A novel method for simultaneous 3D B(1) and T(1) mapping: the method of slopes (MoS)

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantitative MRI
• Biophysics

Background:

• Accurate B(1) and T(1) parameter mapping is crucial for quantitative MRI.
• Existing methods like Variable Flip Angle (VFA) T(1)-mapping have limitations in consistency and robustness.

Purpose of the Study:

• Introduce a novel three-dimensional simultaneous B(1) and T(1) mapping method: the Method of Slopes (MoS).
• Address limitations of current T(1)-mapping techniques, ensuring consistency and eliminating noise bias.

Main Methods:

• Exploit the linearity of spoiled gradient recalled echo (SPGR) signal versus flip angle.
• Employ two-point extrapolation for B(1) mapping with a correction scheme.
• Utilize slopes of SPGR signal vs flip angle curves for T(1) mapping, incorporating a non-linear fitting algorithm with high SNR data.

Main Results:

• MoS ensures consistency between B(1) and T(1) maps.
• The sampling scheme is independent of T(1) values.
• Noise bias and singularity are eliminated by using the full SPGR signal equation, yielding accurate and robust results via simulations and in vivo experiments.

Conclusions:

• The Method of Slopes (MoS) provides accurate and robust simultaneous 3D B(1) and T(1) mapping.
• MoS overcomes limitations of existing VFA T(1)-mapping methods.
• Demonstrated feasibility in vivo for brain imaging, with potential for other motion-free regions.