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Magnetic Moment of a Spin, Its Equation of Motion, and Precession
Publication Name:
Current Protocols in Magnetic Resonance Imaging
Unit Number:
Unit B1.1
DOI:
10.1002/0471142719.mib0101s14
Online Posting Date:
December, 2007
Abstract
This unit discusses the basic spin properties of the proton. The motion of a spin in an magnetic field that give rise to magnetic moment, is also discussed. The key to grasping much of MRI lies in understanding the concept of precession. Famous Bloch equation that basically leads to the description of the precession of a spin in the presence of an external magnetic field is also explained.
Figures
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Figure B1.1.1 A loop with current I lying in a plane. The perpendicular unit vector 
points up from the side where the area A is on our left if we were to walk along the current path in the direction of current flow. The magnetic moment for the loop is 
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Figure B1.1.2 Clockwise precession of a proton's spin about a magnetic field. As shown, the differential d is negative. -
Figure B1.1.3 The transverse part of the magnetic moment from a top view. The magnetic moment precesses through an angle in the x-y plane in a time t. -
Figure B1.1.4 Circular current loop depicted in two different orientations relative to a uniform magnetic field. The forces on representative differential current segments are shown (one 
is explicitly shown in each case). The first panel (A) shows the current plane perpendicular to the field where there is no net twist (torque); the second panel (B) shows the current plane at an arbitrary angle to the field where there is a nonzero torque. -
Figure B1.1.5 A circular current loop lying in the x-y plane experiencing a constant magnetic field. The field lies in the z-y plane.
Videos
Literature Cited
| Key References | |
| Beall, P.T., Amtey, S.R., and Kasturi, S.R. 1984. NMR Data Handbook for Biomedical Applications. Pergamon Press, New York. | |
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This text has a more comprehensive list of active NMR elements (i.e., those with nonzero spin). | |
| Goldstein, H. 1980. Classical Mechanics. Addison-Wesley, Reading, Mass. | |
|
This text reviews fundamental physics of classical mechanics. | |
| Haacke, E.M., Brown, R.W., Thompson, M.R., and Venkatesan, R. 1999. Magnetic Resonance Imaging: Physical Principles and Sequence Design. John Wiley & Sons, New York. | |
|
This text covers the technical aspects presented here, but in more detail, and also discusses more advanced materials. | |
| Halliday, D., Resnick, R., and Krane, K.S. 1992. Physics. John Wiley & Sons, New York. | |
|
This is a good freshman physics textbook. | |
| Jackson, J.D. 1975. Classical Electrodynamics. John Wiley & Sons, New York. | |
|
This is an advanced textbook of classical electromagnetism. | |
