In 1972, Raymond Damadian filed the pioneer patent for magnetic resonance imaging (MRI) technology, titled "Apparatus and Method for Detecting Cancer in Tissue." Indomitable, as the apparatus came to be called, consisted of a chamber surrounded by the first human-sized superconducting magnets (later machines would employ permanent magnets or iron-frame electromagnets).

MRI technology is based on nuclear magnetic resonance (NMR) technology. In both, when hydrogen nuclei (usually water molecules) are exposed to a strong magnetic field, the nuclei align within the field. The material being scanned is then pulsed with a short radio wave that pushes some of the nuclei out of alignment. The time it takes the nuclei to return to the aligned state is called a relaxation time. Relaxation signals vary in different tissues depending on the composition of nuclei within them. MRI scanners use pulse sequences to produce two scans: T1 and T2. Damadian discovered that by moving the magnet back and forth over a surface, it is possible to focus the relaxation signals and locate objects spatially against background information. This technique he called field-focusing nuclear magnetic resonance (FONAR). By using powerful magnets, it was possible to penetrate the human body noninvasively to detect relaxation times from embedded tissues. T1 and T2 are used as a diagnostic pair: T1 provides anatomical details, and T2 is used for the detection of pathologies. Typically, lesions show up brightly in T2. By referencing T2 values to T1, the lesions can be located and evaluated as to size and invasiveness. Because relaxations are based on inherent cellular chemistry--the response of atoms to a magnetic field and radio pulse--no contrasting agents are required to detect differences in composition.  As nuclei relax, they in turn emit their own radio signals.

An MR scanner uses the radio signals emitted from cells to map the body. Relaxation times and density differences account for the contrast and anatomical detail that are unique to MRI and that allow the mapping of soft tissues. This discovery, coupled with the ability to capture the signals emitted, was part of the 1972 patent. Emitted signals can be converted to pixels captured on a screen; the stronger the emission, the brighter the pixel signal and the greater the nuclei component of the tissue. Because every normal tissue has a certain background density associated with it, it becomes relatively easy to detect lesions or defects based on intensity variations from the expected pattern.

Free term papers are not written to satisfy your specific instructions. You can use our professional writing services to buy a custom written research paper, term paper, or essay on Health at affordable price. CustomTermPapers is the best solution for those who seek help in writing term papers, essays, and research papers related to Health and other relevant topics.