Abstract
PurposeUpon inhalation, xenon diffuses into the bloodstream and is transported to the brain, where it dissolves in various compartments of the brain. Although up to five chemically distinct peaks have been previously observed in 129Xe rat head spectra, to date only three peaks have been reported in the human head. This study demonstrates high resolution spectroscopy and chemical shift imaging (CSI) of 129Xe dissolved in the human head at 1.5 Tesla.MethodsA 129Xe radiofrequency coil was built in‐house and 129Xe gas was polarized using spin‐exchange optical pumping. Following the inhalation of 129Xe gas, NMR spectroscopy was performed with spectral resolution of 0.033 ppm. Two‐dimensional CSI in all three anatomical planes was performed with spectral resolution of 2.1 ppm and voxel size 20 mm × 20 mm.ResultsSpectra of hyperpolarized 129Xe dissolved in the human head showed five distinct peaks at 188 ppm, 192 ppm, 196 ppm, 200 ppm, and 217 ppm. Assignment of these peaks was consistent with earlier studies.ConclusionHigh resolution spectroscopy and CSI of hyperpolarized 129Xe dissolved in the human head has been demonstrated. For the first time, five distinct NMR peaks have been observed in 129Xe spectra from the human head in vivo. Magn Reson Med 75:2227–2234, 2016. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights
Hyperpolarized (HP) 129Xe MRI has gained interest ever since the first image was acquired from a biological sample [1]
The upfield chemical shift of this 129Xe gas in the smaller airways of the lungs could be due to a combination of effects, including; bulk magnetic susceptibility shift effects [5], the chemical shift associated with mixing with oxygen [23] and the fact that while an average adult head is positioned at the isocenter, the lungs lie further away from the isocenter at a lower static magnetic field strength than the isocenter and would experience a lower Larmor frequency
From the anatomical location of the 129Xe NMR peaks in the chemical shift images superimposed on corresponding 1H images in Figure 5, we propose the assignment of each individual peak to a particular compartment of the head as follows: FIG. 3
Summary
Hyperpolarized (HP) 129Xe MRI has gained interest ever since the first image was acquired from a biological sample [1]. Studies involving NMR spectroscopy and chemical shift imaging (CSI) of HP 129Xe dissolved in the brain have been conducted in rats [14,15,16,17] and in humans [4,18]. Kershaw et al and Nakamura et al [19,20] observed five peaks in 129Xe spectra from the rat head, which they attributed to jaw muscle (187–191 ppm), white matter (191–194 ppm), gray matter (193–197 ppm), fat tissue outside the brain (197–201 ppm), and red blood cells (210 ppm). Kilian et al [18,21] reported preliminary results of HP 129Xe CSI in the human brain at 3.0 Tesla (T) and estimated T1 relaxation of HP 129Xe dissolved in gray matter and white matter to be 14 s and 8 s, respectively
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