VMAT to arclet plan conversion in a treatment planning system : Feasibility and dosimetric relationship between VMAT,...

The aim of this study was to make dynamic rotation treatment with mARC available for the non-dedicated Philips Pinnacle treatment planning system by converting SmartArc plans, offering insight into the relationship between SmartArc, mARC, and stationary field irradiation.

A scripting solution is presented that can be run in the Pinnacle system. This allows for the conversion of SmartArc plans into mARC format. The dose distribution of the converted mARC plan can be evaluated both in the form of a "real" mARC plan with arclets and-as is generally done in treatment planning systems certified for mARC planning-by approximating the arclets as stationary fields. We present the proof of principle and dosimetric comparisons.

The converted plans were irradiated without problems. For the measured 3D dose distributions, on average over 90 % points agreed with the calculated dose distributions (mARC and stationary field plans) within the gamma criteria of 3 % deviation in the local dose, 3-mm distance to agreement, for all dose values above 10 % of the maximum. The agreement between the three calculated dose distributions (SmartArc with both converted plans) was above 87 % (above 92 % when comparing mARC with stationary fields).

Our solution offers the possibility of mARC planning in Pinnacle. The dose comparisons furthermore prove that the dosimetric differences between SmartArc and mARC, when appropriately translated, are minor.