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The feasibility of brain MRI with laser-polarized 129Xe in a small animal model is demonstrated. Naturally abundant 129Xe 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 accumulates in brain tissue. Spectroscopic studies reveal a single, dominant, tissue-phase NMR resonance in the head at 194.5 ppm relative to the gas phase resonance. Images of 129Xe in the rat head were obtained with 98-microliter voxels by 2D chemical shift imaging and show that xenon is localized to the brain. This work establishes that nuclear polarization produced in the gas phases survives transport to the brain where it may be imaged. Increases in polarization and delivered volume of 129Xe will allow clinical measurements of regional cerebral blood flow.

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We have measured the ratio g& /F& over the range 0.029 ( x ( 0.8 and 1.3 ( Q~( 10 (GeV/c) using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral fo g~(x, Q2) dx at fixed Q2 = 3 (GeV/c)2 yields 0.127~0.004(stat)~0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160~0.006. In the quark-parton model, this implies Aq = 0.27~0.10.PACS numbers: 13.60. Hb, 11. 55.Hx, 13.88.+e, 14.20.Dh Measurements of the longitudinal and transverse spindependent structure functions gi(x, Q ) and gq(x, Q ) for deep-inelastic lepton-nucleon scattering have become an increasingly important tool in unraveling the complex structures of the proton and neutron.Of particular interest are the integrals I t (Q ) = f"g (x,tQ )dx the proton and I i (Q ) = ftI gi (x, Q ) dx for the neutron.

The first magnetic resonance imaging studies of laser-polarized 129 Xe, dissolved in the blood and tissue of the lungs and the heart of Sprague-Dawley rats, are described. 129 Xe resonances at 0, 192, 199, and 210 ppm were observed and assigned to xenon in gas, fat, tissue, and blood, respectively. One-dimensional chemical-shift imaging (CSI) reveals xenon magnetization in the brain, kidney, and lungs. Coronal and axial twodimensional CSI show 129 Xe dissolved in blood and tissue in the thorax. Images of the blood resonance show xenon in the lungs and the heart ventricle. Images of the tissue resonance reveal xenon in lung parenchyma and myocardium. The 129 Xe spectrum from a voxel located in the heart ventricle shows a single blood resonance. Time-resolved spectroscopy shows that the dynamics of the blood resonance match the dynamics of the gas resonance and demonstrates efficient diffusion of xenon gas to the lung parenchyma and then to pulmonary blood. These observations demonstrate the utility of laser-polarized 129