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Transverse relaxation and flip angle mapping: Evaluation of simultaneous and independent methods using multiple spin
Kelly C McPhee1,2, Alan H Wilman1,2
1Department of Physics, University of Alberta, Edmonton Alberta, Canada.
Magnetic Resonance in Medicine
|July 2, 2016
Summary
Bloch simulations provide accurate transverse relaxation (T2) and flip angle mapping from spin echoes. Extended Phase Graph (EPG) methods yield less accurate flip angles, impacting T2 measurements.
Area of Science:
- Magnetic Resonance Imaging
- Quantitative MRI
Background:
- Accurate transverse relaxation (T2) and flip angle quantification are crucial for MRI.
- Signal pathway modeling of multiple spin echoes offers a promising approach for improved relaxometry.
Purpose of the Study:
- To evaluate T2 and flip angle maps derived from signal pathway modeling of multiple spin echoes.
- To compare simultaneous or independent T2 and flip angle fitting methods.
Main Methods:
- Examined indirect and stimulated echo compensated T2 relaxometry using multiple spin echoes.
- Evaluated T2 and flip angle accuracy in simulations, phantoms, and human brain.
- Modeled signal pathways using Bloch simulations or Extended Phase Graph (EPG) with approximations for slice profiles.
Main Results:
- Slice-selective decay curves varied significantly between models.
- EPG methods yielded inaccurate flip angles, though T2 values were relatively accurate.
- Bloch methods improved both T2 and flip angle results, while simultaneous fitting could lead to multiple T2 solutions.
Conclusions:
- EPG fitting offers reasonable T2 accuracy but is limited by flip angle inaccuracy.
- Bloch simultaneous fitting provides excellent T2 and flip angle results, especially when incorporating a flip angle map.
- Accurate flip angle determination is essential for reliable T2 relaxometry in MRI.
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