The value of specific MRI features in the evaluation of suspected placental invasion

• Published in: Magnetic resonance imaging 2007, Vol.25 (1), p.87-93
• Main Authors: Lax, Allison, Prince, Martin R, Mennitt, Kevin W, Schwebach, J. Reid, Budorick, Nancy E
• Format: Article
• Language: English
• Subjects: Case-Control Studies; Female; Humans; Magnetic Resonance Imaging - methods; MRI; Placenta; Placenta - diagnostic imaging; Placenta - pathology; Placenta accreta; Placenta Accreta - diagnosis; Placenta Accreta - diagnostic imaging; Placenta Accreta - pathology; Placenta Previa - diagnosis; Placenta Previa - diagnostic imaging; Placenta Previa - pathology; Placental invasion; Pregnancy; Pregnancy Trimester, Second; Pregnancy Trimester, Third; Radiology; Retrospective Studies; Ultrasonography
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2006.10.007

Abstract Objective The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. Subjects and Methods A retrospective review of the prenatal MR scans of 10 patients with a diagnosis of placenta accreta, placenta increta or placenta percreta made by pathologic and clinical reports and of 10 patients without placental invasion was performed. Two expert MRI readers were blinded to the patients' true diagnosis and were asked to score a total of 17 MRI features of the placenta and adjacent structures. The interrater reliability was assessed using κ statistics. The features with a moderate κ statistic or better ( κ >.40) were then compared with the true diagnosis for each observer. Results Seven of the scored features had an interobserver reliability of κ >.40: placenta previa ( κ =.83); abnormal uterine bulging ( κ =.48); intraplacental hemorrhage ( κ =.51); heterogeneity of signal intensity on T2 -weighted (T2W) imaging ( κ =.61); the presence of dark intraplacental bands on T2W imaging ( κ =.53); increased placental thickness ( κ =.69); and visualization of the myometrium beneath the placenta on T2W imaging ( κ =.44). Using Fisher's two-sided exact test, there was a statistically significant difference between the proportion of patients with placental invasion and those without placental invasion for three of the features: abnormal uterine bulging (Rater 1, P =.005; Rater 2, P =.011); heterogeneity of T2W imaging signal intensity (Rater 1, P =.006; Rater 2, P =.010); and presence of dark intraplacental bands on T2W imaging (Rater 1, P =.003; Rater 2, P =.033). Conclusions MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.