SNR and total acquisition time analysis of multi-echo FLASH pulse sequence for current density imaging

Area of Science:

• Biophysics
• Medical Imaging
• Magnetic Resonance Imaging

Background:

• Magnetic Resonance Current Density Imaging (MRCDI) provides crucial internal current density (J¯) data.
• Clinical use of MRCDI is limited by the sensitivity to noisy current-induced magnetic flux density (B∼_z) distributions.

Purpose of the Study:

• To develop a novel analysis for optimizing RF spoiled gradient echo (FLASH) and multi-echo FLASH (ME-FLASH) pulse sequences in MRCDI.
• To investigate the impact of sequence parameters, gradient utilization, and magnetohydrodynamic (MHD) flow on B∼_z SNR and acquisition time (TAT).

Main Methods:

• A new analytical framework was developed to assess the combined effects of FLASH sequence parameters on B∼_z SNR and TAT.
• The analysis was extended to ME-FLASH sequences, leveraging combined echoes for improved SNR.
• Sequence parameters were optimized for maximal SNR within a given TAT or minimal TAT for a desired SNR.

Main Results:

• The analysis provides optimized parameters for achieving high SNR B∼_z distributions in MRCDI.
• ME-FLASH sequences demonstrate potential for higher SNR compared to single-echo acquisitions.
• The study investigated the influence of gradient strength and MHD flow on B∼_z distributions.

Conclusions:

• The developed analysis enables optimization of MRCDI sequences for enhanced SNR and efficiency.
• Experimental validation using a brain white matter phantom confirms the analytical findings.
• This work contributes to improving the clinical applicability of MRCDI.