Proton magnetic resonance spectroscopy and ultrasound for hepatic fat quantification.

Aim: The increasing prevalence of fatty liver disease requires routine assessment methods. Proton magnetic resonance spectroscopy (¹H MRS) is increasingly used for steatosis measurement, but due to cost, is unlikely to become a widely-used screening tool. Ultrasound is cheaper and more widely available, although subject to observer variability. Our aim was to determine the sensitivity and specificity of ultrasound against ¹H MRS, using MRS as a gold standard, for the detection and quantification of hepatic fat content. Methods: Fifty adults participated (43 men, seven women) in this study. Hepatic steatosis was assessed by ultrasound and ¹H MRS. Images were graded by two independent radiologists to classify severity and distribution of liver fat. Results: Ultrasound detected liver fat infiltration in 82% of cases measurable by ¹H MRS, while liver fat was detectable in 44% of cases graded absent by ultrasound. Ultrasound grading was subjective, with the radiologists in agreement in 53% of cases (κ = 0.39, P = 0.002). Considerable overlap in intrahepatocellular lipid content was observed between different grades: absent (0.0–1.58%), mild (2.2–16.2%), moderate (4.9–26.7%) and severe (8.1–76.8%) steatosis. Ultrasound could not detect liver fat levels below 2% as measured by ¹H MRS Conclusion: Ultrasound is less sensitive than ¹H MRS in detecting very low levels of liver fat content, but is sensitive to fatty infiltration greater than 2%. There is a tendency of higher ultrasound grades to correlate with higher degrees of fatty infiltration, although some overlap exists. Our findings are still consistent with ultrasound being useful as a low cost screening tool. [ABSTRACT FROM AUTHOR]