Brain imaging and function

Until the advent of computerized tomography (CT) in the 1970s, it was impossible to non-invasively image the brain (Eisenberg, 1992). However, once introduced, CT imaging rapidly advanced the technology of brain imaging and today remains one of the cornerstone technologies, especially for the assessment of acute neurologic symptom onset (i.e. a stroke) or injury.

Simultaneous with the development of CT imaging were tremendous improvements in computer technology, with faster processors and increased memory capacity. This provided the backdrop for essentially all other improvements that have occurred in brain imaging, once the breakthrough technology of CT imaging had been introduced. The physics and mathematics behind CT technology also became the inspiration for applying the principles of nuclear magnetic resonance (NMR) to human brain imaging. NMR principles had long been known and were, in fact, the basis for the Nobel Prize in Physics in 1952, but essentially had only been applied to physics and engineering (Eisenberg, 1992). In the 1970s researchers realized that radio frequency (RF) waves could reflect differences in biological tissues, such as the brain, since atoms within the molecules that form grey matter of the brain would ‘resonate’ differently in response to a pulsed magnetic field than those within white matter or cerebrospinal fluid. Detecting these differences in emitted RF waves – following the application of brief, pulsed, but very strong magnetic fields – could then be reconstructed to create an image of the brain (or any other biological tissue).