A semiconductor device whose RF resistance varies in proportion to an applied DC bias current. PIN diodes are essential elements for rapid switching of RF coils between transmit and receive modes and for coil decoupling.

Single turn solenoid is a transmit and receive RF imaging coil that, in general, has a cylindrical shape. The solenoidal configuration of this coil is a further developed planar surface coil. While surface coils have a strong coupling and high signal to noise ratio to nearby signals they have a marked loss of signal beyond one radius from the center of the coil. With a solenoidal coil design the imaging object lies within one radius from the coil center, which improved imaging (of extremities, such as wrist or knee).

See also Radio Frequency Coil and Imaging of the Extremities.

Methods of selectively enhancing or suppressing the signal from a particular molecular substance by using its spin properties, typically through spin spin coupling, e.g. J-modulation.

For the wide uses of NMR spectroscopy (from mineralogy to medicine) there is a variety of different spectroscopic imaging techniques available.
A short listing of the most frequent variations:

Edward Purcell and Felix Bloch discovered the basic of spectroscopy in 1946 (see MRI History). Nuclear magnetic resonance spectroscopy (NMR Spectroscopy or MRS) is an analytical tool, based on nuclei that have a spin (nuclei with an odd number of neutrons and/or protons) like 1H, 13C, 17O, 19F, 31P etc.
Through nuclear magnetic principles as precession, chemical shift, spin spin coupling etc., the analysis of the content, purity, and molecular structure of a sample is possible. The spectrum produced by this process contains a number of peaks; the highs and the positions of these peaks allow the exact analysis. Unknown compounds can be matched against spectral libraries. Even very complex organic compounds as enzymes and proteins can be determined. For the wide uses of NMR spectroscopy (from mineralogy to medicine) there is a variety of different techniques available.
See Spectroscopic Imaging Techniques.