Simultaneous B₁ and T₁ mapping using spiral multislice variable flip angle acquisitions for whole-brain coverage in...

Area of Science:

• Magnetic Resonance Imaging
• Quantitative MRI
• Biomedical Engineering

Background:

• Variable Flip Angle (VFA) T1 quantification is sensitive to B1 inhomogeneities and incomplete spoiling.
• Accurate B1 and T1 mapping is crucial for various clinical applications.

Purpose of the Study:

• To develop and validate a rapid spiral VFA acquisition scheme for simultaneous whole-brain B1 and T1 mapping.
• To improve the accuracy and efficiency of T1 quantification by addressing B1 inhomogeneities and T2 dependency.

Main Methods:

• A steady-state prepared spiral 2D multislice spoiled gradient-echo sequence was used with two flip angles.
• Acquisition involved 10 and 20 spiral interleaves at 1.5T and 3T, with parallel imaging acceleration at 3T.
• B1 quantification utilized the free induction decay from a preparation pulse sampled by a single-shot spiral readout.

Main Results:

• In vitro and in vivo validations showed good agreement between spiral VFA B1/T1 maps and reference maps.
• Human brain acquisitions produced artifact-free B1 and T1 maps with high reproducibility at 1.5T and 3T.
• The technique demonstrated robustness across different field strengths.

Conclusions:

• Simultaneous B1 and T1 quantification using the proposed spiral VFA method is feasible and reliable.
• Whole-brain coverage was achieved in less than one minute at clinically relevant resolutions.
• This rapid mapping technique holds promise for efficient and accurate quantitative MRI.