RADIATION PROTECTION IN RADIOTHERAPY DEPENDS ON UNCERTAINTIES IN SMALL FIELD DOSIMETRY
English

Sonja Petkovska, Margarita Ginovska, Hristina Spasevska, Yasin Acarbas
2018 RAD Association Journal  
Technological improvements in radiotherapy machines using small fields (SF) have improved mechanical accuracy and stability, as well as dosimetric control. Small fields are nonstandard radiation fields, for which reference dosimetry cannot be reliably performed using the existing protocols. Field size definition, difficulties of accurate measurements, modeling of SF dose calculations in Treatment Planning System (TPSs), calibration protocol establishing, reference condition achievements, are
more » ... chievements, are some of the challenges in SF Dosimetry. Small and Intensity Modulated Radiation Therapy (IMRT) field dosimetry can be very complex -large perturbation effects could make a significant impact on reference dosimetry procedures and output factors. Comparison between different detectors provides valuable information. The aim of this paper is to evaluate the differences of dose profiles and depth dose measured in the same conditions for standard and non-standard radiation fields. Measurements are performed using detectors with different sensitive volumes. Beam quality as well as symmetry and flatness are analyzed. Results from the measurements show that the differences for SF are obvious at the edge of the profiles and in the penumbra region, as well as in the build-up region into depth dose curves. To avoid the uncertainties, for static SF where reference conditions cannot be met and for IMRT fields where delivery conditions are far removed from calibration conditions, the new formalism should be implemented.
doi:10.21175/radj.2018.02.018 fatcat:nufrql4vyjgfre7h2gdnbo7yvu