What is a SPECT Scan Commonly Used For?

SPECT Scan

SPECT scan, or Single-Photon Emission Computerized Tomography, is a non-invasive nuclear imaging technique. This special imaging technique employs a radioactive tracer and a special camera to construct a 3-D image of the organs. It is used to visualize different internal organs of the body in a very detailed manner.

What is SPECT scan used for?

The SPECT scan makes use of computed tomography (CT) technology with a radioactive tracer. A single photon emission computed tomography (SPECT) scan is an imaging test that shows how blood flows into and within tissues and organs. It is used to help diagnose seizures, strokes, stress fractures, infections, and tumors in the spine.

How is it different from the other imaging techniques?

The most common imaging techniques show an image of the internal organ, and we are able to see their size and location . In a SPECT scan, one can also see the live function of the target organ. For example, one is able see the pattern of blood flow in the heart. We can also determine which part of the brain is currently active through SPECT. It is done by initially injecting a gamma-emitting radioisotope into your body. 

The SPECT scan is similar to Magnetic Resonance Imaging (MRI); however, it is more advanced as it shows live movement. In MRI, we can see a detailed anatomy of the internal organ but not blood flow or the functioning . Both MRI and SPECT scans are 3-D scans.

When to get a SPECT scan?

SPECT scan is done mainly to diagnose or monitor brain, heart or bone-related disorders.

• Neuroimaging or brain imaging: Neuroimaging helps in detecting which part of the brain is affected if you have memory loss, seizure, blood clot in the brain, stroke, or have suffered brain injury or an epileptic attack.

Some specialists also use this imaging technique to detect psychiatric disorders through neuroimaging. For example, it is used for the diagnosis of attention deficit hyperactivity disorder (ADHD). It is also widely used, either by itself or in combination with MRI, for research purposes. The scanned images serve as data for research with minimal error.

• Cardiac imaging: The imaging technique allows non-invasive imaging of the heart through various methods. SPECT scan can take images of the direction and volume of blood flow. Therefore, it is used to detect any changes in cardiac efficiency. It determines the amount of blood that the heart can pump in a single contraction and the amount that remains in the heart chambers.

It is also used to determine clogged coronary arteries. These are the vessels that supply blood and oxygen to your heart muscles. Sometimes, these vessels develop blockage or become narrow,. This can cause permanent damage to the patch of muscles or the muscle fibres. It can be diagnosed early with SPECT scan and then treated.

• Skeletal imaging: SPECT can detect metastasis (progression of cancer) in the bone. It is also used to detect very minute bone fractures that do not show up in a regular X-ray imaging. These fractures are known as  hidden fractures. It also shows the area of bone generation or healing. Apart from bone cancer, it can identify small fractures, stress fractures, spinal tumors and bone infections.

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Risks associated with SPECT scan

• The imaging technique is generally safe for most individuals. However, injection of the radioisotopes can cause allergic reactions in some people. It may also cause swelling, pain and bleeding at the site of injection. However, the amount of radiation used is very little and therefore does not cause any long-term health risks.
• It is important to note that SPECT scan is unsafe for pregnant and lactating women. This is because the radiation can harm the fetus. The radioactive tracer can pass to the uterus or breast milk, harming the baby.
• The tracer is radioactive, which means your body is exposed to radiation. This exposure is limited, however, because the radioactive chemicals have short half-lives. They break down quickly and are removed from the body through the kidneys.
• The long-term risk of radiation exposure is usually worth the benefits of diagnosing serious medical conditions. Your exposure risk could vary, however, depending on how many CT or other scans you have had. If you have concerns about your cumulative radiation exposure, please talk to your doctor.

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How to prepare for the scan?

Ideally, there is not much preparation needed in general. However, the requirement may differ for each individual.

Things to keep in mind:

• Keep your doctor informed of any ongoing medication.
• Inform your doctor if you are pregnant or lactating.
• Inform your doctor of any metal implants in your body and discuss any precautions needed.
• Leave your ornaments and jewellery at home or remove it before the procedure.

What are the steps involved?

 There are two steps involved:

• Injection of radioactive substances: You will be injected with a small amount of radioactive material in your arm. You may be then asked to wait for 20 minutes or an hour. Sometimes, it could be a few hours or even days, allowing the cells to absorb the radioactive substance.

The more active the cells are, the more radioactive material they will absorb. This is how your doctor visualizes the problem area. For example, if you had a seizure and underwent a SPECT scan, it will show more absorption in the affected area of your brain and help your doctor understand the part of the brain that needs attention.

• SPECT scanning: The time taken varies according to the area to be scanned. The SPECT scan is a circular machine with a camera on top. It is fixed on the target organ and rotates itself with any change in position. It can detect minute movements in the internal organ, with regular breathing. It captures images in very fine slices of the body and is then converted to a 3-D image display. 

You should try to lie comfortably on the scanner table and be as still as you can. Any  movement may cause an error in the imaging procedure. The remaining tracer is excreted through urine or is broken down by the body. Your doctor may ask you to drink plenty of fluids to flush out the tracer from your body.

What can your doctor conclude from SPECT?

A radiologist, trained specially in nuclear medicine, interprets the image. The picture may be monochrome or colored. The darker the color on the part of the image, the more tracer was absorbed. It indicates more active cells in that part of the organ.

Frequently Asked Questions (FAQs)

Q. Who will do the scanning?

A trained nuclear medicine technologist performs the scanning process. They are trained in doing the scan and are also capable of taking care of you if you panic or feel nervous.

Q. When do I get the results?

 It depends on the centre where you underwent the scan as well as the workload. It is best to ask the technologist for the expected time of the results. They will notify you. 

Q. Who interprets the scanned image? The nuclear medicine specialist  interprets the image and directly reports to your doctor with the results.

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