Copyright 2004 IEEE — Published in the Proceedings of the 2004 IEEE International Symposium on Biomedical Imaging (ISBI 2004), 15-18 April 2004, Arlington, VA, USA. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copy- righted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966. 531 QUANTITATIVE ANALYSIS OF CIRCUMFERENTIAL PLAQUE DISTRIBUTION IN HUMAN CORONARY ARTERIES IN RELATION TO LOCAL VESSEL CURVATURE Andreas Wahle, 1* Mark E. Olszewski, 1 Sarah C. Vigmostad, 2 Rub´ en Medina, 4 A. ¨ Umit Cos ¸kun, 5 Charles L. Feldman, 6 Peter H. Stone, 6 Kathleen C. Braddy, 3 Theresa M. H. Brennan, 3 James D. Rossen, 3 Krishnan B. Chandran, 2 and Milan Sonka 1 1 The University of Iowa, Electrical and Computer Engineering, Iowa City, IA 2 The University of Iowa, Biomedical Engineering, Iowa City, IA 3 The University of Iowa, Internal Medicine, Iowa City, IA 4 Universidad de Los Andes, Facultad de Ingenier´ ıa, M´ erida, Venezuela 5 Northeastern University, Mechanical, Industrial and Manufacturing Engineering, Boston, MA 6 Brigham & Women’s Hospital, Cardiovascular Division, Boston, MA ABSTRACT A common hypothesis is that plaque accumulation in curved vessels is biased towards the inner bend of the curvature rather than the outer bend of the curvature. This bias in circumferential plaque distribution is likely associated with lower wall shear stress on the inner bend of the curved ves- sel. We quantitatively analyzed this effect in a set of 37 in-vivo human coronary artery segments from 31 patients. Three-dimensional models of the arteries were generated by an established system for fusion of image data from X- ray angiography and intravascular ultrasound. Our results showed that the hypothesis held in the majority of vessels (p< 0.001), and that the effect increases with curvature. However, no evidence could be found for a direct relation- ship between plaque distribution and curvature in complex vessel geometries, thus motivating a more detailed analysis of wall shear stress patterns and their impact on circumfer- ential plaque distribution. 1. INTRODUCTION The progression of cardiovascular disease as a function of local hemodynamics and plaque morphology in human vas- culature is of increasing interest [1, 2]. As is frequently ob- served, plaque is not distributed homogeneously and tends to be circumferentially asymmetric (Fig. 1). The purpose of this study was to evaluate if there is a direct relation- ship between the circumferential plaque distribution and lo- Supported in part by grant R01 HL63373 of the National Institutes of Health; by grant BES 9902011 of the National Science Foundation; and by AstraZeneca; Dr. Medina was supported by the Universidad de Los Andes and FONACIT, Venezuela. — * E-mail: a.wahle@ieee.org cal vessel curvature. We have developed a comprehensive system for the fusion of images from biplane angiography and intravascular ultrasound (IVUS), resulting in geomet- rically correct 3-D or 4-D (3-D + time) models of a vessel (Fig. 2). These models can be utilized for accurate hemody- namic and morphologic analyses [2–5]. The local wall shear stress tends to be lower on the inner bend of a curved vessel (“inner curvature”) than on the outer bend (“outer curva- ture”) [2, 6]. Therefore, plaque in native coronary arteries should accumulate more on the inner curvature of a vessel segment as compared to the outer curvature of the vessel. This hypothesis can frequently be confirmed visually in the reconstructed 3-D models obtained from fusion (Fig. 3). In the following sections, we will present a quantification of this effect in a set of patients from the University of Iowa Hospitals & Clinics and Brigham & Women’s Hospital. 2. METHODS The basis of this analysis is the previously developed fu- sion system that utilizes X-ray angiography and IVUS to generate a geometrically correct 3-D model of a vessel seg- ment. This system is described in detail elsewhere [2–4], thus only a brief overview of it will be given. This paper focuses on the determination of local plaque thickness, cur- vature indices, and the classification of vessel regions that either confirm or do not confirm the given hypothesis. 2.1. 3-D fusion The pullback path of the IVUS catheter as well as the vessel lumen outline are extracted from the angiograms (Fig. 3).