Genta Hashimoto

Localized elevation of shear stress is related to coronary plaque rupture: a 3-dimensional intravascular ultrasound study with in-vivo color mapping of shear stress distribution.

OBJECTIVES The purpose of the present study was to assess the relationship between shear stress distribution and coronary plaque rupture by means of a new color-mapping program of shear stress with 3-dimensional intravascular ultrasound (IVUS). BACKGROUND Various in-vitro studies have demonstrated that shear stress of the vascular lumen is one of the important determinants of coronary plaque vulnerability. However, the in-vivo relationship between shear stress and plaque rupture is still unclear. METHODS In the present study, 3-dimensional IVUS was used to obtain spatial information on luminal geometry from 20 patients with acute coronary syndrome having a distinct ulcerative lesion. These 3-dimensional contours for each lumen were first reconstructed into mesh polygons, and then analyzed by means of a program for calculating the fluid dynamics. The flow was considered to be a constant laminar one. Then, colorized mappings of the distribution of the streamline, blood pressure, and shear stress were performed. The original luminal contour for each ruptured lesion was obtained by smoothing and extrapolation. RESULTS All patients had a coronary plaque rupture in the proximal or top portion of the plaque hill. In the color mapping, localized elevation of blood pressure and shear stress could be observed on each plaque surface. The shear stress concentration was frequently correlated with the plaque rupture site (kappa = 0.79). CONCLUSIONS Although the absolute value of shear stress is not sufficient to directly provoke mechanical destruction of the fibrous cap, localized high shear stress might be a trigger of fibrous cap rupture.

Late giant coronary aneurysm associated with a fracture of sirolimus eluting stent: A case report

A 73-year-old female underwent percutaneous coronary intervention (PCI) because of stable angina. An elective PCI for the RCA lesion was first performed with deploying sirolimus eluting stents (SES). Three weeks later, PCI was also provided in the residual LAD lesion. Eight months later, she presented with new angina. CAG revealed an in-stent restenosis in the mid LAD and a large eccentric saccular coronary aneurysm (17 mm x 9 mm) at the proximal RCA. Intravascular ultrasound (IVUS) showed absence of stent struts around the orifice of aneurysm, which suggested a fracture of SES stent. The entry of coronary aneurysm was finally sealed with a polytetrafluoroethylene-covered stent. This report documented a rare case of late giant coronary artery aneurysm associated with a fracture of SES.

Automatic Plaque Boundary Extraction in Intravascular Ultrasound Image by Fuzzy Inference with Adaptively Allocated Membership Functions

This paper describes an automatic plaque boundary extraction in the intravascular ultrasound image by a fuzzy inference. In the proposed method, the membership functions in the antecedent parts of the fuzzy rules are adaptively allocated by using the information of the seed points given by a medical doctor. The present method not only improved the accuracy of plaque boundary extraction but also reduced the workload of medical doctors.

Plaque Boundary Extraction in Intravascular Ultrasound Image in Conjunction with Image Separability and Fuzzy Inference

In the conventional boundary extraction methods, the medical doctors have to put the several seed points on the IVUS image. However, those methods need some iterative processes and take big computing time. To meet with the practical demand in clinic, a quick boundary extraction by a small number of seed points is definitely necessary. In this paper, to cope with those problems, we propose a new fuzzy rule-based boundary extraction method, which achieves a fast, precise and robust extraction of plaque. In the proposed method, a boundary to be extracted is piecewise approximated by polynomial series inferred by fuzzy rules. The proposed method employs not only the information of the seed points itself but also the separability information of the IVUS image. The validity and the effectiveness of the proposed method have been verified by applying it to the practical problem of plaque boundary extraction in clinic.