頸動脈プラーク病変における新生血管について―新画像法から―

Abstract

Carotid artery stenosis should be discussed in relation to its frequency or after NASCET, ECST and ACAS surveys. We normally examine a patient's stenotic frequency through the narrow directions of angiography. It is possible that such evaluation is insufficient. The importance of the futures of a carotid artery wall, which is largely studied through ultrasound sonography, is well understood. The presence of ulceration, the surface condition and sonographic intensity of the plaque are routinely examined, but we focused on the existence of neovascularization in plaques, one of the pathological factors leading to plaque hemorrhage and rupture. This pathological process appears to be responsible for carotid artery stenosis, occlusion and artery-to-artery embolisms. Harmonic image is a contrast specific imaging modality that males use of the nonlinear properties of ultrasound contrast agents by transmitting at the fundamental frequency and receiving at multiples of these frequencies. Pulse inversion harmonic image (PIHI), using pulse inversion to eliminate and strengthen the harmonic frequency, is more effective than conventional harmonic imaging. We can detect a tissue perfusion by contrast sonographic imaging with PIHI. This method has already been reported on the clinical fields, e.g. in imaging cardiac infarction, liver tumors, brain tumors and cerebrovascular diseases. There are 2 routes of vascular wall feeding: diffusion through the endothelium, and diffusion through the vasa vasorum from the adventitious to the outer part of the medium. There is no neovascularization at the inner side of the carotid artery, but some plaques are associated with neovascularization in themselves, so an attempt was made to detect such plaques by the intermittent and real time contrast sonographic imaging method with PIHI. The evaluation of neovascularization by the intermittent method and its classification as Type I to IV, according to the distribution of neovascular vessels in the plaque, have already been reported. The real time contrast sonographic imaging method with PIHI has revealed some characteristics of neovascularization: 1. The newly formed vessels from the advantitia are larger than the ones from the endothelium. 2. There is some anastomosis between the neovasculatures. 3. The distribution of neovascular vessels is concentrated in an inner part of plaque. In addition, these vessels run in a spiral pattern. 4. Neovascular circulation is related to the pulsation of the carotid artery. 5. It seems that many newly formed vessels sprout from the endothelium.