99mTcTetrofosmin

99mTc-tetrofosmin is a radiopharmaceutical used in nuclear medicine for myocardial perfusion imaging. It consists of technetium-99m chelated by the tetrofosmin ligand and is supplied as a kit that forms the radiopharmaceutical upon labeling with technetium-99m from a generator. It is typically administered intravenously for single-photon emission computed tomography (SPECT) studies.

The agent is a lipophilic cation that readily crosses cell membranes and localizes in mitochondria of viable myocardial cells. Its uptake in the heart is influenced by regional myocardial blood flow and cell viability, allowing visualization of perfused and non-perfused areas. On SPECT images, normal uptake surrounds the left ventricle, while perfusion defects indicate potential ischemia or scar. Imaging quality and interpretation depend on timing after injection and whether stress or rest conditions are used.

Clinical use centers on myocardial perfusion imaging to evaluate suspected coronary artery disease and to assess myocardial viability. Protocols may include rest imaging, pharmacologic or exercise-induced stress, or both, with imaging typically performed about 30 to 60 minutes after injection. Some centers perform two-phase studies to distinguish reversible ischemia from scar tissue, aiding in risk stratification and treatment planning.

Administration and safety: 99mTc-tetrofosmin is given intravenously, with activities commonly in the hundreds of megabecquerels per injection. The tracer emits 140 keV gamma photons suitable for gamma cameras, enabling SPECT imaging. Radiation dose is in line with other 99mTc-labeled perfusion agents. Contraindications include pregnancy and lactation; adverse reactions are uncommon.

Compared with 99mTc-sestamibi, tetrofosmin differs in its pharmacokinetic properties and biodistribution, which can influence image quality in some patients.