title: Detection of suspected placental invasion by MRI: do the results depend on observer' experience?
abstract: OBJECTIVE
  To evaluate the diagnostic value of previously described MR features used for detecting suspected placental invasion according to observers' experience.
  
  
  METHODS
  Our population included 25 pregnant women (mean age 35.16) investigated by prenatal MRI (1.5T, T1- and T2-weighted MR-sequences without i.v. contrast), among them 12 with histopathologically proven placental invasion and 13 women (52%) without placental invasion used as control group. Two senior and two junior radiologists blindly and independently reviewed MR-examinations in view of 6 previously defined MR-features indicating presence and degree of placental invasion (placenta increta, accreta or percreta). For each reader the sensibility, specificity, and receiver operating curve (ROC) were calculated. Interobserver agreements between senior and junior readers were determined. Stepwise logistic regression was performed including the 6 MR-features predictive of placental invasion.
  
  
  RESULTS
  Demographics between both groups were statistically equivalent. Overall sensitivity and specificity for placental invasion was 90.9% and 75.0% for seniors and 81.8% and 61.8% for juniors, respectively. The best single MR-feature indicating placental invasion was T2-hypointense placental bands (r(2)=0.28), followed by focally interrupted myometrial border, infiltration of pelvic organs and tenting of the bladder (r(2)=0.36). Interobserver agreement for detecting placental invasion was 0.64 for seniors and 0.41 for juniors, thus substantial and moderate, respectively. Seniors detected placental invasion and depth of infiltration with significantly higher diagnostic certitude than juniors (p=0.0002 and p=0.0282, respectively).
  
  
  CONCLUSIONS
  MRI can be a reliable and reproducible tool for the detection of suspected placental invasion, but the diagnostic value significantly depends on observers' experience.
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland. leonor.alamo@chuv.ch
authors.forename: Leonor
authors.initials: L
authors.lastname: Alamo
authors.forename: Anass
authors.initials: A
authors.lastname: Anaye
authors.forename: Jannick
authors.initials: J
authors.lastname: Rey
authors.forename: Alban
authors.initials: A
authors.lastname: Denys
authors.forename: Georg
authors.initials: G
authors.lastname: Bongartz
authors.forename: Sylvain
authors.initials: S
authors.lastname: Terraz
authors.forename: Simona
authors.initials: S
authors.lastname: Artemisia
authors.forename: Reto
authors.initials: R
authors.lastname: Meuli
authors.forename: Sabine
authors.initials: S
authors.lastname: Schmidt
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015588:Observer Variation; D010921:Placenta Accreta / Q000473:pathology*; D011247:Pregnancy; D011361:Professional Competence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity