Scans for radiotherapy
This page tells you about the scans you might need when you have radiotherapy. There is information about
A CT scan is a special type of X-ray. Like an X-ray, it is painless and you don't feel anything while you have it. This is a 360° photo of a CT scanner. Use the arrows to look around the room.
The machine takes a lot of pictures from different angles and these are put together to give a series of cross sections or slices through the part of the body being scanned.
Cross sections from radiotherapy planning CT scanners give a very accurate picture of where the cancer is and how big it is. They also show how close major body organs are to the treatment area. So the doctor can plan the radiotherapy to give as low a dose as possible to these organs.
For a radiotherapy planning CT scan you lie in the position in which you will be treated. So that you stay very still the couch is hard and not padded. It can be a bit uncomfortable. You may also have equipment such as masks or moulds to hold you in position.
We have information about having a radiotherapy planning CT scan in this section.
MRI scans are made using a powerful magnetic field instead of the X-rays used by CT scanners. Like a CT or X-ray, the scan is painless, but the scanner is very noisy when it is being used. Some people find it a bit claustrophobic inside the scanner.
The scanner can create pictures as cross sections like the CT scan. The MRI can show other angles too, depending on what is the most helpful for the doctor. MRI scans have been found to be very useful for looking at many types of cancer. They can be fed into the radiotherapy planning scanner to give more detail about the exact size and position of tumours.
PET stands for Positron Emission Tomography. This type of scan can show how body tissues are working, as well as what they look like. A PET scan can help to show the size and exact position of some cancers and whether they have spread to other areas of the body. You have an injection of a very small amount of a radioactive drug (tracer). After the injection you rest for about an hour before having the scan. The scan itself can take up to an hour. We have information about having a PET scan in this section.
Bone scans help doctors to see if there are any changes in the bone. They can help doctors to know if cancer has spread to the bones. Cancer that has spread to the bone is often treated with radiotherapy treatment. Bone scans can help doctors to see exactly where to give the radiotherapy treatment.
In a bone scan, a very small dose of radioactive dye is injected into the bloodstream. The dye finds its way to the bones and the radiation is photographed with a special camera called a gamma camera. Any areas where the bone is repairing itself takes up more dye and shows up as a bright area, called a hot spot, on the scan.
Bone scans cannot always tell whether damage to a bone is due to arthritis, a fracture, or from a cancer spreading to the bones. So, sometimes you may need to have other tests, such blood tests, X-rays, CT scans or MRI scans to see whether your cancer has spread. The doctor will also ask you about any symptoms you may have, such as pain.
Some people have ultrasound scans before radiotherapy. There are other particular types of scans for certain cancers. For example, you can have a scan for thyroid tissue that uses a small amount of radioactive iodine. Or a test called an MIBG scan for a rare cancer called phaeochromocytoma. Ask your doctor or nurse to explain if you need to have a scan that is not mentioned here.
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