Quantitative and noninvasive assessment of chronic liver diseases using two-dimensional shear wave elastography

Table 1 Comparison of currently available noninvasive methods in patients with chronic liver disease

Content	Methods
	TE	pSWE	2D-SWE	MRE
Technical principle	TE was the first commercially available elastography method developed for measuring liver stiffness using a dedicated device that includes an amplitude modulation (A) mode image for organ localization	pSWE can be implemented on a common ultrasound diagnostic system. It uses a regular ultrasonic probe to emit a single impulse of acoustic radiation force and generates a shear wave to detect the shear wave propagation velocity	2D-SWE is the combination of a radiation force applied to the tissues by focused ultrasonic beams and a very high frame rate US imaging sequence, which is able to capture the propagation of resulting the shear waves in real time	MRE enables the measurement of liver stiffness with an MRI-compatible generator; mechanical shear waves are delivered to the tissue and displayed as elastograms using phase-contrast image sequences
Reference point	▪Young’s modulus (kPa)	▪Shear wave speed (m/s) ▪Young’s modulus (kPa)	▪Shear wave speed (m/s) ▪Young’s modulus (kPa)	▪Shear wave speed (m/s) ▪Young’s modulus (kPa)
Selected example	▪FibroScan (Echosens, France)	▪VTQ using ARFI imaging (Siemens Healthcare, Germany) ▪ElastPQ (Philips Healthcare, Netherlands) ▪Shear Wave Measurement (Hitachi Aloka Medical, Japan)	▪SWE (SuperSonic Imagine, France) ▪Virtual Touch IQ (Siemens Healthcare, Germany) ▪Logiq E9 (GE Healthcare, United Kingdom) ▪Aplio 500 (Toshiba Medical Systems, United Kingdom)	▪MR Touch (GE Healthcare, United Kingdom) ▪MRE (Philips Healthcare, Netherlands; Siemens Healthcare, Germany)
Advantages	▪Most widely used and validated technique ▪Quality criteria well defined ▪ User friendly, rapid, easy to measure at the bedside ▪Good reproducibility ▪Good performance for noninvasive assessments of liver fibrosis staging ▪Excellent diagnostic accuracy for excluding liver cirrhosis ▪Prognostic value in cirrhosis	▪Can be performed using a regular US machine ▪ The ROI can be positioned under B-mode visualization ▪Higher applicability than TE (not limited by ascites or obesity) ▪pSWE is equal to the performance of TE for significant fibrosis and cirrhosis	▪Can be performed using a regular US machine ▪ Simple and fast to use ▪ The ROI can be positioned under B-mode visualization ▪ A larger ROI than that of TE and pSWE ▪Good applicability (not limited by ascites or obesity) ▪Good stability and reproducibility ▪Generates a real-time quantitative map of liver tissue stiffness ▪Can avoid large vessels and the gallbladder ▪ High performance for cirrhosis	▪Can be performed using a regular MRI machine ▪ Good stability and reproducibility ▪Scans the whole liver ▪Higher applicability than TE (not limited by ascites or obesity) ▪Excellent diagnostic accuracy for noninvasive staging of liver fibrosis and cirrhosis
Disadvantages	▪Requires a special device and probe ▪ ROI size is rather small and cannot be chosen ▪Lack of applicability (limited by ascites, severe obesity) ▪No B-mode orientation ▪ Cannot avoid large vessels or the gallbladder ▪Unable to distinguish between intermediate stages of liver fibrosis	▪ROI size is smaller than that of TE and cannot be modified ▪Quality criteria not yet well defined ▪Narrow range of values ▪Unable to distinguish between intermediate stages of liver fibrosis	▪Quality criteria not well defined ▪ No further prospective studies published ▪ Many factors cause failed measurements in clinical practice ▪Unable to distinguish between intermediate stages of liver fibrosis	▪Time-consuming ▪Even more costly than SWE and TE ▪ Failure can occur due to claustrophobia and iron overload ▪Affected by respiratory movement ▪ Hepatic MRE signal may be so low that waves cannot be adequately visualized with a gradient-echo based MRE sequence

2D-SWE: Two-dimensional shear wave elastography; MRE: Magnetic resonance elastography; MRI: Magnetic resonance imaging; pSWE: Point shear wave elastography; ROI: Region of interest; TE: Transient elastography; US: Ultrasound; VTQ: Virtual touch tissue quantification.