Investigation of Surface Dose Using Film Dosimetry and Commercial Treatment Planning System for Larynx Cancer Treatment with Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy

Abstract

OBJECTIVESurface dose measurement is challenging, and algorithms of treatment planning systems (TPS) cannotaccurately calculate the surface dose. The aim of this study was to investigate the surface dose withradiochromic film measurement and TPS calculation for larynx cancer treatment using intensity-modulatedradiotherapy (IMRT) and volumetric modulated arc therapy (VMAT).METHODSIMRT and VMAT plans for 5 larynx cancer patients were created using TPS. The plans were transferredto a Rando phantom for radiochromic film measurement. TPS calculations and film measurements werecompared for surface doses.RESULTSTPS underestimated the surface dose for both IMRT and VMAT plans. The average difference betweenTPS calculations and film measurements were found to be 12.9±6.1% and 12.4±7.7% for IMRT andVMAT, respectively. Surface dose was found to be lower in VMAT technique at all measurement points.CONCLUSIONTPS have an important role in radiotherapy treatments. Yet, they are still not adequate for dose measurementsin shallow depths. Underestimations or overestimations in calculations can occur. The error ratioof TPS, which should be considered while evaluating the radiotherapy plans, can be determined by dosimetricmeasurements. Radiochromic films are suitable equipments for this process.