Intensity-modulated radiation therapy [IMRT] is a form of External Beam Radiation Therapy [EBRT] but with the ability to deliver different doses to different regions of the high risk volumes. It is a high precision type of radiotherapy treatment that uses computer-controlled linear accelerators to deliver high dose radiation to cancerous tumours by ‘sculpting’ the edges of a radiation beam.
For example, by using IMRT, one is able to deliver a higher dose to the tumor mass as well as deliver different doses to the surrounding lymph nodes, depending on the lymph node risk level of harbouring disease. This is known as dose painting. It is also used to increase the level of normal tissue sparing, so as to lower the risk of unwanted side effects. This form of treatment is used frequently in head and neck cancers, prostate cancers and pelvic tumors.
In the IMRT, radiation beams are precisely modulated, or controlled, to conform to the shape of the 3D mapped image of the tumour. The increased precision and accuracy significantly minimises damage to the surrounding healthy tissue, resulting in fewer side effects from treatment.