Dosimetric Verification for Primary Focal Hypermetabolism of Nasopharyngeal Carcinoma Patients Treated with Dynamic Intensity-modulated Radiation Therapy

Objective: To make sure the feasibility with 18FFDG PET/CT to guided dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma patients, by dosimetric verification before treatment.
Methods: Chose 11 patients in Ⅲ~ⅣA nasopharyngeal carcinoma treated with functional image-guided IMRT and absolute and relative dosimetric verification by Varian 23EX LA, ionization chamber, 2DICA of I’mRT Matrixx and IBA detachable phantom. Drawing outline and making treatment plan were by different imaging techniques (CT and 18FFDG PET/CT). The dose distributions of the various regional were realized by SMART.
Results: The absolute mean errors of interest area were 2.39%±0.66 using 0.6cc ice chamber. Results using DTA method, the average relative dose measurements within our protocol (3%, 3 mm) were 87.64% at 300 MU/min in all filed.
Conclusions: Dosimetric verification before IMRT is obligatory and necessary. Ionization chamber and 2DICA of I’mRT Matrixx was the effective dosimetric verification tool for primary focal hyper metabolism in functional image-guided dynamic IMRT for nasopharyngeal carcinoma. Our preliminary evidence indicates that functional image-guided dynamic IMRT is feasible.