title: In vivo estimation of perineal body properties using ultrasound quasistatic elastography in nulliparous women.
abstract: OBJECTIVE
  The perineal body must undergo a remarkable transformation during pregnancy to accommodate an estimated stretch ratio of over 3.3 in order to permit vaginal delivery of the fetal head. Yet measurements of perineal body elastic properties are lacking in vivo, whether in the pregnant or non-pregnant state. The objective of this study, therefore, was to develop a method for measuring perineal body elastic modulus and to test its feasibility in young nulliparous women.
  
  
  METHODS
  An UltraSONIX RP500 ultrasound system was equipped with elastography software. Approximately 1 Hz free-hand sinusoidal compression loading of the perineum was used to measure the relative stiffness of the perineal body compared to that of a custom reference standoff pad with a modulus of 36.7 kPa. Measurements were made in 20 healthy nulliparous women. Four subjects were invited back for second and third visits to evaluate within- and between-visit repeatability using the coefficient of variation.
  
  
  RESULTS
  The mean ± SD elastic compression modulus of the perineal body was 28.9 ± 4.7 kPa. Within- and between-visit repeatability averaged 3.4% and 8.3%, respectively.
  
  
  CONCLUSIONS
  Ultrasound elastography using a standoff pad reference provides a valid method for evaluating the elastic modulus of the perineal body in living women.
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA. Electronic address: luyunc@umich.edu.
authors: Luyun
authors: L
authors: Chen
authors: School of Nursing and Women׳s Studies, University of Michigan, Ann Arbor, MI, USA.
authors: Lisa Kane
authors: LK
authors: Low
authors: Division of Gynecology, Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA.
authors: John Ol
authors: JO
authors: DeLancey
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors: James A
authors: JA
authors: Ashton-Miller
mesh_terms: D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D017773:Pelvic Floor / Q000000981:diagnostic imaging / Q000502:physiology; D010502:Perineum / Q000000981:diagnostic imaging* / Q000502:physiology; D019047:Phantoms, Imaging
keywords: Elastic modulus; Perineal body; Ultrasound elastography