What characteristic of Tc exametazime (HMPAO) aids its brain localization?

• A. Hydrophylicity
• B. High molecular weight
• C. Lipophilicity
• D. Low solubility

Answer: (C)

Tc exametazime (HMPAO) is known for its lipophilic nature, which significantly aids in its localization within the brain. The lipophilicity of HMPAO allows it to easily cross the blood-brain barrier, a critical factor for imaging brain activity. Once it has traversed this barrier, HMPAO becomes polar upon encountering the brain's physiological environment, which prevents it from leaving the brain tissue and thus allows for effective imaging of cerebral perfusion and activity.

This characteristic is particularly advantageous because it helps in accurately locating regions of the brain that are metabolically active or identifying areas with impaired blood flow, which can be crucial for diagnosing various neurological conditions. The ability to effectively target brain tissue due to its lipophilic nature makes it an optimal choice in nuclear medicine for brain imaging studies.