Implementation of a novel uncertainty budget determination methodology for small field dosimetry

Abstract

This paper presents the implementation of a novel methodology for the determination of the uncertainty associated to the process of beam measurement in small fields. Field output factors were measured for different fields sizes in a 6 MV photon beam. The uncertainties related to the detector’s positioning were taken into account, as well as its characteristics. Contributions of the beam limiting device, scanning system, instrumental and correction factors introduced for field output factor calculations were also analyzed. A broad range of detectors, including ionization chambers with different active volumes and one stereotactic diode for radiosurgery were used. Expanded uncertainty levels under 3% for k = 3 were obtained with the stereotactic diode for all the studied field sizes. Ionization chambers’ uncertainty levels were substantially larger in most cases.