Home Education Sequences Equipment ...
Body Physics Section So how does that MRI machine work? There are plenty of books out there that will enlighten you on the theory behind MR image. Each scanner is a little bit different and each new sequence is a variation of one of few themes. Most of the MRI sequences are based on basic acquisitions such as spin echo or gradient echo techniques. There are also fancy new sequences, which exploit movement of protons in the blood stream and, at times, even artifacts to the advantage of highlighting a particular property of a given tissue. Below, we attempt to explain physics of MRI in the simplest possible terms. If you have ever taken college level physics and chemistry courses, you should be able to follow along with ease.
One fundamental principle required to understand MR imaging is the concept of electromagentic energy. Radio receiver in your car accepts radiofrequency (RF) waves, which represent one form of electromagnetic energy. Similarly, protons in living tissues are able to accept electromagentic energy in the form of RF pulse. This RF pulse "excites" the protons to a higher energy level. As the protons "relax", energy is emitted back to the antennas in MR machines.
Unfortunatelly, the amount of energy that is emitted back from the protons is very small. So a few tricks are performed to maximize signal to noise ratio. | |
|
