Improved gradient echo magnitude- and phase-based mapping of T 2 $$ {\mathrm{T}}_2 $$ using multiple RF spoiling...

Area of Science:

• Magnetic Resonance Imaging
• Quantitative Imaging
• Biomedical Engineering

Background:

• Transverse relaxation time (T1) mapping is crucial for clinical and research applications.
• Conventional spin-echo T1 mapping methods are time-consuming and involve high radiofrequency power deposition.
• Existing gradient echo (GRE) phase-based T1 mapping methods have limitations in accuracy.

Purpose of the Study:

• To develop and validate a modified magnitude- and phase-based T1 mapping approach.
• To improve T1 estimation accuracy by simultaneously fitting T1 and signal amplitude across multiple RF spoiling phase increments.
• To overcome the limitations of previous GRE phase-based methods by not assuming a fixed T1 value.

Main Methods:

• The proposed method was assessed using simulations, phantom, and in vivo experiments with 3D-EPI GRE imaging.
• Magnitude- and phase-based T1, T2, and proton density (PD) estimations were compared against phase-based T1 and spoiled GRE multi-parameter mapping.
• Skipped-CAIPI technique was employed for rapid GRE imaging.

Main Results:

• The proposed magnitude-phase-based method demonstrated higher agreement with ground truth and reference T1 values compared to the phase-based method.
• Phase-based T1 overestimation was observed to increase with actual T1 and T2 values, whereas the proposed method maintained accuracy.
• Improved precision in T1 estimation was achieved, with in vivo results corroborating simulation and phantom findings.

Conclusions:

• Accurate magnitude-phase-based T1 mapping is feasible with scan times under 5 minutes.
• The method provides 1 mm nominal isotropic whole-head coverage at both 3T and 7T field strengths.
• This technique offers a rapid and precise alternative for quantitative T1 imaging.