Triple‐Pulse <scp> ²³ Na MRI </scp> Sequence ( <scp>TriNa</scp> ) for Simultaneous Acquisition of Spin‐Density‐Weighted and Fluid‐Attenuated Images

ABSTRACT Purpose This study proposes a Triple‐pulse Na (TriNa) MRI sequence for simultaneous acquisition of spin density‐weighted (SD) and fluid‐suppressed (FS) Na images. Methods TriNa employs three rectangular pulses and two ultrashort‐TE readouts to simultaneously obtain spin density‐weighted (TriNa‐SD) and fluid‐suppressed (TriNa‐FS) Na images in one acquisition. Additionally, a correction model incorporating relaxation dynamics was developed to reduce residual fluid artifacts. Simulations, phantom and in vivo experiments at 7T were performed to assess TriNa's SNR efficiency, quantitative accuracy, and robustness against off‐resonance artifacts, in comparison to standalone SD and FS Na sequences. Results TriNa‐SD exhibited high linear correlation with sodium concentration in the phantom. Phantom and in vivo experiments demonstrated that TriNa achieved high SNR efficiency in acquiring SD and FS images. The proposed off‐resonance correction model effectively reduced fluid artifacts in TriNa‐FS using TriNa‐SD and an additional B map. Conclusion The proposed sequence design enables simultaneous dual‐contrast Na MRI with high SNR efficiency and the proposed post‐processing correction mitigates off‐resonance artifacts in the TriNa‐FS image.