RapidArc
Varian's volumetric-modulated arc therapy (VMAT) implementation. During beam delivery, the gantry rotates continuously while the multileaf collimator (MLC), gantry speed, and dose rate all modulate simultaneously. RapidArc delivers a full IMRT-equivalent fractional dose in a single gantry rotation (or two) — substantially shorter beam-on time than static-gantry IMRT. Ships standard on TrueBeam, Edge, TrueBeam STx, and Halcyon; available as an upgrade on late-production Clinac iX.
Why it matters to buyers: RapidArc reduces per-fraction treatment time materially — clinically meaningful for throughput and patient motion. A RapidArc-capable Varian linac is a substantially different clinical workflow than a static IMRT platform.
Why it matters to engineers: RapidArc is a software and control-system licensing bundle that coordinates MLC, gantry, and dose-rate dynamics. Commissioning includes end-to-end RapidArc dose verification against treatment-planning predictions. Not all legacy Clinac hardware supports RapidArc; license + control-software revision matter.