Truebeam

The radiation oncology department consists of six clinics across the healthcare system with 11 linear accelerators (three Varian TrueBeam, three Elekta Synergy, and five Varian Trilogy). All clinics utilize the Eclipse Treatment Planning System (Varian Medical Systems, v16.1) and the Mosaiq Oncology Information System (Elekta Inc., v2.84) for record and verify.

Patients were treated using the stereotactic linear accelerator (Varian 60°C before 2013; Varian Truebeam Stx after 2013) and Gammaknife (Elekta Gammaknife 4C unit before 2017; Elekta Gammaknife  iCON after 2018). Treatment planning was performed on the BrainLab iPLAN for LINAC and Elekta Leksell Gammaplan for gamma knife surgery.
Gross tumor volume (GTV) was defined as the contrast enhancing tumor on T1-weighted MR images for intact meningioma and the surgical tumor bed plus residual tumor for postoperative meningioma. Clinical target volume (CTV) was considered as GTV for WHO grade I meningioma. For WHO grade II or III and post-operative meningiomas, CTV was GTV plus a margin of 1–2 cm with adjustment of anatomical boundaries. The planning target volume (PTV) was define as CTV with a margin of 0–2 mm.  A median dose of 15 Gy single fraction for SRS, 25 Gy in 5 fractions for hypofractionated, and 54 Gy in 30 fractions (1.8 or 2 Gy/fraction) for FSRT was utilized. Hypofractionated radiotherapy and SRS were considered together.

Measurements and empirical calculations were conducted to evaluate the neutron and gamma capture dose rates at the maze entrance of the Varian TrueBeam and Elekta Versa HDTM linear accelerators. The linacs operate at 15 MV, 10 MV, and 10 MV flattened filter-free (FFF). The experimental measurements were performed at the King Abdallah Oncology Center in Riyadh, Saudi Arabia.