Which organ also has a significant dose when administering Tc exametazime (HMPAO)?

• A. Heart
• B. Lungs
• C. Bladder
• D. Stomach

Answer: (C)

When administering Tc exametazime (HMPAO), the bladder receives a significant dose due to the way radiopharmaceuticals are processed and excreted by the body. HMPAO is a lipophilic compound that crosses the blood-brain barrier and is taken up by the brain for imaging purposes. However, once it is introduced into the bloodstream, it also circulates through the kidneys and is eventually excreted in urine.

The kidneys filter the substance, and as the radiopharmaceutical is eliminated from the body, it accumulates in the bladder. This leads to a notable radiation dose to the bladder because the organ is in close proximity to where the excreted radioactivity is stored. This characteristic is particularly important for patient safety and planning appropriate imaging protocols.

In imaging with Tc exametazime, while other organs like the heart, lungs, and stomach may receive some dose, the bladder stands out because of its role in radiopharmaceutical elimination, which can lead to a more significant radiation exposure compared to the other organs listed.