The chamber primary calibration factors, N xand N D , w60 Co , are traceable to the Canadian primary standards laboratory (NRCC). We also present estimated dose changes between the two protocols when calibration factors are traceable to NIST in the United States.