Single Photon Emission Computed Tomography (SPECT)

Single Photon Emission Computed Tomography or SPECT is among the standard imaging tests used in the diagnosis and management of neurological disorders. SPECT is also called Nuclear Imaging Testing. This is because it involves the use of a nuclear, radioisotope that is injected into the blood. The activity of this agent within the brain tissue helps to assess various types of brain functions. SPECT testing is seldom done as a standalone procedure. Usually, it is combined with other, brain imaging/scanning technologies like MRI or PET for comprehensive diagnosis of suspected neurological disorders. Many times, SPECT is ordered as a follow-up to a PET or MRI for confirming the cause of neurological problems such as internal infections, tumors, degenerative diseases or stress fractures.
Understand SPECT Procedure
The nuclear agent used during SPECT is similar to the radioactive isotope used in PET scanning. This agent has specific binding properties. It can easily bind to certain bio-chemicals found in human blood. Thus, once injected into the body through the intravenous route, its ability to reach the brain tissues is guaranteed. Once within the brain tissue, the concentration of this tracer helps to indicate the level of brain activity. Parts of the brain that are more active will need more oxygen and hence, tend to absorb more oxygenated blood. Thus, they will show a higher concentration of the isotope while those that have become inactive due to an illness or injury will show negligible uptake of the isotope.
When the patient is lying on the testing table, a gamma ray camera is made to rotate around his head. This camera is capable of recording every part of the brain where the radioisotope has reached. This is because the isotope emits low levels of gamma rays that in turn attract the camera. This information is recorded by a computer and converted into cross-sectional slices, i.e. cross-section images of the brain. These slices are later put together for creating a 3-dimensional image that depicts activity levels within the brain.
SPECT Applications
When compared with PET, which is quite similar to SPECT in its overall testing approach, SPECT is a bit cheaper and more easily available. The detailed images obtained via SPECT allow physicians in identifying and managing neurologic and psychiatric problems. Commonly referred to as Brain SPECT, this test has many variations. For instance, it can be done with perfusion agents or dense imaging radio-pharmaceuticals.. This kind of testing is even done as a part of evaluating a patient’s response-to-therapy and for differentiating between benign and malignant tumors besides helping neurosurgeons to decide what kind of surgical approach would be best suited.. Apart from this, some other established uses of SPECT are among:

  • Understanding pharmaceutical implications of neurological medications
  • Evaluating effects of psychiatric drugs