Magnetic Resonance Microscopy

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This book is the fourth in the Wiley-VCH series on Magnetic Resonance Microscopy , a series linked in spirit to the International Conference on Magnetic Resonance Microscopy (ICMRM). Winfried Kuhn and Bernhard Blümich organized the first meeting of this biannual conference in 1991 in Heidelberg, which led to the first book in this series. That Heidelberg meeting is also when Paul Callaghan burst upon the scene (with his student Yang Xia, who remains active in these meetings) with his new, but now classic, book Principles of Nuclear Magnetic Resonance Microscopy (Oxford University Press) – what timing! The wider appearance of magnetic gradient fields in the portfolio of magnetic resonance methods for imaging and studies of molecular transport phenomena was an exciting prospect. It motivated the still ongoing ICMRM conference series and the associated books, which summarize the progress in this field with chapters written by leading experts, among them Nobel Prize awardees Paul Lauterbur and Sir Peter Mansfield as well as Sir Paul Callaghan, who shaped that community like a force of nature from then on until his untimely death in 2012. Also, our brilliant colleague Robert Blinc from Slovenia attended the first ICMRM but had to leave early following an announcement during one of the sessions effectively saying “Professor Blinc, you are needed back in your country,” at which Robert Blinc stood up and left to facilitate the independence of Slovenia from Socialist Federal Republic of Yugoslavia. We were witnessing the birth of a country, a unique experience for most of us. At the third meeting in Würzburg, the brave suggestion to hold a meeting in North America was accepted. Thus, the fourth meeting was in Albuquerque and ICMRM has now a truly international presence, having ventured as far away as Utsunomiya and Beijing. These meetings, originally dubbed the Heidelberg Meetings, have been at the forefront of amazing developments and accompanying applications of magnetic resonance. Despite the inclusion of the word microscopy in their name, they represent the much broader area of magnetic resonance with spatial resolution, which is expressed by the title of the second book from the Albuquerque meeting, Spatially Resolved Magnetic Resonance , as well as the organizing Division of Spatially Resolved Magnetic Resonance of the AMPERE Society . Thanks to the advances over three decades, we have micrometer spatial resolution in magnetic resonance imaging today, while in the early days the word microscopy was understood as a tool to see things hard to visualize just by eye. We believe the broad range of the science and applications of magnetic resonance represented in these meetings is unique to all science and the field displays no hint of imminent stagnation – welcome news to all of us. I would like to close this Foreword with the observation that Bernhard Blümich, who with Winfried Kuhn founded these meetings 30 years ago, is still actively involved here as one of the editors of this book. I salute him for his continued contributions to the field and support of this conference.

Eiichi Fukushima

Albuquerque, 2021

Magnetic resonance microscopy (MRM) has focused on magnetic resonance imaging (MRI) applied to objects of smaller scale and higher spatial resolution for more than three decades. After the pioneering work by Eccles, Callaghan, Aguayo, Blackband, Johnson et al. in 1986, MRM quickly spread to, among other fields, chemistry, histology, and materials research. Since 1992, the edited book series Magnetic Resonance Microscopy has provided an important voice describing the latest developments in spatially resolved magnetic resonance methods and their applications far beyond the scope of medical diagnostics. An excellent introduction to MRM, focusing on the practical aspects of high magnetic fields and on the study of biological systems, was authored in 2017 by Luisa Ciobanu: Microscopic Magnetic Resonance Imaging: A Practical Perspective (Pan Stanford, Singapore, 2017). Our book complements this monograph by showing the use of MRM and related techniques in a much broader area and on a wider scale, which extends from chemical engineering to plant research and battery applications, highlighting the interdisciplinary nature of MRM.

The book opens with a section on hardware and methodology, covering aspects of micro-engineering, magnet technology, coil performance, and hyperpolarization to improve signal-to-noise ratio, a major bottleneck of MRM. Specific pulse sequences and developments in the field of mobile nuclear magnetic resonance are further topics of this first chapter. The following parts, 2 and 3, review essential processes such as filtration, multi-phase flows and transport, and a wide range of systems from biomarkers via single cells to plants and biofilms. Part 4 focuses on energy research, which is becoming increasingly important due to the globally growing environmental problems. It reports on battery types and their developments and how battery states can be recorded and characterized with MRM. However, we would like to point out to the reader that only a small sample of applications could be addressed in Chapters 1to 4. Finally, the last chapter advocates that theory and applications should not be treated separately, because much can be gained from their complementarity.

The main aim of this book is to convince aspiring and established scientists from all fields that MRM is a versatile nuclear magnetic resonance (NMR) method that is capable of answering many questions from both the laboratory and everyday life. The book seeks to inspire a new readership from industries and innovative research directions to create synergies by adding MRM to their expertise.

The editors thank all the authors for contributing their invaluable knowledge to this book during a time challenged by COVID-19. Our thanks also go to the kind staff of the Wiley books department, who helped us with advice and support throughout the whole editing process.

Sabina Haber-Pohlmeier

Luisa Ciobanu

Bernhard Blümich

Summer 2021

Neil MacKinnon, Jan G. Korvink, and Mazin Jouda

Institute of Microstructure Technology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany

Thirty years have passed since 1991 when Paul Callaghan published his book on magnetic resonance microscopy [1], and many works have subsequently appeared that have made numerous advances in this exciting field possible. Our goal for this chapter is to (informally) revisit some of Callaghan’s analysis, to reflect on it, and then take account of some of the advances and insights that have been reported since then.

Paul Callaghan’s book [1] is perhaps the first publication to consider magnetic resonance imaging (MRI) in the same light as optical microscopy. This will also be our starting point.

Until the advent of super-resolution microscopy, refractive optical microscopy was essentially a radiation scattering method, in which a beam of photons from an independent light source was sent on its way to scatter off objects, followed by traversal of the beam through a focusing objective on its way back to a detector, to thereby reveal the structure and composition of the scattering object. The limitations of this approach, in terms of resolution, is known as the Abbe limit δ = λ/(2 n sin θ), where n is the refractive index, θ the half-angle of the spot subtended by the lens, and λ the radiation wavelength.