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Respiratory Gating

In 2005 Ipswich Hospital introduced respiratory gating into the Radiotherapy Department.

A patient being filmed with a camera to produce measurements used for respiratory gatingRespiratory gating is used in tumours which move as the patient breathes.

It can improve the quality of radiotherapy to the lung for those patients who require a large dose of radiation. The technique uses knowledge of the patient’s breathing to ensure that the tumour is always irradiated.

What are the clinical advantages of respiratory gating?
Respiratory gating uses measurements of the patient’s breathing cycle to accurately define the region in which the tumour will move. This prevents us irradiating larger volumes than are necessary and reduces the radiation dose to healthy lung.

How does the technique work?
Reflective markers are placed on the patient’s chest.  As the patient breathes the movement of these markers is tracked by an infra-red beam.

The movement of the markers allows us to produce a graph showing the patient’s breathing cycle.

The patient has a CT scan. Images are acquired in a fraction of a second, allowing many images to be produced in a single breath. These images are grouped together according to which stage of the breathing cycle the patient is in at the time the image is acquired.

The respiratory gating cycleThis technique allows us to visualise the motion of the tumour. This motion can then be taken into account by the oncologist when they define the volume to irradiate.