title: Three-dimensional biomechanical properties of the human rectum evaluated with magnetic resonance imaging.
abstract: A method to evaluate the three-dimensional (3-D) geometry of the human gastrointestinal wall may be valuable for understanding tissue biomechanics, mechano-sensation and function. In this paper we present a magnetic resonance imaging (MRI) based method to determine rectal geometry and validation of data obtained in three volunteers. A specially designed rectal bag was filled in a stepwise manner while MRI and bag pressure were recorded. 3-D models of curvatures, radii of curvature, tension and stress were generated and the circumferential and longitudinal strains were calculated. The computed bag volumes corresponded to the infused volumes. A pronounced bag elongation and decrease in wall thickness was observed during the bag filling. The spatial distributions of the biomechanical parameters were distinctly different between individuals and non-homogeneous throughout the rectal wall due to its complex geometry. The average tension and stress increased as a function of infused volume and circumferential strain. The present study provides a method for characterizing the complex in vivo 3-D geometry of the human rectum. The non-homogenous spatial curvature distribution suggests that simple estimates of tension based on pressure and volume do not reflect the true 3-D biomechanical properties of the rectum.
authors.affiliation: Center for Visceral Biomechanics and Pain, Aalborg Hospital, Aarhus University Hospital, Denmark.
authors.forename: J B
authors.initials: JB
authors.lastname: Frøkjaer
authors.forename: D
authors.initials: D
authors.lastname: Liao
authors.forename: A
authors.initials: A
authors.lastname: Bergmann
authors.forename: B P
authors.initials: BP
authors.lastname: McMahon
authors.forename: E
authors.initials: E
authors.lastname: Steffensen
authors.forename: A M
authors.initials: AM
authors.lastname: Drewes
authors.forename: H
authors.initials: H
authors.lastname: Gregersen
mesh_terms: D000328:Adult; D000465:Algorithms; D019412:Anatomy, Cross-Sectional; D001696:Biomechanical Phenomena; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D011859:Radiography; D012007:Rectum / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000502:physiology*