Arterial spin labeling MRI study of age and gender effects on brain perfusion hemodynamics

Abstract

Normal aging is associated with diminished brain perfusion measured as cerebral blood flow (CBF), but previously it is difficult to accurately measure various aspects of perfusion hemodynamics including: bolus arrival times and delays through small arterioles, expressed as arterial-arteriole transit time. To study hemodynamics in greater detail, volumetric arterial spin labeling MRI with variable postlabeling delays was used together with a distributed, dual-compartment tracer model. The main goal was to determine how CBF and other perfusion hemodynamics vary with aging. Twenty cognitive normal female and 15 male subjects (age: 23-84 years old) were studied at 4 T. Arterial spin labeling measurements were performed in the posterior cingulate cortex, precuneus, and whole brain gray matter. CBF declined with advancing age (P < 0.001). Separately from variations in bolus arrival times, arterial-arteriole transit time increased with advancing age (P < 0.01). Finally, women had overall higher CBF values (P < 0.01) and shorter arterial-arteriole transit time (P < 0.01) than men, regardless of age. The findings imply that CBF and blood transit times are compromised in aging, and these changes together with differences between genders should be taken into account when studying brain perfusion. Magn Reson Med 68:912-922,

Cerebral Perfusion in Insulin Resistance and Type 2 Diabetes

“…There is also evidence that nitric oxide is an important mediator of CO 2 -related vasodilatation. 33 In agreement with the literature 34,35 we observed the dependence of resting cortical flow on sex. Cerebral blood flow in women is~10% larger than in men.…”

“…This phenomenon could be explained by~10% lower hemoglobin and heamatocrit levels in women, combined with the hypothesis that CBF is regulated to maintain constant oxygen delivery across different hemoglobin levels. 34,35 Our study showed a strong association between resting GM CBF and general cognitive functioning measured by multiple psychometric test scores. This association was not expected and it appears to be reported in only one other study.…”

“…Individuals in the insulin-resistant group did not meet T2DM criteria as determined by HbA 1c or glucose tolerance test, but had fasting hyperinsulinemia, leading to quantitative insulin-sensitivity check index (QUICKI)o0. 35. The QUICKI incorporates fasting glucose and insulin levels and has been validated against the hyperinsulinemic-euglycemic glucose clamp.…”

Cerebral Arterial Bolus Arrival Time is Prolonged in Multiple Sclerosis and Associated with Disability

“…The time from ASL to this point is defined here, as previously, as the BAT. 18 Other scan parameters were: TR 4,000 milliseconds, TE 23 …”

Temporal and Spatial Variances in Arterial Spin-Labeling Are Inversely Related to Large-Artery Blood Velocity

“…For instance, age is associated with a decreased signal-to-noise ratio, due, in part, to increased variance between individual control-tag difference images. 14 Arterial transit time is another velocity-sensitive hemodynamic characteristic associated with aging 15 and the presence of white matter hyperintensities (WMH). 16 Prolonged transit time is visualized by localized regions of hyperintense ASL signal, contributing to greater spatial variance in whole-brain CBF.…”