Welcome to Ipswich Hospital
Our Passion, Your Care

Tuesday, 17 October 2017
Planning your Treatment

The planning radiographer produces an individualised treatment plan for every patient.

This plan must deliver the prescribed dose of radiation to the site of disease whilst minimising dose to healthy tissue.

Treatment planning occurs ‘behind the scenes’. We will start to plan your treatment after you have been seen in the simulator or had a CT scan. We work closely with both the oncologist and the Radiotherapy Physics team.

The oncologist prescribes the dose of radiation to be delivered and the area to be treated. If you have had a CT scan, the target volume and areas of healthy tissue can be drawn on the scan, as shown in the diagram below. In this example the planning radiographer will decide the best way to irradiate the target volume whilst minimising dose to the lungs and the spinal cord. They have used three beams which enter the body from different angles. Notice that only one of them goes through the spinal cord.

 

Minimising the dose to healthy tissue reduces the side effects of the treatment. One way that we can do this is to use a device called a multi-leaf collimator, or MLC. This conforms the irradiation beam to the shape of the tumour, as shown below. The MLCs are found in the head of the treatment machine. They consist of two rows of tungsten leaves that can move in and out to create different shapes.

The computer planning system calculates the dose that the patient will receive, as shown below. Ideally the areas of high dose should conform to the target volume. We will continuously make changes until the optimum plan for the patient has been produced.

When the radiographer is happy with the plan, it will need to be approved by the oncologist. The plan will then be checked by a radiotherapy physicist to ensure that there are no errors and that the dose has been calculated correctly. This is routine procedure to guarantee patient safety.