In vivo magnetic resonance vascular imaging using laser-polarized 3He microbubbles

Laser-polarized gases (He-3 and Xe-129) are currently being used in magnetic resonance imaging as strong signal sources that can be safely introduced into the lung. Recently, researchers have been investigating other tissues using Xe-129. These studies use xenon dissolved in a carrier such as lipid vesicles or blood. Since helium is much less soluble than xenon in these materials, He-3 has been used exclusively for imaging air spaces. However, considering that the signal of He-3 is more than 10 times greater than that of Xe-129 for presently attainable polarization levels, this work has focused on generating a method to introduce He-3 into the vascular system. We addressed the low solubility issue by producing suspensions of He-3 microbubbles. Here, we provide the first vascular images obtained with laser-polarized He-3. The potential increase in signal and absence of background should allow this technique to produce high-resolution angiographic images. In addition, quantitative measurements of blood flow velocity and tissue perfusion will be feasible.