Volumetric modulated arc therapy (VMAT) is a novel radiation therapy technique that delivers the radiation dose continuously as the treatment machine rotates. This technique accurately shapes the radiation dose to the tumour, while minimising the dose to the organs surrounding the tumour. Both the angle, as well as the dose rate of the radiation treatment, are constantly adjusted to enable the radiation dose to be shaped.
The linear accelerator has a device called a multi-leaf collimator which is made up of thin leaves. These leaves move independently and form shapes that fit precisely around the treatment area. This technique allows the dose to be shaped to the tumour by modulating — or controlling — the intensity of the radiation beam.
VMAT allows more difficult tumours, such as ones wrapped around other important structures, to be targeted precisely.