Fig. 1

Thickness measurement of the lower uterine segment (LUS) and definitions in 3 T MRI. Findings also demonstrate possible pitfalls in ultrasound diagnostics. Black arrow = inner border of the LUS, white arrow = outer border of the LUS, white double headed arrow = measured LUS-thickness, asterisk = lower uterine front wall, black point = amniotic fluid. a Myometrial LUS thickness measurement from the interface amniotic fluid/ LUS (black arrows) to the interface urinary bladder wall/LUS (white arrows) when LUS and urinary bladder are well definable. b Full LUS thickness measurement from the interface amniotic fluid/LUS (black arrows) to the interface urinary bladder wall/urine (white arrows), an alternative in cases with undefinable interface urinary bladder wall/ LUS. c Measurements for atypically located hysterotomy scars within the cervix (black arrow head). Measurements in typical location (thin arrows) might miss the correct diagnosis. d Demonstration of a hypointense LUS with characteristics of a uterine scar (black arrow heads) in an atypical location above the urinary bladder. Due to altered anatomy, common measurement standards would not be appropriate. e Illustration of an important limitation of full LUS thickness measurement. Due to the varying thickness of the urinary bladder wall and the interstitial tissue, this approach would overestimate the “real” LUS thickness up to several millimeters that had to be measured at the cesarean scar level (black arrow head). f Typical finding of a uterine dehiscence (abrupt interruption of the LUS/myometrium with change in diameter (white arrow head) and a lamellar-like thinning (thin arrows)). The thin dehiscent uterine front wall is often not definable from adjacent fetal head or urinary bladder wall and might be missed if LUS thickness was only measured in the typical location at the urinary bladder level