B1 mapping of short T2 * spins using a 3D radial gradient echo sequence.

Area of Science:

• Magnetic Resonance Imaging
• Radiofrequency Field Mapping
• Pulse Sequence Design

Background:

• Accurate radiofrequency (B1) field mapping is crucial in MRI.
• Short T2* signals pose a challenge for conventional B1 mapping techniques.
• Existing methods struggle to maintain signal integrity under these conditions.

Purpose of the Study:

• To develop a novel method for acquiring 3D B1 field maps.
• To address the limitations of existing techniques with short T2* signals.
• To improve the accuracy and reliability of B1 mapping.

Main Methods:

• The study adapted the actual flip angle imaging (AFI) technique.
• A radial 3D gradient-echo sequence, COncurrent Dephasing and Excitation (CODE), was employed.
• CODE was integrated with Gradient-modulated Offset-Independent Adiabaticity (GOIA) pulses and a modified correlation method.

Main Results:

• The modified correlation method effectively handled gradient modulations, preserving image quality.
• GOIA-CODE AFI produced flip angle maps comparable to conventional AFI with GRE for long T2* signals.
• The technique demonstrated robust performance for short T2* signals.

Conclusions:

• The proposed GOIA-CODE AFI technique enables 3D B1 field map acquisition.
• This method is effective even when imaging spins with short T2*.
• It offers a valuable tool for advanced MRI applications requiring accurate B1 mapping.