title: Quantitative ultrasound assessment of the rat cervix.
abstract: OBJECTIVE
  The purpose of this research was to detect cervical ripening with a new quantitative ultrasound technique.
  
  
  METHODS
  Cervices of 13 nonpregnant and 65 timed pregnant (days 15, 17, 19, 20, and 21 of pregnancy) Sprague Dawley rats were scanned ex vivo with a 70-MHz ultrasound transducer. Ultrasound scatterer property estimates (scatterer diameter [SD], acoustic concentration [AC], and scatterer strength factor [SSF]) from the cervices were quantified and then compared to hydroxyproline and water content. Insertion loss (attenuation) was measured in 3 rats in each of the 6 groups. Discriminant analysis was used to predict gestational age group (cervical ripening) from the ultrasound variables SD, SSF, and AC.
  
  
  RESULTS
  Differences were observed between the groups (SD, AC, and SSF; P < .0001). Quantitative ultrasound measures changed as the cervix ripened: (1) SD increased from days 15 to 21; (2) AC decreased from days 15 to 21; and (3) SSF was the greatest in the nonpregnant group and the least in the day 21 group. Cervix hydroxyproline content increased as pregnancy progressed (P < .003) and correlated with group, SD, AC, and SSF (P < .001). Discriminant analysis of ultrasound variables predicted 56.4% of gestational group assignment (P < .001) and increased to 77% within 2 days of the predicted analysis. Cervix insertion loss was greatest for the nonpregnant group and least for the day 21 group.
  
  
  CONCLUSIONS
  Quantitative ultrasound predicted cervical ripening in the rat cervix, but before use in humans, quantitative ultrasound will need to predict gestational age in the later days of gestation with more precision.
authors.affiliation: Department of Maternal Child Nursing, University of Illinois at Chicago, IL 60612, USA. bmcfar1@uic.edu
authors.forename: Barbara L
authors.initials: BL
authors.lastname: McFarlin
authors.forename: William D
authors.initials: WD
authors.lastname: O'Brien
authors.forename: Michael L
authors.initials: ML
authors.lastname: Oelze
authors.forename: James F
authors.initials: JF
authors.lastname: Zachary
authors.forename: Rosemary C
authors.initials: RC
authors.lastname: White-Traut
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D020070:Cervical Ripening; D002584:Cervix Uteri / Q000000981:diagnostic imaging* / Q000378:metabolism; D016002:Discriminant Analysis; D005260:Female; D006909:Hydroxyproline / Q000378:metabolism; D066298:In Vitro Techniques; D009584:Nitrogen / Q000378:metabolism; D011247:Pregnancy; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D014463:Ultrasonography
chemical_list: D009584:Nitrogen; D006909:Hydroxyproline