VMAT
VMAT (Volumetric Modulated Arc Therapy) is a technique where the grantry continously revolves around the patient
while irradiating. The main advantage is reduction of treatment time, but additionally the plans are also
better in terms of conformality.
The reduced treatment time has several advantages:
- Patient comfort
- Less intra-fraction motion effects
- More treatments for the facility
The increased patient comfort is a direct result of requiring less time to lie absolutely still on the treatment
couch. As lying fixed in a certain position becomes increasingly more difficult with increase of time, the
probability of patient movement during the irradiation siginificantly reduces with a shorter treatment.
Intra-fraction motion reduces the effectiveness of the treatment, and may require larger tumour margins
to compensate.
Another result of reduced treatment is requiring less time on the treatment device. A direct consequence is
more treatments per device. In other words: with the same amount of hardware, a facility can treat more
patients.
VMAT vs Conventional
Demonstration of the differences between VMAT treament (left) and a conventional
static 9 beam treatment (right). This video shows an accelerated treatment (25x).
Where a conventional treatment fraction takes about 13 minutes for a head-and-neck
case, the VMAT technique reduces this to 5 minutes, with an improved plan quality.