抄録
Since the surveys of the NASCET, ECST and ACAS, it has been debatable whether the carotid artery stenosis rate should be evaluated or not. The stenosis rate in patients is usually checked through angiography in limited orentations, and therefore some data may be lacking. Harmonic imaging is a contrast-specific imaging modality that can exploit the nonlinear properties of ultrasound contrast agents by transmitting at the fundamental frequency and receiving at multiples of these frequencies. Pulse inversion harmonic imaging (PIHI), using pulse inversion to eliminate and strengthen the harmonic frequency, is more effective than conventional harmonic imaging. It is possible to detect tissue perfusion by contrast sonographic imaging with PIHI, and its clinical application has already been reported, for example in myocardial infarction. liver tumor, brain tumor and cerebrovascular diseases.
The importance of carotid artery wall characteristics is now acknowledged. and this is largely studied using ultrasonography. Ulceration, surface condition and the sonographic intensity of plaque can be examined, although we are now focusing on the detection of neovascularization in plaque using contrast sonographic imaging with PIHI. Plaque neovascularization is one of the pathological factors responsible for plaque hemorrhage and rupture, and is suggested to be involved in carotid artery stenosis. occlusion and artery-to-artery embolism.
There are several routes of vascular wall feeding. One is diffusion through the endothelium and the other is the vasa vasorum from the adventitious to the outer part of the media. Therefore there is no neovascularization on the inner side of the carotid artery. However, as some plaques show neovascularization within them. we have tried to detect them by intermittent and real time contrast sonographic imaging with PIHI. We have already reported the evaluation of neovascularization by the intermittent method and classified it as type l to type IV according to the distribution of the neovasculature in the plaque.
Real-time contrast sonographic imaging with PIHI has revealed some characteristics of neovascularization, as follows.
1.The neovascular vessels from the adventitia are larger than those from the endothelium.
2. There is some anastomosis between the neovascular vessels.
3. The distribution of neovascular vessels is predominant in the inner part of the plaque, an in addition, they show a spiral course.
4. The neovascular circulation is related to the pulsation of the carotid artery.
5. Many neovascular vessels originate from the endothelium.
Neovascularization can also be observed by real-time 3D CAWP using a matrix array.
