Non-invasive evaluation of liver steatosis with imaging modalities: New techniques and applications

Table 1 Characteristics of imaging techniques for hepatic steatosis evaluation

Techniques	Clinical characteristics	Limitations
CAP	Low cost; High availability; Time-saving	High measurement failure rate
	Allows simultaneous evaluation of steatosis and fibrosis	Measurement without B-mode ultrasound image
	Moderate to high diagnostic accuracy for detecting and grading steatosis	The cutoff value for diagnosing steatosis is poorly standardized
	Moderate to high repeatability and reproducibility
	Well validated
ATI, ATT and UGAP	Outperform or have comparable diagnostic accuracy compared with CAP	The measurement may be influenced by liver fibrosis
	High repeatability and reproducibility	Fairly small number of studies
	Strong correlation with liver histology or MRI-PDFF
	Low measurement failure rate
	Measured on B-mode ultrasound images
Att. PLUS	Measurement is obtained at the same time as the sound speed measurement	Fairly small number of studies
	Comparable diagnostic accuracy with CAP	No study comparing this technique with liver histology or MRI-PDFF
TAI and TSI	High diagnostic accuracy for detecting and grading steatosis	Fairly small number of studies
	Strong correlation with MRI-PDFF
	High repeatability and reproducibility
BSC	Uses a reference phantom to reduce sources of variability due to ultrasound systems or operators	Fairly small number of studies
	High diagnostic accuracy for detecting and grading steatosis
	Strong correlation with liver histology or MRI-PDFF
	High repeatability and reproducibility
UDFF	Is a combination of both attenuation coefficient and backscatter coefficient	Fairly small number of studies
	UDFF approximates MRI-PDFF
ASQ and NLV	Moderate to high diagnostic accuracy for detecting and grading steatosis	Weak correlation with liver histology
	Strong correlation with CAP	The correlation with MR-based techniques is controversial
		The influence of fibrosis on measurement is controversial
		Fairly small number of studies
SS	Moderate to high diagnostic accuracy for detecting and grading steatosis	Fairly small number of studies
	Strong correlation with CAP
MRS and MRI-PDFF	High diagnostic accuracy for detecting and grading steatosis	High cost; low availability
	Considered as the reference standard	Time-consuming

CAP: Controlled attenuation parameter; ATI: Attenuation imaging; ATT: Attenuation measurement function; UGAP: Ultrasound-guided attenuation parameter; Att. PLUS: Attenuation plane-wave ultrasound; TAI: Tissue attenuation imaging; TSI: Tissue scatter distribution imaging; BSC: Backscatter coefficient; UDFF: Ultrasound-derived fat fraction; ASQ: Acoustic structure quantification; NLV: Normalized local variance; SS: Speed of sound; MRS: Magnetic resonance spectroscopy; MRI-PDFF: Magnetic resonance imaging-proton density fat fraction.