About SPECT - Single-Photon Emission Computed Tomography
A SPECT scan combines two different imaging techniques: A CT scan and a isotope bone scan. The latter is a type of nuclear medicine investigation, where a weak radioisotope is injected into a vein. This connects to various cells, including those which are responsible for the production of bone cells (osteoblasts). These cells can be activated by a variety of conditions and therefore the SPECT scan is not specific for a particular condition and in the spine is often used with other investigations such as MRI. The isotope bone scan is taken some time after the injection - up to 3-4hours - to give enough time for the radioisotope to reach the targeted cells. The CT adds very detailed anatomical pictures and once the pictures of the two scans are combined, produce a 'colourful' CT image.
What does it show?
It can be useful in investigating inflammation of the spine in severe degenerative disease. Sometimes surgeons use it before a spinal fusion to exclude subtle inflammation above or below the level of the operation.
What does it not show?
It does not differentiate the causes of the increased bone activity. There are also other inflammatory processes such as bone oedema which might show up better on an MRI. It does not show pain but potential pain generators.
When it should be done
In most patients, this will be an additional investigation to others like MRI. It is a specialist investigation which should only be requested by a spine specialist with a very specific question.
When it should not be done
It should not be done to 'just have a look what might cause the pain'.
Commonly asked questions
Is the radiation harmful?
Any radiation is potentially harmful, which is why it needs a very clear indication. SPECT combines radiation by a weak radioisotope and x-ray radiation from the CT. Both are weak and usually do not cause any harm.
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Does the scan show my pain?
The answer is simple: It sadly does not! However, it shows potential pain generators but needs to be taken in context with a clinical history and examination as well as other investigations.