In utero perfusing fraction maps in normal and growth restricted pregnancy measured using IVIM echo-planar MRI

The aim of this study was to measure and portray blood movement in the placenta in vivo in normal and growth restricted pregnancies, using Intra Voxel Incoherent Motion (IVIM) magnetic resonance imaging. Thirteen patients with apparently normal healthy pregnancies were scanned at 31+/-7 (mean+/-s.d.) weeks gestation and seven patients with intrauterine growth restriction (IUGR) were scanned at 31+/-4 weeks. A region of interest (ROI) was defined encompassing the placenta between the decidual and chorionic plates. The volume of moving blood within each imaging voxel of the ROI was then calculated as a percentage of the total voxel volume (f per cent). This information was colour coded to produce maps of moving blood volume. The placenta was segmented length ways into two zones of approximately equal area, termed inner and outer, the latter being adjacent to the uterine wall. f was fitted for the average in the outer zone (f(out)) and inner zone (f(in)). The parameter (f(out)-f(in)) was then calculated for each subject. This was positive in 12/13 of the normal cases and zero for one case (+10 per cent+10, mean+/-s.d.). For pregnancy affected by IUGR this value was negative in all cases (-4 per cent+/-3). Perfusion fraction mapping identified differences in function within the normal placenta in vivo, and between the placentae of normal and IUGR pregnancies. The technique has potential applications in managing, and investigating the aetiology of, pregnancy compromise.