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Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging.

ABSTRACT: Hyperpolarized magnetic resonance imaging (MRI) is a powerful technique enabling real-time monitoring of metabolites at concentration levels not accessible by standard MRI techniques. A considerable challenge this technique faces is the T1 decay of the hyperpolarization upon injection into the system under study. Here we show that A(n)A'(n)XX' spin systems such as (13)C2-1,2-diphenylacetylene ((13)C2-DPA) sustain long-lived polarization for both (13)C and (1)H spins with decay constants of almost 4.5 min at high magnetic fields of up to 16.44 T without spin-locking; the T1 of proton polarization is only 3.8 s. Therefore, storage of the proton polarization in a (13)C2-singlet state causes a 69-fold extension of the spin lifetime. Notably, this extension is demonstrated with proton-only pulse sequences, which can be readily implemented on standard clinical scanners.

SUBMITTER: Feng Y

PROVIDER: S-EPMC3732746 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging.

Feng Yesu Y Theis Thomas T Liang Xiaofei X Wang Qiu Q Zhou Pei P Warren Warren S WS

Journal of the American Chemical Society 20130624 26

Hyperpolarized magnetic resonance imaging (MRI) is a powerful technique enabling real-time monitoring of metabolites at concentration levels not accessible by standard MRI techniques. A considerable challenge this technique faces is the T1 decay of the hyperpolarization upon injection into the system under study. Here we show that A(n)A'(n)XX' spin systems such as (13)C2-1,2-diphenylacetylene ((13)C2-DPA) sustain long-lived polarization for both (13)C and (1)H spins with decay constants of almos ...[more]

PMID: 23781874

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Project description:OBJECTIVES:The aim of this study was to determine if hyperpolarized [1,4-13C2]malate imaging could measure cardiomyocyte necrosis after myocardial infarction (MI). BACKGROUND:MI is defined by an acute burst of cellular necrosis and the subsequent cascade of structural and functional adaptations. Quantifying necrosis in the clinic after MI remains challenging. Magnetic resonance-based detection of the conversion of hyperpolarized [1,4-13C2]fumarate to [1,4-13C2]malate, enabled by disrupted cell membrane integrity, has measured cellular necrosis in vivo in other tissue types. Our aim was to determine whether hyperpolarized [1,4-13C2]malate imaging could measure necrosis after MI. METHODS:Isolated perfused hearts were given hyperpolarized [1,4-13C2]fumarate at baseline, immediately after 20 min of ischemia, and after 45 min of reperfusion. Magnetic resonance spectroscopy measured conversion into [1,4-13C2]malate. Left ventricular function and energetics were monitored throughout the protocol, buffer samples were collected and hearts were preserved for further analyses. For in vivo studies, magnetic resonance spectroscopy and a novel spatial-spectral magnetic resonance imaging sequence were implemented to assess cardiomyocyte necrosis in rats, 1 day and 1 week after cryo-induced MI. RESULTS:In isolated hearts, [1,4-13C2]malate production became apparent after 45 min of reperfusion, and increased 2.7-fold compared with baseline. Expression of dicarboxylic acid transporter genes were negligible in healthy and reperfused hearts, and lactate dehydrogenase release and infarct size were significantly increased in reperfused hearts. Nonlinear regression revealed that [1,4-13C2]malate production was induced when adenosine triphosphate was depleted by >50%, below 5.3 mmol/l (R2 = 0.904). In vivo, the quantity of [1,4-13C2]malate visible increased 82-fold over controls 1 day after infarction, maintaining a 31-fold increase 7 days post-infarct. [1,4-13C2]Malate could be resolved using hyperpolarized magnetic resonance imaging in the infarct region one day after MI; [1,4-13C2]malate was not visible in control hearts. CONCLUSIONS:Malate production in the infarcted heart appears to provide a specific probe of necrosis acutely after MI, and for at least 1 week afterward. This technique could offer an alternative noninvasive method to measure cellular necrosis in heart disease, and warrants further investigation in patients.

Project description:We report a systematic study of relaxation dynamics of hyperpolarized (HP) propane and HP propane-d6 prepared by heterogeneous pairwise parahydrogen addition to propylene and propylene-d6 respectively. Long-lived spin states (LLS) created for these molecules at the low magnetic field of 0.0475 T were employed for this study. The parahydrogen-induced overpopulation of a HP propane LLS decays exponentially with time constant (TLLS) approximately 3-fold greater than the corresponding T1 values. Both TLLS and T1 increase linearly with propane pressure in the range from 1 atm (the most biomedically relevant conditions for pulmonary MRI) to 5 atm. The TLLS value of HP propane gas at 1 atm is ~3 s. Deuteration of the substrate (propylene-d6) yields hyperpolarized propane-d6 gas with TLLS values approximately 20% shorter than those of hyperpolarized fully protonated propane gas, indicating that deuteration does not benefit the lifetime of the LLS HP state. The use of pH2 or Xe/N2 buffering gas during heterogeneous hydrogenation reaction (leading to production of 100% HP propane (no buffering gas) versus 43% HP propane gas (with 57% buffering gas) composition mixtures) results in (i) no significant changes in T1, (ii) decrease of TLLS values (by 35±7% and 8±7% respectively); and (iii) an increase of the polarization levels of HP propane gas with a propane concentration decrease (by 1.6±0.1-fold and 1.4±0.1-fold respectively despite the decrease in TLLS, which leads to disproportionately greater polarization losses during HP gas transport). Moreover, we demonstrate the feasibility of HP propane cryo-collection (which can be potentially useful for preparing larger amounts of concentrated HP propane, when buffering gas is employed), and TLLS of liquefied HP propane reaches 14.7 seconds, which is greater than the TLLS value of HP propane gas at any pressure studied. Finally, we have explored the utility of using a partial Spin-Lock Induced Crossing (SLIC) radio frequency (RF) pulse sequence for converting the overpopulated LLS into observable 1H nuclear magnetization at low magnetic field. We find that (i) the bulk of the overpopulated LLS is retained even when the optimal or near-optimal values of SLIC pulse duration are employed, and (ii) the overpopulated LLS of propane is also relatively immune to strong RF pulses-thereby, indicating that LLS is highly suitable as a spin-polarization reservoir in the context of NMR/MRI detection applications. The presented findings may be useful for improving the levels of polarization of HP propane produced by HET-PHIP via the use of an inert buffer gas; increasing the lifetime of the HP state during preparation and storage; and developing efficient approaches for ultrafast MR imaging of HP propane in the context of biomedical applications of HP propane gas, including its potential use as an inhalable contrast agent.

Dataset Information

Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging.

Publications

Storage of hydrogen spin polarization in long-lived 13C2 singlet order and implications for hyperpolarized magnetic resonance imaging.

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