MRI of stroke using hyperpolarized 129Xe.

Because there is no background signal from xenon in biological tissue, and because inhaled xenon is delivered to the brain by blood flow, we would expect a perfusion deficit, such as is seen in stroke, to reduce the xenon concentration in the region of the deficit. Thermal polarization yields negligible xenon signal relative to hyperpolarized xenon; therefore, hyperpolarized xenon can be used as a tracer of cerebral blood flow. Using a rat permanent right middle cerebral artery occlusion model, we demonstrated that hyperpolarized (129)Xe MRI is able to detect, in vivo, the hypoperfused area of focal cerebral ischemia, that is the ischemic core area of stroke. To the best of our knowledge, this is the first time that hyperpolarized (129)Xe MRI has been used to explore normal and abnormal cerebral perfusion. Our study shows a novel application of hyperpolarized (129)Xe MRI for imaging stroke, and further demonstrates its capacity to serve as a complementary tool to proton MRI for the study of the pathophysiology during brain hypoperfusion.