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

Laser-polarized gases ((3)He and (129)Xe) 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 (129)Xe. 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, (3)He has been used exclusively for imaging air spaces. However, considering that the signal of (3)He is more than 10 times greater than that of (129)Xe for presently attainable polarization levels, this work has focused on generating a method to introduce (3)He into the vascular system. We addressed the low solubility issue by producing suspensions of (3)He microbubbles. Here, we provide the first vascular images obtained with laser-polarized (3)He. 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.