Radionuclide bone scan
What is a bone scan?
This is a way of imaging the entire skeleton to detect abnormal areas of bone. It involves the injection of a radio-active substance (called a radiopharmaceutical or radioactive tracer) into the blood stream via a vein and then taking pictures at various times with a special camera (called a Gamma camera).
The tracer is specially designed to zoom in on the bones. The Gamma camera detects the radioactivity from the substance and forms an image of the skeleton. Abnormal bone takes up the tracer in a different way to normal bone and depending on the type of abnormality can either show increased uptake which appears more intense (a so-called hot-spot ) or decreased uptake which appears less intense (a “cold spot”).
What are the common uses?
- Looking for fractures which are not visible on X-ray (so-called occult fractures and stress fractures)
- Looking for bony spread of some cancers
- Early assessment of primary bone tumours (tumours of the bone itself which can be benign or malignant)
- Looking for bone infections (osteomyelitis)
- Looking for joint infections (septic arthritis)
- Other inflammatory joint conditions (such as rheumatoid arthritis)
- Problems with blood supply to the areas of the bone (avascular necrosis)
- Diffuse diseases of the bone (such as Paget’s)
- Other diseases which can affect the bones (such as sickle cell anaemia)
How should I prepare?
- You need to tell your doctor if you are or may be pregnant.
- If you are breast feeding you will need to change to formula for 1 - 2 days to allow excretion of the tracer.
- If you have had a radiological procedure within the last 4 days which involved barium (such as a barium enema), this may interfere with test results.
- You will be asked to empty your bladder immediately prior to injection.
- Bring something to read or a crossword puzzle to fill in as there will be a long waiting period between the injection and the taking of pictures.
How is it performed?
- You will be required to remove your clothing and jewellery and wear a hospital gown to avoid interfering with the test.
- You will have a needle inserted into your arm for the injection of the tracer.
- You will then need to wait between 1 and 3 hours before the pictures are taken. During this time you will be asked to drink 4 – 6 glasses of water to help clear the excess tracer from your bloodstream into your bladder.
- You will need to empty your bladder again immediately prior to the pictures being taken
- You will then be asked to lie on a table while the camera is moved into various positions around you. You may also be asked to move into different positions, but will have to lie very still during the actual taking of pictures.
- The actual scan takes about an hour.
What are the risks?
- Any exposure to radiation carries the risk of cell or tissue damage, but the level of radiation in this case is very low.
- You will slowly eliminate the radioactive substance from your body over a couple of days and it will be present in urine and stool. Although the level of radiation is very low you should still flush the toilet immediately and wash your hands thoroughly.
- Because the level of radiation is so low there is no risk to people around you.
What are the limitations of the procedures?
- This a very sensitive test and can pick up abnormalities before they are apparent on X-ray.
- The whole body can also be scanned – if this was done with conventional X-rays you would receive a very large radiation dose!
- However this a very non-specific test as it only detects areas of abnormality and doesn’t characterise them (other than to say there is increased or decreased uptake of the tracer). This means that it may be difficult to separate the relevant problem (for example looking for bone spread of tumour) from underlying incidental conditions (such as osteoarthritis in older patients)