# Volumetric modulated arc therapy (VMAT)

Source: https://onco.cc/technologies/vmat/  
OnCo record `vmat` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The linac sweeps around the patient in one or two arcs while the beam shape, dose rate and speed all change, delivering an IMRT-quality plan in a couple of minutes.

## Summary

VMAT is the arc form of intensity-modulated radiotherapy: the gantry rotates continuously while the multileaf collimator reshapes the beam and the dose rate varies, so a full treatment is delivered in one to three arcs rather than many fixed fields. Otto described the optimisation in 2008 and it became the default technique for most curative treatments within a decade. Plans match fixed-field IMRT in target coverage with shorter treatment times and fewer monitor units, at the cost of a larger low-dose bath.

## Fields

- Kind: Technology
- Status: established
- Last checked: 2026-09-16
- Tags: radiation-wave1
- Principle: Simultaneous modulation of gantry speed, dose rate and collimator leaf positions during a rotating arc, optimised by inverse planning to sculpt dose around organs at risk.
- Since: 2008
- Strengths: Treatment in two to four minutes; Highly conformal dose with steep gradients; Fewer monitor units than fixed-field IMRT
- Limitations: Larger volume receiving low doses; Sensitive to patient motion during the arc; Demands rigorous machine quality assurance

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Radiation_therapy#Volumetric_modulated_arc_therapy

## Connected records

- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Radiotherapy treatment planning and QA software](https://onco.cc/technologies/treatment-planning-systems/)
- terms: [GTV, CTV and PTV (target volumes)](https://onco.cc/terms/planning-target-volume/), [IMRT / IGRT / VMAT (modern external beam radiotherapy)](https://onco.cc/terms/imrt-term/), [Organs at risk and dose constraints](https://onco.cc/terms/organs-at-risk/)
- trials: [NRG CC001](https://onco.cc/trials/nrg-cc001/)

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