title: Automatic ultrasound technique to measure angle of progression during labor.
abstract: OBJECTIVE
  To evaluate the accuracy and reliability of an automatic ultrasound technique for assessment of the angle of progression (AoP) during labor.
  
  
  METHODS
  Thirty-nine pregnant women in the second stage of labor, with fetus in cephalic presentation, underwent conventional labor management with additional translabial sonographic examination. AoP was measured in a total of 95 acquisition sessions, both automatically by an innovative algorithm and manually by an experienced sonographer, who was blinded to the algorithm outcome. The results obtained from the manual measurement were used as the reference against which the performance of the algorithm was assessed. In order to overcome the common difficulties encountered when visualizing by sonography the pubic symphysis, the AoP was measured by considering as the symphysis landmark its centroid rather than its distal point, thereby assuring high measurement reliability and reproducibility, while maintaining objectivity and accuracy in the evaluation of progression of labor.
  
  
  RESULTS
  There was a strong and statistically significant correlation between AoP values measured by the algorithm and the reference values (r = 0.99, P < 0.001). The high accuracy provided by the automatic method was also highlighted by the corresponding high values of the coefficient of determination (r2= 0.98) and the low residual errors (root mean square error = 2°27' (2.1%)). The global agreement between the two methods, assessed through Bland-Altman analysis, resulted in a negligible mean difference of 1°1' (limits of agreement, 4°29').
  
  
  CONCLUSIONS
  The proposed automatic algorithm is a reliable technique for measurement of the AoP. Its (relative) operator-independence has the potential to reduce human errors and speed up ultrasound acquisition time, which should facilitate management of women during labor. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: F
authors.identifier: http://orcid.org/0000-0002-9537-8334
authors.initials: F
authors.lastname: Conversano
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Peccarisi
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Pisani
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Di Paola
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: T
authors.initials: T
authors.lastname: De Marco
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Franchini
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Greco
authors.affiliation: Department of Obstetrics and Gynecology, Hospital Santa Caterina Novella, Galatina, Lecce, Italy.
authors.forename: G
authors.initials: G
authors.lastname: D'Ambrogio
authors.affiliation: National Research Council, Institute of Clinical Physiology, Lecce, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Casciaro
mesh_terms: D000328:Adult; D000465:Algorithms; D005240:Feasibility Studies; D005260:Female; D005323:Fetal Monitoring; D005333:Fetus / Q000000981:diagnostic imaging*; D006801:Humans; D007746:Labor Presentation; D007748:Labor Stage, Second / Q000502:physiology*; D007743:Labor, Obstetric / Q000502:physiology*; D011247:Pregnancy; D011631:Pubic Symphysis / Q000033:anatomy & histology; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal
keywords: childbirth; intrapartum ultrasound; labor monitoring; medical decision support; progression angle; ultrasonic imaging