Abstract

Magnetic resonance techniques were developed in the mid-1940s to analyze the structures of chemical compounds. In the last 10 years, however, the same principles have been evolved, along with advances in magnet, computer, and display technology into one of the most exciting imaging methods available in the medical field today. Magnetic resonance imaging utilizes the property that certain nuclei when placed in a magnetic field can be stimulated into a resonance condition by external radio-frequency radiation. In recovering from this disturbance, the nuclei in turn emit rf signals (whose frequencies depend on the magnetic field strength in which the nuclei are located). To image the human body, the patient is placed in a large solenoidal magnet (field strength typically 0.5-1.5 T), and the magnetic field Is coded in various ways by the application of gradient fields, causing the protons within the volume to resonate with a range of frequencies. Relating these frequencies to positions within this volume is performed by a Fourier analysis of the signal. Reconstructed images are displayed to the user as slices of the 3-D volume being imaged.

© 1987 Optical Society of America