Measurements of restricted diffusion using an oscillating gradient spin-echo sequence.

An oscillating gradient spin-echo (OGSE) pulse sequence was used to measure the apparent diffusion coefficient (D(app)) of water in the short diffusion time regime in the presence of restrictions. The diffusion coefficients of water in a simple water sample and a water and oil mixture were measured to be the same for different periods of the gradient oscillation, as expected when there are no restriction effects. The D(app) of water in the spaces between closely packed beads was also measured as a function of the gradient oscillation periods in the range 11 to 80 ms. The D(app) of water in restricted systems varies with the period of the gradient oscillation and the dispersion depends on the scale of the restriction. For a sample of packed beads of diameter 9.1 +/- 0.7 microm, the pore surface-to-volume ratio was estimated experimentally by this method to be 1.3 +/- 0.1 microm(-1), corresponding to a mean pore diameter of 6.4 +/- 0.7 microm. A Monte Carlo computer simulation of the NMR OGSE signal from the spins diffusing in a system of compartments was also implemented and the D(app) demonstrated similar behavior with gradient oscillation periods.

[1]  R. Ramasamy,et al.  The design of macrocyclic ligands for monitoring magnesium in tissue by 31P NMR , 1995, NMR in biomedicine.

[2]  K G Helmer,et al.  The application of porous‐media theory to the investigation of time‐dependent diffusion in in vivo systems , 1995, NMR in biomedicine.

[3]  J. Gore,et al.  Theoretical Model for Water Diffusion in Tissues , 1995, Magnetic resonance in medicine.

[4]  P. Callaghan,et al.  Generalized Analysis of Motion Using Magnetic Field Gradients , 1996 .

[5]  P. Callaghan,et al.  Pulsed Gradient Spin-Echo NMR "Diffusive Diffraction" Experiments on Water Surrounding Close-Packed Polymer Spheres , 1994 .

[6]  E. Stejskal.  Use of Spin Echoes in a Pulsed Magnetic‐Field Gradient to Study Anisotropic, Restricted Diffusion and Flow , 1965 .

[7]  J. Kucharczyk,et al.  Early detection of regional cerebral ischemia in cats: Comparison of diffusion‐ and T2‐weighted MRI and spectroscopy , 1990, Magnetic resonance in medicine.

[8]  Schwartz,et al.  Short-time behavior of the diffusion coefficient as a geometrical probe of porous media. , 1993, Physical review. B, Condensed matter.

[9]  Sen,et al.  Effects of microgeometry and surface relaxation on NMR pulsed-field-gradient experiments: Simple pore geometries. , 1992, Physical review. B, Condensed matter.

[10]  Janez Stepišnik,et al.  Analysis of NMR self-diffusion measurements by a density matrix calculation , 1981 .

[11]  J. E. Tanner,et al.  Spin diffusion measurements : spin echoes in the presence of a time-dependent field gradient , 1965 .

[12]  W. T. Dixon,et al.  Measuring diffusion in inhomogeneous systems in imaging mode using antisymmetric sensitizing gradients , 1992 .

[13]  K. Svoboda,et al.  Time-dependent diffusion of water in a biological model system. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[14]  M E Moseley,et al.  Comparison of diffusion‐ and T2‐weighted MRI for the early detection of cerebral ischemia and reperfusion in rats , 1991, Magnetic resonance in medicine.

[15]  Joseph W. Haus,et al.  Diffusion in regular and disordered lattices , 1987 .

[16]  Schwartz,et al.  Diffusion propagator as a probe of the structure of porous media. , 1992, Physical review letters.

[17]  John Crank,et al.  The Mathematics Of Diffusion , 1956 .

[18]  D. P. Haughey,et al.  Structural properties of packed beds — A review , 1969 .