Diffusion-weighted imaging of bacteria colonies in the STRAFI plane

Imaging colonies of bacteria in water suspension using NMR requires that th e water inside the bacteria can be differentiated from the surrounding wate r. This is commonly carried out by using diffusion-weighted pulsed field gr adient techniques, However, it is also possible to use the diffusion sensit ivity inherent in stray field imaging (STRAFI). In STRAFI, the subject to b e imaged is normally moved along the axis of a superconducting magnet so th at 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 sur face induction coil, a diffusion-weighted one-dimensional projection profil e can be obtained across the sensitive slice. Profiles from a water phantom and from. a bacteria suspension show convincing discrimination between int racellular and extracellular water. (C) 2000 Academic Press.