The Endless Capabilities of Magnetic Resonance, from Zero to High Fields

Magnetic resonance techniques (NMR, MRI, EPR) continue to play ever expanding roles in biomedical research and modern medicine. NMR and MRI detect the angular momentum (“spin”) of atomic nuclei like ¹H, ²H, ¹³C, ³¹P, and ²³Na, while EPR detects the spin of unpaired electrons, in molecules. Despite the passage of several decades since its discovery, intense research on magnetic resonance continues on many fronts, leading to new ways to interrogate spins and to access otherwise unmeasurable properties of a vast variety of molecular systems. Although early magnetic resonance signals were produced by sweeping a magnetic field in the presence of a constant radiofrequency field (B₁), nowadays pulsed radiofrequency techniques tend to dominate applications of NMR, MRI, and EPR. Yet, as time goes by, advances in frequency-swept techniques are showing the many advantages of this old strategy. These include the ability to excite resonances spanning a wide range of frequencies, e.g., across bandwidths from tens of kilohertz to multiple megahertz. Such capability is creating new opportunities for the field, like enabling NMR and MRI with compact magnets that, despite their relatively large field inhomogeneity, perform as needed. With this approach, we have recently developed a compact 0.7 Tesla human head-only MRI scanner that’s transportable and weighs less than 500 kg. My lecture will introduce these enabling technologies, as well as examples of compact NMR, MRI, and EPR systems recently developed in our laboratory.