Nuclear magnetic resonance signal dynamics of liquids in the presence of distant dipolar fields, revisited.
The description of the nuclear magnetic resonance magnetization dynamics in the presence of long-range dipolar interactions, which is based upon approximate solutions of Bloch-Torrey equations including the effect of a distant dipolar field, has been revisited. New experiments show that approximate analytic solutions have a broader regime of validity as well as dependencies on pulse-sequence parameters that seem to have been overlooked. In order to explain these experimental results, we developed a new method consisting of calculating the magnetization via an iterative formalism where both diffusion and distant dipolar field contributions are treated as integral operators incorporated into the Bloch-Torrey equations. The solution can be organized as a perturbative series, whereby access to higher order terms allows one to set better boundaries on validity regimes for analytic first-order approximations. Finally, the method legitimizes the use of simple analytic first-order approximations under less demanding experimental conditions, it predicts new pulse-sequence parameter dependencies for the range of validity, and clarifies weak points in previous calculations.
Vanderbilt University Medical Center, Institute of Imaging Science, AA-1105 MCN, Nashville, Tennessee 37232-2310, USA. wbarros@cfa.harvard.edu
Wilson
W
Barros
Daniel F
DF
Gochberg
John C
JC
Gore
D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics; D008956:Models, Chemical