Your radiotherapy team carefully work out how much radiation you need to treat the cancer and exactly where you need it.
As cancer cells may sometimes spread into the tissues close to the tumour, your radiotherapy specialist will decide on the exact area to be treated around the cancer. They will also make allowances for possible movement of the tumour during treatment due to breathing or normal movement of body organs.
About external radiotherapy planning
The radiotherapy planning makes sure that the cancer gets the prescribed dose of radiation while normal body tissues get as little as possible.
The area of your body exposed to radiation is called the radiotherapy field.
Some normal tissue immediately around the tumour will be exposed to the same dose but your doctors aim to keep this as low as possible to reduce the risk of side effects.
To plan the treatment your doctor will take into account:
- your type of cancer
- the position of the cancer in the body
- the size of the cancer
- whether it is close to structures that are sensitive to radiation
- how far the radiation needs to travel into the body
- your general health and medical history
More than one planning session may be needed. It depends on the size and position of the tumour.
Before your planning, your nurse or radiographer will ask you to sign a consent form.
If you have any questions about the treatment, make sure that you ask them before you sign your form. You can take a copy of the form home with you if you want to.
It's important to feel that you are involved in your treatment, so ask as many questions as you like. The more you understand your treatment, the easier it is to cope.
Your planning appointment
Your planning appointment may take from 15 minutes up to a couple of hours.
You will have a planning CT scan. The scan shows the cancer and the structures around it.
You lie on the scanner couch with the treatment area exposed. The radiographers cover you up as much as possible.
They put some markers on your skin. The markers show up on the scan as bright white dots. Your radiographers use them to position you for your radiotherapy.
You have to lie very still so that the measurements are accurate and the radiographers can record your exact position. This record means the radiographer can make sure you are lying in the correct position every time you have treatment.
They may need to use some equipment to support you in the right position, such as a chest board, neck rest or arm pole.
Once you are in position the radiographers move the couch up and through the scanner. The scanner is a doughnut shape.
The radiographers leave the room and the scan starts. It takes about 5 minutes. You won't feel anything. The radiographers watch from the next door room and you can talk to them on an intercom if you need to.
Before the planning appointment
You may also have an MRI scan, PET scan or x-rays. This is so that your radiotherapy doctor (clinical oncologist) has as much information as possible about your treatment needs.
They can feed the other scans into the planning scanner as part of the planning process.
How you have radiotherapy planning
The radiographer measures your body size and shape in the treatment area. Sometimes they need to do extra things to get a clear picture of your body structures. For example:
- you may have an injection of dye to show up your kidneys
- you may have wires put on scars or around lumps
- before the scan you may need to drink a jug of liquid containing a dye that shows up your bladder
- if you are having treatment to your chest area, you may have a barium liquid drink to show up your food pipe (oesophagus) and stomach
While planning your radiotherapy, the radiographers may make pin point sized tattoo marks on your skin.
These marks make sure they treat exactly the same area every day. They may also highlight the tattoo with pen marks that make it look like a cross.
Moulds or masks
If you are having treatment to your head or neck, you may need to have a mould (shell) made to keep you perfectly still while you have treatment.
You may also have a mould if you have to keep an arm or leg perfectly still. The moulds are made in the mould room or in the CT scanning room.
The video below shows you what happens at radiotherapy planning:
Dan (radiographer) : Radiotherapy planning will involve you coming for an appointment for a CT scan in the radiotherapy department. The idea behind this is that the doctor needs to work out exactly where needs to be treated and where we need to avoid and so that scan starts us off on that process.
For the CT scan, most of the time no preparation is needed beforehand but if any is then you’ll receive that in a letter so for example, depending on what you having treated there might need to be a contrast agent introduced or you may need to have a full or an empty bladder depending on what is necessary for the scan.There are a number of things we do to help people keep still and make sure the cancer is treated.
It is important that you lie in the same position every time you have treatment. This is to make sure the radiotherapy is directed at the cancer and normal tissues are avoided. We may put equipment in place to fix your position. If you are having radiotherapy for a head and neck cancer you will have a mask made. The mask helps you to keep your head really still during treatment. We also line up the scanner and mark your skin with a felt pen where the light lines from the machine need to be aimed.
They’ll then leave the room and start the scanner and that scan lasts usually about 2 to 3 minutes. Because pen marks can rub easily the radiographer makes them permanent after your scan by tattooing very small marks on your skin.
After the scan the radiographers will give you any information that you need before starting treatment and answer any questions that you’ve got then you are free to go home.
Patient: When I came for the first meeting to plan the treatment. It was a case of having a scan and then lying, remaining on the scan machine and then the technicians took some measurements some dimensions and when they were satisfied that they had the right angles they tattooed me.
Dan (radiographer): The next part of planning is your doctor looking at the scan and marking out on the computer where you need treatment. Once that’s been done a physicist or a dosimetrist will start to plan your treatment. And they use very powerful computers to work out exactly what dose needs to be given and from which directions it needs to come on from.
After your planning session
You may have to wait a few days or up to 2 weeks before you start treatment. During this time the physicists and your radiotherapy doctor decide the final details of your plan.
Your doctor will plan the areas that need treatment and outline areas to limit the dose or avoid completely. They call this contouring.
Then the physicists and staff called dosimetrists plan the treatment very precisely using advanced computers.