What is a disadvantage of using Tc-99m for certain imaging studies?

• A. High availability
• B. Long half-life
• C. Potential for allergic reactions
• D. Low energy gamma emissions

Answer: (C)

Selecting potential for allergic reactions as a disadvantage of using Tc-99m highlights a valid concern in the realm of radiopharmaceuticals. While Tc-99m is generally considered safe and is used widely in various imaging modalities due to its favorable properties, it is still crucial to acknowledge that some patients may have hypersensitivity reactions to the Tc-99m compound or its associated components. Such allergic reactions can range from mild to severe and may complicate imaging procedures, requiring additional precautions or alternative imaging strategies.

In contrast, while high availability is an advantage of Tc-99m, the long half-life is actually a disadvantage when considering optimal imaging timelines. A longer half-life may lead to unnecessary radiation exposure and complicate scheduling for imaging studies if the radiotracer remains in the body longer than needed. Low energy gamma emissions could be interpreted as a limitation in terms of detection sensitivity, as lower energy emissions could reduce the quality of the imaging data collected. However, Tc-99m primarily emits gamma radiation in a range that is highly suitable for imaging and is optimized for detection by Gamma cameras. Therefore, potential allergic reactions emerge as the most significant drawback in the context of patient safety and procedural efficiency.