BRAIN MRI WITH LASER-POLARIZED XE-129

The feasibility of brain MRI with laser-polarized Xe-129 in a small an imal model is demonstrated. Naturally abundant Xe-129 is polarized and introduced into the lungs of Sprague-Dawley rats. Polarized xenon gas dissolves in the blood and is transported to the brain where it accum ulates in brain tissue. Spectroscopic studies reveal a single, dominan t, tissue-phase NMR resonance in the head at 194.5 ppm relative to the gas phase resonance. Images of Xe-129 in the rat head were obtained w ith 98-mu l voxels by 2D chemical shift imaging and show that xenon is localized to the brain. This work establishes that nuclear polarizati on produced in the gas phases survives transport to the brain where it may be imaged. Increases in polarization and delivered volume of Xe-1 29 will allow clinical measurements of regional cerebral blood flow.