High-resolution low-field molecular magnetic resonance imaging of hyperpolarized liquids.

Coffey AM, Kovtunov KV, Barskiy DA, Koptyug IV, Shchepin RV, Waddell KW, He P, Groome KA, Best QA, Shi F, Goodson BM, Chekmenev EY
Anal Chem. 2014 86 (18): 9042-9

PMID: 25162371 · PMCID: PMC4165454 · DOI:10.1021/ac501638p

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.

MeSH Terms (9)

Carbon Isotopes Contrast Media Hydrogen Magnetic Resonance Imaging Magnetic Resonance Spectroscopy Protons Pyridines Signal-To-Noise Ratio Succinic Acid

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