1. An automated computer-based method of evaluating a segment of a lumen of a blood vessel, the method comprising the steps of: a. collecting a set of data regarding a lumen of length L using an optical coherence tomography system, the set comprising a plurality of cross sectional areas at a plurality of positions along the length; b. determining a vascular resistance ratio (VRR) using a processor and at least a portion of the set of data; and c. determining a characteristic of at least a portion of the segment disposed along the length L in response to the vascular resistance ratio.