In which organs is Tc exametazime (HMPAO) normally distributed?

• A. Heart and lungs
• B. Bone and intestines
• C. Brain, kidneys, bladder, liver
• D. Pancreas and spleen

Answer: (C)

Tc exametazime (HMPAO) is a radiopharmaceutical primarily used for imaging brain perfusion and assessing cerebral blood flow. When administered, it is taken up significantly by the brain due to its high lipid solubility, allowing it to cross the blood-brain barrier. In addition to the brain, a portion of the radiotracer is also distributed to other organs, including the kidneys where it is filtered and excreted, the bladder where it collects, and the liver where metabolism can occur.

The correct answer highlights the organs where Tc exametazime is most notably distributed. Given its design for assessing cerebral activity, brain uptake is expected and significant. Additionally, the renal and hepatic systems play a role in processing the compound, thus illustrating the distributions seen in the specified organs. The presence in the bladder primarily corresponds to the excretion pathway of the radiopharmaceutical.

In contrast, the other choices focus on organ systems that do not have the same significance or uptake characteristics when it comes to Tc exametazime. The heart and lungs, while important in other imaging studies, do not exhibit the same distribution patterns for this specific radiopharmaceutical. Similarly, bone and intestines, and pancreas and spleen do not play