2-dimensional shear wave elastography: Interobserver agreement and factors related to interobserver discrepancy

A novel objective evaluation method, shear wave elastography, in the treatment of atrophic vaginitis by nonablative intravaginal Er:YAG laser, a randomized-sham controlled pilot study

OBJECTIVE

The aim of the study was to investigate the effectiveness of intravaginal Er:YAG laser for treating atrophic vaginitis in postmenopausal women utilizing shear wave elastography.

METHODS

In this prospective randomized sham-controlled double-blind pilot study, 20 participants were included (laser group [n = 12] / sham-control group [n = 8]). A nonablative (Smooth mode) Er:YAG laser with a wavelength of 2,940 nm was used. Objective evaluation of laser treatment efficacy was conducted using a special ultrasonic technique: shear wave elastography. Ultrasonic velocity measurements were taken from the anterior and posterior vaginal walls. Mean elasticity (E mean ) was expressed in kilopascals (kPa). Additional outcome parameters were vaginal pH, Vaginal Health Index (VHI), Female Sexual Function Index (FSFI), and visual analog scale (VAS) scores for dyspareunia.

RESULTS

Baseline clinical characteristics, vaginal pH, VHI, VAS and FSFI scores, and E mean values were comparable between the laser and sham-control groups. Statistically significant differences were observed in the final E mean values of the anterior vaginal wall (13.1 ± 6.3 vs 20.0 ± 3.3 kPA, P = 0.01) and posterior vaginal wall (12.7 ± 10.3 vs 19.4 ± 6.9 kPA, P = 0.04) between the laser and sham-control group. Despite comparable baseline E mean values, significant differences in vaginal wall stiffness posttreatment indicated a notable increase in tissue elasticity following laser treatment. Statistically significant differences were also observed in final vaginal pH values, VHI, VAS scores, and FSFI score improvement in favor of laser treatment.

CONCLUSIONS

Shear wave elastography may be considered as a reliable and objective technique for evaluating the efficacy of Er:YAG laser treatment in women with atrophic vaginitis. However, additional studies with larger sample sizes are necessary to establish conclusive evidence.

Diagnostic Performance of 2D Shear Wave (2D-SWE) for Liver Fibrosis in Adults Undergoing Bariatric Surgery

BACKGROUND

Among the most recent methods to diagnose liver fibrosis is 2D shear wave elastography (2D-SWE). However, the evidence in the Latin population is limited, and there is no consensus on the cutoff points for each stage of fibrosis.

AIM

To evaluate the diagnostic performance of 2D-SWE for liver fibrosis in adults with obesity who underwent bariatric surgery (BS).

METHODS

We conducted a cross-sectional study on patients with obesity who underwent BS between 2020 and 2021. Liver stiffness measurement was reported as the mean of valid measurements in kilopascals made with the 2D-SWE. The outcome was biopsy-proven liver fibrosis. ROC curves were constructed for significant fibrosis (F≥2) and advanced fibrosis (F≥3), with their respective area under the curve (AUC). To obtain the best cutoff point for each scenario, we used the Youden index. The 95% confidence intervals (95% CI) for each cutoff point were estimated by bootstrap with 1000 replications.

RESULTS

We analyzed data from 227 patients. The mean age was 37.8 ± 11.1 years and 65.2% were women. Overall, the AUC for significant and advanced fibrosis was 0.54 (95% CI: 0.47-0.62) and 0.73 (95% CI: 0.60-0.87), respectively. For advanced fibrosis, higher AUCs were found among women (AUC: 0.82; 95% CI: 0.59-1.00) and among patients with morbid obesity (AUC: 0.78; 95% CI: 0.61-0.99).

CONCLUSION

The 2D-SWE appears to be a valuable tool for screening advanced liver fibrosis in candidates for BS, mainly in the female population and in adults with morbid obesity.

2D-shear wave elastography: number of acquisitions can be reduced according to clinical setting

BACKGROUND

The factors affecting intra-operator variability of two-dimensional shear wave elastography (2D-SWE) have not been clearly established. We evaluated 2D-SWE variability according to the number of measurements, clinical and laboratory features, and liver stiffness measurements (LSM).

METHODS

At least three LSM were performed in 452 patients who underwent LSM by 2D-SWE (supersonic shear imaging) out of an initial database of 1650 patients. The mean value of the three LSM was our best measurement method. Bland-Altman plots were used to evaluate intra-operator variability when considering only one, or the first two measurements. Variability was assessed by taking the absolute value of the difference between the first LSM and the mean of the three LSM. Logistic regression was used to assess the factors associated with the highest tertile of variability.

RESULTS

The limit of agreement was narrower with the mean of the first and second measurements than with each measurement taken separately (- 2.83 to 2.99 kPa vs. - 5.86 to 6.21 kPa and - 5.77 to 5.73 kPa for the first and second measurement, respectively). A BMI ≥ 25 kg/m2 and a first LSM by 2D-SWE ≥ 7.1 kPa increased the odds of higher variability by 3.4 and 3.9, respectively. Adding a second LSM didn't change the variability in patients with BMI < 25 and a first LSM by 2D-SWE < 7.1 kPa.

CONCLUSIONS

Intra-operator variability of LSM by 2D-SWE increases with both a high BMI and high LSM value. In patients with BMI < 25 kg/m2 and a first LSM < 7.1 kPa we recommend performing only one LSM.

Refraction artifact on abdominal sonogram

Ultrasonography (US) is the first-line diagnostic tool for observing the whole abdomen. Unfortunately, a wide spectrum of refraction-related artefactual images is very frequently encountered in routine US examinations. In addition, most practitioners currently perform abdominal US examinations without sufficient knowledge of refraction artifacts (RAs). This review article was designed to present many representative RA images seen in the clinical setting, with a brief explanation of the mechanism of these images, in certain cases through an analyzed and reconstructed method using computer simulation that supports clinical observations. RAs are encountered not only with B-mode US but also with Doppler US, contrast-enhanced US, and shear wave elastography. RAs change their appearance according to the situation, but they always have a significant effect on detailed interpretation of abdominal US images. Correct diagnosis of abdominal US relies on a deep understanding of each characteristic artifactual finding, which necessitates knowledge of basic US physics. When analyzing mass lesions, computer simulation analysis helps to reveal the global images of RAs around a lesion.

Comparison of 2 shear wave elastography systems in reproducibility and accuracy using an elasticity phantom

This study aimed to compare the accuracy and inter- and intra-observer reproducibility of the measured elasticity between 2 shear wave elastography systems. Three breast radiologists examined 8 targets of 4 different levels of stiffness (size: 11 mm, 4 mm) in an elasticity phantom (Customized 049A Elasticity QA Phantom, CIRS, Norfolk, VA, USA) using 2 different shear wave ultrasound elastography systems: SuperSonic Imagine (SSI) (SSI, Aix en Provence, France) and ShearScan (RS-80A, Samsung Medison, Seoul, Korea). Three radiologists performed ultrasound (US) elastography examinations for the phantom lesions using 2 equipment over a 1-week interval. Intra- and inter-observer reproducibility and the accuracy of the measured elasticity were analyzed and compared between the 2 systems. The accuracy of shape was also analyzed by shape-matching between B-mode and elastography color image. Intra-class correlation coefficients (ICC) were used in statistical analysis. For measured elasticity, the intra-observer and inter-observer reproducibility were excellent in both SSI and ShearScan (0.994 and 0.998). The overall accuracy was excellent in both systems, but the accuracy in small lesions (4 mm target) was lower in SSI than ShearScan (0.780 vs 0.967). The accuracy of shape-matching on the elastography image was 59.0% and 81.4% in the SSI and ShearScan, respectively. In conclusion, the SSI and ShearScan showed excellent intra- and inter-observer reproducibility. The accuracy of the Young's modulus was high in both the SSI and ShearScan, but the SSI showed decreased accuracy in measurement of elasticity in small targets and poor shape-matching between the B-mode image and color-coded elastography image.

Technical Performance of Two-Dimensional Shear Wave Elastography for Measuring Liver Stiffness: A Systematic Review and Meta-Analysis

Objective

To assess the technical performance of two-dimensional shear wave elastography (2D-SWE) for measuring liver stiffness.

Materials and Methods

The Ovid-MEDLINE and EMBASE databases were searched for studies reporting the technical performance of 2D-SWE, including concerns with technical failures, unreliable measurements, interobserver reliability, and/or intraobserver reliability, published until June 30, 2018. The pooled proportion of technical failure and unreliable measurements was calculated using meta-analytic pooling via the random-effects model and inverse variance method for calculating weights. Subgroup analyses were performed to explore potential causes of heterogeneity. The pooled intraclass correlation coefficients (ICCs) for interobserver and intraobserver reliability were calculated using the Hedges-Olkin method with Fisher's Z transformation of the correlation coefficient.

Results

The search yielded 34 articles. From 20 2D-SWE studies including 6196 patients, the pooled proportion of technical failure was 2.3% (95% confidence interval [CI], 1.3–3.9%). The pooled proportion of unreliable measurements from 20 studies including 6961 patients was 7.5% (95% CI, 4.7–11.7%). In the subgroup analyses, studies conducting more than three measurements showed fewer unreliable measurements than did those with three measurements or less, but no intergroup difference was found in technical failure. The pooled ICCs for interobserver reliability (from 10 studies including 517 patients) and intraobserver reliability (from 7 studies including 679 patients) were 0.87 (95% CI, 0.82–0.90) and 0.93 (95% CI, 0.89–0.95), respectively, suggesting good to excellent reliability.

Conclusion

2D-SWE shows good technical performance for assessing liver stiffness, with high technical success and reliability. Future studies should establish the quality criteria and optimal number of measurements.

Diagnostic problems in two-dimensional shear wave elastography of the liver

Two-dimensional shear wave elastography (2D-SWE) is used in the clinical setting for observation of the liver. Unfortunately, a wide spectrum of artifactual images are frequently encountered in 2D-SWE, the precise mechanisms of which remain incompletely understood. This review was designed to present many of the artifactual images seen in 2D-SWE of the liver and to analyze them by computer simulation models that support clinical observations. Our computer simulations yielded the following suggestions: (1) When performing 2D-SWE in patients with chronic hepatic disease, especially liver cirrhosis, it is recommended to measure shear wave values through the least irregular hepatic surface; (2) The most useful 2D-SWE in patients with focal lesion will detect lesions that are poorly visible on B-mode ultrasound and will differentiate true tumors from pseudo-tumors (e.g., irregular fatty change); and (3) Measurement of shear wave values in the area posterior to a focal lesion must be avoided.

Ultrasonographic and elastographic biometry in adult major salivary glands: a preliminary case-control report

Specifications about the size and stiffness of healthy salivary glands with ultrasound (US) are not available for Asian people. Using a Toshiba Apolio 500 US platform, we determined the size (including anterior-posterior median length, median paramandibular depth dimension, and cranio-caudal height) and hardness of 100 healthy submandibular and parotid glands in volunteers without a history of disease affecting the salivary glands or post-radiation, and compared the dimensions to those of 36 parotid glands and 37 submandibular glands in post-irradiated patients. The dimensions of the parotid and submandibular glands were significantly correlated with body weight. However, the dimension of the parotid glands was not significantly correlated with that of patients with prior radiation; the shear wave velocity (SWV) significantly increased (1.99 m/s versus 2.43 m/s, p-value < 0.01). The dimension of the submandibular glands was significantly correlated with prior radiation, where the SWV also significantly increased (2.32 m/s versus 2.50 m/s, p-values < 0.01). We find that US is a useful tool for assessment of the reference dimensions and hardness of major salivary glands that may be altered by irradiation.

Propagation Imaging in the Demonstration of Common Shear Wave Artifacts

In this article, we describe our experience with shear wave propagation imaging (SWPI) as an adjunct to 2-dimensional (2D) shear wave elastography (SWE) in a cohort of patients being evaluated for diffuse liver disease. Two-dimensional SWE has been extensively studied in previous publications; however, 2D SWE using propagation images has not been widely described in the literature to date. We observed that when certain artifacts occurred on the color elastograms, highly characteristic changes to shear wave propagation contours were seen, which can help clarify the cause of the artifacts. To our knowledge, the use of SWPI to explain the etiology of artifacts has never been published before. The artifacts described in this article include the capsule reverberation artifact, penetration limitation or dropout artifact, artifact due to blood vessels, shadowing artifact, tissue motion artifact, and near-field distortion/precompression artifact. Hence, the purpose of this article is to show examples of common artifacts seen on 2D SWE as depicted on corresponding SWPI to demonstrate that both types of image displays are complementary to each other.

Ultrasound or MR elastography of liver: which one shall I use?

Liver stiffness is now a well-established noninvasive biomarker for assessing fibrosis in chronic liver disease. MRI-based and ultrasound-based dynamic elastography techniques have been introduced for assessment of liver stiffness and useful in clinical staging of hepatic fibrosis. Several different elastography techniques are now available with each method having inherent strengths and limitations. The published literature generally indicates that MR elastography has a higher diagnostic performance and fewer technical failures than ultrasound-based elastography techniques in assessing hepatic fibrosis. There is also significant potential to further develop elastography techniques to implement multiparametric methods that have promise for distinguishing between processes such as inflammation, fibrosis, venous congestion, and portal hypertension that can result in increased liver stiffness. In this commentary, we compare MR and ultrasound elastography methods and their utility in clinical practice.