Hyperpolarized 129 Xe imaging of the brain: Achievements and future challenges.

Hyperpolarized (HP) xenon-129 ( Xe) brain MRI is a promising imaging modality currently under extensive development. HP Xe is nontoxic, capable of dissolving in pulmonary blood, and is extremely sensitive to the local environment. After dissolution in the pulmonary blood, HP Xe travels with the blood flow to the brain and can be used for functional imaging such as perfusion imaging, hemodynamic response detection, and blood-brain barrier permeability assessment. HP Xe MRI imaging of the brain has been performed in animals, healthy human subjects, and in patients with Alzheimer's disease and stroke. In this review, the overall progress in the field of HP Xe brain imaging is discussed, along with various imaging approaches and pulse sequences used to optimize HP Xe brain MRI. In addition, current challenges and limitations of HP Xe brain imaging are discussed, as well as possible methods for their mitigation. Finally, potential pathways for further development are also discussed. HP Xe MRI of the brain has the potential to become a valuable novel perfusion imaging technique and has the potential to be used in the clinical setting in the future.