Hyperpolarization via dissolution dynamic nuclear polarization: new technological and methodological advances
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REVIEW
Hyperpolarization via dissolution dynamic nuclear polarization: new technological and methodological advances Arthur C. Pinon1 · Andrea Capozzi1,2 · Jan Henrik Ardenkjær‑Larsen1 Received: 10 August 2020 / Revised: 4 October 2020 / Accepted: 23 October 2020 © European Society for Magnetic Resonance in Medicine and Biology (ESMRMB) 2020
Abstract Dissolution-DNP is a method to boost liquid-state NMR sensitivity by several orders of magnitude. The technique consists in hyperpolarizing samples by solid-state dynamic nuclear polarization at low temperature and moderate magnetic field, followed by an instantaneous melting and dilution of the sample happening inside the polarizer. Although the technique is well established and the outstanding signal enhancement paved the way towards many applications precluded to conventional NMR, the race to develop new methods allowing higher throughput, faster and higher polarization, and longer exploitation of the signal is still vivid. In this work, we review the most recent advances on dissolution-DNP methods trying to overcome the original technique’s shortcomings. The review describes some of the new approaches in the field, first, in terms of sample formulation and properties, and second, in terms of instrumentation. Keywords Hyperpolarization · Dynamic nuclear polarization · dDNP · Non-persistent radicals · Cross-polarization · Cryogen-free · Bullet-DNP
Introduction Nuclear Magnetic Resonance (NMR) and its two main applications, i.e., Magnetic Resonance Spectroscopy (MRS) and Magnetic Resonance Imaging (MRI), play a crucial part in many different fields ranging from material science, to molecular biology and clinical applications. MRS is considered one of the most powerful analytical techniques due to the detailed information that it can provide about molecular and macromolecular structures, dynamic processes, and chemical reactions in both material and biological studies, to name few. MRI is a medical diagnostic technique characterized by high anatomical resolution and a plurality of image contrast mechanisms; able to highlight, as appropriate, various pathologies and their response to treatment. Moreover, * Jan Henrik Ardenkjær‑Larsen [email protected] 1
Department of Health Technology, Center for Hyperpolarization in Magnetic Resonance, Technical University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark
Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Route Cantonale, 1015 Lausanne, Switzerland
2
unlike computed tomography (CT) and positron emission tomography (PET), the absence of ionizing radiations makes MRI a completely non-invasive diagnostic technique. Nevertheless, NMR has a main drawback: many of its applications suffer from lack of sensitivity, which translates into long acquisitions and poor temporal resolution. The NMR signal is proportional to the nuclear magnetization (M) that, in turn, increases linearly with the nuclear spin polarization PI:
M = N𝜇I PI ,
(1)
where N represents the number of spins p
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