Tc99msestamibi

Technetium-99m sestamibi is a radiopharmaceutical used in nuclear medicine for myocardial perfusion imaging and other diagnostic applications. It comprises the technetium-99m radioisotope bound to the lipophilic cation methoxyisobutylisonitrile, commonly referred to as MIBI. After intravenous administration, Tc-99m sestamibi rapidly distributes in the body and is taken up by tissues with high mitochondrial content; in the heart, uptake reflects regional blood flow and cellular viability. The radiopharmaceutical emits gamma photons suitable for gamma camera imaging, and the physical half-life of technetium-99m is about 6 hours, allowing delayed imaging if needed.

Uses and imaging: The principal indication is myocardial perfusion imaging (MPI) to evaluate suspected or known coronary artery disease. Imaging is typically performed at rest and after stress, using either physical exercise or pharmacologic stressors. Planar and single-photon emission computed tomography (SPECT) techniques are used, with SPECT often enhanced by CT for attenuation correction. The resulting perfusion maps help identify regions of reduced blood flow and distinguish scar from reversible ischemia.

Other applications: Tc-99m sestamibi is also used to localize hyperfunctioning parathyroid glands in primary hyperparathyroidism and, in some centers, for breast imaging to characterize lesions or aid in specific diagnostic scenarios.

Safety and dosing: Adverse effects are rare. Contraindications include pregnancy; lactation should be discussed with a clinician. Radiation exposure is minimized by using the lowest effective dose, typically in the range of 20–30 millicuries per injection, with rest and/or stress protocols contributing to a total study dose in the low to moderate range of millisieverts, depending on protocol and patient factors.