What radiopharmaceutical is known to effectively cross the intact blood-brain barrier?

The radiopharmaceutical known to effectively cross the intact blood-brain barrier is Tc99-Bicisate. This agent is specifically designed to traverse the blood-brain barrier and is utilized in brain imaging due to its ability to assess cerebral blood flow and the integrity of the blood-brain barrier itself. Its effectiveness is largely attributed to its lipophilic properties, allowing it to easily penetrate the barrier and accumulate where needed in the brain.

Other options, while valuable in various imaging modalities, either do not cross the blood-brain barrier or are not specifically intended for that purpose. For instance, Tc99m-HMPAO and I-123-IMP are also used in brain perfusion studies, but they may not penetrate the blood-brain barrier as effectively as Tc99-Bicisate. Tc99m-Sestamibi, while useful in cardiac imaging and certain tumors, primarily concentrates in myocardial tissues and does not target the brain in the same effective manner. This characteristic marks Tc99-Bicisate as the distinct choice for crossing the barrier effectively.