June 25, 2019
Halcyon Planning Advanced with EZFluence

Varian’s Halcyon is a 6 MV single-energy linear accelerator with a flattening filter free (FFF) beam. Halcyon has built-in imaging and a 100 cm bore to quickly deliver coplanar VMAT and IMRT plans. The Halycon machine is unique in that it does not have jaws but instead two layers of offset MLCs.

While the FFF beam leads to faster treatments for IMRT, 3D plans are traditionally planned using the field-in-field (FiF) technique on a flat beam of a C-arm linac. Varian has addressed this concern with a dynamic beam flattening (DBF) technique to flatten the FFF beam with the upper MLCs. While this makes FiF possible, the time and MUs needed increases substantially to deliver a comparable plan on a c-arm linac. The alternative to FiF planning is the electronic compensator or the irregular surface compensator.

While manual fluence editing can be time-consuming, EZFluence offers an automated approach. EZFluence is an Eclipse TPS plugin that generates the optimal fluences based on the patient’s anatomy and fields provided. EZFluence is compatible with the Halcyon system and can generate 3D plans in seconds. Also, EZFluence will preserve blocks and generate fluence for the flash region all while not needing any manual fluence editing.

In addition, EZFluence aims to deliver the most homogenous plan possible. Even though the Halycon only offers the one energy of 6 MV, clinics are still able to generate homogenous plans where they would normally add high energy beams.