Final answer:
HMPAO, also known as exametazime, does cross the intact blood-brain barrier, and its distribution does follow cerebral blood flow, without significant redistribution in the brain.
Step-by-step explanation:
The substance HMPAO (hexamethylpropylene amine oxime), also known as exametazime, is a radiopharmaceutical used in nuclear medicine, specifically in brain perfusion imaging. When considering the assertions about HMPAO, it's important to note that HMPAO does cross the intact blood-brain barrier (BBB), and its distribution follows cerebral blood flow once inside the brain. Furthermore, one unique characteristic of HMPAO is that it does not significantly redistribute after being taken up by brain tissue, which allows for accurate imaging. Therefore, the statement that 'it does not significantly redistribute in the brain' is indeed true, contradicting the potential answer choice that it is not true.