Nuclear magnetic resonance imaging: a tool for microscopists?

Nuclear magnetic resonance (NMR) imaging is revolutionizing the field of noninvasive diagnosis because of its excellent resolution and inherent high soft-tissue contrast. It is also feasible to use NMR imaging in the microscopic milieu. However, application at this level is handicapped by several technical and theoretical limitations. Foremost among these is the difficulty of obtaining sufficient signal from voxels of microscopic dimensions in sufficiently short time scales to make the technique practical. Other limitations include the effects of Brownian motion and the inherent frequency dispersion over each voxel. These constraints limit three-dimensional resolution to 1-10 micron. Even within these limits, the nondestructive nature of the technique and its unique sensitivity to the state of water within cells and tissues promise to make it a valuable tool for future microscopists.