Introduction
Superb microvascular Imaging (SMI), a recent blood flow imaging
technique produced by Canon Medical Systems (Japan), employs a unique
algorithm to minimize motion artifacts by eliminating signals based on
the analysis of tissue movement. Compared to the conventional color
Doppler imaging methods, SMI can significantly better visualize
low-velocity blood flow in small vessels 1, which
allows depiction of the pathology and diagnoses of placental
abnormalities. Placental pathological examination is retrospectively
performed after delivery to evaluate placental abnormalities that could
have resulted in complications during pregnancy. However, if it is
possible to predict the pathological findings antenatally using
ultrasound examination, it would be useful to understand the disease
state and predict the prognosis. Therefore, we investigated the
evaluation of placental pathologic findings using SMI.
Using SMI, in a normal placenta, villous blood vessels can be visualized
from the umbilical cord insertion to the stem villi and terminal villi.
Additionally, slow blood flow in the intervillous space from the spiral
artery is also visualized as a ”scatter” that matches the heart rate of
the mothers. In contrast, we previously demonstrated, in placenta
increta, not only the thin myometrium with invasive placental tissue,
but also the avascularity of the peripheral villous tree and congested
stem vessels using SMI 2.
Furthermore, in a pilot study, we demonstrated various placental
pathological findings antenatally using SMI and compared them with
placental pathological findings 3. According to our
investigations, pathologically confirmed placental infarctions are
expressed in echo-free space without both villous trees and background
scatters. In cases of avascular villi, only background ’scatter’ was
expressed in SMI. Consequently, it was confirmed that the findings of
SMI match the pathological findings.
In the present study, in order to
demonstrate objectivity and reproducibility, the diagnostic accuracies
of various ultrasound findings of the pathologic placenta were
evaluated. The aim of the present study was to clarify the accuracy of
antenatal ultrasound evaluation using SMI for placental pathological
findings.