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

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 (𝑂𝐹𝑥𝑂𝐹𝑑𝑖𝑎𝑚𝑜𝑛𝑑)⁄, the relative output factor values were 0.859 and 0.104 for both Diode/Diamond (𝑅𝑂𝐹𝐷𝑖𝑎𝑚𝑜𝑛𝑑𝑑𝑖𝑜𝑑𝑒) and Film/Diamond(𝑅𝑂𝐹𝐷𝑖𝑎𝑚𝑜𝑛𝑑𝑓𝑖𝑙𝑚), combinations, respectively. Conclusion: We found that the diamond detector is the most appropriate detector for the small field dosimetry with high accuracy.