An independent software for IMRT dose verification in CT-based patient data

Abstract

The patient specific dose verification is necessary process in advanced radiation therapy. In this study, the independent software (ISOFT) was developed to calculate absolute dose from 3 dimensional conformal radiation therapy (3D-CRT) and intensity modulated radiation therapy (IMRT) field in CIRS thorax phantom by combining modified Clarkson integration with 3D beam subtraction method (3D-BSM). The overall of percent deviation of point dose between measured by ion chamber and calculated by ISOFT and Eclipse system for square, rectangular and shaped MLC field at 1.5 to 15 cm depths in homogeneous phantom was within 2%. For the verification of 3D-CRT and IMRT plans, the doses from ISOFT and Eclipse system were compared with ion chamber and EDR2 film in CIRS thorax phantom. The measured lung dose presented mostly the lower dose than calculated by ISOFT and Eclipse system. The percent deviation between measurement and ISOFT was within 5% which reached the acceptable criteria. So ISOFT can be used as an independent software to verify absolute dose of 3D-CRT and IMRT field in inhomogeneous medium for CT base patient data. The correction of external body contour was included. The limitation of ISOFT was the only one field can be applied at 90 degree gantry angle. The build up doses at the surface and interface could not be determined correctly.