Technical noteWater and lipid diffusion MRI using chemical shift displacement-based separation of lipid tissue (SPLIT)

- Water and lipid diffusion weighted images (DWIs) play important roles in the assessment of fatty acid and metabolism.
- We devised a novel method utilizing chemical shift displacement based separation of lipid tissue (SPLIT).
- The proposed method enables simple and simultaneous acquisition of water and lipid DWIs without special pulse sequence.

PurposeTo obtain water and lipid diffusion-weighted images (DWIs) simultaneously, we devised a novel method utilizing chemical shift displacement-based separation of lipid tissue (SPLIT) imaging.Materials and methodsSingle-shot diffusion echo-planar imaging without fat suppression was used and the imaging parameters were optimized to separate water and lipid DWIs by chemical shift displacement of the lipid signals along the phase-encoding direction. Using the optimized conditions, transverse DWIs at the maximum diameter of the right calf were scanned with multiple b-values in five healthy subjects. Then, apparent diffusion coefficients (ADCs) were calculated in the tibialis anterior muscle (TA), tibialis bone marrow (TB), and subcutaneous fat (SF), as well as restricted and perfusion-related diffusion coefficients (D and D*, respectively) and the fraction of the perfusion-related diffusion component (F) for TA.ResultsWater and lipid DWIs were separated adequately. The mean ADCs of the TA, TB, and SF were 1.56 ± 0.03 mm2/s, 0.01 ± 0.01 mm2/s, and 0.06 ± 0.02 mm2/s, respectively. The mean D*, D, and F of the TA were 13.7 ± 4.3 mm2/s, 1.48 ± 0.05 mm2/s, and 4.3 ± 1.6%, respectively.ConclusionSPLIT imaging makes it possible to simply and simultaneously obtain water and lipid DWIs without special pulse sequence and increases the amount of diffusion information of water and lipid tissue.