Objective Combined use of optical coherence tomography (OCT) and intravascular ultrasound (IVUS) is a potential method for accurate assessment of plaques characteristics and vulnerability. five atherosclerotic-model rabbits and a swine were imaged. Images were obtained in these animals without complications. Linear regression shows a high correlation between rabbit plaque sizes decided from histology and OCT/IVUS estimated plaque sizes (R2=0.955 P<0.001 between OCT and histology; R2=0.970 P<0.001 between IVUS and histology). Classification of plaque types and quantitative analysis of plaque sizes were performed using cadaver coronary segments (n=14). Conclusions For the first time this study shows that an integrated intracoronary OCT-IVUS system is usually feasible and safe to use to detect atherosclerotic plaques. This technique provides high resolution and deep penetration capability simultaneously which can facilitate a more powerful tool to explore the development of plaques and may lead to a more accurate assessment of vulnerable plaques in patients. cap fibroatheroma is usually shown in Fig. 1 row I. IVUS enables the visualization of the layer structure of the artery wall. Intimal thickening and a low density acoustic signal region (denoted by the arrow in Fig. 1 Ia) demonstrate plaque in the IVUS image. However this image also illustrates the inability of IVUS to determinate the plaque type and the plaque cap boundary. At the same site in the OCT image (Fig. 1 Ib) a homogenous-boundary and weak-signal region under a high-signal region indicates that this plaque is usually a necrotic/lipid plaque with an overlying fibrous cap. Also the minimum thickness of the cap can be easily measured to be ~200 μm by OCT which is usually indicative of a thick cap fibroatheroma. The classification Mouse monoclonal antibody to Hsp70. This intronless gene encodes a 70kDa heat shock protein which is a member of the heat shockprotein 70 family. In conjuction with other heat shock proteins, this protein stabilizes existingproteins against aggregation and mediates the folding of newly translated proteins in the cytosoland in organelles. It is also involved in the ubiquitin-proteasome pathway through interaction withthe AU-rich element RNA-binding protein 1. The gene is located in the major histocompatibilitycomplex class III region, in a cluster with two closely related genes which encode similarproteins. of plaque type is usually validated by the corresponding histology photo (Fig. 1 Ic) which shows loose necrotic material. This area is usually covered by easy muscle and fibrous proliferations at the luminal surface which is usually consistent with a fibrous cap. All IVUS-OCT images of rabbit aortas Ferrostatin-1 were matched with histology for accuracy correlation. Linear regression showed a high correlation between plaque circumference percentage (PCP defined as the circumference of lumen where there is usually plaque divided by the entire lumen circumference) decided from histology and the estimated PCP of OCT and IVUS (R2=0.955 P<0.001 between OCT and histology; R2=0.970 P< 0.001 between IVUS and histology). Physique 1 Top row: imaging of rabbit abdominal aorta with OCT-IVUS system Second a female Yorkshire white swine was imaged by conventional femoral access and angiography guidance under the same flushing procedure as the rabbits to test the feasiblity of translating this technology for clinical applications (Figs. 1 row II). In the IVUS image (Fig. 1 IIa) the three-layer structure of the swine artery (wall thickness ~0.4 mm) is barely visualized with an IVUS resolution of 60 μm. In Fig. 1 IIb the OCT image differentiates the three structural layers of the artery wall. Last Ferrostatin-1 we collected 14 cadaver coronary arteries from 6 patients who died of complications from ACS or were diagnosed with atherosclerotic heart disease. Representative OCT-IVUS image pairs of a fibrous plaque calcified plaque and lipid plaque from different cadavers are shown in Fig. 1 row III IV and V respectively. An acoustic shadow in Fig. 1 IVa shows the location of a calcified plaque. However it is usually difficult Ferrostatin-1 to classify the plaque morphology in Fig. 1 IIIa and Fig. 1 Va using IVUS imaging because of intrinsically limited resolution and low Ferrostatin-1 soft tissue contrast. The OCT imaging is able to classify plaque morphology by optical scattering contrast of different tissue types (see Figure 1 legend). However with limited penetration depth the OCT image cannot provide a clear visualization of the media and adventitia layer at this intima-thickening coronary segment. These results clearly demonstrate Ferrostatin-1 the complementary nature of OCT and IVUS imaging. A total of 28 OCT-IVUS image pairs obtained from 14 plaque samples (two pairs from each sample pull-back and repull-back) were analyzed for quantitative validation of the technique’s accuracy and reproducibility. Linear regression showed a high accuracy (R2=0.911 P<0.001 for OCT-histology; R2=0.923 P<0.001 for IVUS-histology) and high reproducibility (R2=0.937 P<0.001 for OCT and R2=0.971 P<0.001 for IVUS) of PCP measurements. Our fully integrated imaging system has high resolution to identify the thin cap and deep penetration to visualize the necrotic core simultaneously..