MRI of Empty Spaces by Hyperpolarization

MRI of Empty Spaces by Hyperpolarization

Author: Sarah Millar

Despite the impressive diagnostic power of conventional magnetic resonance imaging (MRI) and computed tomography (CT), there is a fundamental challenge in imaging void spaces such as lungs owing to very low tissue density. As a result, many pulmonary diseases cannot be imaged for early detection or for monitoring treatment response.
Hyperpolarization MRI techniques increase nuclear spin polarization by 4–6 orders of magnitude, enabling the use of exogenous hyperpolarized (HP) contrast agents. However, HP 13C, 129Xe, and other hetero-nuclei contrast agents require radio-frequency (rf) channels and rf probes that are not standard in commercially available preclinical and clinical MRI scanners.

Kirill Kovtunov, Novosibirsk State University, Russia, Eduard Chekmenev, Vanderbilt University, Nashville, USA, and colleagues have developed a 1H-based hyperpolarization technique that uses HP propane gas produced by a Rh/TiO2 catalyst with Rh particle size of 1.6 nm. 3D MRI images of the flowing HP propane were collected with subsecond scan times, microscale spatial resolution, and a large imaging matrix. Despite the significant improvement in spatial resolution and addition of the third dimension compared with similar 2D techniques previously reported, the total scan time for the 3D MRI was approximately 30 times shorter. This improvement was attributed to the relatively large proton hyperpolarization of HP propane gas. In addition, the HP propane gas signal was strong enough to potentially overshadow the signal from background water protons.

The team hopes that these results may enable imaging of porous media or human lungs without requiring isotopic enrichment of HP contrast media and by using a relatively simple hyperpolarization setup and conventional (i.e., proton) MRI hardware.

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