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Monday, 23 October 2017
Image guided radiotherapy equipment
Image Guided Radiotherapy

In 2005 Ipswich Hospital introduced image guided radiotherapy (IGRT) after purchasing a treatment machine with specialised imaging facilities.

IGRT uses images of the patient to precisely target the radiation to the site of disease.

Low-energy X-rays image the patient whilst they are in the treatment position. These images allow the radiographers to verify and correct the patient’s position before their treatment. This ensures that the radiation is accurately delivered to the target volume.

What are the clinical advantages of IGRT?

  • To deliver radiotherapy accurately, the patient must be precisely positioned on the treatment couch, often to within a few millimetres.
  • IGRT allows corrections to be applied that account for twists and tilts in the body, or changes in body weight.
  • IGRT can also correct for motion caused by internal organs, such as bowel movements or bladder filling.
  • Better targeting potentially allows smaller radiation fields to be used. 
  • This can reduce the side effects of the treatment.


How do we perform IGRT?

(i) Two dimensional imaging
Two X-rays of the patient are acquired; one from the front and one from the side. The X-rays visualise bony anatomy, such as the jaw bone and spine. The radiographers can match the anatomy with images acquired during the initial planning stages of the treatment. The treatment couch is then moved to ensure that the patient is in the same position for each daily treatment.

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(ii) Cone-beam CT
The imaging device on the treatment unit can also acquire a three dimensional image of the patient. This image is called a cone-beam CT. As well as visualising bones, it can be used to see the soft tissue in the body, such as the tumour and organs like the bladder and rectum. The cone-beam CT shown here indicates the size of the patient’s bladder during treatment.

Cone-beam CT imaging

Cone –beam CT images can be used to assess how changes inside the body, such as weight loss, affect the quality of treatment.  Based on this information an adjustment to the treatment may sometimes be made.