Table 2.

Comparison of imaging based assessments of hepatic steatosis in NAFLD

	MRS	MRI	Ultrasound	CAP
Measurement	Directly measures differences in water and fat peaks on a resonance frequency domain	Indirect CSI assessment of signal interface between water and fat peaks during OP and IP echoes	Assessment through proxies (i.e. attenuation and echogenicity)	VCTE guided assessment using a ultrasonic controlled attenuation parameter algorithm
Dynamic Range	Single area (8cm3 voxel) manually placed in liver parenchyma using 3-plane localizing imaging	Quantification over a full dynamic range (0 – 100%) throughout parenchyma	Limited when overall content of hepatic steatosis is < 20%	Sub-optimal quantification over a broad dynamic range in ROI
Application	Not available on routine scanners and requires expertise	Readily applied to routine scanners with some expertise required	Readily available in routine practice for use	Point of care testing
Accuracy	High diagnostic accuracy not significantly impacted by demographics, histologic activity, or co- xisting hepatic conditions	High diagnostic accuracy not significantly impacted by demographics, histologic activity, or co- existing hepatic conditions	Modest diagnostic accuracy; significantly limited by demographics (obesity), and co-existing hepatic conditions	Higher diagnostic accuracy than standard ultrasound based assessments but lower than MRI; limited by obesity, inflammation, stage of fibrosis
Reliability	High precision with minimal variability	Higher precision and lower variability than MRS and histologic assessments	Modest reliability and agreement with training	Improved precision and reduced variability than ultrasound through assessment of acquisition validity but lower than MRI
Responsiveness	Responsive to changes in steatosis in single area	Highly responsive to changes in steatosis throughout parenchyma	Limited responsiveness and unable to co-localize ROI for response	Improved responsiveness over standard ultrasound
Co-localization of fibrosis	Requires alternative imaging modality for co- localizing elasticity	Co-localization with MRE	Unable to co-localize	Co-localization with VCTE

MRS: magnetic resonance spectroscopy; MRI-PDFF: magnetic resonance imaging proton density fat fraction; NAFLD: nonalcoholic fatty liver disease; CSI: chemical shift imaging; OP: opposed phase; IP: in-phase; MRE: magnetic resonance elastography; ROI: regions of interest; CAP: controlled attenuation parameter; VCTE: vibration controlled transient elastography