What is intensity modulated radiotherapy?

Intensity modulated radiotherapy (IMRT) is a specialised way of delivering radiotherapy and is used to treat many different types of cancer. By using IMRT dosimetrists are able to mould and vary the strength of each radiotherapy beam to match the size, shape and position of the tumour more precisely than conventional, or ‘conformal’ radiotherapy.

Understanding IMRT

IMRT uses many small beams within a main radiotherapy beam to intersect the tumour from a number of angles. The ability to spread the dose out in this way helps to lower or negate the dose to nearby healthy tissue or organs. The intensity of each smaller beam can be controlled during treatment to deliver precise and varying doses to different parts of a tumour maximising its effectiveness.

Planning for IMRT may take longer than planning conformal radiotherapy, but this degree of targeting is impossible with conventional radiotherapy, which delivers the same dose across the whole beam to both tumour and healthy tissue.

For a tumour to be precisely targeted using IMRT its size and position must be accurately measured and the correct dose defined in advance. This is achieved using specialist imaging and computer technology during the CT planning and dosimetry stage of the care plan.

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