Using Magnetic Resonance Imaging To Assess The Change Of Cerebral Blood Flow At Sea Level And High Altitude

Purposes:It is well known hypobaric hypoxia occurs with exposure to high altitude, with commonly associated change of cerebral blood flow (CBF). Past attempts include the use of transcranial Doppler (TCD) at high altitude or measure of CBF in simulated hypoxia, both of which have methodological shortcomings. In this work,3D pseudo-continuous arterial spin labeling (3D pCASL) was used to assess the CBF of normal subjects. Based on the data, magnetic resonance imaging (MRI), clinical tests and hematology were used to assess the change of CBF to further extending our understanding of acute mountain sickness (AMS).Material and Methods:3D pCASL was used to assess the CBF of 80 normal subjects. Based on the data,12 subjects were chosen for the study of CBF at high altitude. All subjects received clinical tests, hematology and MRI examinations at sea level and high altitude. Identical 3.0 T MR scanners with 8-channel head coils were used at both sea level and high altitude with the same experimental procedures.Results:CBF in young females was higher than in the young males, whereas the CBF in older females and older males showed no difference. CBF decreased significantly in older females compared with young females, whereas no such age-related effect was present in males. With acute exposure to high altitude, the CBF in AMS subjects was higher (P<0.05), while the CBF of non-AMS subjects was lower (P>0.05) compared with those at sea level. Magnetic resonance angiography (MRA) in both AMS and non-AMS subjects showed a significant increase in the cross-sectional areas of internal carotid artery (ICA), basilar artery (BA), and middle cerebral artery (MCA) on the first day at high altitude. With acclimatization to high altitude, the CBF in all subjects declined and the cross-sectional areas of ICA, BA and MCA declined. The CBF in all subjects continued to decline returning to sea level, and the cross-sectional areas of ICA, BA and MCA showed no difference with those before the exposure to high altitude.Conclusions:CBF is affected by gender and age. The selection of subjects for experiments on CBF should take the female-to-male ration, age and menstrual cycle into consideration. AMS may be related to an increased CBF rather than the changes of the cross-sectional areas of ICA, BA and MCA. Thus, using 3D pCASL for absolute CBF measurement at both sea level and high altitude has substantial advantages over the use of TCD.