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

We present a comprehensive evaluation of three different dosimeters in 6 MV flattening filter-free beam (FFF) under charged particle dis-equilibrium conditions.
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. 
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.
We found that the diamond detector is the most appropriate detector for the small field dosimetry with high accuracy.