Nuclear Medicine — MCQs

Question 241: Most commonly used isotope in myocardial perfusion scan is:

• A. Stannous pyrophosphate
• B. Technetium (Correct Answer)
• C. Gallium
• D. Thallium

Explanation: ***Technetium*** - **Technetium-99m (Tc-99m)** is the most widely used radionuclide in myocardial perfusion imaging (MPI) due to its favorable physical properties, including a short half-life and suitable gamma energy. - It is often chelated with agents like **sestamibi** or **tetrofosmin** to allow uptake by viable myocardial cells proportional to blood flow. *Thallium* - **Thallium-201** was historically used for MPI but has been largely replaced by technetium-based agents due to its longer half-life and lower energy photons, which result in poorer image quality. - While still used in some specific cases, it is not the primary isotope for modern myocardial perfusion scans. *Stannous pyrophosphate* - **Stannous pyrophosphate (PYP)** is used for imaging **amyloidosis** and **myocardial infarction** (specifically for detecting acutely necrotic myocardium), not for routine myocardial perfusion imaging. - It localizes to areas of **calcium deposition** in damaged myocardial tissue. *Gallium* - **Gallium-67** is primarily used for imaging **inflammation** and **infection**, such as in detecting lymphomas or osteomyelitis. - It is not used for assessing myocardial perfusion.