For MRI, the strong magnetic field needed for these techniques is generated inside the all too familiar tube that causes many patients claustrophobia, which can require sedation before a procedure. Once inside the magnet, each nucleus broadcasts its identity by emitting radio waves at its unique precession frequency, which depends on its interaction with surrounding atoms as well as the magnetic field strength.
The interaction with surrounding atoms is what makes NMR such a useful tool for chemists and biologists, allowing them to identify different chemical environments and molecular structures.
For MRI, it is the interaction of the nuclei with the magnetic field that is key, as magnetic field strength varies with location, enabling a researcher to code different parts of the body with different frequencies. Through the measurement of the atomic precession frequencies, an MRI radiologist can reconstruct a two-dimensional or three-dimensional image that accurately depicts the interior of a patient's body.
In performing such measurements, scientists often need to invert the nuclei so they are aligned against the magnetic field. Inverting the nuclei of people inside MRI scanners can reveal such things as cancer tumors, whose slightly different interaction with the nuclear spins can be used to detect their presence amid surrounding healthy tissue.
This is where adiabatic processes come into play. The inversions are often done "adiabatically", by
|Contact: Josh Chamot|
National Science Foundation