Biopsy specimens were obtained from cadaveric RAs and discarded portions of clinical RAs to confirm the diagnosis of vascular trauma. To exactly calibrate the OCT images against the corresponding histopathologic sections, the vessel site where the biopsy specimen was obtained was marked externally at the location of the catheter, visualized by gross examination of the infrared light at the catheter tip (13). These image-guided biopsy specimens were embedded and frozen in cutting compound (Tissue-Tek O.C.T., Redding, CA), then sectioned at 5 μm and analyzed for endothelial integrity as described [15].