Alternating Look-Locker for quantitative T₁ , T_1ρ and B₁ 3D MRI mapping

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantitative MRI
• Biomedical Engineering

Background:

• Accurate measurement of relaxation times (T1, T2, T2*) is crucial for various MRI applications.
• Existing methods for quantitative mapping can be time-consuming or less robust.
• Development of novel MRI techniques is needed for improved accuracy and efficiency.

Purpose of the Study:

• To introduce and validate a novel MRI method, alternating Look-Locker (aLL), for 3D quantitative mapping.
• To enable simultaneous measurement of T1, T2, and T2* relaxation times.
• To assess the performance and robustness of the aLL method compared to existing techniques.

Main Methods:

• Utilized an alternating Look-Locker (aLL) scheme combined with 3D Multi-Band Sweep Imaging with Fourier Transformation (MB-SWIFT) readout.
• Derived analytical solutions for spin evolution and corrections for segmented acquisition.
• Demonstrated simultaneous T1 and T2 mapping on phantoms and in vivo (rat head); T2* mapping was also assessed.

Main Results:

• The aLL method accurately maps T1 and T2 simultaneously with magnetization preparation (MP) modules.
• Without MP modules, aLL enables simultaneous T1 and T2* mapping.
• aLL demonstrated robust quantitative mapping comparable to steady-state methods but without requiring additional scans for T2*.

Conclusions:

• The proposed alternating Look-Locker (aLL) method provides a flexible and efficient tool for 3D quantitative mapping of T1, T2, and T2*.
• aLL offers improved robustness and efficiency compared to conventional steady-state techniques.
• The aLL method is adaptable and can be integrated with various readout schemes beyond MB-SWIFT.