SPARCQ: A new approach for fat fraction mapping using asymmetries in the phase-cycled balanced SSFP signal profile

Giulia M C Rossi; Adèle L C Mackowiak; Berk Can Açikgöz; Katarzyna Pierzchała; Tobias Kober; Tom Hilbert; Jessica A M Bastiaansen

doi:10.1002/mrm.29813

SPARCQ: A new approach for fat fraction mapping using asymmetries in the phase-cycled balanced SSFP signal profile

Magn Reson Med. 2023 Dec;90(6):2348-2361. doi: 10.1002/mrm.29813. Epub 2023 Jul 26.

Authors

Giulia M C Rossi^{1

2

3}, Adèle L C Mackowiak^{1

2

3}, Berk Can Açikgöz^{1

2}, Katarzyna Pierzchała^{4

5}, Tobias Kober^{3

6

7}, Tom Hilbert^{3

6

7}, Jessica A M Bastiaansen^{1

2}

Affiliations

¹ Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
² Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland.
³ Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
⁴ CIBM Center for Biomedical Imaging, Lausanne, Switzerland.
⁵ Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
⁶ Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland.
⁷ LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.

PMID: 37496187
DOI: 10.1002/mrm.29813

Abstract

Purpose: To develop SPARCQ (Signal Profile Asymmetries for Rapid Compartment Quantification), a novel approach to quantify fat fraction (FF) using asymmetries in the phase-cycled balanced SSFP (bSSFP) profile.

Methods: SPARCQ uses phase-cycling to obtain bSSFP frequency profiles, which display asymmetries in the presence of fat and water at certain TRs. For each voxel, the measured signal profile is decomposed into a weighted sum of simulated profiles via multi-compartment dictionary matching. Each dictionary entry represents a single-compartment bSSFP profile with a specific off-resonance frequency and relaxation time ratio. Using the results of dictionary matching, the fractions of the different off-resonance components are extracted for each voxel, generating quantitative maps of water and FF and banding-artifact-free images for the entire image volume. SPARCQ was validated using simulations, experiments in a water-fat phantom and in knees of healthy volunteers. Experimental results were compared with reference proton density FFs obtained with ¹ H-MRS (phantoms) and with multiecho gradient-echo MRI (phantoms and volunteers). SPARCQ repeatability was evaluated in six scan-rescan experiments.

Results: Simulations showed that FF quantification is accurate and robust for SNRs greater than 20. Phantom experiments demonstrated good agreement between SPARCQ and gold standard FFs. In volunteers, banding-artifact-free quantitative maps and water-fat-separated images obtained with SPARCQ and ME-GRE demonstrated the expected contrast between fatty and non-fatty tissues. The coefficient of repeatability of SPARCQ FF was 0.0512.

Conclusion: SPARCQ demonstrates potential for fat quantification using asymmetries in bSSFP profiles and may be a promising alternative to conventional FF quantification techniques.

Keywords: 3 T; PDFF; bSSFP; balanced steady-state free precession; phase-cycling; profile asymmetry; proton density fat fraction; quantitative MRI; water-fat quantification.

Grants and funding

PCEFP2_194296/SNSF_/Swiss National Science Foundation/Switzerland