Peripheral and surface dose assessment using diode and Gafchromic EBT3 films dosimeters for different radiotherapy techniques

Purpose: Treatment planning systems (TPSs) still face challenges in determining the peripheral and surface doses specially when using thermoplastic mask and bolus. This study aims to assess the peripheral and surface dose using diode and Gafchromic EBT3 films dosimeters. In addition to investigate the impact of thermoplastic mask with different thickness of bolus on these doses.Methods: The measurements were performed for an Alderson Rando phantom. The maxilla and prostate were delineated as the target, because the maxilla is close to the surface, to determine the impact of thermoplastic mask and bolus on the skin dose.Results: The measured surface dose for IMRT was higher compared to TPS with an average difference of 21.5%, 20.2%, 18.7%, and 13.4% in the absence of thermoplastic mask and bolus, with mask, with bolus 5 mm and with bolus 10 mm respectively. For 3D-CRT, the measured surface dose was also higher compared to TPS with an average difference of 20.7%, 19.6%, 16.1%, and 13.3% in the absence of thermoplastic mask and bolus, with mask, with bolus 5 mm and with bolus 10 mm respectively. For the prostate, the PD that is close to the target was in good agreement between peripheral dose measured with diode and acquired from TPS. Whereas TPS underestimated the PD for both 3D-CRT and IMRT at locations that are away from the target. Moreover, when comparing 3D-CRT to IMRT for PD, 3D-CRT resulted in higher for distances close to the target, whereas the IMRT indeed delivered higher than 3D-CRT to locations that are away from the target.Conclusions: This study showed that diode dosimeter is recommended to estimate both peripheral and surface doses whereas EBT3 films dosimeter is recommended to estimate surface dose and not for PD.