title: Long-lived spin States for low-field hyperpolarized gas MRI.
abstract: Parahydrogen induced polarization was employed to prepare a relatively long-lived correlated nuclear spin state between methylene and methyl protons in propane gas. Conventionally, such states are converted into a strong NMR signal enhancement by transferring the reaction product to a high magnetic field in an adiabatic longitudinal transport after dissociation engenders net alignment (ALTADENA) experiment. However, the relaxation time T1 of ∼0.6 s of the resulting hyperpolarized propane is too short for potential biomedical applications. The presented alternative approach employs low-field MRI to preserve the initial correlated state with a much longer decay time TLLSS =(4.7±0.5) s. While the direct detection at low-magnetic fields (e.g. 0.0475 T) is challenging, we demonstrate here that spin-lock induced crossing (SLIC) at this low magnetic field transforms the long-lived correlated state into an observable nuclear magnetization suitable for MRI with sub-millimeter and sub-second spatial and temporal resolution, respectively. Propane is a non-toxic gas, and therefore, these results potentially enable low-cost high-resolution high-speed MRI of gases for functional imaging of lungs and other applications.
authors.affiliation: Laboratory of Magnetic Resonance Microimaging, International Tomography Center, SB RAS, 3A Institutskaya St., Novosibirsk 630090 (Russia) and Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090 (Russia).
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Kovtunov
authors.forename: Milton L
authors.initials: ML
authors.lastname: Truong
authors.forename: Danila A
authors.initials: DA
authors.lastname: Barskiy
authors.forename: Igor V
authors.initials: IV
authors.lastname: Koptyug
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Coffey
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Waddell
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
mesh_terms: D005740:Gases / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*
chemical_list: D005740:Gases; D006859:Hydrogen
keywords: NMR imaging; gases; hyperpolarization; long-lived spin states; propane