Practical Approaches to Bone Marrow Fat Fraction Quantification Across Magnetic Resonance Imaging Platforms

Abstract

Background: Quantification of fat by proton density fat fraction (PDFF) measurements may be valuable for the quantification and follow-up of pathology in multicenter clinical trials and routine practice. However, many centers do not have access to specialist methods (such as chemical shift imaging) for PDFF measurement. This is a barrier to more widespread trial implementation.

Purpose/hypothesis: To determine the agreement between fat fraction (FF) measurements derived from 1) basic vendor-supplied sequences, 2) basic sequences with offline correction, and 3) specialist vendor-supplied methods.

Study type: Prospective.

Population: Two substudies with ten and five healthy volunteers.

Field strength/sequence: Site A: mDixon Quant (Philips 3T Ingenia); Site B: IDEAL and FLEX (GE 1.5T Optima MR450W); Site C: DIXON, with additional 5-echo gradient echo acquisition for offline correction (Siemens 3T Skyra); Site D: DIXON, with additional VIBE acquisitions for offline correction (Siemens 1.5T Avanto). The specialist method at site A was used as a standard to compare to the basic methods at sites B, C, and D.

Assessment: Regions of interest were placed on areas of subchondral bone on FF maps from the various methods in each volunteer.

Statistical tests: Relationships between FF measurements from the various sites and Dixon methods were assessed using Bland-Altman analysis and linear regression.

Results: Basic methods consisting of IDEAL, LAVA FLEX, and DIXON produced FF values that were linearly related to reference FF values (P < 0.0001), but produced mean biases of up to 10%. Offline correction produced a significant reduction in bias in both substudies (P < 0.001).

Data conclusion: FF measurements derived using basic vendor-supplied methods are strongly linearly related with those derived using specialist methods but produce a bias of up to 10%. A simple offline correction that is accessible even when the scanner has only basic sequence options can significantly reduce bias.

Level of evidence: 2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;52:298-306.

Keywords: chemical shift imaging; imaging biomarker; inflammation; spondyloarthritis.