ABSTRACT
CONDENSATION: A mathematical formula to estimate the levator ani subtended volume parameter based on magnetic resonance imaging linear measurements from one axial and one sagittal view. OBJECTIVE: To estimate the levator ani subtended volume based on MRI linear measurements. METHODS: The 3D Slicer was used to obtain the Levator Ani Subtended Volume (LASV) from 35 women with Pelvic Organ Prolapse (POP), that were assumed as reference values. The linear measurements that best fitted our criteria were chosen. The subjects were divided in two groups, 1 and 2. The coefficients of the mathematical equation were obtained from group 1 through a regression analysis using the 3D rendering volume as a dependent variable. To validate the mathematical equation, two observers, blinded to POP ordinal stages, performed new measurements. The 3D rendering and the estimated volumes were compared and correlated with POP-Q measurements and POP ordinal stages. A residual analysis was performed to validate the mathematical equation. Finally, a reliability analysis was performed. RESULTS: The predictors chosen were M-line, H-line, and width of levator hiatus. An equation to estimate the volume was determined: eLASV = -72.838 + 0.598H-line + 1.217M-line + 1.136WLH1. The estimated values showed similar correlation with POP-Q individual measurements and ordinal stages. The residual analysis showed normal distribution of the estimate values and the errors, from both observers. The intra and interclass evaluation of the estimated values indicated a good reliability of the eLASVs. CONCLUSION: The LASV can be estimated using well known Magnetic Resonance linear measurements, showing good correlation with correspondent 3D rendering volumes. The clinical relevance of this parameter should be proved in further studies.
Subject(s)
Image Interpretation, Computer-Assisted/methods , Magnetic Resonance Imaging , Models, Theoretical , Pelvic Floor/diagnostic imaging , Pelvic Organ Prolapse/diagnostic imaging , Anatomic Landmarks , Female , Humans , Imaging, Three-Dimensional , Observer Variation , Predictive Value of Tests , Prognosis , Reproducibility of Results , Retrospective Studies , Severity of Illness Index , SoftwareABSTRACT
OBJECTIVE: We describe a new parameter based on magnetic resonance 3-dimensional (3D) reconstructions proposed to evaluate levator ani muscle (LAM) laxity in women with pelvic organ prolapse (POP). STUDY DESIGN: This is an institutional review board-approved, retrospective chart review of 35 women with POP, stages I-IV. The 3D Slicer software package was used to perform 2-dimensional and 3D measurements and the levator ani subtended volume (LASV) was described. Basically, the LASV represents the volume contained by LAM between 2 planes, which coincides with pubococcygeal line and H line. Correlations among measurements, ordinal POP stages, POP Quantification (POPQ) individual measurements, and validated questionnaires were performed. RESULTS: The LASV differentiated major (III and IV) from minor (I and II) POPQ stages, which positively correlated to POP stages and POPQ individual measurements. CONCLUSION: The LASV is a promising parameter to evaluate the LAM laxity.
