Methods comprising the use of optical coherence tomography to examine a harvested conduit for its suitability for grafting, to examine a candidate conduit prior to harvesting for coronary artery bypass graftings to assess the quality of an anastomosis, to assess the quality of the suturing of a small vessel or duct with a suture coated with a contrast agent, and to detect coronary artery disease in a harvested donor heart prior to transplantation.