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Producing your radiotherapy plan

Nurse and patients talking about cancer

This page tells you about how your radiotherapy team produces your treatment plan. There is information about

 

Scans and simulation

Your treatment team uses CT scans or an X-ray machine called a simulator to plan your radiotherapy treatment. It is called a simulator because it is like (simulates) a radiotherapy machine, but does not give the treatment. The pictures it creates are used, along with any scans or X-rays, to show and position the area to be treated.

When planning your treatment, the radiographer takes some measurements of your body. They may also measure the distance from the treatment couch to the skin markings on your body. This is because the distance between the radiotherapy machine and the cancer is very important in working out the radiotherapy dose.

Putting all this information together allows the planning computers to work out the best positioning of the radiotherapy beams to treat the cancer but avoid healthy body organs in the area.

 

Reading CT or MRI scans

Reading a CT scan

This picture shows a typical CT scan cross section (slice). The slice shown is of the bottom of the rib cage. Note that the left on this scan is actually the right side of the body. This is what you can see

  • On the left is a large crescent – this is the liver
  • On the right, at the bottom, is a round shape – this is the kidney
  • In the centre, at the bottom, is a lighter round shape – this is the spinal cord inside the backbone
  • In the middle is an irregular shape, which is the pancreas with a cancer inside it
 

Looking at the tumour in 3D

Tumour in 3D

When the physicist or doctor puts together a number of CT scans or MRI scans a computer can create a 3D picture of the cancer. This picture shows a 3D computer image. This is what you can see

  • The cancer is shown in red
  • The liver is shown in brown
  • The spleen is shown in blue/green
  • The left kidney is shown in pink
  • The spine is shown in yellow

Looking at a 3D picture can be very useful, as it can be rotated and looked at from different angles. This is very helpful when planning treatment. It helps the radiotherapy doctor (clinical oncologist) to work out the best way to arrange the radiotherapy beams to cover the whole cancer and miss the major organs.

 

Building the radiotherapy plan

The 2D plan

To treat cancers deep within the body, 2, 3 or 4 beams are pointed at the cancer from different angles. The area where all the beams meet is where the tumour is. This is where the highest dose of radiotherapy is given. This picture shows how 3 beams can be directed at the tumour. The picture is of the bottom of the rib cage.

  • On the left is a large crescent – this is the liver
  • On the right, at the bottom, is a round shape – this is the kidney
  • In the centre, at the bottom, is a smaller round shape – this is the spinal cord inside the backbone
  • In the middle is an irregular shape – this is the pancreas with a cancer inside it

The straight lines are the radiotherapy beams. One beam is aimed from in front of the patient. This is the beam at the top of the picture. The other two beams are aimed from the sides at an angle so that they avoid the spinal cord and kidney.

 

Marking your skin

Once the treatment area is lined up, marks are made on the skin. These skin marks are used by the radiographers to set up the radiotherapy machine in the same way every day.

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Updated: 2 July 2012