Spatially varying steady state longitudinal magnetization in distant dipolar field-based sequences.

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Physics

Background:

• Distant dipolar field (DDF) sequences offer potential for advanced spectroscopy and imaging.
• Spatial variations in longitudinal magnetization (Mz(s)) can lead to artifacts in DDF sequences if not managed by relaxation, diffusion, or spoiling.
• These artifacts arise from spatial harmonics in the steady-state MzSS(s) profile, even in uniform samples.

Purpose of the Study:

• To develop an analytical expression for the steady-state longitudinal magnetization (MzSS(s)) profile in DDF sequences.
• To investigate the impact of diffusion on the MzSS(s) profile when diffusion effects are minimal within the repetition time (TR).
• To experimentally validate the derived analytical expression.

Main Methods:

• Development of an analytical expression for the MzSS(s) profile under specific conditions (negligible diffusion smearing within TR).
• Experimental imaging of the MzSS(s) profile after achieving a steady state.
• Comparison of experimental MzSS(s) profiles with the derived analytical expression.

Main Results:

• An analytical expression for the MzSS(s) profile in DDF sequences was successfully derived.
• The derived expression accurately predicts the MzSS(s) profile when diffusion effects are negligible during the TR period.
• Experimental validation confirmed the accuracy of the analytical model.

Conclusions:

• Understanding and accurately modeling the steady-state MzSS(s) profile is crucial for DDF sequences.
• The developed analytical expression provides a valuable tool for predicting and mitigating artifacts in DDF-based spectroscopy and imaging.
• This work enhances the reliability and precision of novel DDF applications.