MEDRADSC 3DE3 Lecture Notes - Lecture 12: Spin–Lattice Relaxation, Heating Element, Transverse Plane

• School: McMaster University
• Department: Medical Radiation Sciences
• Course: MEDRADSC 3DE3
• Professor: Alana Trainor

Document Summary

T1 recovery times of enhancing structures are shorten by gd so they approach the t1 recovery time of fat. Tissues begin recovery from full inversion as opposed to from transverse plane as in conventional spin echo. 0. 69 x t1 relaxation time for any given tissue. Enables shorter trs & as a result a short scan time. Gradient echo pulse sequence uses an rf excitation pulse that is variable. Flips nmv through any angle, not just 90 degrees. This means that the nmv is flipped through a lower angle than in a spin echo sequence, when a larger 90 degree flip angle is used. As nmv is move through smaller angle in excitation phase, less time to achieve full relaxation once rf pulse is removed. Means we have full t1 recovery achieved in shorter tr - since tr is a scan time parameter, this leads to shorter scan times. After rf excitation pulse is withdrawn, we have an fid.