SPECT (Single-Photon Emission Computerized Tomography) Scan


Single-photon emission computed tomography (SPECT) is a nuclear medicine imaging technique often used to diagnose disease.

The principle of SPECT tomography involves using radioactive substances and a specialized nuclear medicine camera to obtain images of the targeted area. It provides detailed information about the functioning of various organs.

What is SPECT Scan?

A SPECT scan is an advanced imaging technique used to diagnose various diseases. The scan comprises injecting a radioactive tracer into the bloodstream and taking images of the body parts through special cameras.

The radioactive tracer compounds used in SPECT imaging include iodine-123 and technetium-99m. Thallium-201 is also used in certain cases.

The choice of radioactive tracer depends on the organ being scanned. For instance, technetium-99m is usually used for the diagnosis of brain disorders.

Types of SPECT Scans

Depending on the organ examined, there are different types of SPECT scans. The following are the different types of SPECT medical imaging:

What is the Purpose of a SPECT Scan?

The following are the purposes of a SPECT scan:

What Does a SPECT Scan Involve?

A SPECT scan involves injecting the radioactive tracer and obtaining the images through nuclear medicine cameras. The camera rotates around the targeted organ to reconstruct the images.

Instead of obtaining images of a particular site, the SPECT scan detects the level of biological activity at the analysis site.

How does SPECT Scan Work?

A SPECT scan consists of two steps:

Injecting a Radiotracer

During the initial step of the SPECT scan, the doctor injects the radiotracer. A radiotracer is a radioactive substance that highlights specific areas of the body. Sometimes, the patients may be required to inhale or swallow the radiotracer substance.

As the radiotracer substances move into the blood, they accumulate in specific areas of the body.

Obtaining Images with a Gamma Camera

A nuclear or gamma camera is used to take images of organs by detecting the presence of a radioactive tracer.

Gamma cameras do not emit radiation; rather, they detect energy sources or radiation, such as radioactive tracers. The images obtained allow doctors to analyze the functioning of the organs or tissues.

What Should You Expect During a SPECT Medical Imaging Scan?

The patient is seated in a dimly lit, quiet room and cannot speak before the radiotracer injection. The doctor injects the radioactive tracer. If required, the patient may be given sedation after the radiotracer injection.

The patient must wait for a few minutes, which gives time for the radiotracer to circulate within the system. The waiting time may be as low as 15 minutes for a cardiac stress test and as high as 90 minutes for a cerebral examination.

The patient is then taken to the detector apparatus to obtain the images.

Advantages of SPECT Imaging

What are the Risks Associated with a SPECT Scan?

The most common complications associated with the SPECT scan are allergic reactions to the drugs, such as vasodilators, used during the scan. If allergic reactions occur, they are generally mild and may include flushing, GI distress, light-headedness, and headache.

Some patients may also have more severe side effects, such as chest discomfort, arrhythmia, hypotension, and AV blockade. Rarely do patients have allergic reactions to the radioactive tracer.

Who Shouldn't Undergo a SPECT Scan?

Pregnant women should avoid SPECT scans, and clinicians should perform a detailed risk-benefit analysis before recommending SPECT scans. A SPECT scan involves radiation that might affect fetal health. Further, clinicians should avoid using radioactive tracers because of fetal iodine uptake.

SPECT is also not recommended for patients with a history of allergic reactions to radioactive tracers.

Why Should You Choose HCG for the SPECT Scan?

SPECT is an advanced imaging modality that requires specialized machines and experts to perform the procedure. HCG Cancer Centre is an advanced center for diagnosing and treating various cancers.

The hospital's SPECT scan facility comprises state-of-the-art scanners for clear and detailed images. Further, the radiologists performing the SPECT scan are highly experienced, ensuring an excellent patient experience during the procedure.


A SPECT scan is an imaging technique that assists in diagnosing various diseases, especially those of the heart, brain, and bones. It uses a radioactive tracer and a nuclear camera to obtain real-time images.

The scan is contraindicated in pregnant women and those with a history of allergy to radioactive tracer substances.

Frequently Asked Questions

SPECT uses radiotracers and nuclear medicine cameras to create images, while MRI uses magnetic fields and radio waves to produce images. MRI provides information about anatomical characteristics, while SPECT gives details of physiological function.

The SPECT scan results may be received within 2 to 3 days after the procedure. The radiologists may provide you with preliminary information about the results. However, the detailed results may be handed to you or sent to the doctor within 2 to 3 days.

A SPECT scan uses a radiotracer and specialized cameras to create images that show how different organs function. A CT scan uses X-rays to create anatomical images.

MRI provides excellent structural information, whereas SPECT provides both structural and functional information. In certain cases, SPECT scans may offer better results, whereas, in some cases, MRI scans offer better imaging results.

For instance, studies have reported that SPECT is superior to CT or MRI for traumatic brain injury as it provides the status of the flow of blood to the brain. Studies have also shown that MRI scans offer better imaging support in diagnosing certain heart conditions.

SPECT scans may be used to detect inflammation in various parts of the body. Simultaneous use of SPECT/CT machines may help in the detection of inflammation sites and the extent of inflammation.

SPECT scans are helpful in the detection of inflammatory conditions, namely rheumatoid arthritis and psoriasis.

SPECT scans provide valuable information about the pathophysiology of the brain and thereby help in diagnosing mental illnesses.

A SPECT scan aids in detecting the less and more active parts of the brain, and they play an important role in diagnosing anxiety.

After the SPECT scan, patients are advised to drink a significant amount of fluid to flush the radiotracer out of the system.