title: Placental recess accompanied by a T2 dark band: a new finding for diagnosing placental invasion.
abstract: Our aim was to assess the usefulness of a new magnetic resonance imaging (MRI) finding, the placental recess, for diagnosing placental invasion.
  
  
  
  This retrospective study included 51 patients (mean age 34.1 years, range 26-43 years) with suspected placental invasion who underwent cesarean section. Preoperative MRI was performed using a 1.5-T unit and included axial, sagittal, and coronal T2-weighted imaging (T2WI) with half-Fourier fast spin-echo sequences. Overall, 9 patients showed placental invasion, and 42 did not. Placental recess was defined as a placental deformity with contraction of the placental surface and outer rim of the uterus accompanied by a T2 dark band. Two radiologists independently assessed the presence of the placental recess and conventional findings including uterine bulging, abnormal placental vascularity, placental heterogeneous intensity on T2-weighted imaging (T2WI), and the T2 dark band. Fisher's two-sided exact test was used to compare findings between patients with and without placental invasion. Interobserver reliability was assessed using the kappa statistic.
  
  
  
  MRI features had interobserver reliability of >0.40. Placental recess yielded the highest kappa value (0.898). Significant differences were identified between patients with and without placental invasion regarding abnormal placental vascularity, placental heterogeneous intensity, a T2 dark band, and the placental recess on T2WI (p = 0.0282, 0.0003, 0.0003, <0.0001, respectively). The placental recess had sensitivity, specificity, positive and negative predictive values, and accuracy of 56, 100, 100, 91, and 92%, respectively.
  
  
  
  The placental recess was useful for diagnosing placental invasion, with high interobserver variability and accuracy.
authors.affiliation: Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan. tomomi.sato.e2@tohoku.ac.jp.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Diagnostic Radiology, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8574, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mori
authors.affiliation: Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Hasegawa
authors.affiliation: Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shigihara
authors.affiliation: Department of Obstetrics and Gynecology, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan.
authors.forename: Keiya
authors.initials: K
authors.lastname: Fujimori
authors.affiliation: Department of Diagnostic Pathology, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tasaki
authors.affiliation: Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima, Fukushima, 960-1295, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Shishido
mesh_terms: D000328:Adult; D002585:Cesarean Section; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010921:Placenta Accreta / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: Placenta accreta; Placenta increta; Placenta percreta; Placental invasion; Placental recess; T2 dark band