  Stroke is the second leading cause of disability worldwide. In order to
minimize disability, the goal of stroke treatment is to preserve tissue in the
area where blood supply is decreased but sufficient to stave off cell death.
Thrombectomy has been shown to offer fast and efficient reperfusion with high
recanalization rates. However, due to the inherent risks of thrombectomy,
indications including evidence of good collateral circulation should be
present. Currently, methods for evaluating collateral circulation are limited.
In this work, we present an automated technique to compute a collateral
circulation score based on differences seen in mean intensities between left
and right cerebral hemispheres in 4D angiography images. In this preliminary
study, we analyzed scans of 28 subjects: 4 with normal collateral circulation,
7 with good, 10 with intermediate, and 7 with poor collateral circulation,
(based on radiologist score) and found a good correlation between the computed
score and radiologist score (r2 = 0.71) and good separation between good and
intermediate/poor groups. This work shows promise as the first step in building
an automated collateral circulation score.
