Espy M.A., Kraus R.H., Magnelind P.E., Volegov P.L. Ultra-low field nuclear magnetic resonance: A new MRI regime

Oxford, Oxford University Press, 2014. — 264 p. — ISBN: 9780199349043,0199349045,0199796432,978-0-19-979643-4.This book is designed to introduce the reader to the field of NMR/MRI at very low magnetic fields, from milli-Tesla to micro-Tesla, the ultra-low field (ULF) regime. The book is focused on applications to imaging the human brain, and hardware methods primarily based upon pre-polarization methods and SQUID-based detection. The goal of the text is to provide insight and tools for the reader to better understand what applications are best served by ULF NMR/MRI approaches. A discussion of the hardware challenges, such as shielding, operation of SQUID sensors in a dynamic field environment, and pulsed magnetic field generation are presented. One goal of the text is to provide the reader a framework of understanding the approaches to estimation and mitigation of low signal-to-noise and long imaging time, which are the main challenges. Special attention is paid to the combination of MEG and ULF MRI, and the benefits and challenges presented by trying to accomplish both with the same hardware. The book discusses the origin of unique relaxation contrast at ULF, and special considerations for image artifacts and how to correct them (i.e. concomitant gradients, ghost artifacts). A general discussion of MRI, with special consideration to the challenges of imaging at ULF and unique opportunities in pulse sequences, is presented. The book also presents an overview of some of the primary applications of ULF NMR/MRI being pursued.Fundamental Principles of NMR and MRI at ULFCharacteristics of the NMR Signal
Introducing Signal-to-Noise and Contrast-to-Noise
NMR and MRI at ULF
MRI Eff ects
New Regimes of Physics Accessible at ULF
Summary of MRI at ULF
Summary of HF and ULF MRI ComparisonsNuts and Bolts of ULF MRIGeneral Concepts of Pre-Polarization Field Generation
Generation of Measurement Field, Gradients, and Spin-flip
Sensing the ULF MR Signals
Magnetic ShieldingMagnetic Resonance Phenomena at ULF
Interaction Between the Electromagnetic Radiation and the Nuclear Spins at ULF
Quantum Mechanical Description of Interaction between the Electromagnetic Radiation and the Nuclear Spins
NMR RelaxationImaging Techniques at ULFGeneral Imaging Concepts (How to Do MRI)
ULF MRI
Imaging Techniques: Making the Most of What You've Got
On the Plus SideApplications in ULF MRI
Multimodal Imaging of Human Brain Anatomy and Function: MEG and ULF MRI
New Approaches to Image Human Brain Function Uniquely Enabled by ULF MRI
MagViz and ULF NMR Relaxometers
A Final Word