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.
Medical imaging
A magnetic resonance imaging instrument (MRI scanner), or "nuclear magnetic resonance (NMR) imaging" scanner as it was originally known, uses powerful magnets to polarize and excite hydrogen nuclei (i.e., single protons) of water molecules in human tissue, producing a detectable signal which is spatially encoded, resulting in images of the body. The MRI machine emits a radio frequency (RF) pulse at the resonant frequency of the hydrogen atoms on water molecules. Radio frequency antennas ("RF coils") send the pulse to the area of the body to be examined. The RF pulse is absorbed by protons, causing their direction with respect to the primary magnetic field to change. When the RF pulse is turned off, the protons "relax" back to alignment with the primary magnet and emit radio-waves in the process. This radio-frequency emission from the hydrogen-atoms on water is what is detected and reconstructed into an image. The resonant frequency of a spinning magnetic dipole (of which protons are one example) is called the Larmor frequency and is determined by the strength of the main magnetic field and the chemical environment of the nuclei of interest. MRI uses three electromagnetic fields: a very strong (typically 1.5 to 3 teslas) static magnetic field to polarize the hydrogen nuclei, called the primary field; gradient fields that can be modified to vary in space and time (on the order of 1 kHz) for spatial encoding, often simply called gradients; and a spatially homogeneous radio-frequency (RF) field for manipulation of the hydrogen nuclei to produce measurable signals, collected through an RF antenna.