Diffusion-weighted imaging of bacteria colonies in the STRAFI plane

Imaging colonies of bacteria in water suspension using NMR requires that the water inside the bacteria can be differentiated from the surrounding water. This is commonly carried out by using diffusion-weighted pulsed field gradient techniques. However, it is also possible to use the diffusion sensitivity inherent in stray field imaging (STRAFI). In STRAFI, the subject to be imaged is normally moved along the axis of a superconducting magnet so that it passes through the sensitive slice. However, by moving the sample in the transverse direction and by using a long copper strip in place of a surface induction coil, a diffusion-weighted one-dimensional projection profile can be obtained across the sensitive slice. Profiles from a water phantom and from a bacteria suspension show convincing discrimination between intracellular and extracellular water.