Medical Physics Seminar – Monday, December 03, 2012
Small and Nonstandard Photon Field Dosimetry
Stephanie Junell (student of Dr. Larry DeWerd)
Research Assistant, Department of Medical Physics, UW-School of Medicine & Public Health, Madison, WI - USA -
Location: 1345 (HSLC) Health Sciences Learning Center, 750 Highland Avenue, Madison, WI
This work evaluated the feasibility of the joint IAEA/AAPM working group’s new formalism for reference dosimetry for small and non-standard fields. The proposed formalism introduces two calibration methods for performing reference dosimetry of small and non-standard fields. The first method involves small static ﬁeld geometry and the second involves composite ﬁeld geometry.
Measurements of beam quality correction factors corresponding to this formalism were performed for three different models of ionization chambers: a Farmer-type ionization chamber, a thimble ionization chamber, and a small volume ionization chamber. Beam quality correction factor measurements were made in a cylindrical acrylic phantom and a water phantom using thermoluminescent dosimeters (TLDs) and alanine dosimeters to determine dose to water. The behavior of the beam quality correction factor was observed as it transfers the calibration coefficient from the University of Wisconsin (UW) Accredited Dosimetry Calibration Laboratory’s 60Co reference beam to the calibration conditions of the small field formalism.