Liver fibrosis staging with a new 2D-shear wave elastography using comb-push technique: Applicability, reproducibility, and diagnostic performance

Abstract

Objective: To evaluate the applicability, reproducibility, and diagnostic performance of a new 2D-shear wave elastography (SWE) using the comb-push technique (2D CP-SWE) for detection of hepatic fibrosis, using histopathology as the reference standard.

Materials and methods: This prospective study was approved by the institutional review board, and informed consent was obtained from all patients. The liver stiffness (LS) measurements were obtained from 140 patients, using the new 2D-SWE, which uses comb-push excitation to produce shear waves and a time-aligned sequential tracking method to detect shear wave signals. The applicability rate of 2D CP-SWE was estimated, and factors associated with its applicability were identified. Intraobserver reproducibility was evaluated in the 105 patients with histopathologic diagnosis, and interobserver reproducibility was assessed in 20 patients. Diagnostic performance of the 2D CP-SWE for hepatic fibrosis was evaluated by receiver operating characteristic (ROC) curve analysis.

Results: The applicability rate of 2D CP-SWE was 90.8% (109 of 120). There was a significant difference in age, presence or absence of ascites, and the distance from the transducer to the Glisson capsule between the patients with applicable LS measurements and patients with unreliable measurement or technical failure. The intraclass correlation of interobserver agreement was 0.87, and the value for the intraobserver agreement was 0.95. The area under the ROC curve of LS values for stage F2 fibrosis or greater, stage F3 or greater, and stage F4 fibrosis was 0.874 (95% confidence interval [CI]: 0.794-0.930), 0.905 (95% CI: 0.832-0.954), and 0.894 (95% CI: 0.819-0.946), respectively.

Conclusion: 2D CP-SWE can be employed as a reliable method for assessing hepatic fibrosis with a reasonably good diagnostic performance, and its applicability might be influenced by age, ascites, and the distance between the transducer and Glisson capsule.

Fig 1. Flow diagram of the study population.

Fig 2. Applicability of 2D comb-push shear wave elastography (SWE) measurements.

(A) Applicable SWE examination with technical success and reliable measurement in a 43-year-old male liver donor with a body mass index (BMI) of 25.73 kg/m². The region of interest (ROI) was placed in the right upper lobe, avoiding large vessels and areas with artifacts, and 17.7mm away from the Glisson capsule. Sufficient color maps covering more than 50% of the sampling area for all acquisitions were obtained, which was regarded as a technical success. The interquartile range/median ratio was 6.51%, which was lower than 30% and was considered as a reliable measurement. The median liver stiffness (LS) value was 4.15kPa, and the histologic fibrosis was proven to be stage F0. Note that the distance between the transducer and Glisson capsule was 17.5mm. (B) Non-applicable SWE examination with technical failure in a 68-year-old female patient with a BMI of 21.26kg/m²,who was awaiting liver transplantation. The ROI was placed in the right upper lobe, devoid of large vessels and areas of artifacts, and 15.4mm away from the Glisson capsule. Despite 12 trials, color filling of the elastography map was insufficient, which was regarded as a technical failure. Note that this was the only case of technical failure in our study, and the distance between the transducer and Glisson capsule was 34.0mm.

Fig 3. Box-and-whisker plot shows the liver stiffness (LS) values at each fibrosis staging.

The boxes represent LS values from the 25^th to 75^th quartile, and the lines at the center of the boxes indicate the median. The whiskers represent the 9^th and 91^st percentiles. LS values are expressed in kilopascals.

Fig 4. Scatterplots show good intra-and interobserver correlations for 2D comb-push shear wave elastography.

The Pearson correlation, r and the intra-class correlation, ICC are shown in the plot.

Fig 5. When applying the cutoff values from our study, the live stiffness (LS) values obtained by the 2D comb-push shear wave elastography (2D CP-SWE) could predict histologic fibrosis staging.

A)The median LS value of 5.98kPa was achieved by the 2D CP-SWE in a 64-year-old man, which was greater than the cutoff value of F2 (5.33kPa) and less than the cutoff value of F3 (6.84kPa). The patient underwent surgical resection for hepatocellular carcinoma (HCC), after which the fibrosis staging was histologically confirmed to be F2. B) The median LS value of 7.38kPa was measured by the 2D CP-SWE in a 66-year-old man, which was greater than the cutoff value of F3 (6.84kPa) and less than the cutoff value of F4 (7.59kPa). The patient underwent surgical resection for HCC, after which the fibrosis stage was histologically confirmed as F3. C) Despite massive ascites, reliable LS values were successfully measured by 2D CP-SWE in a 57-year-old woman. The median LS value of 13.45kPa was greater than the cutoff value of F4 (7.59kPa). The patient underwent liver transplantation. The fibrosis stage was histologically proven to be F4, and the macronodular cirrhosis was associated with alcohol consumption. D) Reliable LS values were successfully measured by 2D CP-SWE in a 49-year-old obese man with a body mass index of 31.33kg/m². The median LS value of 8.14kPa was greater than the value of F4 (7.59kPa). The patient underwent liver transplantation. The fibrosis stage was histologically proven to be F4, and macronodular cirrhosis was associated with hepatitis B virus infection and alcohol consumption.