Sestamibi Scan

• A Sestamibi Scan is a nuclear medicine test using a radioactive tracer to assess organ function.
• It is commonly employed to diagnose coronary artery disease and identify overactive parathyroid glands.
• The procedure involves tracer injection, imaging at different times, and specific preparation.
• Results are interpreted by specialists to guide diagnosis and treatment planning.
• The scan is generally safe, involving low levels of radiation exposure.

What is a Sestamibi Scan?

A Sestamibi Scan is a type of nuclear medicine imaging test that uses a small amount of a radioactive substance, technetium-99m sestamibi, to create images of organs and tissues. This tracer is injected into the bloodstream and absorbed by specific cells, allowing doctors to visualize their activity and blood flow. The primary sestamibi scan uses and purpose include assessing myocardial perfusion (blood flow to the heart muscle) and identifying hyperactive parathyroid glands. For cardiac evaluations, it helps diagnose coronary artery disease by showing areas of reduced blood flow. In parathyroid imaging, it can pinpoint adenomas, which are benign tumors causing hyperparathyroidism. The scan provides functional information that traditional imaging like X-rays or CT scans cannot.

Sestamibi Scan Procedure and Preparation

The sestamibi scan procedure typically involves two main phases: tracer injection and imaging. For cardiac scans, it often includes both rest and stress components. During the stress phase, patients may walk on a treadmill or receive medication to simulate exercise, followed by tracer injection and imaging. For parathyroid scans, the tracer is injected, and images are taken at various intervals over several hours. The sestamibi tracer is absorbed by metabolically active cells, including heart muscle cells and overactive parathyroid cells, which then emit gamma rays detected by a special camera.

Preparation for a Sestamibi Scan varies depending on the specific type of scan being performed:

• For cardiac scans: Patients are usually asked to avoid caffeine and certain medications for 12-24 hours prior. Fasting for a few hours before the scan may also be required.
• For parathyroid scans: No specific dietary restrictions are typically needed, but patients should inform their doctor about any medications they are taking.

It is crucial for patients to follow all pre-scan instructions provided by their healthcare team to ensure accurate results. The entire procedure, including preparation and imaging, can take several hours, especially for cardiac studies with both rest and stress components.

Interpreting Sestamibi Scan Results

Understanding sestamibi scan results explained requires expertise from a nuclear medicine physician or a radiologist. The images generated from the scan show how the sestamibi tracer has been absorbed by the target tissues. In cardiac imaging, areas of the heart muscle that receive adequate blood flow will show normal tracer uptake, appearing bright on the scan. Areas with reduced blood flow (ischemia) or damaged tissue (infarction) will show less or no tracer uptake, appearing as “cold spots.” Comparing rest and stress images helps differentiate between reversible ischemia and permanent damage. For parathyroid scans, an overactive parathyroid gland (adenoma) will retain the sestamibi tracer longer than normal thyroid tissue, appearing as a persistent “hot spot” on delayed images. These findings help clinicians confirm diagnoses, determine the extent of disease, and guide treatment decisions, such as the need for angioplasty, bypass surgery, or parathyroidectomy.