2A01-PHOTON AND ELECTRON BEAM DOSIMETRY

Faiz M. Khan, Ph.D.

The theory of measurement and calculation of absorbed dose using ion chamber will be discussed.  By considering ionization chamber as a Bragg-Gray cavity, relationships are derived between the ionization charge measured and the absorbed dose in the medium. The formalism, which is based on the AAPM TG-21 protocol, involves cavity-air calibration factor, restricted stopping power ratios of medium to air, and various chamber perturbation factors.  The TG-21 protocol will be compared with the IAEA TRS-277 protocol.