Spatial accuracy of the stereotactic Leksell? Vantage? head frame in comparison with the standard stereotactic Leksell? G Frame for Gamma-Knife

Purpose. Since January 2021, the Leksell (R) Vantage head frame (V-frame) is used for Gamma Knife (R) treatments in addition to the historical Leksell (R) G-Frame known as the reference. The aim of this study was to compare the spatial accuracy of treatments with these two frames. Methods. Firstly, the constancy of the geometric accuracy of the system according to the Elekta quality assurance process was carried out during sixteen months with V and G-frames' adaptors. Then, End-to-end test was carried out with both V and G-frame using an anthropomorphic phantom and Gafchromic (R) films. The overall precision of the radiation center was calculated as the displacement vector for a 4 mm collimator shot. Additionally, the Cone Beam Computed Tomography (CBCT) positioning system was used to assess the precision of the Leksell coordinates system defined by V-frames on 64 patients in comparison to G-frames for 46 patients. To ensure that patient's head movement was not possible during treatment with the V-frame, the High Definition Motion Management (HDMM) system was used and a final CBCT was performed at the end of the irradiation. Results. The QA constructor's tests done with the G-frame and V-frame adaptor gave similar results over sixteen months. End-to-end tests demonstrated that the mean positioning accuracy was 0.54 mm (SD of 0.14 mm) and 0.70 mm (SD of 0.14 mm) with V-frame and G-frame respectively. The displacement vector given by CBCT ranged from 0.02 to 1.05 mm with a mean value of 0.38 mm (SD of 0.18 mm) for the 64 V-framed patients and from 0 to 0.92 mm with a mean value of 0.31 mm (SD of 0.18 mm) for the 46 G-framed patients. The mean translation movement between the beginning and the end of the 64 treatments with V-frame was 0.08 mm (SD of 0.04 mm, maximum value of 0.19 mm). Conclusion. We estimated that V-frames are as precise as G-frames with a targeting accuracy of less than 1 mm.