MR pelvimetry measurements, analysis of inter- and intra-observer variation

Simple pelvimetry predicts the pelvic manipulation time in robot-assisted low and ultra-low anterior resection for rectal cancer

PURPOSE

This study explored the difficulty factors in robot-assisted low and ultra-low anterior resection, focusing on simple measurements of the pelvic anatomy.

METHODS

This was a retrospective analysis of the clinical data of 61 patients who underwent robot-assisted low and ultra-low anterior resection for rectal cancer between October 2018 and April 2023. The relationship between the operative time in the pelvic phase and clinicopathological data, especially pelvic anatomical parameters measured on X-ray and computed tomography (CT), was evaluated. The operative time in the pelvic phase was defined as the time between mobilization from the sacral promontory and rectal resection.

RESULTS

Robot-assisted low and ultra-low anterior resections were performed in 32 and 29 patients, respectively. The median operative time in the pelvic phase was 126 (range, 31-332) min. A multiple linear regression analysis showed that a short distance from the anal verge to the lower edge of the cancer, a narrow area comprising the iliopectineal line, short anteroposterior and transverse pelvic diameters, and a small angle of the pelvic mesorectum were associated with a prolonged operative time in the pelvic phase.

CONCLUSION

Simple pelvic anatomical measurements using abdominal radiography and CT may predict the pelvic manipulation time in robot-assisted surgery for rectal cancer.

A comparative study of two pelvimetry methods: 3D models based on CT and MRI

INTRODUCTION AND HYPOTHESIS

To compare 3D models based on magnetic resonance imaging (MRI) and 3D models based on computed tomography (CT) in pelvimetry.

METHODS

A retrospective analysis of 141 patients who underwent both pelvic 3D MRI and 3D CT pelvimetry for gynecological diseases from December 2009 to October 2020 was performed. The two pelvimetry methods were compared by paired Student's t test, Pearson's correlation coefficient, Bland-Altman analysis and intraclass correlation coefficient (ICC).

RESULTS

The differences between methods for each diameter were statistically significant, except for those of the posterior sagittal diameter of the pelvic inlet (t:-0.71, P = 0.5) and the anteroposterior pelvic outlet diameter (t:0.02, P = 0.98). 3D MRI and 3D CT pelvimetry strongly correlated with each other (r: min 0.7, max: 0.96, P < 0.01). The Bland-Altman results indicate that the difference points of each pelvic diameter line greater than 95 % are within the 95 % limits of agreement. The ICC was good to very good for all pelvimetric measurements using either MRI-3D (ICC: 0.64-0.98) or CT-3D (ICC: 0.72-0.98) between the two readers.

CONCLUSIONS

3D MRI and 3D CT pelvimetry have good agreement and reproducibility, indicating that 3D MRI is reliable for pelvimetry.

Accuracy and Reliability of Pelvimetry Measures Obtained by Manual or Automatic Labeling of Three-Dimensional Pelvic Models

(1) Background: The morphology of the pelvic cavity is important for decision-making in obstetrics. This study aimed to estimate the accuracy and reliability of pelvimetry measures obtained when radiologists manually label anatomical landmarks on three-dimensional (3D) pelvic models. A second objective was to design an automatic labeling method. (2) Methods: Three operators segmented 10 computed tomography scans each. Three radiologists then labeled 12 anatomical landmarks on the pelvic models, which allowed for the calculation of 15 pelvimetry measures. Additionally, an automatic labeling method was developed based on a reference pelvic model, including reference anatomical landmarks, matching the individual pelvic models. (3) Results: Heterogeneity among landmarks in radiologists' labeling accuracy was observed, with some landmarks being rarely mislabeled by more than 4 mm and others being frequently mislabeled by 10 mm or more. The propagation to the pelvimetry measures was limited; only one out of the 15 measures reported a median error above 5 mm or 5°, and all measures showed moderate to excellent inter-radiologist reliability. The automatic method outperformed manual labeling. (4) Conclusions: This study confirmed the suitability of pelvimetry measures based on manual labeling of 3D pelvic models. Automatic labeling offers promising perspectives to decrease the demand on radiologists, standardize the labeling, and describe the pelvic cavity in more detail.

The relation between head circumference and mid pelvic circumference: A simple index for cephalo-pelvic disproportion evaluation

INTRODUCTION

Cephalo-pelvic-disproportion (CPD) is one of the most common obstetric complications. Since CPD is the disproportion between the fetal head and maternal bony pelvis, evaluation of the head-circumference (HC) relative to maternal bony pelvis may be a useful adjunct to pre-labor CPD evaluation. The aim of the present study was a proof-of-concept evaluation of the ratio between HC to pelvic circumference (PC) as a predictor of CPD.

METHODS

Of 11,822 deliveries, 104 cases that underwent an abdomino-pelvic CT for any medical indication and who underwent normal vaginal deliveries (NVD) (n=84) or cesarean deliveries (CD) due to CPD (n=20) were included retrospectively. Maternal pelvis dimensions were reconstructed and neonatal HC, as a proxy for fetal HC, were measured. The correlation between cases of CPD and Cephalo-Pelvic Circumference Index (CPCI), which represents the ratio between the HC and PC in percent (HC/PC *100) was evaluated.

RESULTS

The mid-pelvis cephalo-pelvic circumference index (MP-CPCI) was larger in CD groups as compared to the NVD group: 103±11 vs. 97±8% respectively (p=0.0003). In logistic regression analysis, the MP-CPCI was found to be independently associated with CD due to CPD: each 1% increase in MP-CPCI increased the likelihood of CD for CPD by 11% (aOR 1.11, CI 95% 1.03-1.19, p=0.004). The adjusted odds ratio for CD due to CPD increased incrementally as the MP-CPCI increased, from 3.56 (95%CI, 1.01-12.6) at MP-CPCI of 100, to 5.6 (95%CI, 1.63-19.45) at 105, 21.44 (95%CI, 3.05-150.84) at 110, and 28.88 (95%CI, 2.3-362.27) at MP-CPCI of 115 Conclusions: The MP-CPCI, representing the relative dimensions of the fetal HC and maternal PC, is a simple tool that can potentially distinguish between parturients at lower and higher risk of CPD. Prospective randomized studies are required to evaluate the feasibility of prenatal pelvimetry and MP-CPCI to predict the risk of CPD during labor.

Computed tomography based cross-sectional anatomy of the pelvis predicts surgical outcome after rectal cancer surgery

Purpose

Narrow pelvis has been considered an adverse factor for postoperative and oncologic outcomes after rectal cancer surgery. The aim of this study was to investigate the validity of using only axial CT scan images to calculate the pelvic cross-sectional area for the prediction of adverse outcomes after rectal cancer surgery.

Methods

The medical records of patients who underwent rectal cancer surgery were reviewed and analyzed retrospectively. Axial images of CT scan were used to measure the pelvic cross-sectional area. Pelvic surgical site infection (SSI), positive resection margin, and early local recurrence were adopted as end-points to analyze the impact of pelvimetry on surgical outcome.

Results

The mean pelvic cross-sectional area was 84.3 ± 10.9 cm². Males had significantly smaller pelvic areas than females (P < 0.001). Comparing pelvic cross-sectional areas according to the surgical outcomes, the results indicated that patients with pelvic SSI and local failure (positive resection margin or local recurrence within 1 year) have significantly smaller cross-sectional-area than SSI and local failure-free patients (P = 0.013 and P = 0.031). A calculated cross-sectional area of 88.8 cm² was determined as the cutoff value for the prediction of pelvic SSI and/or local failure, which was significant in a validating analysis.

Conclusion

The pelvic cross-sectional area obtained from a routine axial CT scan image was associated with pelvic SSI, positive resection margin, and early local recurrence. It might be an intuitive, feasible, and easily adoptable method for predicting surgical outcomes.

How reproducible are classical and new CT-pelvimetry measurements?

PURPOSE

The objective of this study was to assess the reliability and reproducibility of existing and new computed tomography (CT)-pelvimetry measurements.

MATERIAL AND METHODS

A retrospective cohort study of 63 women with a mean age of 33.9±5.2 (SD) years (range: 19-49 years) was conducted. Classical pelvimetry measurements were collected including the obstetric conjugate (OC), median transverse diameter (MTD), and interspinous diameter (ISD). Additionally, we used multiplanar reconstruction (MPR) mode to define two oblique planes: inlet pelvic plane (IPP) and mid-pelvic plane (MPP) and measure new pelvic parameters, including anteroposterior (APD), transverse diameters and circumference of both IPP and MPP (inletAPD, inletMTD, inletCIRC and midAPD, ISD, midCIRC, respectively). The reproducibility (intra- and inter-observer) of our results were assessed. Multivariate analyses using principal component analysis and clustering methods were conducted to analyze the association between pelvimetry measurements and identify patient sub-groups.

RESULTS

All linear measurements (OC, inletAPD, MTD, inletMTD, midAPD, and ISD) showed statistically "almost perfect" intra- and inter-observer correlation coefficients (range: 0.924-0.980). Circumferences (inletCIRC and midCIRC) showed statistically "almost perfect" intra- (range: 0.847-0.857) and inter-observer correlation coefficients (range: 0.923-0.957). The measurement of 6 pelvimetric parameters allowed determining three groups of pelvis size.

CONCLUSION

New pelvic measurements have excellent reproducibility and are similar to the classical measurements, based on the MPR analysis of CT planes adjusted to the inner bony pelvis.

Intra- and inter-rater reliability in a comparative study of cross-sectional and spiral computed tomography pelvimetry methods

Background

Different low-dose computed tomography (CT) pelvimetry methods can be used to evaluate the size of birth canal before delivery. CT pelvimetry might generate an acceptable low fetal radiation dose but its measurement accuracy is unknown.

Purpose

To investigate intra- and inter-rater measurement reliability of cross-sectional and two spiral CT pelvimetry methods: standard spiral and short spiral.

Material and Methods

Ten individuals (age ≥60 years, body mass index ≥30 kg/m²) having a CT scan of the abdomen also had CT pelvimetry scans. Three radiologists made independent measurements of each pelvimetry method on two occasions and also in consensus for a reference pelvimetry computed from the standard-dose CT scan of the abdomen. Inter- and intra-rater reliability was analyzed by intraclass correlation coefficient.

Results

Measurements in the short spiral pelvimetry demonstrated excellent intra- and inter-rater reliability, intraclass correlation coefficient ≥0.93, and good to excellent 95% confidence interval 0.87–0.99. Corresponding results of the standard spiral and cross-sectional pelvimetry showed good to excellent intraclass correlation coefficient ≥0.85 and ≥0.76, and 95% confidence interval was least good and moderate 0.73–0.98 and 0.59–0.97, respectively. Intraclass correlation coefficient between reference pelvimetry and other CT methods showed analogous results.

Conclusion

The short spiral pelvimetry demonstrated high and best reliability in comparison to other methods. Standard spiral method showed also good measurement reliability but the short spiral pelvimetry generates lower fetal radiation dose. This method might be suitable for measurements at narrow pelvis. Patient acceptance and attitude to CT pelvimetry should be investigated.

Study on the cephalopelvic relationship with cephalic presentation in nulliparous full-term Chinese pregnant women by MRI with three-dimensional reconstruction

PURPOSE

To analyze the relationship between fetal head size and maternal pelvis size using magnetic resonance imaging (MRI) with a 3-D reconstruction technique.

METHODS

A total of 301 nulliparous full-term Chinese pregnant women with cephalic presentation were enrolled and received MRI examinations before labor onset. Data were collected and imported into Mimics software to reconstruct the maternal pelvis and fetus.

RESULTS

Of 301 pregnant women, 212 underwent vaginal delivery and 32 received cesarean section. The body mass index (BMI) was significantly different between the vaginal delivery group and the suspected cephalopelvic disproportion (CPD) group; the larger the BMI, the higher was the risk of CPD. The transverse diameter of the pelvic inlet and the posterior sagittal diameter of the midpelvis were significantly larger in the vaginal delivery group, compared with the suspected CPD group. Fetal weight > 3.5 kg could be used as a diagnostic indicator for CPD.

CONCLUSIONS

BMI is a risk factor for CPD, and fetal weight < 3.5 kg is an important diagnostic indicator for natural delivery in Chinese pregnant women.

Fetal head circumference and subpubic angle are independent risk factors for unplanned cesarean and operative delivery

INTRODUCTION

The aim of this study was to ascertain whether combined ultrasound assessment of fetal head circumference (HC) and maternal subpubic angle (SPA) prior to the onset of labor may predict the likelihood of an unplanned operative delivery (UOD) in nulliparous women at term.

MATERIAL AND METHODS

Prospective cohort study of singleton pregnancies in cephalic presentation. Pregnancies experiencing UOD secondary to fetal distress were excluded. HC was assessed transabdominally and SPA values were obtained from a reconstructed coronal plane on three-dimensional (3D) ultrasound performed translabially at 36-38 weeks of gestation. Maternal characteristics, HC expressed as multiple of median, and SPA were compared according to the mode of delivery. Logistic regression and receiver operating characteristics curve analyses were used to analyze the data.

RESULTS

597 pregnancies were included in the study. Spontaneous vaginal delivery occurred in 70.2% of the cases and UOD was required in 29.8%. There was no difference in pregnancy characteristics and birthweight between women who had a spontaneous vaginal birth compared with UOD. The HC multiple of median was larger (1.00 ± 0.02 vs. 1.03 ± 0.02, p ≤ 0.0001), whereas SPA was narrower in the UOD group (124.02 ± 13.64 vs. 102.61 ± 16.13, p ≤ 0.0001). At logistic regression, SPA (OR 0.91, 95% CI 0.89-0.93), HC multiple of median (OR 1.13, 95% CI 1.09-1.17) and maternal height (OR 0.95, 95% CI 0.92-0.99) were independently associated with UOD. When combined, the diagnostic accuracy of a predictive model integrating HC, SPA and maternal height was highly predictive of UOD with an area under the curve of 0.904 (95% CI 0.88-0.93).

CONCLUSIONS

Ultrasound assessment of fetal HC and maternal SPA after 36 weeks of gestation can identify a subset of women at higher risk of UOD during labor, for whom early planned delivery might be beneficial.

CT-based measurement of the inner pelvic volume

Background Surgery in the lesser pelvis is associated with a high complication rate as surgeons are spatially limited by solid anatomic structures and soft tissue borders. So far, only two-dimensional (2D) parameters have been used for risk stratification. Purpose To precisely measure the inner pelvic volume a computed tomography (CT)-based three-dimensional (3D) approach was established and compared to approximations by 2D parameter combinations. Material and Methods Thin-layered multi-slice CT datasets were used retrospectively for slice by slice depiction of the inner pelvic surface. The inner pelvic volume was then automatically compounded. Combinations of two to four 2D dimensions determined in 3D volume rendered reconstructions were correlated with the inner pelvic volume. Pearson's correlation coefficient and Chi square test were used for statistical calculations. Significance level was set at P < 0.05. Results In total 142 patients (91 men, 51 women) aged 64.8 ± 10.6 years at surgery were included in the study. Mean calculated pelvic volume was 1031.13 ± 180.06 cm³ (men, 996.57 ± 172.43 cm³; women, 1093.34 ± 178.39 cm³). Best approximations were obtained by combination of the 2D measurements transverse inlet and pelvic height for men (r = 0.799, P < 0.05) as well as transverse inlet, obstetric conjugate, interspinous distance and pelvic depth for women (r = 0.855, P < 0.05). Conclusion We describe a precise and reproducible CT-based method for pelvic volumetry. A less time consuming but still reliable approximation can be achieved by combination of two to four 2D dimensions.

Which Foetal-Pelvic Variables Are Useful for Predicting Caesarean Section and Instrumental Assistance?

OBJECTIVE

To assess the variables useful to predict caesarean delivery (CD) and instrumental assistance, through the analysis of a large number of foetal-pelvic variables, using discriminant analysis.

MATERIALS AND METHODS

One hundred and fourteen pregnant women were included in this single-centre prospective study. For each mother-foetus pair, 43 pelvic and 18 foetal variables were measured. Partial least squares-discriminant analysis was performed to identify foetal-pelvic variables that could statistically separate the 3 delivery modality groups: spontaneous vaginal delivery (SVD), CD, and instrument-assisted delivery (IAD).

RESULTS

For the SVD versus CD model, voluminous foetuses and women with a narrow pelvic inlet had a greater risk for requiring CD. The most efficient variables for discrimination were the transverse diameter and foetal weight. The antero-posterior inlet and obstetric conjugate were considered in this model, with the former being a useful variable but not the latter. For the SVD versus IAD model, the most important variables were the foetal variables, particularly the bi-parietal diameter. Women with a reduced antero-posterior outlet diameter and a narrow pubic arch were more at risk of requiring an IAD.

CONCLUSION

The antero-posterior inlet was an efficient variable unlike the obstetric conjugate. The obstetric conjugate diameter should no longer be considered a useful variable in estimating the arrest of labour. Antero-posterior inlet diameter was a sagittal variable that should be taken into account. The comparison of sub-pubic angle and bi-parietal and antero-posterior outlet diameters was useful in identifying a risk of requiring instrumental assistance.

New MRI Criteria for Successful Vaginal Breech Delivery in Primiparae

Background

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.

Methods

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.

Results

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.

Conclusion

The additional use of ISD may predict successful vaginal breech delivery and may be superior to the CV, which is more commonly used.

Trial Registration

DRKS00009957

Pelvimetry by Three-Dimensional Computed Tomography in Non-Pregnant Multiparous Women Who Delivered Vaginally

Background

We assessed retrospectively the reference values of pelvic dimensions by 3D CT performed for non-obstetrical indications in non-pregnant multiparous women with a successful vaginal delivery. We further aimed to evaluate the impact of maternal short stature on these parameters.

Material/Methods

The 3D CT pelvimetry was performed retrospectively in 203 non-pregnant women selected consecutively if they had at least one singleton term delivery with head presentation and if there was no history of maternal or fetal birth trauma or cerebral palsy after childbirth. With standard sagittal and reformatted axial-oblique views, anteroposterior including three conjugates of pelvic inlet, transverse, posterior sagittal diameters of pelvic inlet, the plane of greatest diameter, the plane of least diameter, and pelvic outlet were measured. Selected obstetric parameters were collected.

Results

Overall, the pelvises had transverse oval appearance in inlet and size of the female pelvis. The diagonal conjugate was at least 15 mm longer than the obstetric conjugate. Women with short stature had lower maximal birth weight, and this was in accordance with their somewhat lower pelvic diameters.

Conclusions

The findings of this study present the reference values of the main planes of the true pelvis by 3D CT pelvimetry in a relatively large group of multiparous women who passed a trial of labor successfully. Overall, the pelvises had features of female pelvic bony structure although pelvic diameters were somewhat lower in multiparous women with short stature. The 3D pelvimetry with CT applications may be used as an adjunct to clinical and ultrasonographic examinations to rule out cephalopelvic dystocia in selected cases.

Assessment of bony pelvis and vaginally assisted deliveries

Objective. To evaluate whether pelvic measurements have any association with operative vaginal deliveries and the duration of the second stage of the delivery. Study design. A retrospective study of pregnant women at an increased risk of fetal-pelvic disproportion during 2000-2008 in North-Carelian Central Hospital. The mode of the vaginal delivery was chosen to represent the reference standard. The target condition was spontaneous vaginal delivery. Patients were divided into subgroups according to the size of the fetus and also by the parity to evaluate the variability reflecting differences in patient groups. Receiver operating characteristic (ROC) curves were established. Results. A total of 226 participants with fetal cephalic presentation delivered vaginally; of these, 184 women delivered spontaneously, and 42 women required operative vaginal delivery with vacuum extraction. There were no clinically or statistically significant differences between the size of the maternal pelvic outlet and the different modes of delivery types within these subgroups. With respect to the pelvic inlet and outlet, the areas under the curve in ROC were 0.566 with the P value of 0.18 and 95% confidence interval (CI) of 0.465-0.667 and 0.573 (95% CI: 0.484-0.622; P = 0.14). Conclusions. The maternal bony pelvic dimensions exhibited virtually no correlation with the need for operative vaginal deliveries.