Hyperpolarized and Inert Gas MRI: The Future

Abstract

Magnetic resonance imaging (MRI) is a potentially ideal imaging modality for noninvasive, nonionizing, and longitudinal assessment of disease. Hyperpolarized (HP) agents have been developed in the past 20 years for MR imaging, and they have the potential to vastly improve MRI sensitivity for the diagnosis and management of various diseases. The polarization of nuclear magnetic resonance (NMR)-sensitive nuclei other than (1)H (e.g., (3)He, (129)Xe) can be enhanced by a factor of up to 100,000 times above thermal equilibrium levels, which enables direct detection of the HP agent with no background signal. In this review, a number of HP media applications in MR imaging are discussed, including HP (3)He and (129)Xe lung imaging, HP (129)Xe brain imaging, and HP (129)Xe biosensors. Inert fluorinated gas MRI, which is a new lung imaging technique that does not require hyperpolarization, is also briefly discussed. This technique will likely be an important future direction for the HP gas lung imaging community.

Pulmonary ventilation imaging in asthma and cystic fibrosis using oxygen‐enhanced 3D radial ultrashort echo time MRI

“…[1][2][3][4][5] However, HP gas MRI requires specialized equipment and isotopically enriched gases that add cost and limit access for multicenter clinical research studies. 6 While fluorinated gases offer one alternative to hyperpolarized gases, multinuclear hardware and specific oxygen-fluorinated gas mixtures 6,7 are still required, adding cost and complexity compared to conventional proton MRI.…”

A Structural Basis for 129Xe Hyper‐CEST Signal in TEM‐1 β‐Lactamase

“…MRI is a non‐invasive, non‐ionizing imaging technique that offers good spatial and temporal resolution at virtually unlimited penetration depths. However, conventional 1 H MRI is characterized by low sensitivity as MR contrast arises from the net magnetization that results from the small population difference between the nuclear Zeeman energy levels of 1 H nuclei . Additionally, any MR contrast produced by a reporter gene must be detectable against background signal of water protons present in tissue at ∼90 M .…”

Imaging of Brown Adipose Tissue: State of the Art

“…Owing to the relatively low degree of polarization inducible by MR magnets, conventional MR imaging is limited to signal generated by proton spins in water or lipids. Hyperpolarized MR imaging uses in vitro nuclear spin polarization, providing orders of magnitude improvement in the signalto-noise ratio, as well as access to new substrates as contrast agents (87). For instance, breakdown of hyperpolarized 13 C-pyruvate into bicarbonate and lactate was recently demonstrated in norepinephrine-activated interscapular BAT in rats (88).…”