Measurement of the self-diffusion coefficient of water as a function of position in wheat grain using nuclear magnetic resonance imaging.

A pulsed field gradient spin echo sequence has been incorporated in a nuclear magnetic resonance (NMR) imaging experiment to provide an image contrast dependent on local molecular self-diffusion. The consequent image attenuation is shown to exhibit a dependence on applied magnetic field gradient consistent with the Stejskal-Tanner relationship. The method used represents a novel extension of microscopic imaging and demonstrates the possibility of measuring localized motion.Water self-diffusion rates normal to the transverse 1.3-mm section of a wheat grain have been measured in structural features at 150-mum resolution. The results are consistent with averaged measurements in the bulk grain obtained by other methods while local differences in water mobility correlate with differences in physiological function.