SU-E-T-895: A Comparison of RapidArc® and HybridArc® Treatment Plans for Cranial SRS/SRT

Abstract

Purpose: This work evaluates two arc therapy techniques: HybridArc (Brainlab, AG), and RapidArc (Varian Medical Systems) for treating cranial tumors with stereotactic radiosurgery/radiotherapy (SRS/SRT). Methods: HybridArc is a new treatmentdelivery technique which combines optimized dynamic conformal arc therapy with fixed port IMRT. The result is a single dose distribution calculated by summing the distribution from dynamic arcs with the distribution from a number of fixed‐port IMRT beams. In a retrospective study of crainial SRS/SRT patients, we compared the dosimetric results of a single 350 degree RapidArc dose distribution, with a single 350 degree HybridArc distribution containing three fixed‐port IMRT fields. For each case, a comparison of target and OAR dose volume histograms, maximum and minimum target dose, and conformity index was used to evaluate each planning technique. For each technique the same target dose constraints and OAR maximum dose constraints were used. Results: Both the RapidArc and HybridArc produced comparable plans for a single iteration of their respective optimization routines, however, the HybridArc plans showed superior coverage by the 95% isodose surface and a lower maximum dose, compared with RapidArc. The conformity indices for the minimum covering isodose were improved for the HybridArc distributions thus providing much more sparing of normal tissues. The HybridArc plan is computed in under a minute as compared with 10–15 minutes for RapidArc which greatly improves planning efficiency. Conclusions: For cranial lesions, the new HybridArc technique from Brainlab produces a more conformal distribution than RapidArc in the case of a single arc. The short calculation time of the HybridArc algorithm allows a HybridArc plan to be produced in one tenth of the time compared to RapidArc.