Aims: The elastic properties of circumscribed tissues (e.g., tendons, lymph nodes, prostates, brain tumors) are of considerable clinical interest. The purpose of this study was thus to compare the Intra-/Inter-observer variation and accuracy in vitro of point shear wave elastography (pSWE) with that of 2D-SWE and to assess 2D-SWE’s precision with variable ROI (vROI) incircumscribed objects.Material and methods: Round targets (Elasticity QA Phantom Model 049) were examined for varying degrees of stiffness (8, 14, 45, and 80 kPa) and diameters (20/10 mm). Three ultrasound systems and four probes were applied (pSWE: Acuson/S3000 9L4/4C1 and Epiq7 C51, 2D-SWE: Aplio/500 PVT375BT). Three different ROIs were used, namely fixed ROI (fROI) and variable ROI: rectangular-best-fitted ROI, and round-best-fitted ROI. Each measurement was performed twice by four observers.Results: A total of 3,604 measurements were conducted. The intra-observer variation of 2D-SWE measurements indicated better agreement (Intraclass Correlation Coefficient (ICC) = 0.971; 95% CI=[0.945; 0.985]), than for the pSWE measurements (ICC = 0.872; 95% CI=[0.794; 0.92]). With both methods, the shear wave elastography applied showed low inter-observer variation: ICC = 0.980; 95% CI=[0.970; 0.987]. However, a significant difference was observed between fROI (pSWE) and vROI (2D-SWE) on circumscribed objects in terms of accuracy. The lowest degree of observationerror was detected in situations where the ROI was not “best fitted”, but placed within the target of 3mm from the border (target diameter: 20mm; mean relative error = 0.15).Conclusions: When estimating the elastic properties of circumscribed tissues, the different measurement techniques performed by commercial shear wave elastography systems reveal a strong susceptibility for observational errors, depending upon the fixed vs. variable ROI of the pSWE vs. 2D-SWE technique.

Purpose To evaluate whether intraoperative ultrasound-guided detection and resection of the uterine scar during repeat/second cesarean can reduce the number of scars and improve uterine scar architecture. Materials and methods A prospective controlled clinical intervention trial was performed with the following groups: control group 1 (CS1-G): first cesarean; control group 2 (CS2-G): second cesarean utilizing the usual procedure and intervention group (Int-G): repeat/second cesarean with intervention. Transvaginal ultrasound scans were performed 6-9 months after each cesarean. Both primary (double scarring rate) and secondary outcomes [deficiency ratio=d/(b+d)] were analyzed. The deficiency ratio describes the thinning of the remaining myometrium (d=residual myometrial thickness) over the "apparent" defect (b=scar depth). Results In total, 124 of the 156 recruited women were examined, eight were excluded from analysis. The double scarring rate decreased from 42.9% (12/28) in CS2-G to 7.1% (2/28) in the Int-G [difference: 35.8%; 95% confidence interval (CI) (13.2, 54.5); P=0.002]. Two-way analysis of variance (ANOVA) revealed a significant difference between CS2-G and the Int-G in the deficiency ratio adjusted for elective/primary cesareans, with thicker remaining myometrium over the scar defect in the Int-G [difference: -0.24; 95% CI (-0.34, -0.15); P<0.001]. Conclusion Ultrasound-guided resection of the uterine scar area during repeat cesareans reduces the scarring rate and improves thickness of the remaining myometrium as detected by ultrasonography 6-9 months postoperatively.

NCT02827604.

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