Dosimetric comparison between RapidArc and fixed gantry dynamic IMRT for central-type lung cancer radiotherapy

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic IMRT (dIMRT) for central-type lung cancer radiotherapy. Methods Therapy for 10 patients previously treated with dIMRT was replanned with RapidArc. Dose prescription was 66 Gy/33 fraction. Comparative endpoints were planning target volume (PTV) dose, doses to surrounding structures,number of monitor units, and treatment delivery time. Results There was no significant dosimetric difference between RapidArc and dIMRT. Compared with dIMRT, RapidArc slightly elevated target volume dose, lung V5, V10. The average values of lung V20, V30 and heart V30 were larger in dIMRT than those in RapidArc. The number of monitor units was reduced by 32% and the treatment time by 66% in RapidArc.Conclusions Both RapidArc and dIMRT plans could meet the clinical therapy needs. RapidArc could achieve similar target coverage and sparing of organs at risk, with fewer monitor units and shorter delivery time than dIMRT. Key words: RapidArc;  Dynamic intensity modulated radiation