title: High-resolution low-field molecular magnetic resonance imaging of hyperpolarized liquids.
abstract: We demonstrate the feasibility of microscale molecular imaging using hyperpolarized proton and carbon-13 MRI contrast media and low-field (47.5 mT) preclinical scale (38 mm i.d.) 2D magnetic resonance imaging (MRI). Hyperpolarized proton images with 94 × 94 μm(2) spatial resolution and hyperpolarized carbon-13 images with 250 × 250 μm(2) in-plane spatial resolution were recorded in 4-8 s (largely limited by the electronics response), surpassing the in-plane spatial resolution (i.e., pixel size) achievable with micro-positron emission tomography (PET). These hyperpolarized proton and (13)C images were recorded using large imaging matrices of up to 256 × 256 pixels and relatively large fields of view of up to 6.4 × 6.4 cm(2). (13)C images were recorded using hyperpolarized 1-(13)C-succinate-d2 (30 mM in water, %P(13C) = 25.8 ± 5.1% (when produced) and %P(13C) = 14.2 ± 0.7% (when imaged), T1 = 74 ± 3 s), and proton images were recorded using (1)H hyperpolarized pyridine (100 mM in methanol-d4, %P(H) = 0.1 ± 0.02% (when imaged), T1 = 11 ± 0.1 s). Both contrast agents were hyperpolarized using parahydrogen (>90% para-fraction) in an automated 5.75 mT parahydrogen induced polarization (PHIP) hyperpolarizer. A magnetized path was demonstrated for successful transportation of a (13)C hyperpolarized contrast agent (1-(13)C-succinate-d2, sensitive to fast depolarization when at the Earth's magnetic field) from the PHIP polarizer to the 47.5 mT low-field MRI. While future polarizing and low-field MRI hardware and imaging sequence developments can further improve the low-field detection sensitivity, the current results demonstrate that microscale molecular imaging in vivo is already feasible at low (<50 mT) fields and potentially at low (~1 mM) metabolite concentrations.
authors.affiliation: Vanderbilt University Institute of Imaging Science (VUIIS) and Department of Radiology, Vanderbilt University , Nashville, Tennessee 37232, United States.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Coffey
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Kovtunov
authors.forename: Danila A
authors.initials: DA
authors.lastname: Barskiy
authors.forename: Igor V
authors.initials: IV
authors.lastname: Koptyug
authors.forename: Roman V
authors.initials: RV
authors.lastname: Shchepin
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Waddell
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.forename: Kirsten A
authors.initials: KA
authors.lastname: Groome
authors.forename: Quinn A
authors.initials: QA
authors.lastname: Best
authors.forename: Fan
authors.initials: F
authors.lastname: Shi
authors.forename: Boyd M
authors.initials: BM
authors.lastname: Goodson
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D011725:Pyridines / Q000737:chemistry; D059629:Signal-To-Noise Ratio; D019802:Succinic Acid / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D003287:Contrast Media; D011522:Protons; D011725:Pyridines; D006859:Hydrogen; D019802:Succinic Acid; C023666:pyridine