Subsecond Three-Dimensional Nitrogen-15 Magnetic Resonance Imaging Facilitated by Parahydrogen-Based Hyperpolarization

Abstract

Magnetic resonance imaging (MRI) provides unique information about the internal structure and function of living organisms in a non-invasive way. The use of conventional proton MRI for the observation of real-time metabolism is hampered by the dominant signals of water and fat, which are abundant in living organisms. Heteronuclear MRI in conjunction with the hyperpolarization methods does not encounter this issue. In this work, we polarized 15 N nuclei of [ 15 N 1 ]fampridine (a drug used for the treatment of multiple sclerosis) to the level of 4% in nuclear magnetic resonance (NMR) experiments and 0.7% in MRI studies using spin-lock-induced crossing combined with signal amplification by reversible exchange. Consequently, threedimensional 15 N MRI of the hyperpolarized 15 N-labeled drug was acquired in 0.1 s with a signal-to-noise ratio of 70. In addition, the NMR signal enhancements for 15 N-enriched fampridine and fampridine with a natural abundance of 15 N nuclei were compared and an explanation for their difference was proposed.

LIGHT-SABRE Hyperpolarizes 1-13C-Pyruvate Continuously without Magnetic Field Cycling

“…The low magnetic field is also beneficial for 1- 13 C-pyruvate LIGHT-SABRE because it preserves the singlet spin state of pH 2 after association with the Ir-complex. Although LIGHT-SABRE was proposed and used at high magnetic fields to polarize pyridine, nicotinamide, and 4-amido pyridine, in such cases, pH 2 -derived protons (IrHH) had the same chemical shifts. This is not the case for pyruvate, where the hydride–hydride chemical shift difference is 2 ppm .…”

“…This principle is used in the technique known as SABRE in shield enables alignment transfer to heteronuclei, SABRE-SHEATH. − After hyperpolarization in SABRE-SHEATH experiments, the magnetic field is typically elevated to a few Tesla for detection. An alternative approach to transferring the pH 2 spin order to 1 H, 13 C, or 15 N is to use RF pulse sequences at a constant field; − however, this approach has not yet been demonstrated for pyruvate.…”

“…[24][25][26][27][28] After hyperpolarization in SABRE-SHEATH experiments, the magnetic field is typically elevated to a few Tesla for detection. An alternative approach to transfer the pH2 spin order to 1 H, 13 C, or 15 N is to use RF pulse sequences at a constant field, [29][30][31][32][33][34][35] however, this approach has not yet been demonstrated for pyruvate.…”