  The head down tilt (HDT) position is commonly used to simulate vascular and
tissue fluid dynamics during spaceflights. In HDT position, the cerebral
autoregulation faces difficulties to adjust the vascular tone while the
cephalad fluid shifts may yield increased intracranial pressures and altered
mechanical properties. Recent MRI T2 mapping in HDT position have shown fluid
overpressure in the brain and resulting loss of water contents in the CSF and
orbital compartments. Brain MRE was performed here in similar HDT conditions.
It was sensitive enough to provide new insights on the overall mechanical
response of brain tissues in microgravity analogous conditions. Summary of Main
Findings/Short Synopsis Brain fluid overpressure and resulting loss of water
contents in CSF and orbital compartments were confirmed by T2 mapping in head
down tilt position. The overall brain mechanical response in such microgravity
analogous conditions, cerebral tissue stiffening, was revealed by whole brain
MRE.
