Magnetic field inhomogeneity effects on spin echo NMR diffusion measurements

Journal Article · Wed Nov 01 04:00:00 EST 1995 · IEEE Transactions on Magnetics

DOI:https://doi.org/10.1109/20.489577· OSTI ID:186923

Yee, O P; Nyenhuis, J A; Stroshine, R L ^[1]; Wai, W K ^[2]

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1. Purdue Univ., West Lafayette, IN (United States)
2. Magnetic Instrumentation, Indianapolis, IN (United States)

In this work, the authors evaluate the impact of field inhomogeneity on nuclear magnetic resonance (NMR) measurement of diffusion via the spin echo technique. Computer simulations, using a model that accounts for diffusion within samples, indicate that echo ratio measurements can differ from Carr-Purcell theory predictions by as little as a few tenths of a percent and by as much as 30% for a 0.073 m diameter sample under a 0.035 T/m gradient. Experiments with water as the test sample corroborate that measured echo ratios deviate from Carr-Purcell theory with larger sample sizes and larger applied magnetic field gradients, regardless of whether diffusion or T{sub 2} decay is the dominant mechanism acting on echo ratio. This difference can be attributed to imperfect flipping angles of magnetization across the samples, associated with the finite duration of the 180{degree} rf refocusing pulses.

• OSTI ID: 186923
• Report Number(s): CONF-950404--
• Journal Information: IEEE Transactions on Magnetics, Journal Name: IEEE Transactions on Magnetics Journal Issue: 6Pt2 Vol. 31; ISSN IEMGAQ; ISSN 0018-9464
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COMPUTERIZED SIMULATION
DIFFUSION
MAGNETIC FIELDS
NUCLEAR MAGNETIC RESONANCE
SPIN ECHO
USES
VARIATIONS