FTP, identify this chemistry phenomenon that forms the basis for MRI.
Two-dimensional applications of this technique include J-resolved, which accounts for J-coupling; and COSY, which relies on the application of two 90-degree pulses to a spin system.  Its occurrence relies on the strength of the magnetic field, the frequency of absorption, and the gyromagnetic ratio of the proton in question.  First observed in 1946 by Felix Bloch and Edward Purcell, this phenomenon is based on the precession of a proton as it is exposed to two magnetic fields, thereby indicating the presence of particular compounds in its namesake spectroscopy.  FTP, identify this chemistry phenomenon that forms the basis for MRI.
Two-dimensional applications of this technique include J-resolved, which accounts for J-coupling; and COSY, which relies on the application of two 90-degree pulses to a spin system.  
NMR or nuclear magnetic resonance