Complex B₁⁺ mapping with Carr-Purcell spin echoes and its application to electrical properties tomography

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Medical Physics

Background:

• Accurate B1+ field mapping is crucial for quantitative MRI.
• Existing methods may not capture the full complexity of the B1+ field.
• Electrical properties tomography requires precise B1+ information.

Purpose of the Study:

• To introduce a novel complex-valued B1+ mapping technique.
• To utilize Carr-Purcell (CP) spin echoes for enhanced B1+ estimation.
• To enable electrical properties tomography with improved accuracy.

Main Methods:

• A dictionary-based approach accounting for slice profile and T2 relaxation was employed.
• The Carr-Purcell echo train was used to estimate B1+ magnitude and phase.
• Validation was performed using phantom studies and in vivo brain imaging at 3 Tesla.

Main Results:

• The CP method demonstrated excellent agreement with Actual Flip Angle Imaging (AFI) for B1+ magnitude.
• Reconstructed permittivity and conductivity values in phantoms matched expected values.
• In vivo brain imaging yielded electrical properties consistent with prior research.

Conclusions:

• The CP sequence enables simultaneous estimation of B1+ magnitude and phase.
• This allows for a complete reconstruction of electrical properties.
• The method holds promise for advanced MRI applications, including electrical properties tomography.