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Figure 1 Calculation of the symmetry index and inflow/outflow angles. The symmetry index is measured as the ratio of the area of each border of the stenosis in the two-dimensional representation (a and b respectively, b being conventionally greater than a) (A). It ranges from 0% (asymmetry) to 100% (symmetry). The inflow/outflow angles are calculated from the diameter function (B). The stenosis inlet corresponds to the distance between the proximal boundary of the stenosis (P) and maximal obstruction (O) and the stenosis outlet to the area between maximal obstruction and the distal boundary of the stenosis (D). The inflow and outflow geometric angles are calculated as the angles of lines drawn between P and O and between O and D, respectively. The average angles correspond to the angles of the linear regressions of the diameter function between P and O and between O and D, respectively. The maximal angles are calculated as the maximal slopes of the inflow and outflow diameter function respectively. All angles are corrected for the tapering (ß) of the analyzed segment.
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