Özet:

OBJECTIVE Surface dose measurement is challenging, and algorithms of treatment planning systems (TPS) cannot accurately calculate the surface dose. The aim of this study was to investigate the surface dose with radiochromic film measurement and TPS calculation for larynx cancer treatment using intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). METHODS IMRT and VMAT plans for 5 larynx cancer patients were created using TPS. The plans were transferred to a Rando phantom for radiochromic film measurement. TPS calculations and film measurements were compared for surface doses. RESULTS TPS underestimated the surface dose for both IMRT and VMAT plans. The average difference between TPS calculations and film measurements were found to be 12.9±6.1% and 12.4±7.7% for IMRT and VMAT, respectively. Surface dose was found to be lower in VMAT technique at all measurement points. CONCLUSION TPS have an important role in radiotherapy treatments. Yet, they are still not adequate for dose measurements in shallow depths. Underestimations or overestimations in calculations can occur. The error ratio of TPS, which should be considered while evaluating the radiotherapy plans, can be determined by dosimetric measurements. Radiochromic films are suitable equipments for this process.

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