International Circulation: There are many studies on OCT in the assessment of extant coverage such as evaluating vascular healing after coronary stenting. So， what are the advantages of OCT in this area and would the application of OCT decrease the risk of late-stent thrombosis.

Prof. Akasaka: I see， it is an important point. I think the great advantage of OCT is its higher resolution. The resolution of OCT is ten times higher that IVUS， so we can get about 10 micron level images by OCT. And after the development of drug-eluting stents， neo-tissue coverage after stent deployment is less than 100 microns. By previously using IVUS， we could not get this kind of think neo-tissue， only OCT can identify neo-tissue coverage after drug-eluting stent deployment. And also， we can identify a malapposition of stent by OCT clearly. So， we are expecting to identify the mechanism of late stent thrombosis.

International Circulation: And obviously that is a real advantage. How about limitations? One limitation is the need to occlude the vessel during the use of OCT， so what are the advances in OCT in this area and what are the improvements we can make in OCT?

Prof. Akasaka: Right， this is also a very important point. Time domain OCT needed to occlude the vessel to flush the blood to get a clear image. But with the recently developed frequency domain OCT we do not need to occlude the vessel， just to flush from the guiding cluster is enough to get the image. So， in the near future we will be able to get a clear image without balloon occlusion.

International Circulation: And， how about the benefits of OCT in detecting vulnerable plaques in the coronary artery. Can you share your experience in using either OCT or IVUS in diagnosis of coronary heart disease?

Prof. Akasaka: Yes， histology shows us that there are a lot of characteristics in vulnerable plaques. One of the typical characteristics is thin-cap coverage over lipid. By IVUS we cannot identify the thin-cap， but by using an OCT we can clearly identify a very thin cap up to 10 micron level， so by using OCT we can clearly identify thin-cap fibrous atheroma. In addition， if we use OCT to follow this kind of atheroma， we can get a natural history and we can check the effect of drugs. And also， we can get information after stent deployment on that kind of atheroma.

International Circulation: Are there any other advances? You mentioned before being able to use OCT without occluding the vessel. Are there any other new advances that you can talk about， and perhaps also talk about the use of virtual histology， and any other advances or new developments in the field?

Prof. Akasaka: I see， yes. We can expect a similar virtual histology as with analysis by OCT， analysis of backscatter and attenuation， or as information， using OCT allows us to clearly differentiate between differences of histology in plaque. So， with IVUS virtual history we can do that but also OCT can produce more detail with which to identify the plaque characteristics.