In a cardiac imaging study, which agent is typically used for myocardial perfusion imaging at rest?

Myocardial perfusion imaging is primarily conducted to assess blood flow to the heart muscle and to identify areas that may be ischemic due to coronary artery disease. In this context, one of the most commonly used radiopharmaceutical agents is Tc99m-Sestamibi. This agent is a lipophilic compound that readily enters myocytes when there is adequate blood flow, making it ideal for observing perfusion at rest and under stress conditions.

Tc99m-Sestamibi is particularly suited for cardiac imaging because it is taken up by viable myocardial cells and remains there long enough to allow imaging, providing clear assessment of perfusion patterns. The agent's distribution correlates well with the underlying blood flow, which is crucial during both resting and exercise states in myocardial perfusion studies.

Other agents listed, while they may have distinct applications in nuclear medicine, do not fulfill the specific requirements for myocardial perfusion imaging effectively as Tc99m-Sestamibi does. For instance, Tc99m-MDP is primarily used for bone scanning and would not provide the necessary information about myocardial blood flow. Similarly, while I-123 has utility in certain cardiac studies, it is more commonly used in other contexts. Tc99m-Testa does not have widespread recognition