Direct enhancement of nitrogen-15 targets at high-field by fast ADAPT-SABRE

Soumya S Roy,Gabriele Stevanato,Peter J Rayner,Simon B Duckett

doi:10.1016/j.jmr.2017.10.006

Abstract

Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends on coherent spin mixing, which can be achieved naturally at a low magnetic field. The optimum transfer field to spin-1/2 heteronuclei is technically demanding, as it requires field strengths weaker than the earth’s magnetic field for efficient spin mixing. In this paper, we illustrate an approach to achieve strong 15N SABRE hyperpolarization at high magnetic field by a radio frequency (RF) driven coherent transfer mechanism based on alternate pulsing and delay to achieve polarization transfer. The presented scheme is found to be highly robust and much faster than existing related methods, producing ∼3 orders of magnitude 15N signal enhancement within 2 s of RF pulsing.

Highlights

Despite the huge success of NMR in a wide assortment of research fields ranging from structural material characterization to the imaging of internal human organs, it is still regarded to be underexploited based on its theoretical potential [1,2]
Most of the successes of NMR and MRI applications have been achieved utilizing the thermal level of nuclear spin polarization which is only of the order of 10À5 at room temperature in a standard high field spectrometer [2]: only one spin in 30,000 contributes to the NMR signal for protons in a 9.4 T magnet
Improving this poor sensitivity would make NMR and MRI more widespread and cost-efficient. The solution to this challenge is offered by hyperpolarization methods that enhance the nuclear spin polarization by up to 5 orders of magnitude compared to standard thermal polarization [3]

Summary

Introduction

Despite the huge success of NMR in a wide assortment of research fields ranging from structural material characterization to the imaging of internal human organs, it is still regarded to be underexploited based on its theoretical potential [1,2]. Most of the successes of NMR and MRI applications have been achieved utilizing the thermal level of nuclear spin polarization which is only of the order of 10À5 at room temperature in a standard high field spectrometer [2]: only one spin in 30,000 contributes to the NMR signal for protons in a 9.4 T magnet Improving this poor sensitivity would make NMR and MRI more widespread and cost-efficient. The solution to this challenge is offered by hyperpolarization methods that enhance the nuclear spin polarization by up to 5 orders of magnitude compared to standard thermal polarization [3]. This large sensitivity enhancement enables the completion of high-end MRI applications e.g. in vivo study of human cancer, which could otherwise not be performed due to sensitivity issues [4,5,6].

Methods

Results

Conclusion