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Fast-spin-echo versus rapid gradient-echo for 3D magnetization-prepared acquisitions: Application to inhomogeneous
Manuel Taso1, Fanny Munsch1, Olivier M Girard2
1Division of MRI Research, Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
Magnetic Resonance in Medicine
|October 28, 2022
Summary
Fast spin echo (FSE) imaging improves thermal SNR for inhomogeneous magnetization transfer (ihMT) imaging. However, ihMT-FLAIR sequences best mitigate physiological noise, offering superior overall SNR for ihMT quantification.
Area of Science:
- Magnetic Resonance Imaging
- Biophysics
- Medical Imaging Technology
Background:
- Magnetization-prepared sequences are crucial for advanced MRI contrasts.
- Inhomogeneous magnetization transfer (ihMT) provides unique tissue contrast.
- Rapid gradient-echo (RAGE) and fast spin echo (FSE) are common pulse sequences with different noise characteristics.
Purpose of the Study:
- To compare the performance of FSE-based ihMT imaging against RAGE-based ihMT imaging.
- To evaluate the impact of cerebrospinal fluid (CSF) suppression on ihMT imaging quality.
- To assess image quality, noise levels, and quantification accuracy of different ihMT sequences.
Main Methods:
- A modified 3D FSE sequence with ihMT preparation (ihMT-FSE) was developed, including an optional inversion-recovery based CSF suppression (ihMT-FLAIR).
- Numerical simulations were performed to assess Signal-to-Noise Ratio (SNR) benefits.
- ihMT-RAGE, ihMT-FSE, and ihMT-FLAIR sequences were compared in healthy volunteers, analyzing image quality, thermal and physiological noise, and ihMT saturation (ihMTsat) quantification.
- Preliminary imaging of the cervical spinal cord was conducted.
Main Results:
- ihMT-FSE demonstrated significant improvements in thermal SNR compared to simulations.
- Physiological noise was notably higher in ihMT-FSE than ihMT-RAGE.
- ihMT-FLAIR effectively mitigated physiological noise, achieving the highest total SNR (+74% white matter, +49% gray matter vs. ihMT-RAGE).
- Accurate ihMTsat quantification was achieved across all sequences with strong correlations (r² > 0.75).
Conclusions:
- FSE sequences generally offer superior SNR for magnetization-prepared contrasts like ihMT compared to gradient-echo methods.
- Physiological noise is a critical factor, but inversion-recovery based CSF suppression effectively reduces motion artifacts.
- ihMT-FLAIR presents a promising sequence for robust ihMT imaging, including potential applications in spinal cord imaging.
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