The coronary artery has been successfully imaged by OCT in various studies.9 Carotid arteries, however, having large diameters and high blood flow rate, are not easily imaged with conventional Time Domain OCT systems owing to their slow imaging speed. There were only a handful of studies attempting to image the carotid artery in vivo.10,11 Recently, a new state-of-the-art OCT system (Lightlab Imaging, St. Jude Medical Inc. St. Paul, Minnesota, USA) has been cleared by the FDA for clinical use in coronary imaging. With this high speed OCT system, a pilot study has been conducted on human to image stented carotid arteries after their CAS procedures.12 Images obtained could clearly show the vessel wall anatomy and could delineate the degree of stent apposition to the vessel wall, plaque prolapse through the stent tines and the presence of a dissection flap (i.e., a tear in one of the layers of the vessel wall) or mural thrombus. These are promising results. To date, however, no animal studies on OCT imaging of carotid arteries using the state-of-the-art high speed OCT system have been conducted and experimental details have not been fully optimized. In the study described above, un-occluded saline or contrast injection was quickly ruled out because of several unsuccessful attempts and the images were obtained using two occlusion balloons in the common and external carotid arteries. Our study reported in this paper therefore, was in part to define blood clearing technique to improve OCT imaging. If a proper blood flushing protocol is not developed there are side effects such as stroke, aneurysm, and poor image quality.