Short- and Long-Term Reproducibility of Intrahepatic Lipid Quantification by 1H-MR Spectroscopy and CT in Obesity

Abstract

Objective To assess short- and long-term reproducibility of intrahepatic lipid (IHL) quantification by 1H-MRS and CT. Methods Sixteen obese subjects underwent 1H-MRS using a single-voxel PRESS sequence at 3T and non-contrast single-slice CT of the liver. Measurements were repeated after 6 weeks and 6 months. Clinical parameters (weight, activity, serum lipids) were collected. Short-term (baseline-6-weeks) and long-term (baseline-6-month) reproducibility of IHL was assessed by coefficient of variance (CV), standard deviation (SD), and intraclass correlation coefficient (ICC). Results Short-and long-term reproducibility of 1H-MRS were as follows: CV 5.9–18.8%, SD 0.7–1.9 and ICC 0.998–0.995 (95% CI 0.942–0.999). Short- and long-term reproducibility of CT were as follows: CV 4.4–14.2%, SD 2.4–8.7 and ICC 0.766–0.982 (95% CI 0.271–0.994). There was no significant change in clinical parameters (p>0.3). Conclusions 1H-MRS and CT are reproducible methods for short- and long-term quantification of IHL content. Our results can guide sample size calculations for interventional and longitudinal studies.

Ectopic lipid deposition in muscle and liver, quantified by proton magnetic resonance spectroscopy

“…Only a few studies have looked at longer term variability [90,106]. Although the reported CVs at 4 to 6 weeks [90,106] were within the range of the CVs obtained within 1 day, the CV after 6 months was a bit higher (18.8%) [106]. Factors that may contribute to this higher variability include natural biological variations in metabolite concentrations and changes related to BMI, physical activity, diet, or medication use, as well as nonbiological factors related to equipment instability, voxel placement, and patient repositioning [106].…”

“…Most studies have focused on the intraday repeatability by repositioning participants between scans, reporting CVs between 5% and 19% in the case of IMCL [70,73,[101][102][103] and between 3.6% and 10% in the case of IHL [3,44,104,105]. Only a few studies have looked at longer term variability [90,106]. Although the reported CVs at 4 to 6 weeks [90,106] were within the range of the CVs obtained within 1 day, the CV after 6 months was a bit higher (18.8%) [106].…”

Quantitative Imaging of Body Composition

“…42 Importantly, quantification of IMCL by 1H-MRS strongly correlates with insulin resistance and has been an important surrogate in clinical research in states of insulin resistance, such as obesity, type 2 diabetes, and human immunodeficiency virus lipodystrophy. 45,46 In the liver, 1H-MRS has demonstrated the ability to quantify intrahepatic lipids noninvasively, with excellent reproducibility, 47,48 and it is the noninvasive standard against which other imaging methods (e.g., Dixon imaging) are compared. Fat accumulation in the liver is exclusively intracellular, which lends itself to a simple but robust measurement by breath-hold single-voxel 1H-MRS. 47 One downside of such measures is the limited sampling coverage of the organ when compared with Dixon imaging because the single-voxel technique will yield data only from a localized tissue volume.…”