In the pursuit of perfect planning: Comparison between Lightning Inverse Planning and GammaPlan Wizard for gamma knife radiosurgery

Background: The Lightning® software, was added to the Gamma Knife's Leksell GammaPlan® as a fully automated inverse planner, differently from the prior software, Wizard®. In this paper we compare their treatment planning capacity and quality. Materials and methods: Thirty-eight cases were compared under four different planning techniques. First, manual forward planning aided by the Wizard® optimization tool. Second, inverse planning with Wizard®. The third and fourth plans used Lightning® with and without consideration for organs at risk (OAR). They were analysed for: planning time, number of shots, coverage, selectivity, gradient index, bean-on time, and OAR dose. Comparison based on pathology was added due to their idiosyncrasies. For quality comparison, dose-volume histograms (DVH) were compared to plans developed under our treatment standards. Tumor's volume and time to plan were correlated with Pearson's coefficient. Results: Lightning® had better coverage (8%) and gradient index (15%) but had 12% decrease in selectivity. Planning and delivery times had a reduction of 57% and 5% respectively, despite having three times the number of shots. Only Lightning® with protection of OAR met the dose constrains in all plans. DVH showed similar plan qualities. Conclusions: Lightning® allowed the planner to explore different optimization parameters to achieve a plan that suits the clinical problem at hand. It took less time to calculate shots placement, OAR protection and the ideal isodose line than the Wizard®. This can be useful to plan multiple and complex targets at a faster time, increase the patient's tolerance and, may have a radiobiological advantage by impacting intra-fraction repair.