Quantitative susceptibility mapping using single-shot echo-planar imaging.

Area of Science:

• Neuroimaging
• Medical Physics
• Radiology

Background:

• Quantitative susceptibility mapping (QSM) is crucial for assessing brain iron content, a biomarker for neurodegenerative diseases.
• Traditional QSM methods require lengthy acquisition times, limiting their clinical applicability.
• Subcortical gray matter harbors significant iron concentrations, making it a key region for QSM studies.

Purpose of the Study:

• To develop and validate a rapid quantitative susceptibility mapping (QSM) technique using echo-planar imaging (EPI).
• To assess the feasibility of measuring iron in subcortical gray matter using this accelerated EPI-QSM method.
• To compare the performance of rapid EPI-QSM with conventional gradient-recalled echo (GRE) QSM.

Main Methods:

• Whole-brain QSM was performed using single-shot gradient echo-planar imaging (EPI) on a 1.5 T MRI system in under 7 seconds.
• The rapid EPI-QSM method was compared against a standard 6-minute GRE-QSM acquisition in healthy subjects.
• Region-of-interest analyses were conducted in six subcortical gray matter nuclei and two white matter territories.

Main Results:

• EPI-QSM achieved similar mean susceptibility values to standard GRE-QSM in iron-rich subcortical gray matter.
• The EPI-QSM method demonstrated a >50-fold reduction in scan time compared to conventional GRE-QSM.
• Despite minor edge blurring, EPI-QSM measurements of subcortical nuclei showed high correlation (R²=0.96) with estimated iron content.

Conclusions:

• Rapid EPI-QSM is a viable technique for quantitative brain iron assessment in subcortical gray matter.
• The significantly reduced acquisition time makes EPI-QSM suitable for time-constrained imaging scenarios.
• This accelerated method can be integrated into existing MRI studies utilizing gradient echo EPI sequences.