Optimization of Signal Intensity andT1-Dependent Contrast with Nonstandard Flip Angles in Spin-Echo and Inversion-Recovery MR Imaging
✍ Scribed by Jean-Marie Bonny; Loic Foucat; Wilfried Laurent; Jean-Pierre Renou
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 172 KB
- Volume
- 130
- Category
- Article
- ISSN
- 1090-7807
No coin nor oath required. For personal study only.
✦ Synopsis
Theoretical expressions of flip angle values maximizing signal [a x -TE/2-b y -TE/2-echo-(TR-TE) -], [1] intensity and T 1 -dependent contrast are derived for spin-echo and inversion-recovery sequences. Experimental data and theoretical where a and b are respectively the nutating and refocusing predictions are closely correlated for experiments carried out on pulse angles about the axis denoted by the subscript. Here, phantoms, despite the nonideal shape of the RF refocusing pulse we consider no coherence of transverse magnetization beused for slice selection. The use of nonstandard angles is justified tween cycles of excitation (because of T 2 relaxation when when rapid MR acquisitions are needed and/or large T 1 species TR ӷ T 2 or by appropriate spoiling) and we neglect the must be imaged with refocused sequences.