ABSTRACT
Objective To compare the dosimetric difference of RapidArc and fixed gantry angle dynamic IMRT (dIMRT) for loco-regionally advanced nasopharyngeal carcinoma.Methods Ten previously treated patients with loco-regionally advanced nasopharyngeal carcinoma were replanned with RapidArc and dIMRT, respectively.The prescription dose was GTV 70 Gy/33 f and PTV 60 Gy/33 f.All plans met the requirement:95% of PTV was covered by 60 Gy.Dose-volume histogram data, isodose distribution, monitor units,and treatment time were compared.Results Dose distribution has no significant difference between the two techniques.RapidArc reduced the dose of the brainstem, mandible, and other normal tissues compared with dIMRT.Mean monitor units were 589.5 and 1381.0 for RapidArc and dIMRT (reduced by 57% relatively).Mean treatment time was 2.33 min and 7.82 min for RapidArc and dIMRT (reduced by 70% relatively).Conclusions Compared with dIMRT, RapidArc achieves equal target coverage and OAR sparing while using fewer monitor units and less time during radiotherapy for patient with loco-regionally advanced nasopharyngeal carcinoma.