• Lisa Ruby, Ahmet Kunut, Dominik N Nakhostin, Florian A Huber, Tim Finkenstaedt, Thomas Frauenfelder, Sergio J Sanabria, and Marga B Rominger.
• Zurich Ultrasound Research and Translation (ZURT), Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Rämistrasse 100, 8091, Zürich, Switzerland. lisa.ruby@usz.ch.
• Eur Radiol. 2020 Oct 1; 30 (10): 5272-5280.

ObjectivesTo compare speed of sound (SoS) ultrasound (US) of the calves with Dixon magnetic resonance imaging (MRI) for fat content quantification.Materials And MethodsThe study was approved by the local ethics committee. Fifty calf muscles of 35 women (age range 22-81 years) prospectively underwent an US and subsequent MRI (Dixon sequence) examination as well as body weight and impedance fat measurements. SoS (in m/s) was calculated positioning a reflector on the opposite side of a conventional US machine probe with the calf in between. Fiducial nitroglycerin markers were placed on the calf at the reflector and US probe end positions for later registration of the US sonification volumetric section. An automatic segmentation algorithm separated MRI adipose tissue, muscle and bone regions. MRI fat fraction of the entire leg slice (total) and intramuscular and adipose tissue fat fraction were calculated and correlation analysis and correlation coefficient comparison were performed.ResultsMedian SoS demonstrated a very strong (r = - 0.83 (95% CI - 0.90; - 0.72); p < 0.001) correlation with MRI total fat fraction, a strong (r = - 0.61 (95% CI - 0.76; - 0.40); p < 0.001) correlation with MRI adipose tissue fat fraction and a moderate (r = - 0.54 (95% CI - 0.71; - 0.31); p < 0.001) correlation with MRI intramuscular fat fraction. Impedance body fat percentage correlated strongly with SoS (r = - 0.72 (95% CI - 0.85; - 0.51); p < 0.001) and MRI total fat fraction (r = 0.61 (95% CI 0.34; 0.78); p < 0.001). For electrical impedance, significantly lower correlations (p = 0.033) were found for MRI total fat fraction compared with SoS.ConclusionsCorrelations of SoS with Dixon MRI fat fraction measurements were very strong to moderate.Key Points• Correlations of speed of sound with Dixon MRI fat fraction measurements of the same body location were very strong to moderate. • Speed of sound measurements showed a high repeatability. • Speed of sound provides a sufficient discrimination range for fat fraction estimates.

22 keywords...

hide…