Laser-polarized (3)He as a probe for dynamic regional measurements of lung perfusion and ventilation using magnetic resonance imaging.

Magnetic resonance imaging (MRI) using laser-polarized noble gases, such as (129)Xe and (3)He, allows unparalleled noninvasive information on gas distribution in lung airways and distal spaces. In addition to pulmonary ventilation, lung perfusion assessment is crucial for proper diagnosis of pathological conditions, such as pulmonary embolism. Magnetic resonance perfusion imaging usually can be performed using techniques based on the detection of water protons in tissues. However, lung proton imaging is extremely difficult due to the low proton density and the magnetically inhomogeneous structure of the lung parenchyma. Here we show that laser-polarized (3)He can be used as a noninvasive probe to image, in a single MRI experiment, not only the ventilation but also the perfusion state of the lungs. Blood volume maps of the lungs were generated based on the (3)He signal depletion during the first pass of a superparamagnetic contrast agent bolus. The combined and simultaneous lung ventilation and perfusion assessments are demonstrated in normal rat lungs and are applied to an experimental animal model of pulmonary embolism. Magn Reson Med 44:1-4, 2000. Copyright 2000 Wiley-Liss, Inc.