Shape matching algorithm to validate the tracing protocol of placental chorionic surface vessel networks

Abstract

Variability in placental chorionic surface vessel networks (PCSVNs) may mark developmental and functional changes in fetal health. Here we report a protocol of manually tracing PCSVNs from digital 2D images of post-delivery placentas and its validation by a shape matching method to compare the similarity between paint-injected and unmanipulated (uninjected and deflated vessels) tracings of PCSVNs. We show that tracings of unmanipulated vessels produce networks that are very comparable to the networks obtained by tracing paint-injected PCSVNs. We suggest that manual tracings of unmanipulated PCSVNs can extract features of PCSVN growth and structure that may impact fetal wellbeing.

A shape-context model for matching placental chorionic surface vascular networks

“…In comparison, 27 out of 38 matches were reported in Shah et al (2015) when small vessels are removed. The results in Table 1 suggest that our model is robust to parameter variations and capable of producing matches with a consistently high success rate.…”

“…Our data is obtained from 19 singleton fullterm birth placentas and is the same as that used in Shah et al (2015). The placentas in the data set were cleaned, paint-injected, and photographed in New York-Presbyterian Brooklyn Methodist Hospital (see, e.g., Fig.…”

“…4a). The PCSVN of each placenta, before and after the paint-injection, was then traced manually by a trained expert using the software GIMP and following the protocol described in Shah et al (2015). In short, the tracer distinguishes the placental chorionic surface arterial network from the subjacent venous network and uses different colors and pencil sizes to mark different vessel thicknesses and locations of the chorionic plate boundary and umbilical cord insertion.…”

“…During the paint-injection process, many important placental characteristics such as tortuosity and the number of vessel endpoints are altered. In (Shah et al, 2015), tracings of PCSVNs before and after paint-injection were shown to be comparable, with unsatisfactory matching scores. Their work concluded that the vascular networks of un-manipulated and paint-injected placentas are similar with roughly 71% confidence; however, the sources that caused the remaining 29% to mismatch were not identified.…”

Scaling of the surface vasculature on the human placenta

“…1. Figure 1(a) shows a hand-tracing [15] of the arteries on a digital image of a placenta. Starting from the umbilical cord (the origin) and moving along the edges (blood vessels), a vertex at the beginning of an edge is called the parent of the vertex at the end of that edge, and the vertex at the end of an edge is called a child of the parent vertex.…”