Dixon water-fat separation in PROPELLER MRI acquired with two interleaved echoes.

Purpose: To propose a novel combination of robust Dixon fat suppression and motion insensitive PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI.

Methods: Two different echoes were acquired interleaved in each shot enabling water-fat separation on individual blades. Fat, which was blurred in standard PROPELLER because the water-fat shift (WFS) rotated with the blades, was shifted back in each blade. Additionally, field maps obtained from the water-fat separation were used to unwarp off-resonance-induced shifts in each blade. PROPELLER was then applied to the water, corrected fat, or recombined water-fat blades. This approach was compared quantitatively in volunteers with regard to motion estimation and signal-to-noise ratio (SNR) to a standard PROPELLER acquisition with minimal WFS and fat suppression.

Results: Shifting the fat back in each blade reduced errors in the translation correction. SNR in the proposed Dixon PROPELLER was 21% higher compared with standard PROPELLER with identical scan time. High image quality was achieved even when the volunteers were moving during data acquisition. Furthermore, sharp water-fat borders and image details were seen in areas where standard PROPELLER suffered from blurring when acquired with a low readout bandwidth.

Conclusion: The proposed method enables motion-insensitive PROPELLER MRI with robust fat suppression and reduced blurring. Additionally, fat images are available if desired.