On Simulated Weightlessness Based On Perfusion And Metabolism Functional Magnetic Resonance Imaging

During the course of normal flight,pilots are often in mild weightlessness state.Relatived to vertigo and redout caused by severe weightlessness,mild weightlessness is generally overlooked.Because the loss of hydrostatic fluid pressure difference,more blood can flow to the head,which can affect cerebral perfusion and metabolism,and cause brain dysfunction.Sepecially,pilots’ execution abilities could be impaired after long-term weightlessness.Therefore,it is of great importance to study the effects of weightlessness on cerebral perfusion and metabolism.In this thesis,we aimed to access the mechanisms of cerebral blood flow(CBF)and cerebral metabolic rate of oxygen(CMRO2)of human body under simulated mild weightlessness.Firstly,the approach of-10° head-down tilt was used to simulate pilots in mild weightlessness state.Medical imaging examinations were performed to asscess changes in cerebral perfusion and metabolism before and after mild weightlessness.Secondly,perfusion and metabolic functional magnetic resonance imaging techniques were used to noninvasively measure CBF and CMRO2 based on arterial spin labeling and T2 relaxation under spin tagging MRIs.Thirdly,pre and post-weightless changes in CBF and CMRO2 were studied in human brain.We found that CBF signicifantly changed in precentral gyrus,postcentral gyrus,parietal,frontal,precuneus,and cingulate brain region and CMRO2 increased in whole brain level.This study found that mild weightlessness could affect the cerebral perfusion and metabolism of pilots.Noninvasive functional MRI techniques were applied which could provide objective evaluations for pilots.