8 Commissioning of 4–10 mm conical collimators with Novalis TX® using TRS 483 protocol

Introduction. Stereotactic radiosurgery (SRS) of very small lesions such as the trigeminal nerve, with a very high prescribed dose (80 Gy) delivered in a single focused fraction on the target, requires the use of 4 mm to 10 mm conical collimators. This study focuses on the acquisition of basic dosimetry data for the implementation of SRS using conical collimators in the TPS iPlan (BrainLab) with the main objective of minimizing the uncertainties about the dose delivery. The collimator output factors (OF) measurement is one of the most critical points for very small beams characterization. The purpose of this work is to compare the measured OF using different detectors by applying the TRS 483 protocol.