99mTcSestamibi

99mTc-sestamibi, also known as technetium-99m sestamibi, is a radiopharmaceutical used in nuclear medicine for functional imaging. It consists of the radionuclide technetium-99m bound to the lipophilic cation sestamibi, which allows it to cross cell membranes and accumulate in mitochondria. After intravenous injection, uptake in tissues parallels regional blood flow and mitochondrial activity, enabling assessment of perfusion and viability in various organs.

In cardiology, 99mTc-sestamibi is employed for single-photon emission computed tomography (SPECT) myocardial perfusion imaging. Rest and stress imaging assess ischemia and scar, with examinations typically performed 1–4 hours after injection. Protocols often use two injections (stress and rest) or a combined approach, and the administered activity is in the tens of millicuries, depending on protocol and patient factors.

Uptake in the heart is influenced by perfusion and cellular viability; hepatic and biliary excretion leads to activity in the liver and bowel, which can complicate image interpretation. Attenuation and careful interpretation improve diagnostic accuracy in perfusion assessment.

Outside cardiac imaging, 99mTc-sestamibi is used to localize parathyroid adenomas with two-phase scintigraphy, exploiting higher mitochondrial density in adenomas. It is also used off-label for breast imaging and, in select settings, tumor characterization.

Safety considerations are similar to other technetium-99m radiopharmaceuticals. The procedure involves ionizing radiation with a low to moderate effective dose; adverse reactions are rare. Pregnancy and breastfeeding are typically considered contraindications, and use should follow institutional guidelines.