A Comparison of the AAPM
TG51 Protocol and the IAEA Absorbed-Dose-To-Water Based Code of Practice for Dosimetry
Calibration of High Energy Photon Beams
M. Saiful Huq*, Murshed Hossain
Radiation Oncology, Jefferson Medical College of Thomas Jefferson University
Philadelphia, PA,
and
P. Andreo
IAEA
Vienna, Austria.Both the AAPM and the IAEA have recently developed a new generation of
protocols that are based on standards of absorbed dose to water. The recommended dosimetry
procedures in these protocols are based upon the use of an ionization chamber that has
been calibrated in terms of absorbed dose to water in a standards laboratory’s 60Co
beam. This is different from the recommendations given in the earlier generation of
protocols, which were based upon either an exposure or air-kerma calibration factor of an
ionization chamber. The purpose of this work is to compare the recommendations of the two
protocols using two widely used Farmer type ionization chambers: PTW N30001 (PMMA wall)
and NEL 2571 (graphite wall). This comparison was accomplished by determining the absorbed
dose-to-water with both chambers irradiated in a water phantom using 6 and 25MV photon
beams. Beam quality correction factors kQ,Qo, determined by following
the recommendations of the two protocols, were found to differ by up to 0.2% at the
highest energy. Despite significant differences in the method of beam quality
specification, the overall agreement between the two protocols was found to be within 0.1%
for the chambers and energies investigated in this study.
Comparison of Absorbed Doses-to-Water Determined by Following the
Recommendations of the TG51 and IAEA Protocols.
Abstracts Submitted to 1999 Annual AAPM Meeting | Medical Physics Home |
