Magnetic Resonance in Chemistry and Medicine

by Freeman, Ray

• ISBN13: 9780199262250
• ISBN10: 019926225X
• Format: Paperback
• Copyright: 2003-06-19
• Publisher: Oxford University Press

Summary

Magnetic resonance (MR) measures the tiny radio frequency signals emitted by the nucleus of the atom when living or inanimate material is placed in a magnetic field. On the one hand, these signals allow scientists to picture the architecture of molecules too small to be seen under the most powerful microscope, while on the other hand they give medical doctors a detailed picture of the internal structure of the human body without resorting to surgery of any kind. These two applications (high-resolution NMR spectroscopy and the MRI scanner) seem to be worlds apart, but the underlying physical principles are the same, and it makes sense to treat them together. Chemists and clinicians who use magnetic resonance have much to learn about each other's specialities if they are to make the best use of magnetic resonance technology. Many in the medical fraternity will benefit from a general appreciation of how high-resolution NMR has advanced our understanding of human biochemistry, diagnostic medicine, and the search for new drugs. A broad general understanding of magnetic resonance should prove of interest to doctors who make use of the MRI scanner, and to those of their patients who wish to learn more about these daunting machines, even if it is only the question of their own personal safety. At the other end of the spectrum, chemists and biochemists who use high-resolution NMR spectroscopy in their everyday investigations will benefit by broadening their horizons to cover the exciting new developments in MR imaging and in vivo spectroscopy, as one justification for their research is the eventual benefit to health care. Finally, anyone interested in how the human mind works (cognitive neuroscience) will find a chapter devoted to the exciting new developments in functional magnetic resonance imaging of the brain. Each disparate group has something useful to learn from the others. The treatment is pictorial rather than mathematical.

Author Biography

Ray Freeman read chemistry at Oxford University and completed his doctorate with R. E. Richards on nuclear magnetic resonance (NMR) spectroscopy. After two years' postdoctoral research at the French Atomic Energy Commission at Saclay, France, he moved to the National Physical Laboratory in Teddington, Middlesex. In 1961 he joined Varian Associates in Palo Alto, California, and worked on the methodology of NMR, the design of commercial NMR spectrometers, and the development of new Fourier transform techniques. In 1973 he was appointed Lecturer at Oxford University and a Tutor and Fellow of Magdalen College, building up a research group on NMR methodology in the Physical Chemistry Laboratory. He was elected Fellow of the Royal Society in 1979. In 1987 he was appointed to the John Humphrey Plummer chair of Magnetic Resonance in the University of Cambridge, and Fellow of Jesus College, Cambridge.

Table of Contents

Introduction	1	(12)
Imaging and spectroscopy	1	(2)
Nuclear magnetism	3	(2)
Resonance	5	(1)
Spies at work	6	(4)
A word about jargon	10	(3)
Excitation of magnetic resonance	13	(20)
Equipment	13	(1)
The magnet	14	(4)
The radiofrequency	18	(1)
Polarization	19	(2)
The rotating reference frame	21	(2)
The vector representation	23	(2)
The free precession signal	25	(1)
Field inhomogeneity	26	(3)
Hard and soft radiofrequency pulses	29	(4)
Detection of magnetic resonance	33	(21)
The magnetic resonance response	33	(1)
The radiofrequency coil	34	(6)
Amplification	40	(1)
Quadrature detection	41	(2)
Sampling the time-domain signal	43	(2)
Dynamic range	45	(1)
Fourier transformation	46	(5)
Display	51	(3)
Relaxation	54	(16)
Spin-lattice relaxation	54	(2)
Relaxation curves	56	(3)
Cross-relaxation	59	(4)
Spin temperature	63	(1)
Spin-spin relaxation	64	(4)
Relationship between T1 and T2	68	(2)
Sensitivity	70	(10)
The Boltzmann factor	70	(1)
The receiver coil	71	(1)
The sample	72	(1)
Thermal noise	73	(2)
Smoothing	75	(1)
Time averaging	76	(1)
Artefacts	76	(1)
Hyperpolarized systems	77	(2)
Conclusions	79	(1)
Resolving power	80	(8)
The natural linewidth	81	(1)
Instrumental limitations	82	(3)
The patient	85	(1)
Resolution enhancement	86	(2)
The chemical shift	88	(17)
Chemical shifts	88	(3)
Theory of shielding	91	(1)
The empirical approach	92	(3)
Referencing	95	(2)
Nuclei other than hydrogen	97	(2)
Solvent effects	99	(1)
Lanthanide shift reagents	100	(1)
Fast and slow chemical exchange	101	(1)
Hydrogen bonds	102	(1)
Isotope shifts	103	(1)
Implications for MRI	104	(1)
Spin--spin coupling	105	(14)
Interactions between spins	105	(1)
Spin multiplets	106	(5)
`Splitting' and `coupling'	111	(2)
Strong coupling	113	(2)
Decoupling	115	(4)
Spin echoes	119	(14)
Time reversal?	119	(2)
Gradient-recalled echoes	121	(1)
The Carr--Purcell echo	122	(3)
Diffusion	125	(2)
The Hahn echo	127	(1)
The stimulated echo	127	(3)
Echo modulation	130	(2)
Compensation effects	132	(1)
NMR in solids	133	(12)
The dipole-dipole interaction	134	(4)
Magic angle spinning	138	(1)
Multiple-pulse methods	139	(1)
Dipolar decoupling	140	(1)
Cross-polarization	140	(2)
Partially-aligned liquids	142	(3)
Two-dimensional spectroscopy	145	(35)
Correlation by double resonance	145	(2)
NMR in two frequency dimensions	147	(2)
Exchange spectroscopy (EXSY)	149	(3)
Cross-relaxation (NOESY)	152	(1)
Correlation spectroscopy (COSY)	153	(7)
Hartmann-Hahn experiments	160	(1)
Heteronuclear correlation	161	(3)
Polarization transfer (INEPT)	164	(3)
Multiple-quantum spectroscopy	167	(2)
Molecular topology (INADEQUATE)	169	(4)
Separation of NMR parameters	173	(3)
Diffusion-ordered spectroscopy (DOSY)	176	(4)
Magnetic resonance imaging	180	(35)
Basic principles	180	(3)
Magnetic field gradients	183	(2)
Slice selection	185	(3)
The readout stage	188	(1)
Phase encoding	189	(4)
The concept of k-space	193	(3)
Echo planar imaging	196	(2)
Imaging in three dimensions	198	(1)
Contrast	199	(4)
Motion artefacts	203	(2)
Magnetic resonance angiography	205	(4)
Diffusion	209	(3)
Magnetic resonance microscopy	212	(3)
How safe is magnetic resonance imaging?	215	(8)
The magnetic field	216	(2)
Free radical reactions	218	(1)
Time-varying magnetic fields	219	(1)
Radiofrequency heating	220	(2)
Conclusions	222	(1)
Magnetic resonance spectroscopy	223	(17)
NMR spectra in vivo	223	(1)
Phosphorus spectra	224	(1)
Surface coils	224	(3)
Other nuclear species	227	(3)
Localization techniques	230	(1)
ISIS (Image-selected in vivo spectroscopy)	231	(1)
PRESS (Point-resolved spectroscopy)	232	(3)
STEAM (Stimulated echo acquisition mode)	235	(2)
Chemical shift imaging	237	(3)
High-resolution NMR of body fluids	240	(8)
Chemistry and medicine meet	240	(1)
Blood plasma	241	(2)
Toxicity	243	(1)
Disease	244	(2)
Drug metabolism	246	(2)
The search for new drugs	248	(6)
Screening procedures	248	(3)
Design strategies	251	(2)
Molecular recognition	253	(1)
Functional imaging of the brain	254	(11)
Blood flow	255	(1)
Blood oxygen	256	(2)
Pinpointing the response	258	(2)
Time-scale	260	(1)
Degenerative brain disease	261	(1)
How does the brain work?	262	(3)
Permissions	265	(2)
References	267	(6)
Index	273