Revealing a third dissolved-phase Xenon-129 resonance in blood caused by hemoglobin glycation

Hyperpolarized (HP) xenon-129 ($^{129}$Xe), when dissolved in blood, has two NMR resonances: one in red blood cells (RBC) and one in plasma. The impact of numerous blood components on these resonances, however, has not yet been investigated. This study evaluates the effects of elevated glucose levels on the chemical shift (CS) and T*$_{2}$ relaxation times of HP $^{129}$Xe dissolved in sterile citrated sheep blood for the first time. HP $^{129}$Xe was mixed with sheep blood samples premixed with a stock glucose solution using a liquid–gas exchange module. Magnetic resonance spectroscopy was performed on a 3T clinical MRI scanner using a custom-built quadrature dual-tuned $^{129}$Xe/$^{1}$H coil. We observed an additional resonance for the RBCs ($^{129}$Xe-RBC1) for the increased glucose levels. The CS of $^{129}$Xe-RBC1 and $^{129}$Xe-plasma peaks did not change with glucose levels, while the CS of $^{129}$Xe-RBC2 (original RBC resonance) increased linearly at a rate of 0.015 ± 0.002 ppm/mM with glucose level. $^{129}$Xe-RBC1 T*$_{2}$ values increased nonlinearly from 1.58 ± 0.24 ms to 2.67 ± 0.40 ms. As a result of the increased glucose levels in blood samples, the novel additional HP $^{129}$Xe dissolved phase resonance was observed in blood and attributed to the $^{129}$Xe bound to glycated hemoglobin (HbA$_{1c}$)

Open-Access, Low-Magnetic-Field MRI System for Lung Research

An open-access magnetic resonance imaging (MRI) system is being developed for use in research on orientational/gravitational effects on lung physiology and function. The open-access geometry enables study of human subjects in diverse orientations. This system operates at a magnetic flux density, considerably smaller than the flux densities of typical other MRI systems, that can be generated by resistive electromagnet coils (instead of the more-expensive superconducting coils of the other systems). The human subject inhales air containing He-3 or Xe-129 atoms, the nuclear spins of which have been polarized by use of a laser beam to obtain a magnetic resonance that enables high-resolution gas space imaging at the low applied magnetic field. The system includes a bi-planar, constant-current, four-coil electromagnet assembly and associated electronic circuitry to apply a static magnetic field of 6.5 mT throughout the lung volume; planar coils and associated circuitry to apply a pulsed magnetic-field-gradient for each spatial dimension; a single, detachable radio-frequency coil and associated circuitry for inducing and detecting MRI signals; a table for supporting a horizontal subject; and electromagnetic shielding surrounding the electromagnet coils