0089 Feasibility of Rapid Measurement of Brain Metabolites in Obstructive Sleep Apnea

Abstract

Abstract Introduction Obstructive Sleep Apnea (OSA) affects over 15% of the adult population and is associated with brain dysfunction. Although the dysfunction is well-identified and presents brain morphological changes as shown with structural imaging, it is unclear what pathology underlies these neural alterations. Magnetic resonance spectroscopic imaging (MRSI) can non-invasively measure several metabolites from multiple brain regions in vivo. However, the clinical practicality of the standard MRSI techniques (Cartesian phase-encoding or echo-planar [EP]) is hindered by long scan times. In order to assess clinical populations, our group developed an alternative MRSI technique, “radial” EP-MRSI. To assess the feasibility and calculate effect sizes we did a pilot study of brain metabolites in OSA using radial EP-MRSI. Methods Radial EP-MRSI data with a speed-up (undersampling) factor of 2.5 (compared to a fully-sampled Cartesian MRSI scan) were acquired in 5 OSA patients (3 males, 37±11 yrs., Apnea Hypopnea Index (AHI): 8.2±5.5) and 10 healthy controls (5 males, 28±7 yrs.). Spectra from twelve brain regions were selected from each subject and five metabolites–total choline, myo-inositol (mI), total N-acetylaspartate, glutamine+glutamate (Glx) and lactate (Lac)–were quantified as ratios with respect to creatine (Cr), using “LC Model” software. The brain regions include left/right of: basal ganglia, insula, and gray/white of the frontal and occipital regions. Mean group differences were calculated and compared with independent samples t-tests. Results Glx/Cr was significantly decreased (27%; p<0.05) in OSA vs. control in the left posterior insula. Other metabolites did not show significant differences. mI/Cr trends were consistent with previous findings (higher in OSA) and Lac/Cr trended higher OSA. Conclusion This feasibility study showed that it is possible to measure multiple metabolites in multiple regions and detect effects of OSA. The accelerated technique enabled measurements to be completed in under 4 minutes. Support (If Any)