File:Human placenta vascular 01.jpg

"A placenta was harvested immediately after elective caesarean section and placed in a water bath at 37°C. The umbilical cord was cut off approximately 5 cm proximal to the insertion to the placenta. The amnion was cut off as well. The blood vessels of the umbilical cord were catheterized using three venous catheters (size 17). The venous catheters were fixed to the blood vessels using polyester sutures (2-0 Ethicon) and the umbilical cord was clamped using a suture to prevent reflux of the injected solutions. The placenta was then perfused using saline with 5000 IU/L heparin [11]. The solution was heated to 37°C and 500 mL was injected into the two umbilical arteries with a pressure-controlled pump using the sphygmanometric principle. Contrast mix 1 was then injected using the pump with a pressure ≤ 60 mmHg [12]. During injection, the placenta was placed in a water bath at a temperature of 35-40°C to ensure that the contrast solution remained liquid. It was then positioned in the MR scanner and the 3D MRA protocol was followed by subsequent fixation with 4% formalin or 2.8% FineFix (Milestone Medical Technologies, USA). MRA showed vessels from a number of different generations starting with the cotelydonary arteries branching off into primary, secondary and tertiary stem vessels: even 6th generation blood vessels were visible. Subsequently, the placenta was subjected to CTA (Figure 4), which also showed branching of the vessels down to the 6th generation of stem vessels. In general, MRA was capable of showing considerably more very small vessels than CTA, giving the overall impression that the quality of MRA was as good or better than the results of conventional CTA."

(text from original reference)