An addendum to the AAPM's TG-51 protocol for the determination of absorbed dose to water in megavoltage photon beams is presented. This addendum continues the procedure laid out in TG-51 but new kQ data for photon beams, based on Monte Carlo simulations, are presented and recommendations are given to improve the accuracy and consistency of the protocol's implementation. The components of the uncertainty budget in determining absorbed dose to water at the reference point are introduced and the magnitude of each component discussed. Finally, the consistency of experimental determination of N D,w coefficients is discussed. It is expected that the implementation of this addendum will be straightforward, assuming that the user is already familiar with TG-51. The changes introduced by this report are generally minor, although new recommendations could result in procedural changes for individual users. It is expected that the effort on the medical physicist's part to implement this addendum will not be significant and could be done as part of the annual linac calibration.

Additional Metadata
Keywords absorbed dose calibration coefficients, beam quality conversion factors, dosimetry protocol, ionization chamber, kQ, photon beams, uncertainty analysis
Persistent URL dx.doi.org/10.1118/1.4866223
Journal Medical Physics
Citation
McEwen, M. (Malcolm), Dewerd, L. (Larry), Ibbott, G. (Geoffrey), Followill, D. (David), Rogers, D.W.O, Seltzer, S. (Stephen), & Seuntjens, J. (Jan). (2014). Addendum to the AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon beams. Medical Physics, 41(4). doi:10.1118/1.4866223