Rapid detection of the presence of diffusion exchange.
Diffusion exchange spectroscopy (DEXSY) provides a detailed picture of how fluids in different microenvironments communicate with one another but requires a large amount of data. For DEXSY MRI, a simple measure of apparent exchanging fractions may suffice to characterize and differentiate materials and tissues. Reparameterizing signal intensity from a PGSE-storage-PGSE experiment as a function of the sum, bs=b1+b2, and difference bd=b2-b1 of the diffusion encodings separates diffusion weighting from exchange weighting. Exchange leads to upward curvature along a slice of constant bs. Exchanging fractions can be measured rapidly by a finite difference approximation of the curvature using four data points. The method is generalized for non-steady-state and multi-site exchange. We apply the method to image exchanging fractions and calculate exchange rates of water diffusing across the bulk water interface of a glass capillary array.
['Cai|Teddy X|TX|', 'Benjamini|Dan|D|', 'Komlosh|Michal E|ME|', 'Basser|Peter J|PJ|', 'Williamson|Nathan H|NH|']
Apparent exchange rate Exchange-weighted imaging Inverse Laplace Permeability Porous media Pulsed gradient spin echo NMR Time-domain analysis Transcytolemmal water exchange