Estimates of the levator ani subtended volume based on magnetic resonance linear measurements.
CONCLUSIONS
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.


CONCLUSIONS
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.
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Antonio A
AA
Rodrigues Junior
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Maria C
MC
Herrera-Hernadez
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Renee
R
Bassalydo
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Mona
M
McCullough
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
H Leigh
HL
Terwilliger
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Katheryne
K
Downes
Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, College of Medicine Tampa, University of South Florida, Florida.
Lennox
L
Hoyte
D059925:Anatomic Landmarks; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical; D015588:Observer Variation; D017773:Pelvic Floor / Q000000981:diagnostic imaging*; D056887:Pelvic Organ Prolapse / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012984:Software
H-line; M-line; levator ani subtended volume; levator hiatus; pelvic floor; pelvic organ prolapse; width of levator hiatus