Imaging Human Brain Perfusion with Inhaled Hyperpolarized ¹²⁹Xe MR Imaging

Abstract

Purpose To evaluate the feasibility of directly imaging perfusion of human brain tissue by using magnetic resonance (MR) imaging with inhaled hyperpolarized xenon 129 (Xe). Materials and Methods In vivo imaging with Xe was performed in three healthy participants. The combination of a high-yield spin-exchange optical pumpingXe polarizer, custom-built radiofrequency coils, and an optimized gradient-echo MR imaging protocol was used to achieve signal sensitivity sufficient to directly image hyperpolarized Xe dissolved in the human brain. Conventional T1-weighted proton (hydrogen 1 [H]) images and perfusion images by using arterial spin labeling were obtained for comparison. Results Images of Xe uptake were obtained with a signal-to-noise ratio of 31 ± 9 and demonstrated structural similarities to the gray matter distribution on conventional T1-weightedH images and to perfusion images from arterial spin labeling. Conclusion Hyperpolarized Xe MR imaging is an injection-free means of imaging the perfusion of cerebral tissue. The proposed method images the uptake of inhaled xenon gas to the extravascular brain tissue compartment across the intact blood-brain barrier. This level of sensitivity is not readily available with contemporary MR imaging methods.RSNA, 2017.

Establishing an accurate gas phase reference frequency to quantify129Xe chemical shifts in vivo

“…Across these species, four 129 Xe resonances have been reported within the thorax: airspaces (−5 to 10 ppm), aqueous media (195–199 ppm), red blood cells (mouse, 199–200 ppm; rat, 210–213 ppm; human, 216–221 ppm), and adipose tissue (189–194 ppm). Beyond the thoracic cavity, dissolved 129 Xe has also been imaged in the lung, kidney, and brain, where similar chemical shifts have been reported .…”

Functionalized Lipopeptide Micelles as Highly Efficient NMR Depolarization Seed Points for Targeted Cell Labelling in Xenon MRI

“…Hyper‐CEST enables a switchable Xe MRI contrast through radiofrequency (RF)‐activated saturation transfer, i.e., a controlled depolarization that propagates rapidly into the bulk magnetization pool. MRI of well perfused organs with dissolved Xe from inhalation has made important progress that demonstrates the potential for such a targeted vascular reporter 23–25. The self‐assembling micelle approach with a core of multiple hosts that are accessible for Xe but shielded from other interactions is very promising compared to the administration of individual, bare Xe hosts that have several shortcomings: examples such as cucurbit[6]uril (CB6) are problematic since they are accessible for competitive guests and are difficult to functionalize.…”

“…We consider P‐CrA‐A2 micelles highly promising as future potential MRI reporters for the monitoring of highly vascularized brain regions such as tumors. Clinical lung imaging with Xe is already quite established and has recently been expanded by novel applications for mapping the Xe distribution in other organs like the human brain23,24,53 as well as the kidneys 25. It has benefitted from technical improvements found in modern polarizers,54 optimized RF antenna systems,55,56 and adapted readout protocols that will ultimately also enable (pre)clinical Hyper‐CEST studies.…”

Rapid assessment of pulmonary gas transport with hyperpolarized 129Xe MRI using a 3D radial double golden‐means acquisition with variable flip angles

“…DP MRI, on the other hand, enables the quantification of gas exchange by the lung parenchyma (12–18), as well as pulmonary circulation at the alveolar level (19–26). The transport of DP magnetization throughout the body and more distal organs has also been demonstrated using DP MRI (27–32). …”