Application progress of MRI in diagnosis of placenta accrete spectrum

Placenta accreta spectrum (PAS) is the most dangerous iatrogenic complication of cesarean potentially leading to massive intra-partum haemorrhage or even matemal and fetal death, if were not diagnosed and treated in a timely manner. In recent years, with the improvement of magnetic resonance imaging (MRI) technology and the discovery of some new signs, such as placental dark band, placental recess and bulge, especially conventional heavy T₂WI spin echo combined with diffusion weighted imaging (DWI) which is more sensitive to identify the dark zone in the placenta and the boundary between the placenta and the myometrium, MRI has been significantly improved the accuracy of PAS diagnosis. In this review, we described the pathological classification, risk factors of PAS, imaging techniques, signs of PAS on MRI, and MRI's advantages and disadvantages. (authors)