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.