Placental 3-D power Doppler angiography--regional variation and reliability of two ultrasonic sphere biopsy techniques.

Three-dimensional power Doppler angiography and 4D View allows quantification of placental "vascularity" using sonobiopsy or manual tracing. We used two vascular "biopsy" techniques: nontargeted sphere placement and systematic uniform random sphere placement (SURS). We hypothesised that random application of spheres would result in less reliability and the basal zone would display higher values than the chorionic zone. Forty women between 18+6 to 21+6 weeks gestation were recruited. A single volume of the placenta was acquired. Data was analysed twice by a single observer. Significantly higher values were seen for all vascular indices in the basal zone. Reliability was greatest for the whole placental technique with intraclass correlation coefficients of 0.9 and limits of agreement for flow index (FI) of -3.81 to 2.50 (equivalent to -7.8% to 5.1%) compared with 0.6 and -13.2 to 18.3 (-64.6% to 78.2%) for the nontargeted sphere technique. Whole placental values are more reliable than biopsy techniques with significantly different results seen with each technique.