Creating an Image

The preceding description yields a single number: T2*, the decay rate of the net NMR signal. This signal is conventionally called the free induction decay (FID) of the NMR signal because it is elicited when nothing else is done to the protons—that is, if the system were left free to decay at its own rate. However, this signal represents the net effect of inducing an NMR signal from the entire volume of tissue being subjected to the main magnet and the orientation-flipping RF pulse. To create an image in which different NMR signals are measured for different points in the three-dimensional volume, nonuniform magnetic fields are applied intentionally. The basic idea is to use linear magnetic field gradients, applied at various times and in various orientations, to distinguish the NMR signals arising

Outside the magnet Inside the magnet RF pulse applied
All About Alzheimers

All About Alzheimers

The comprehensive new ebook All About Alzheimers puts everything into perspective. Youll gain insight and awareness into the disease. Learn how to maintain the patients emotional health. Discover tactics you can use to deal with constant life changes. Find out how counselors can help, and when they should intervene. Learn safety precautions that can protect you, your family and your loved one. All About Alzheimers will truly empower you.

Get My Free Ebook

Post a comment