6 mv linac

From 1995 to 2003, meningioma patients underwent “sharp” fixation using a stereotactic head ring and an oral bite plate. A 6-MV Linac (Varian Medical Systems, USA) with an add-on micro multi-leaf collimator (BrainLAB, Germany) was used. Coordinates for SRS were set by a laser-based stereotactic localizer. This setup allowed delivering shaped beams. In 2004, the department started using NovalisTx with beam shaping capability using built-in MLC and image guidance with ExacTrac (Varian Medical Systems, USA and BrainLAB, Germany). The image-guided frameless system enabled us to image the patient at any couch position using a frameless positioning array. A three-dimensional treatment planning based on CT and co-registered MRI was done with Brainscan (BrainLAB, Germany), which was later replaced by iplanRT (BrainLAB, Germany). The GTV was defined as the area of contrast enhancement on T1-weighted MR images and the planning target volume (PTV) included a 1–2 mm isotropic safety margin. The dose was prescribed to a reference point, representing 100%. Patients received 95% of the prescribed dose at the PTV margin. Dose constraints for OAR were as follows: optic nerves, chiasma, and brainstem could receive maximal 54 Gy according to Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) [13 (link)].

Exposures of Caco-2 cells to X-rays were performed with a 6 MV LINAC (Varian) at the IRCCS S. Maugeri (Pavia, Italy). Cells were irradiated with a dose rate of 3 Gy/min and doses in the range 2–10 Gy at room temperature. Sham-irradiated cells experienced the same environmental/procedural conditions of the irradiated ones, without entering the irradiation room (0 Gy).