Changes in cerebral physiology with ageing assessed by respiratory-calibrated MRI

Purpose: Recently, respiratory-calibrated MRI methods capable of providing a non-invasive, quantitative assessment of cerebral physiology have been developed. Although differing slightly in detail, the aim of these methods is the same: to calibrate the MRI signal using a combination of hyperoxic and hypercapnic gas stimuli, and thereby allow quantification of brain energy metabolism and perfusion. To date, work in this area has focussed on methodological development and consequently data published have been acquired exclusively from healthy young volunteers. In order to move towards using respiratory-calibrated MRI techniques in studies of patient groups, the effect of healthy ageing on the quantifiable parameters must first be investigated. Of particular interest when studying a healthy aged subject group is the greater degree of variability in physiological parameters such as blood pressure (BP), body mass index (BMI) and pulse rate. We applied respiratory-calibrated MRI to a group of healthy aged subjects in order to investigate the effect of potentially altered baseline physiology on the parameters quantified by respiratory-calibrated MRI.