OVERVIEW
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:
SPECT Brain Scan
Brain SPECT is performed to evaluate the regional cerebral perfusion. The principle of the SPECT brain scan lies in the close association between cerebral blood flow and neuronal activity. In some cases, the brain SPECT may be accompanied by drugs that increase the cerebral blood flow, such as carbonic anhydrase inhibitors. This allows the assessment of stroke and transient ischemic stroke and helps doctors distinguish the neuronal and vascular causes of dementia. The diseases diagnosed with the SPECT brain scan include dementia, Alzheimer's disease, head trauma, Lyme disease, atrophy, and vasculitis.
SPECT Heart Scan
A SPECT test for the heart is a non-invasive diagnostic technique used to identify various perfusion abnormalities in the heart. A SPECT heart scan assists cardiologists in determining the areas of abnormal blood flow in the heart muscles and the functional capacity of the heart muscles. It also aids in separating the viable and non-viable heart muscles. The SPECT scan for the heart may involve both the stress and the resting test for evaluation of the blood flow into the coronary arteries. The stress tests may be done either through a treadmill or through medication (when a treadmill is not a viable option). The diseases evaluated by the SPECT cardiac scan include coronary artery stenosis, myocardial ischemia, coronary artery disease, and severe coronary calcification.
SPECT Bone Scan
A SPECT bone scan allows orthopedic specialists to determine alterations in skeletal metabolic activity. The uptake of the radioactive tracer by the bone tissues may be increased or decreased due to damage to the bone tissues. A SPECT scan for bones is usually recommended to diagnose various bone diseases, such as reasons for pain in the foot and ankle, wrist fractures, arthritis, bone cancer, and metabolic bone disease, such as renal bone disease and Paget's disease.
What is the Purpose of a SPECT Scan?
The following are the purposes of a SPECT scan:
Clogged Blood Vessels
SPECT scans help detect abnormalities in the flow of blood in the brain. They allow neurologists to diagnose vascular brain diseases, such as Moyamoya disease, in which the brain arteries are either narrowed or completely blocked.
Seizure Disorders
Seizures can lead to increased blood flow in the area of their origin in the brain. A SPECT scan, which determines the blood flow, helps detect the site of seizure initiation. It can be performed during the seizure or between the two seizures.
Parkinson's Disease
It is a progressive neurological disease presented with altered movement. In some cases, the neurologists may advise the patients to undergo a specialized SPECT scan, known as a dopamine transporter scan, for the definitive diagnosis of Parkinson's disease.
Clogged Coronary Arteries
A SPECT scan also assists cardiologists in determining the level of blood flow into the coronary arteries. If the arteries are narrowed or completely blocked, this will affect the blood supply to the cardiac muscles and may affect their health.
Weak Pumping Action
When the arteries are narrowed or blocked, the heart's muscles may not function properly. A SPECT scan helps evaluate the heart's contractile capacity and determines the level of chamber emptying during contractions.
Bone Disorders
A SPECT scan also helps diagnose various bone disorders by determining the level of radiotracer uptake. It detects hidden bone fractures, bone cancer, osteomyelitis, spondylolysis, and parathyroid disease.
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
Safe for People with Pacemakers and other Cardiovascular Implantable Electronic Devices (CIEDs)
The SPECT scan does not use a magnetic field, so it is safe for people with pacemakers or other cardiovascular implantable devices.
Can Find Issues That Other Imaging Methods Can’t Detect
SPECT scans help doctors detect abnormalities of the heart, brain, and bone that are not diagnosed with traditional imaging methods. The technique has 82% sensitivity and 76% specificity for coronary artery disease and 92% sensitivity and 100% specificity for diagnosing Alzheimer's disease.
Analyze the Functioning of Organs
As the SPECT scan helps obtain real-time imaging, it analyzes the physiological functioning of the targeted organs.
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.
Conclusion
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
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.
