Intensity modulated radiotherapy (IMRT), volumetric arc therapy (VMAT) and tomotherapy further improve the shaping of a radiation dose to match the tumour shape, compared to 3D conformal radiation therapy (3D-CRT).
In 3D-CRT, the shape of the radiation dose are essentially limited to simple squares or rectangles because of the uniform intensity across each radiation field.
In IMRT, VMAT or tomotherapy, use of a greater number of radiation fields combined with variation of beam intensity within each radiation field allows the oncologist to create any shape to match the tumour and spare normal organs.
For example, where a tumour wraps round a normal organ, IMRT, VMAT and tomotherapy can create a C-shaped radiation dose to treat the tumour and spare the normal organ in the centre. Whereas in 3D-CRT, the central normal organ would get the same full dose as the surrounding tumour.
IMRT, VMAT and tomotherapy use different methods to achieve the same dose-shaping outcome and are largely interchangeable.
Image-guided radiation therapy (IGRT) can be used to complement IMRT to improve the positional accuracy of the radiation therapy treatment. IGRT uses imaging technology such as X-rays to visualise the position of the tumour so that radiotherapy can be delivered accurately.
IMRT has several advantages such as:
Radiation therapy can cause side effects. They may be the result from the treatment itself or from radiation damage to the healthy cells around the treatment area. Side effects may vary depending on the kind of tissue structures near the tumour being irradiated.
In rare instances, a new cancer different from the first one being treated may develop years later. After treatment, your doctor will regularly check for complications and recurrent or new cancers.
Find out more about the risks of radiation therapy.