Imaging human brain perfusion with inhaled hyperpolarized (129)Xe MR imaging

Purpose To evaluate the feasibility of directly imaging perfusion of human brain tissue by using magnetic resonance (MR) imaging with inhaled hyperpolarized xenon 129 ((129)Xe). Materials and Methods In vivo imaging with (129)Xe was performed in three healthy participants. The combination of a high-yield spin-exchange optical pumping (129)Xe polarizer, custom-built radiofrequency coils, and an optimized gradient-echo MR imaging protocol was used to achieve signal sensitivity sufficient to directly image hyperpolarized (129)Xe dissolved in the human brain. Conventional T1-weighted proton (hydrogen 1 [(1)H]) images and perfusion images by using arterial spin labeling were obtained for comparison. Results Images of (129)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-weighted (1)H images and to perfusion images from arterial spin labeling. Conclusion Hyperpolarized (129)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.