What is image guided radiotherapy?
Image guided radiotherapy (IGRT) is a technique which involves collecting images to verify a tumour’s position before external beam radiotherapy treatment is delivered. The purpose is to ensure the focus of the radiation is the tumour and a minimal amount to surrounding healthy tissue.
Understanding image guided radiotherapy
The term IGRT covers a wide range of techniques and protocols which can vary significantly in how they are performed and the level of accuracy that is achieved.
Tumours move internally in different ways, depending on their location within the body and surrounding organs. A tumour moving internally is natural, can be random and cannot be easily predicted. Additionally, in some circumstances the size and shape of a tumour may change as it shrinks in response to the radiotherapy or other treatments that are happening at the same time, such as chemotherapy.
Without IGRT the risk of part of the tumour being missed is increased. To account for this it is common practice to increase the area of tissue exposed to radiation when planning. This increase in planned margins, as well as the variability and movement of the tumour, can result in healthy organs or tissue receiving radiation, which increases the chance of unpleasant short and long-term side-effects.
Some providers only carry out image guidance at the start or perhaps once or twice during the weeks of treatment. Others may offer daily imaging but it may not be applied on the same day as the treatment session attended.
To ensure a tumour is targeted precisely, Cancer Partners UK uses IGRT DAILY - every time radiotherapy is delivered. By using 3D volumetric cross-sectional scans, known as cone-beam CT scans, soft tissues can be defined and any positional changes to a tumour can be detected. 2D images only provide a match to hard bone structure and therefore cannot.
Research has shown that using DAILY IGRT when delivering radiotherapy is more effective and fewer side effects are experienced. Using IGRT in conjunction with intensity modulated radiotherapy (IMRT) further increases the effectiveness of treatment.