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Background Specific pelvic bone dimensions have been identified as predictors of total mesorectal excision (TME) difficulty and outcomes. However, manual measurement of these dimensions (pelvimetry) is labor intensive and thus, anatomic criteria are not included in the pre-operative difficulty assessment. In this work, we propose an automated workflow for pelvimetry based on pre-operative magnetic resonance imaging (MRI) volumes. Methods We implement a deep learning-based framework to measure the predictive pelvic dimensions automatically. A 3D U-Net takes a sagittal T2-weighted MRI volume as input and determines five anatomic landmark locations: promontorium, S3-vertebrae, coccyx, dorsal, and cranial part of the os pubis. The landmarks are used to quantify the lengths of the pelvic inlet, outlet, depth, and the angle of the sacrum. For the development of the network, we used MRI volumes from 1707 patients acquired in eight TME centers. The automated landmark localization and pelvic dimensions measurements are assessed by comparison with manual annotation. Results A center-stratified fivefold cross-validation showed a mean landmark localization error of 5.6 mm. The inter-observer variation for manual annotation was 3.7 ± 8.4 mm. The automated dimension measurements had a Spearman correlation coefficient ranging between 0.7 and 0.87. Conclusion To our knowledge, this is the first study to automate pelvimetry in MRI volumes using deep learning. Our framework can measure the pelvic dimensions with high accuracy, enabling the extraction of metrics that facilitate a pre-operative difficulty assessment of the TME.

In the field of spinal pathology, sagittal balance of the spine is usually judged by the spatial structure and morphology of pelvis, which can be represented by pelvic parameters. Pelvic parameters, including pelvic incidence, pelvic tilt and sacral slope, are therefore essential for the diagnosis and treatment of spinal disorders, however, it is a time-consuming and laborious procedure to measure these parameters by traditional methods. In this paper, an automatic measurement framework for pelvic CT images was proposed to calculate three-dimensional (3D) pelvic parameters with the support of deep learning technology. Pelvic images were first preprocessed, and 3D reconstruction was then performed to obtain 3D pelvic model by the Visualization Toolkit. DRINet was trained to segment the femoral head region in the pelvic images, and 3D sphere fitting was performed to locate the femoral heads. In addition, VGG16 was adopted to recognize images containing superior sacral endplate, and the plane growth algorithm was used to fit the plane so that the midpoint and normal vector of the superior sacral endplate could be obtained. Finally, 3D pelvic parameters were automatically calculated, and compared with manual measurements for 15 patients. The proposed framework automatically generated 3D pelvic models, and calculated two-dimensional (2D) and 3D pelvic parameters from continuous CT images. Experiments demonstrated that the framework can greatly speed up the calculation of pelvic parameters, and these parameters are accurate when compared with the manual measurements. In conclusion, the proposed framework demonstrates good performance on automatic pelvimetry measurement by incorporating deep learning technology, and can well replace the traditional methods for pelvic parameter measurement.

Purpose Pelvimetry is often recommended in primiparous patients before offering vaginal breech delivery. Later studies show a reduction in perinatal mortality in women undergoing pelvimetry while earlier studies show the opposite. Magnetic resonance imaging (MRI), considered a new technology in 1990, has become the more expensive method for pelvimetry with lower-radiation, believed to prevent unnecessary cesarean sections and “falsely attempted vaginal deliveries”. Methods This retrospective cohort study (November 2019–February 2024) involved 160 primigravidas with breech presentation. The deliveries were attended by a team of experienced obstetricians (defined as attending at least 20 vaginal breech deliveries per year). Our cohort without MRI was compared with four study cohorts with MRI that were also used in a 2022 systematic review assessing delivery outcomes. Results Neonatal outcomes, cesarean section rate and vaginal delivery rate were compared. Umbilical artery pH was significantly lower in two study cohorts (Hoffmann et al. 2016 7.18 vaginal vs. 7.24 caesarean section ( p  < 0.001), our cohort 7.19 vaginal vs. 7.27 cesarean section ( p  < 0.001)). The vaginal delivery rate without MRI (our cohort) was 65.6%. In studies with prior MRI as a selection criterion, the rate was between 65.4% and 67.5% (Hoffmann, Van Loon, Klemt). 25.5% of our patients who had to be delivered by cesarean had non-reassuring fetal heart tones in the second stage of labor. Only 4.4% of the patients attempted delivery with epidural anesthesia. Conclusion Pelvimetry has not been shown to predict neonatal outcome and there is still no consensus on the interpretation of MRI measurements. Many authors argue, as confirmed by our results, that the outcomes are not dependent on pelvimetry, but on the competence of the obstetric delivering team.

Background In rectal cancer surgery, recent studies have found associations between clinical factors, especially pelvic parameters, and surgical difficulty; however, their findings are inconsistent because the studies use different criteria. This study aimed to evaluate common clinical factors that influence the operative time for the laparoscopic anterior resection of low and middle rectal cancer. Methods Patients who underwent laparoscopic radical resection of low and middle rectal cancer from January 2018 to December 2020 were retrospectively analyzed and classified according to the operative time. Preoperative clinical and magnetic resonance imaging (MRI)-related parameters were collected. Logistic regression analysis was used to identify factors for predicting the operative time. Results In total, 214 patients with a mean age of 60.3 ± 8.9 years were divided into two groups: the long operative time group (n = 105) and the short operative time group (n = 109). Univariate analysis revealed that the male sex, a higher body mass index (BMI, ≥ 24.0 kg/m 2 ), preoperative treatment, a smaller pelvic inlet (< 11.0 cm), a deeper pelvic depth (≥ 10.7 cm) and a shorter intertuberous distance (< 10.1 cm) were significantly correlated with a longer operative time ( P  < 0.05). However, only BMI (OR 1.893, 95% CI 1.064–3.367, P  = 0.030) and pelvic inlet (OR 0.439, 95% CI 0.240–0.804, P = 0.008) were independent predictors of operative time. Moreover, the rate of anastomotic leakage was higher in the long operative time group ( P  < 0.05). Conclusion Laparoscopic rectal resection is expected to take longer to perform in patients with a higher BMI or smaller pelvic inlet.

Background The role of MRI pelvimetry and fetal size estimation in predicting mode of birth and risk of operative birth have been studied. However, there are no complete MRI studies that assess the maternal pelvis, fetal dimensions, and the placenta in a single protocol, in order to better inform the likelihood of operative vaginal birth or emergency caesarean section. Therefore, the aim of this pilot study was to assess the feasibility of obtaining a comprehensive prelabour assessment of maternal pelvimetry and fetal biometry using 3D MRI reconstructions, in addition to measures of placental function, in one MR examination. Methods This was a retrospective cohort study of 29 women in late third trimester. Maternal pelvimetry and fetal measurements were performed using structural motion corrected T2 weighted MR images, placental T2* values (an indirect measure of placental oxygenation), and birth outcomes were also collected. Intra and inter-rater variability were calculated for the first 10 patients using the intraclass correlation coefficient. The correlation between manual (measuring the contour area) and calculated circumferences of maternal and fetal structures were also assessed to compare the practicability of performing the two alternative approaches. Results People were imaged between 36 + 1 to 38 + 4 weeks’ gestation. It was possible to obtain comprehensive maternal and fetal measurements. Intra-rater variability was generally excellent, and inter-rater reliability was moderate to excellent. There was a strong correlation between manually obtained and calculated circumferences; Spearman’s ranged from 0.75 to 0.95. Placental volume, mean T2* and kurtosis were available for 23 datasets. The median placental volume was 569.7, the median T2* mean was 44.2, and the median kurtosis was 1.4. Conclusions It is possible to perform maternal pelvimetry, fetal biometry and assess placental oxygenation from one late gestation MRI examination. The approach could be employed in a large, prospective study to ascertain whether we can predict the likelihood of assisted birth or caesarean section, with automation of image analysis to minimise inter-rater variability.

PurposeThe purpose of this study was to correlate MR pelvimetric pelvic inlet measurements with mode of delivery and neonatal outcome in patients with suspected fetopelvic disproportion or breech presentation.MethodsFor this retrospective monocentric study, 237 consecutive MR pelvimetry reports (1999–2016) of pregnant women due to either suspected fetopelvic disproportion, pelvic deformation after trauma, or persistent breech presentation were retrieved from the radiologic database and matched with corresponding information from the obstetric database.ResultsOf 223 included women, 95 (42.6%) underwent planned cesarean section (pCS) and 128 (57.4%) underwent a trial of vaginal labour (TOL), of whom 93 (72.7%) delivered vaginally. Vaginal delivery was successful in 45 out of 64 (70.3%) cephalic cases and in 48 out of 64 (75.0%) breech cases. We found statistically significant differences in conjugata vera obstetrica (CV) and diameter transversalis (DT) between the groups TOL and pCS (CV: 12.5 ± 1.0 vs 12.1 ± 1.2 cm, p value 0.001; DT: 13.3 ± 0.9 vs 12.7 ± 0.9 cm, p value <0.001, respectively). However, there was no significant difference between successful VD and cesarean section after TOL (CV: 12.5 ± 0.9 vs 12.3 ± 1.1 cm, p value 0.194; DT: 13.4 ± 0.9 vs 13.2 ± 0.9 cm, p value 0.358, respectively).ConclusionsIn our cohort, MR pelvimetry was a useful tool for prepartal assessment of the female pelvis in the selection of TOL candidates. Yet, it does not seem to yield additional predictive value for women with a previous vaginal delivery.

BackgroundTotal mesorectal excision (TME) is challenging to perform in a deep, narrow pelvis. While previous studies used pelvimetry to assess bony pelvic structures, there is no consensus on exact definition of deep, narrow pelvis. We hypothesized that the shape of pelvic floor muscle may impact the performance of transabdominal pelvic dissection. We aimed to evaluate which parameters of the shape of pelvic floor muscle impact the difficulty of TME and present a predictive reference value for TME difficulty.MethodsFrom January 2015 to December 2015, 85 consecutive patients who had undergone curative resection for middle to lower rectal cancer were retrospectively studied. Pelvimetry was performed using preoperative T2-weighted magnetic resonance imaging. Predictive factor analysis for surgical duration was studied using linear regression. Mann–Whitney U test, comparing surgical duration between two groups classified by predictive factor, was used for the analysis of reference value.ResultsMultivariate analysis revealed that body mass index, protective stoma, number of surgeon, and incline angle of pelvic floor muscle (β) were independent predictors of surgical duration. Test statistics of Mann–Whitney U for the difference in surgical duration between groups above and below a β of 54° were maximized.ConclusionsThe incline angle of pelvic floor muscle is an independent predictor of surgical duration. In patients with steeper incline of PFM, transabdominal TME is expected to be difficult. This index is novel, but needs to be further validated.

Background Pelvimetry is essential in obstetrics for delivery planning. While computed tomography (CT) is the standard, magnetic resonance imaging (MRI) offers a radiation-free alternative with zero echo time (ZTE) and black bone (BB) sequences providing high bone-to-soft tissue contrast within short scan times. This proof-of-concept study evaluates the reliability of these sequences and the agreement with CT for pelvimetry in a predominantly elderly population. Methods This retrospective study included 21 female patients who underwent 3-T whole-body MRI including ZTE and BB sequences and 18 fluorodeoxyglucose ( 18 F-FDG) positron emission tomography (PET)/CT with optimized low-dose whole-body CT. Obstetric conjugate diameter (OCD), interspinous diameter (ISD), and median transverse diameter (MTD) were measured by five radiologists. Intra-reader, inter-reader, and inter-technique agreement were assessed using intraclass correlation coefficient (ICC) and repeatability/reproducibility coefficients. Results Intra-reader agreement was good regardless of diameter or reader: all ICC ≥ 0.90, repeatability ranging from ± 0.26 to ± 0.48 cm (CT), ± 0.30 to ± 0.52 cm (BB), and ± 0.29 to ± 0.67 cm (ZTE). The inter-reader agreement was good regardless of sequence: all ICC ≥ 0.88, reproducibility ranging from ± 0.39 to ± 0.42 (OCD), ± 0.26 to ± 0.51 cm (ISD), and ± 0.53 to ± 0.58 cm (MTD). ZTE and BB showed similar agreement with CT: ± 0.57 to ± 0.81 cm when including inter-reader variability; ± 0.34 to ± 0.47 cm for only intra-reader variability. Conclusion ZTE and BB sequences provided reliable measurements with good agreement with CT, for obstetric pelvimetry. Further validation in the context of pregnancy is needed. Relevance statement MRI-based pseudo-CT sequences are a promising radiation-free alternative to CT for obstetric pelvimetry, offering the prospect of accurate, reliable measurements of pelvic diameters in pregnant women. Trial registration The population included female patients with suspected multiple myeloma from a previous prospective oncology trial (ClinicalTrials.gov: NCT05381077). Key Points This study explores pseudo-CT MRI sequences for radiation-free non-invasive obstetric pelvimetry. Pseudo-CT zero echo time and black bone sequences provide repeatable and reproducible measurements of pelvic diameters. Pseudo-CT MRI sequences show good inter-technique agreement with the reference CT. Graphical Abstract

Even if lower vaginal delivery success rates and impaired neonatal short-term outcomes have been reported for primiparous women with breech presentation, vaginal breech delivery remains an option for carefully selected patients. Because Magnetic resonance imaging (MRI) pelvimetry can provide additional information on maternal pelvic morphology, we sought to identify new MRI parameters that predict successful vaginal breech delivery. In this retrospective unicentre study, 240 primiparous women with breech presentation at term underwent MRI pelvimetry. For all patients vaginal delivery was planned, according to German guidelines and if the conjugata vera (CV) was ≥12 cm. The patients with uneventful vaginal deliveries and the patients who underwent a secondary caesarean section were compared according to pelvimetric parameters and outcomes. Regression analyses were performed. In the vaginal delivery group (n = 162, (67.5%)), the distance between the spinae ischiadicae (interspinous diameter, ISD) was significantly enlarged. The ISD significantly influenced the mode of delivery in the regression analyses. The CV did not significantly differ between the groups. The patients with successful vaginal deliveries were significantly younger than the patients who underwent caesarean section. In the receiver operating characteristic (ROC) analysis, the area under the curve (AUC) for ISD was 67.7% (p<0.001, 95% CI [0.303-0.642]) and was higher considering the mother's age (AUC = 73.1%, p<0.001, 95% CI [0.662-0.800]). The neonatal short-term outcomes were comparable in both groups. The additional use of ISD may predict successful vaginal breech delivery and may be superior to the CV, which is more commonly used. DRKS00009957.

Pelvimetry is widely used in women with breech presentation at term to select those for whom planned vaginal delivery is appropriate. However, its clinical value has never been established. We evaluated pelvimetry in a randomised controlled trial. The main outcome measures were the elective and emergency caesarean-section rates and the early condition of the neonate. Magnetic-resonance (MR) pelvimetry was done on 235 women. The women were then randomly assigned to two groups–for the study group (n=118), the pelvimetry results were reported to the responsible obstetricians, who used them as the basis for decisions on whether to schedule elective caesarean or trial of labour; for the control group (n=117), the pelvimetry results were not disclosed until 8 weeks post partum, and decisions about obstetric management were made on the basis of clinical factors only. 35 women (15 [13%] study group, 20 [17%] control group) had abnormalities on pelvimetry. The overall caesarean-section rates did not differ significantly between the study and control groups (50 [42%] vs 59 [50%], p=0·24) but the emergency caesarean-selection rate was significantly lower in the study group than in the control group (22 [19%] vs 41 [35%], p=0·0052). The mean 1 min Apgar scores in the study and control groups were 8·1 and 8·0 (p=0·93) and the mean 3 min scores 9·5 and 9·4, respectively (p=0·28). There were no significant differences in the early neonatal outcome for infants born vaginally, by emergency caesarean section, or by elective caesarean section in the two groups, except for a significantly lower Apgar score in the six infants born vaginally to control-group women who had pelvic abnormalities. The use of MR pelvimetry in breech presentation at term did not significantly reduce the overall caesarean-section rate. However, it allowed better selection of the delivery route, with a significantly lower emergency caesarean-section rate. Neonatal outcome was not compromised by use of the pelvimetry data.