ABSTRACT
The photon beam characterization of high-energy medical linear accelerators is essential to Medical Physics practice and relies on derived dosimetric functions from measured values and general beam parameters. These basic quantities and functions describe how dose changes with depth and along a beam profiles as a function of different machine settings. This chapter discusses the basics of photon beam dosimetry and the general beam parameters that affect photon beam output. General measurement conditions for common dosimetric functions are discussed as part of the definition of all quantities and not meant to be in complete detail. The basics of monitor unit hand calculations under an isocentric as well as a constant source to surface distance irradiation setup are also discussed. Finally, a practical outline of the reference dosimetry protocol from the American Association of Physicist's in Medicine Task Group 51 is also discussed.
