The comparison of plan dose and dose verification in volumetric modulated arc therapy for early stage non-small cell lung cancer with non-flattening filter / 中华放射肿瘤学杂志

ABSTRACT

Objective To compare the dose distributions of the volumetric modulated arc therapy ( VMAT) for early stage non?small cell lung cancer ( NSCLC) using conventional flattening filter ( FF) and the flattening filter free ( FFF) beams and to verify the dose calculation accuracy of the FFF beam through a three?dimensional verification system. Methods The treatment plans of 20 patients ( 2015 years hospitalized) treated with SBRT for early stage NSCLC using a TrueBeam accelerator were retrospectively analyzed. The patients were scanned with 4DCT and the average density projection images were used for organ segmentation and treatment planning using an Eclipse plan system. Two volumetric modulated arc therapy ( VMAT) plans with FF and FFF were designed with the same planning parameters for each patient. The dose distributions between the two plans were compared and their dose verifications were assessed with the ArcCheck device. Results With the same dose coverage for the target, there was no significant difference in the dose compatibility index 100%(CI100%) between FF and FFF beams (P=0. 82).CI80% and CI50% of FFF plan were lower than that of FF plan (P=0. 02,0. 01).The dose significantly decreased in the FFF plan comparing with the FF plan for the ipsilateral lung and the total lung (P<0. 01 for both).There was no significant difference between monitor units of the FF and FFF plans ( P=0. 34) ,while the delivery time of FFF was significant shorter than that of FF (P<0. 01).The DVH passing,γ pass rates and the absolute dose deviations of the FF and FFF plans at the central point were not significantly different ( P=0. 05,0. 16, 0. 26) . Conclusions FFF beams for NSCLC patients with VMAT planning can significantly improve the dose distribution compatibility and reduce radiation doses to lung. The beam delivery with FFF beams was also faster. Furthermore,the three?dimensional dose verification confirmed that the dose calculation in Eclipse plan system using FFF beams for VMAT plans were accurate and met the clinical need.