A comparative evaluation of surface dose values: radiochromic film measurements versus computational predictions from...

Accurate prediction of surface doses is crucial for clinical outcomes in radiotherapy. Surface dose distribution must be predicted accurately by calculation algorithms in the treatment planning system (TPS). This study aims to compare surface dose calculations from the Eclipse TPS with radiochromic film measurements to evaluate the reliability of these calculation algorithms. Measurements with radiochromic films were performed using 6 MV photon beams. Treatment plans for 3D conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volumetric arc therapy (VMAT) were generated on the TPS and calculated using various algorithms. Treatment plans were irradiated on Gafchromic EBT3 films with a PTW head and neck phantom. EBT3 films were compared to calculation algorithms via FilmQA™ Pro (version 7.0) software with multi-channel analysis. Dosimetric evaluations were statistically analyzed. Commercial calculation algorithms underestimated the surface dose in 3DCRT, IMRT, and VMAT treatment plans. For 3DCRT, the underestimations were 8.0% with the AAA algorithm and 8.7% with AXB. In VMAT, the underestimations were 10.2% with AAA and 12.9% with AXB. For IMRT, the underestimations were 6.6% with AAA and 7.3% with AXB. The AAA algorithm closely matched surface dose measurements among calculation methods. The dosimetric results indicate that both AAA and AXB algorithms, as implemented in the Eclipse™ TPS, tend to underestimate surface dose compared to EBT3 film measurements. Accurate knowledge of the dose in the superficial region is crucial to prevent acute skin reactions or to deliver an effective dose to superficial tumors in clinically significant cases. Therefore, our surface dose measurements offer more accurate evaluations, making Gafchromic EBT3 films suitable for such cases.