Comparison of muscle fat fraction measurements in the lower spine musculature with non-contrast-enhanced CT and different MR imaging sequences.

Purpose: To assess whether two-point Dixon (TPD) MRI, true fast imaging with steady-state free precession (TRUFI) MRI and non-contrast-enhanced CT (NECT) can accurately measure muscle fat fraction (FF) in the autochthonous back muscles (AM) and the psoas muscle (PM) compared to multi-point Dixon (MPD) MRI.

Method: 29 oncological patients who received MRI including MPD, TPD and NECT imaging in a period of three months were analyzed retrospectively. A sub-cohort of 16 patients additionally underwent TRUFI MRI and were included in a sub-analysis. Region of interest (ROI) measurements for each muscle compartment of the AM and PM were conducted by two examiners. Additionally, the Goutallier classification was used to quantify the amount of fatty infiltration of each muscle. Intermodality correlations were assessed with the Pearson correlation coefficient (r), and interreader and intrareader agreements with the intraclass correlation coefficient (ICC).

Results: Good intermodality correlations were found for NECT (r = 0.969), TPD (r = 0.942) and TRUFI (r = 0.904, all P < 0.001) when assessing FF in the AM and slightly lower in the PM. Interreader agreement showed good correlations and low median deviations (1.1 - 4.1 %, depending on the modality). The Goutallier classification of the AM showed good separation between grades with substantial interreader agreement (κ = 0.627, P < 0.001).

Conclusions: ROI measurements of the AM in NECT, TPD and TRUFI highly correlate with muscle FF measurements in MPD MRI and may be used to assess sarcopenia in oncological patients.