Help- Advice - Information

Image Guided Radiation Therapy

Image Guided Radiotherapy (IGRT) is a treatment technique that takes into account tumour motion. Some tumours are not in a fixed position within the body, meaning their exact location can change slightly from day to day. IGRT involves determining the position of the tumour everyday before giving any radiotherapy treatment and then altering the settings / treatment positioning if the tumour has moved.

In traditional radiotherapy planning the clinical oncologist defines the tumour s/he wishes to treat with the 3D data that was obtained during the planning CT scan. S/he then adds an area ( known as a margin) around this to include any microscopic cells that cannot be seen on the 3D data. A further margin is then added to allow for movement of the tumour. IGRT allows the treatment radiographers to see if the tumour has moved and account for it in the treatment process. The clinical oncologist can then be confident the mobile tumour is in the correct position, so s/he can add less of a margin. This in turn means that less healthy tissue is irradiated / exposed to such a high dose.

The above image was taken with an IGRT treatment machine. The arrow points to the box in the middle which is a matching tool used by the radiographers to ensure the patient is in the correct position.

Reviewed: March 2015