Flip angle calculation for consistent contrast in spoiled gradient echo imaging

✍ Scribed by Reed F. Busse

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 313 KB
• Volume: 53
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.20420

✦ Synopsis

Abstract

In spoiled gradient echo sequences, the T~1~‐weighting of image contrast is strongly affected by a nonlinear interaction of two sequence parameters, repetition time (TR) and flip angle (α). If α is not properly adjusted to compensate for variation in TR due to changing resolution, bandwidth, or number of slices, any optimization of contrast‐to‐noise may be compromised. Currently, there is no direct way to compare or reproduce the contrast properties of one sequence to another with a different TR. Here, it is demonstrated that for short TRs α may be calculated and automatically adjusted such that relative contrast—the shape of the signal‐versus‐T~1~ curve—remains consistent and signal scales proportionally to √TR in all tissues. TR is then free to vary to accommodate a range of sequence parameters without impacting relative contrast and the T~1~‐weighting of one sequence can be compared to, or reproduced in, another study with a different TR. Magn Reson Med 53:977–980, 2005. © 2005 Wiley‐Liss, Inc.