A single photon emission computerized tomography, abbreviated as SPECT scan, is a diagnostic assay that provides distinct images of internal organs in the body. It is essentially a nuclear imaging test which involves a radioactive substance utilised to highlight and display vivid 3D pictures of the interior tissues in the human system.
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Although a SPECT scan involves a similar mechanism to other imaging assays such as a conventional CT scan, MRI scan and PET scan, it is more advanced in being able to assess the normal functions of various organs in the body and exhibit the specific site of health anomalies or abnormalities, such as the location of a seizure and levels of blood circulation within different segments of the brain.

Also Read: Magnetic Resonance Imaging/MRI Scan: Procedure, Risks And Results

Why It Is Done:

A SPECT scan is widely used to detect problems in three key internal organs in the body – the brain, the heart and the bones. Several ailments affecting the cerebral, cardiac and osteo-connective tissues in the system can be identified and evaluated by means of a SPECT scan, such as:

  • Dementia
  • Seizure
  • Epilepsy
  • Blockage of blood vessels within the brain
  • Injuries to the head, skull and brain
  • Clogged coronary arteries in the heart
  • Lowered rate of cardiac muscle activity and pumping of heart valves
  • Specific regions of tissue damage in bone fractures
  • Bone cancer and its progression to more advanced stages

Also Read: Bone Cancer: Causes, Symptoms And Treatment


A SPECT scan is generally performed by a doctor in a hospital under sterile conditions and the patient should inform the medical practitioner if they are already taking any prescription medications or supplements for other pre-existing disorders. Furthermore, while SPECT scans are also advised to women of reproductive age and they should inform the physician of their pregnancy or breastfeeding/lactation status, in which case the doctor advises them not to take the scan, as the radioactive material may pose health risks for the developing foetus or newborn.

Since the SPECT scan entails observing a radioactive dye pass through the internal organs from a SPECT machine that has a camera and is sensitive to magnetic fields, the patient is told to remove all metallic accessories such as watches, earrings, belts prior to the diagnostic test.

The procedure for SPECT scan involves injecting a radioactive dye - termed as tracer – into a vein in the arm employing an intravenous injection. Once this is done, the patient experiences a cold sensation as the tracer traverses across the body which is normal and they are asked to wait for about 20 minutes so that the internal tissues absorb the dye. The tracer material is fabricated such that the more active cells and tissues undergoing intense biochemical reactions owing to inflammation and disease in the body assimilate larger quantities of the dye, thus appearing brighter in the visual images.

The patient is then asked to lie down on a flat bed and the SPECT machine rotates around their body. The SPECT machine is a large circular apparatus that comprises a camera to capture distinct 3D images of internal tissues, organs in the body and these are projected on to a computer attached at the other end of the device.

The entire SPECT scan procedure takes anywhere between 30 minutes – 2 hours depending on the reason for obtaining internal images of the body. Once the test is done, most of the radioactive material dissolves in the body and is eliminated by natural excretion processes in the next few days, and the doctor advises the patient to consume more fluids to facilitate the flushing out of the tracer dye. The patient can go home after the test and resume normal activities at work the same day or rest for a brief period of time if necessary and proceed with routine from the next day onwards.


SPECT scans are generally a very safe procedure and do not trigger any harmful side-effects. Minor bleeding, pain or swelling post the intravenous injection in the region where the needle was inserted in the arm can occur, which diminishes on its own within a day or two.

However, in rare instances, the patient may be allergic to the radioactive dye i.e. the tracer material and hence depending on the hypersensitivity reaction, the doctor may advise the patient not to undergo a SPECT scan and to take up an alternative imaging assay like an MRI scan.


The pictures obtained from a SPECT scan are analysed by a radiologist and the impaired tissues if any in the bone, heart or brain are clearly seen. The test results are then sent to the doctor, who advises the patient on the subsequent additional diagnostic tests or treatment options, depending on what diseases are detected in the bone, brain or heart.