Fonar Corp. v. General Electric Co.
"Fonar" was a dispute between medical device manufacturer Fonar Corporation and General Electric over Fonar's patent on MRI technology. Fonar's founder, Raymond Damadian, was issued U.S. Patent 3,789,832 (priority date 1972-03-17) for an "apparatus and method for detecting cancer in tissue" using the magnetic resonance of atoms. Damadian's patent was the first patent on an MRI machine issued in the United States. Also at issue was a later patent, U.S. Patent 4,871,966 issued in 1989, covering a method for obtaining MRI images of multiple planes at different orientations in a single scan. GE is a major manufacturer of MRI scanners, and Fonar sued GE for infringing these patents by producing its scanners as well as inducing others to infringe.
MRI sequence
Steady-state free precession imaging (SSFP MRI) is an MRI technique which uses steady states of magnetizations. In general, SSFP MRI sequences are based on a (low flip angle) gradient-echo MRI sequence with a short repetition time which in its generic form has been described as the FLASH MRI technique. While spoiled gradient-echo sequences refer to a steady state of the longitudinal magnetization only, SSFP gradient-echo sequences include transverse coherences (magnetizations) from overlapping multi-order spin echoes and stimulated echoes. This is usually accomplished by refocusing the phase-encoding gradient in each repetition interval in order to keep the phase integral (or gradient moment) constant. Fully balanced SSFP MRI sequences achieve a phase of zero by refocusing all imaging gradients.