The value of pre-operative multicompartment pelvic floor ultrasonography: a 1-year prospective study

Automated segmentation and measurement of the female pelvic floor from the mid-sagittal plane of 3D ultrasound volumes

BACKGROUND

Transperineal ultrasound (TPUS) is a valuable imaging tool for evaluating patients with pelvic floor disorders, including pelvic organ prolapse (POP). Currently, measurements of anatomical structures in the mid-sagittal plane of 2D and 3D US volumes are obtained manually, which is time-consuming, has high intra-rater variability, and requires an expert in pelvic floor US interpretation. Manual segmentation and biometric measurement can take 15 min per 2D mid-sagittal image by an expert operator. An automated segmentation method would provide quantitative data relevant to pelvic floor disorders and improve the efficiency and reproducibility of segmentation-based biometric methods.

PURPOSE

Develop a fast, reproducible, and automated method of acquiring biometric measurements and organ segmentations from the mid-sagittal plane of female 3D TPUS volumes.

METHODS

Our method used a nnU-Net segmentation model to segment the pubis symphysis, urethra, bladder, rectum, rectal ampulla, and anorectal angle in the mid-sagittal plane of female 3D TPUS volumes. We developed an algorithm to extract relevant biometrics from the segmentations. Our dataset included 248 3D TPUS volumes, 126/122 rest/Valsalva split, from 135 patients. System performance was assessed by comparing the automated results with manual ground truth data using the Dice similarity coefficient (DSC) and average absolute difference (AD). Intra-class correlation coefficient (ICC) and time difference were used to compare reproducibility and efficiency between manual and automated methods respectively. High ICC, low AD and reduction in time indicated an accurate and reliable automated system, making TPUS an efficient alternative for POP assessment. Paired t-test and non-parametric Wilcoxon signed-rank test were conducted, with p < 0.05 determining significance.

RESULTS

The nnU-Net segmentation model reported average DSC and p values (in brackets), compared to the next best tested model, of 87.4% (<0.0001), 68.5% (<0.0001), 61.0% (0.1), 54.6% (0.04), 49.2% (<0.0001) and 33.7% (0.02) for bladder, rectum, urethra, pubic symphysis, anorectal angle, and rectal ampulla respectively. The average ADs for the bladder neck position, bladder descent, rectal ampulla descent and retrovesical angle were 3.2 mm, 4.5 mm, 5.3 mm and 27.3°, respectively. The biometric algorithm had an ICC > 0.80 for the bladder neck position, bladder descent and rectal ampulla descent when compared to manual measurements, indicating high reproducibility. The proposed algorithms required approximately 1.27 s to analyze one image. The manual ground truths were performed by a single expert operator. In addition, due to high operator dependency for TPUS image collection, we would need to pursue further studies with images collected from multiple operators.

CONCLUSIONS

Based on our search in scientific databases (i.e., Web of Science, IEEE Xplore Digital Library, Elsevier ScienceDirect and PubMed), this is the first reported work of an automated segmentation and biometric measurement system for the mid-sagittal plane of 3D TPUS volumes. The proposed algorithm pipeline can improve the efficiency (1.27 s compared to 15 min manually) and has high reproducibility (high ICC values) compared to manual TPUS analysis for pelvic floor disorder diagnosis. Further studies are needed to verify this system's viability using multiple TPUS operators and multiple experts for performing manual segmentation and extracting biometrics from the images.

Quality of reporting of diagnostic accuracy studies on pelvic floor three-dimensional transperineal ultrasound: a systematic review

OBJECTIVE

In recent years, a large number of studies have been published on the clinical relevance of pelvic floor three-dimensional (3D) transperineal ultrasound. Several studies compare sonography with other imaging modalities or clinical examination. The quality of reporting in these studies is not known. The objective of this systematic review was to determine the compliance of diagnostic accuracy studies investigating pelvic floor 3D ultrasound with the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines.

METHODS

Published articles on pelvic floor 3D ultrasound were identified by a systematic literature search of MEDLINE, Web of Science and Scopus databases. Prospective and retrospective studies that compared pelvic floor 3D ultrasound with other clinical and imaging diagnostics were included in the analysis. STARD compliance was assessed and quantified by two independent investigators, using 22 of the original 25 STARD checklist items. Items with the qualifier 'if done' (Items 13, 23 and 24) were excluded because they were not applicable to all papers. Each item was scored as reported (score = 1) or not reported (score = 0). Observer variability, the total number of reported STARD items per article and summary scores for each item were calculated. The difference in total score between STARD-adopting and non-adopting journals was tested statistically, as was the effect of year of publication.

RESULTS

Forty studies published in 13 scientific journals were included in the analysis. Mean ± SD STARD checklist score of the included articles was 16.0 ± 2.5 out of a maximum of 22 points. The lowest scores (< 50%) were found for reporting of handling of indeterminate results or missing responses, adverse events and the time interval between tests. Interobserver agreement for rating the STARD items was excellent (intraclass correlation coefficient, 0.77). An independent t-test showed no significant mean difference ± SD in total STARD checklist score between STARD-adopting and non-adopting journals (16.4 ± 2.2 vs 15.9 ± 2.6, respectively). Mean ± SD STARD checklist score for articles published in 2003-2009 was lower, but not statistically different, compared with those published in 2010-2015 (15.2 ± 2.5 vs 16.6 ± 2.4, respectively).

CONCLUSION

The overall compliance with reporting guidelines of diagnostic accuracy studies on pelvic floor 3D transperineal ultrasound is relatively good compared with other fields of medicine. However, specific checklist items require more attention when reported. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Interobserver agreement of multicompartment ultrasound in the assessment of pelvic floor anatomy

OBJECTIVE

To assess the interobserver agreement of pelvic floor anatomical measurements using multicompartment pelvic floor ultrasound.

METHODS

Females were recruited from the urogynaecology/gynaecology clinics between July and October 2009 and underwent multicompartment pelvic floor ultrasonography (PFUS) using two-dimensional (2D) transperineal ultrasound (TPUS), high-frequency 2D/three-dimensional (3D) endovaginal ultrasound (EVUS) using a biplane probe with linear and transverse arrays and a 360° rotational 3D-EVUS. PFUS measurements were independently analysed by two clinicians.

RESULTS

158 females had PFUS assessment. Good-to-excellent interobserver agreement was observed for bladder-symphysis distance at rest and valsalva, urethral thickness, urethral length, urethral volume, levator hiatus area and width, anteroposterior diameter and anorectal angle. Lins Correlation was used to calculate the interobserver agreement and Bland-Altman plots were created to demonstrate the agreement between the researchers. There was also a good-to-excellent agreement between the two clinicians for the assessment of pelvic organ prolapse (POP) in the anterior, middle and posterior compartment.

CONCLUSION

Multicompartment PFUS is a reliable tool in the anatomical assessment of pelvic floor measurements and POP.

ADVANCES IN KNOWLEDGE

We found a good-to-excellent agreement between the two assessors in the assessment of pelvic floor measurements for all three pelvic floor compartments and suggest that multicompartment PFUS could be considered as a systematic integrated approach to assess the pelvic floor.

Assessment of urethral vascularity using 2D colour Doppler high-frequency endovaginal ultrasonography in women treated for symptomatic stress urinary incontinence: 1-year prospective follow-up study

INTRODUCTION

Urethral vascularity is responsible for organ perfusion. It is also believed to contribute to maintaining the normal tension in the urethral mucosa and contributes to approximately one third of urethral closure pressure. We hypothesised that in women undergoing treatment for stress urinary incontinence (SUI), there is no change in blood flow intensity.

METHODS

In this pilot study we recruited women attending the urogynaecology clinics between July and October 2009. Exclusion criteria included symptoms of pelvic organ prolapse or urinary tract infection. Colour Doppler ultrasound was performed at the level of the mid-urethra using a high-frequency (9-12 MHz) endovaginal ultrasonography (EVUS) focusing on the following vascular parameters: flow velocity (V), area of the vessels (A), intensity of perfusion (I), Tissue Pulsatility Index (TPI) and Tissue Resistance Index (TRI). Vascular assessments were repeated at 1 year.

RESULTS

We examined 67 women with symptoms of SUI (17 women had surgery and 50 conservative management, i.e., pelvic floor muscle exercises). The mean (± SD) age in the conservative and surgical groups was 46 (±11) and 40 (±9) years respectively and median (range) parity was 2 (0-8) in both groups. Compared to baseline, no statistically significant differences were observed within each group (p > 0.05) or between the values of vascular parameters (V, A, I, TRI and TPI) at 1 year. There was also no difference in vascular parameters between the two groups.

CONCLUSION

At 12 months there is no change in vascularity parameters in women who opt for conservative or surgical treatment of SUI.