Evaluating the Performance of Various Detectors in the Small Field Size by 6 MV Linac

Abstract

Introduction: We present a comprehensive evaluation of three different dosimeters in 6 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 (10x10 cm2) down to (0.5x0.5 cm2) using True Beam Linear Accelerator (Varian) and solid water phantom. Results: The diamond detector presented more accurate results at an ultra-small field size (0.5x0.5 cm2) with a 14.1% deviation of the diode results. On the other hand, all the measurements ranged within 5% for large field sizes “i.e. Larger than 4.0x4.0 cm2”. 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 0.859 and 0.104 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