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What is image guided radiotherapy?


Image guided radiotherapy

Image guided radiotherapy (IGRT) is a way of using X-rays and scans (images) before and during radiotherapy treatment. The X-rays and scans show the size, shape and position of the cancer. 

Doctors plan the radiotherapy to give a high dose to the cancer. It is important that the radiotherapy field covers the whole cancer, plus a border around it. This helps the radiotherapy to work as well as possible in treating the cancer. Doctors try to give as low a dose as possible to the surrounding healthy tissue to reduce the risk of side effects.


Types of image guided radiotherapy

In some areas of the body, tumours may be in a different place for each treatment. An example is the prostate gland, which changes position according to whether the bladder is full or not. With conventional radiotherapy, there is a risk that part of the tumour may be outside the radiotherapy field during some treatment sessions. With some types of IGRT the radiographers can take scans using the radiotherapy machine before each treatment. Then they can make sure the cancer is within the radiotherapy field.

With some types of image guided radiotherapy, the radiographers can take scans with the radiotherapy machine during treatment. So they can make sure the cancer is within the radiotherapy field throughout each treatment session. They call this 4 dimensional (4D) radiotherapy (4D-RT).

In some types of 4D-ART the machine may switch off if the tumour moves out of the radiotherapy field. This type of treatment is helpful for cancers in areas of the body that move when we breathe, such as the lung.


Types of IGRT machine

Some types of image guided radiotherapy use specially designed radiotherapy machines. The CyberKnife machine has a robotic arm that moves around the patient. The arm gives the radiotherapy from many different angles. We have information about CyberKnife.


Tomotherapy is one type of image guided intensity modulated radiotherapy. A Tomotherapy machine combines a CT scanner and an external beam radiotherapy machine. Part of the Tomotherapy machine can rotate completely around the patient to take CT scans and give radiotherapy to a very localised area. 

The machine takes pictures of the tumour just before each treatment session to allow the doctors to target the treatment very precisely. This may reduce the damage to normal body tissues in the area. The treatment is also called helical tomotherapy.


Benefits and possible drawbacks of IGRT

With image adapted radiotherapy, doctors can target the radiotherapy treatment more accurately. This can mean that the treatment works better in curing or controlling a cancer. It can also reduce the risk of side effects. The drawback is that planning the treatment may take longer. Sometimes each radiotherapy session may also take a bit longer.


Image guided therapy in the UK

The National Radiotherapy Implementation Group (NRIG) has issued guidelines that all patients treated with radiotherapy in the UK should have a form of image guided radiotherapy.

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Updated: 17 December 2012