Evaluating the Performance of Various Detectors in the Small Field Size by ۶ MV Linac

Introduction: We present a comprehensive evaluation of three different dosimeters in ۶ MV flattening filter-free beam (FFF) under charged particle dis-equilibrium conditions. Material and Methods: Diamond detector, Gafchromic film, and Un-shielded diode detector were used in this study. The total scatters factor of Jaw-shaped fields was measured starting from (۱۰x۱۰ cm۲) down to (۰.۵x۰.۵ cm۲) using True Beam Linear Accelerator (Varian) and solid water phantom.  Results: The diamond detector presented more accurate results at an ultra-small field size (۰.۵x۰.۵ cm۲) with a ۱۴.۱% deviation of the diode results. On the other hand, all the measurements ranged within ۵% for large field sizes “i.e. Larger than ۴.۰x۴.۰ cm۲”. The relative output factor (ROF) was introduced as a total scatter factor measured by a given dosimeter (x) to total scatter factor measured by diamond detector , the relative output factor values were ۰.۸۵۹ and ۰.۱۰۴ for both Diode/Diamond  and Film/Diamond , combinations, respectively. Conclusion: We found that the diamond detector is the most appropriate detector for the small field dosimetry with high accuracy.

Keywords:

Detectors , Gafchromic film , Film Dosimetry , Radiation Dosimetries