Diffusive Effect Induced by a Strong Magnetic Field Gradient in (1)H-NMR Micro-imaging of Plant Tissues.

A micro-imaging probe, the best planar resolution of which was 0.0125 mm × 0.0125 mm, was devised using an NMR spectrometer with a superconducting magnet (JEOL GSX-270 WB). A strong Z-axis magnetic field (slice) gradient was required to lessen slice thickness. Application of a strong slice gradient around the 180° refocus pulse of the spin-echo 2D-FT method induced extra-reduction of signal intensity beyond that expected. The problem which was considered to be due to a diffusive effect, was overcome by saving the slice gradient on application of the 180° refocus pulse. Using the probe, measuring conditions (combinations of parameters) for a young tomato fruit of several mm in diameter were examined. Reduction of spatial resolution (voxel) was limited by a decline of image quality and the minimum voxel suitable for observation of the sample was 0.05 mm × 0.05 mm planar resolution and 0.25 mm slice thickness corresponding to two or three plant cells vertically aligned. NMR micro-imaging can be used for studying cell conditions in plant materials of small sizes.