Technique of sonographic assessment of lower uterine segment in women with previous cesarean delivery: a prospective, pre/intraoperative comparative ultrasound study.

OBJECTIVE: The purpose of this study was: (A) to establish the effects of different ultrasound measurement methods (linear versus curved array) and measuring conditions [impact of pressure by fetal head/pelvis on the lower uterine segment (LUS)] during LUS-muscular-thickness measurement, (B) to introduce the intraoperative ultrasound measurement of LUS-muscular thickness (reference measurement method), and (C) to evaluate the correlation between different combinations of LUS-muscular-thickness measurement ultrasound techniques at birth planning and preoperative versus intraoperative measurements. METHODS: A prospective clinical observational study of women with the previous cesarean delivery was conducted. LUS-muscular thickness was measured: first at birth planning and second preoperatively using linear and curved probes (transabdominal) and an endocavitar probe (transvaginal), examined with and without pressure by fetal head/pelvis on LUS during measurement and third intraoperatively during repeat cesarean. Bland-Altman plots, paired t tests, Pearson's correlation coefficient, and scatter plots were used. RESULTS: Thirty-three women were included in the study (ultrasound measurements: n = 601). There was no systematic difference between LUS-muscular-thickness measurements with linear versus curved array (mean difference = 0.06 mm; p = 0.24; nm = 133) but between measurements with pressure by the fetus versus without (mean difference = - 0.37 mm; p < 0.001; nm = 243). The highest correlation coefficients were detected for the preoperative (at the day of cesarean section), transabdominal-vaginal approach combined ultrasound measurements versus the intraoperative ultrasound measurements of LUS-muscular thickness-as long as the measurements were made without pressure from the fetal head/pelvis on the LUS [0.86, p < 0.001, n = 24, 95% CI (0.70, 0.94)]. CONCLUSIONS: The systematic application of predetermined measuring conditions, standardized setup criteria improves the performance of LUS thickness measurement by ultrasound near term. CLINICALTRIALS. GOV IDENTIFIER: NCT02827604.

Ultrasound elastography of the lower uterine segment in women with a previous cesarean section: Comparison of in-/ex-vivo elastography versus tensile-stress-strain-rupture analysis.

OBJECTIVES: The purpose of this study was to assess, if the biomechanical properties of the lower uterine segment (LUS) in women with a previous cesarean section (CS) can be determined by ultrasound (US) elastography. The first aim was to establish an ex-vivo LUS tensile-stress-strain-rupture(break point) analysis with the possibility of simultaneously using US elastography. The second aim was to investigate the relationship between measurement results of LUS stiffness using US elastography in-/ex-vivo with results of tensile-stress-strain-rupture analysis, and to compare different US elastography LUS-stiffness-measurement methods ex-vivo. STUDY DESIGN: An explorative experimental, in-/ex-vivo US study of women with previous CS was conducted. LUS elasticity was measured by point Shear Wave Elastography (pSWE) and bidimensional Shear-Wave-Elastography (2D-SWE) first in-vivo during preoperative examination within 24 h before repeat CS (including resection of the thinnest part of the LUS = uterine scar area during CS), second within 1 h after operation during the ex-vivo experiment, followed by tensile-stress-strain-rupture analysis. Pearson's correlation coefficient and scatter plots, Bland-Altman plots and paired T-tests, were used. RESULTS: Thirty three women were included in the study; elastography measurements n = 1412. The feasibility of ex-vivo assessment of LUS by quantitative US elastography using pSWE and 2D-SWE to detect stiffness of LUS was demonstrated. The strongest correlation with tensile-stress-strain analysis was found in the US elastography examination carried out with 2D-SWE (0.78, p < 0.001, 95%CI [0.48, 0.92]). The laboratory experiment illustrated that, the break point - as a surrogate marker for the risk of rupture of the LUS after CS - is linearly dependent on the thickness of the LUS in the scar area (Coefficient of correlation: 0.79, p < 0.001, 95%CI [0.55, 0.91]). Two extremely stiff LUS-specimens (outlier or extreme values) rupture even at less stroke/strain than would be expected by their thickness. CONCLUSION: This study confirms that US elastography can help in determining viscoelastic properties of the LUS in women with a previous CS. The data from our small series are promising. However whether individual extreme values of high stiffness and consecutive restricted biomechanical resilience can explain the phenomenon of rupture during TOLAC in cases of LUS with adequate thickness remains a question which prospective trials have to analyze before US elastography can be introduced into clinical practice.

Does ultrasound-guided intervention during repeat cesarean sections improve uterine scar architecture and reduce the number of scars? A prospective controlled clinical intervention trial.

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.

Intra- and inter-observer variation and accuracy using different shear wave elastography methods to assess circumscribed objects - a phantom study.

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.