1 H-MRS for the assessment of renal triglyceride content in humans at 3T: A primer and reproducibility study

Abstract

Background: Renal steatosis (fatty kidney) is a potential biomarker for obesity-related renal disease; however, noninvasive assessment of renal fat content remains a technical challenge.

Purpose: To evaluate reproducibility and explore clinical application of renal metabolic imaging for the quantification of renal triglyceride content (TG) using proton magnetic resonance spectroscopy (¹ H-MRS).

Study type: Reproducibility and clinical cohort study.

Population: Twenty-three healthy volunteers (mean age 30.1 ± 13.4 years) and 15 patients with type 2 diabetes mellitus (T2DM) (mean age 59.3 ± 7.0 years).

Field strength/sequence: 3T, single-voxel point resolved spectroscopy (PRESS).

Assessment: Intra- and interexamination reproducibility of renal TG was assessed in healthy volunteers, and compared to T2DM patients. Intraexamination differences were obtained by repeating the ¹ H-MRS measurement directly after the first ¹ H-MRS without repositioning of the subject or changing surface coil and measurement volumes. Interexamination variability was studied by repeating the scan protocol after removal and replacement of the subject in the magnet, and subsequent repositioning of body coil and measurement volumes.

Statistical tests: Reproducibility was determined using Pearson's correlation and Bland-Altman analyses. Differences in TG% between healthy volunteers and T2DM patients were assessed using the Mann-Whitney U-test.

Results: After logarithmic (log) transformation, both intraexamination (r = 0.91, n = 19) and interexamination (r = 0.73, n = 9) measurements of renal TG content were highly correlated with the first renal TG measurements. Intraexamination and interexamination limits of agreement of renal log TG% were respectively [-1.36%, + 0.84%] and [-0.77%, + 0.62%]. Backtransformed limits of agreement were [-0.89%,+0.57%] and [-0.55%, + 0.43%] multiplied by mean TG for intra- and interexamination measurements. Overall median renal TG content was 0.12% [0.08, 0.22; 25th percentile, 75th percentile] in healthy volunteers and 0.20% [0.13, 0.22] in T2DM patients (P = 0.08).

Data conclusion: Renal metabolic imaging using 3T ¹ H-MRS is a reproducible technique for the assessment of renal triglyceride content.

Level of evidence: 3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:507-513.

Keywords: 3T; fatty kidney; metabolic imaging; proton magnetic resonance spectroscopy; renal triglyceride content; reproducibility.