How to measure stenosis?
The most accepted way is to calculate the ratio of the luminal diameter of the stenotic vessel segment to the luminal diameter of a normal-appearing vessel segment. This method was adopted from conventional angiography. Although well established, this method may lack precision because it uses a 2D representation of a 3D object to estimate a stenosis. It also relies on the ability to select a normal segment of vessel for use as a reference. This may be problematic because even normal vessels taper distally, and it may be difficult to find an area adjacent to a stenosis that is not aneurysmal or affected by poststenotic dilation. CTA and MRA offer the unique opportunity to evaluate the stenosis precisely, by measurement of the decrease in luminal cross-sectional area. With the development of more automated vessel analysis tools, measurements of luminal cross-sectional areas are expected to become the reference standard.
