Does Patient Posture Affect the Ultrasound Evaluation of Pelvic Organ Prolapse?

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.

Automatic Plane of Minimal Hiatal Dimensions Extraction From 3D Female Pelvic Floor Ultrasound

There is an increasing interest in the applications of 3D ultrasound imaging of the pelvic floor to improve the diagnosis, treatment, and surgical planning of female pelvic floor dysfunction (PFD). Pelvic floor biometrics are obtained on an oblique image plane known as the plane of minimal hiatal dimensions (PMHD). Identifying this plane requires the detection of two anatomical landmarks, the pubic symphysis and anorectal angle. The manual detection of the anatomical landmarks and the PMHD in 3D pelvic ultrasound requires expert knowledge of the pelvic floor anatomy, and is challenging, time-consuming, and subject to human error. These challenges have hindered the adoption of such quantitative analysis in the clinic. This work presents an automatic approach to identify the anatomical landmarks and extract the PMHD from 3D pelvic ultrasound volumes. To demonstrate clinical utility and a complete automated clinical task, an automatic segmentation of the levator-ani muscle on the extracted PMHD images was also performed. Experiments using 73 test images of patients during a pelvic muscle resting state showed that this algorithm has the capability to accurately identify the PMHD with an average Dice of 0.89 and an average mean boundary distance of 2.25mm. Further evaluation of the PMHD detection algorithm using 35 images of patients performing pelvic muscle contraction resulted in an average Dice of 0.88 and an average mean boundary distance of 2.75mm. This work had the potential to pave the way towards the adoption of ultrasound in the clinic and development of personalized treatment for PFD.

The Visualized Urethral Mobility Profile in Stress Urinary Incontinence Described by Four-Dimensional Transperineal Ultrasound

OBJECTIVES

To describe the urethral mobility during urine leaking in stress urinary incontinence (SUI) by transperineal ultrasound (TPUS) with urethral mobility profile (UMP) analysis.

METHODS

This was a prospective study of 380 women who had a cough stress test (CST) with TPUS. UMP software automatically placed six equidistant points from the bladder neck (Point 1) to the external urethral meatus (Point 6) and determined their x and y coordinates relative to the symphysis pubis. Urethral mobility vector of Points 1-6 (Vectors 1-6) and the distance between the six points and the symphysis (Dist. 1-6) were calculated and compared between the two groups. The visualized UMP was created by reproducing the positions of the six points at rest and on Valsalva.

RESULTS

Valid data of 188 women with SUI and 174 continent women were analyzed. The mean age of all 362 women was 49.3 years. Mean body mass index in the SUI group was significantly increased (23.8 vs 22.2 kg/m² , P < .001). During CST, Vectors 1-6 and Dist. 2-6 were significantly increased (all P < .005) in the SUI group. The UMP showed the mid-urethral rotated down around the symphysis pubis. The upper urethral profile in the two groups was similar. But the gap between the mid-urethra and the symphysis was wider in the SUI group.

CONCLUSIONS

The visualized UMP illustrated the mid-urethral hypermobility in SUI by showing a wider gap due to the unstable connection between the mid-urethra and the symphysis pubis.

Abdominal pressure and pelvic organ prolapse: is there an association?

INTRODUCTION AND HYPOTHESIS

The primary aim of this study was to assess for an association between maximal intra-abdominal pressure reached on Valsalva (MAP) and pelvic organ prolapse (POP) on subjective, clinical and sonographic evaluation. Another objective was to test for association between MAP and body mass index (BMI).

METHODS

A retrospective cross-sectional study was carried out on 504 archived datasets of women seen for pelvic floor dysfunction symptoms between January 2017 to September 2019 at a tertiary urogynaecology clinic. Patients underwent a standardized interview including use of visual analogue scores (VAS) to evaluate bother of pelvic floor symptoms, examination using the International Continence Society Pelvic Organ Prolapse Quantification (ICS POP-Q), dual-channel filling and voiding cystometry, test for MAP as well as four-dimensional (4D) transperineal ultrasound. Analysis of ultrasound volumes for pelvic organ descent was performed blinded against all other data.

RESULTS

There was a weak but significant association between MAP and sonographic rectal ampulla descent (p = 0.0275). There was also a significant association between MAP and bother of obstructed defecation symptoms (p = 0.0065). Symptomatic, clinical and sonographic POP in the anterior or the apical compartments was not significantly associated with MAP. On multivariate analysis, the association between MAP and rectal descent remained significant (p = 0.01). There was no significant association between BMI and MAP.

CONCLUSIONS

This cross-sectional study showed an association between MAP and posterior compartment prolapse on imaging as well as between MAP and the bother score of obstructed defecation symptoms. There was no association between BMI and MAP.

Real-time assessment of the behaviour of the bladder neck and proximal urethra during urine leaking in the cough stress test (CST) in supine and standing positions using transperineal ultrasound

INTRODUCTION AND HYPOTHESIS

The objective was to describe the behaviour of the bladder neck and proximal urethra during urine leaking in the cough stress test (CST) in supine and standing positions using transperineal ultrasound (TPUS).

METHOD

We carried out prospective data collection and a retrospective data analysis of 102 women with stress urinary incontinence (SUI) who had a positive CST with TPUS in the supine and/or standing position. On TPUS, the behaviour of the bladder neck and proximal urethra was described by the urethral length, urethral funnelling, bladder neck descent (BND), retrovesical angle (RVA) and urethral rotation angle (URA). Differences between the ultrasound findings in the two positions were evaluated.

RESULTS

In the 102 women, the mean age was 48 years and mean BMI was 23.8 kg/m². On TPUS, urine leakage was detected in the supine or standing position in 102 women and in both positions in 81. Between the two positions, significant differences were found in the URA and RVA. In the standing position, the median RVA of 166° was significantly larger than that of 133° in the supine position (p < 0.001), and the median URA of 35° was significantly smaller than that of 64° in the supine position (p < 0.001).

CONCLUSIONS

TPUS in both positions can be used to detect the real-time behaviour of the bladder neck and urethra in the CST. In the standing position, less rotation and more straightening of the bladder neck and proximal urethra occurred during urine leakage.