Veress Alexander I, Weiss Jeffrey A, Gullberg Grant T, Vince D Geoffrey, Rabbitt Richard D
Department of Bioengineering, Department of Radiology, University of Utah, 50 South Central Campus Drive, Room 2480, Salt Lake City, Utah 84112-9202, USA.
J Biomech Eng. 2002 Dec;124(6):734-41. doi: 10.1115/1.1519279.
Atherosclerotic plaque rupture is responsible for the majority of myocardial infarctions and acute coronary syndromes. Rupture is initiated by mechanical failure of the plaque cap, and thus study of the deformation of the plaque in the artery can elucidate the events that lead to myocardial infarction. Intravascular ultrasound (IVUS) provides high resolution in vitro and in vivo cross-sectional images of blood vessels. To extract the deformation field from sequences of IVUS images, a registration process must be performed to correlate material points between image pairs. The objective of this study was to determine the efficacy of an image registration technique termed Warping to determine strains in plaques and coronary arteries from paired IVUS images representing two different states of deformation. The Warping technique uses pointwise differences in pixel intensities between image pairs to generate a distributed body force that acts to deform a finite element model. The strain distribution estimated by image-based Warping showed excellent agreement with a known forward finite element solution, representing the gold standard, from which the displaced image was created. The Warping technique had a low sensitivity to changes in material parameters or material model and had a low dependency on the noise present in the images. The Warping analysis was also able to produce accurate strain distributions when the constitutive model used for the Warping analysis and the forward analysis was different. The results of this study demonstrate that Warping in conjunction with in vivo IVUS imaging will determine the change in the strain distribution resulting from physiological loading and may be useful as a diagnostic tool for predicting the likelihood of plaque rupture through the determination of the relative stiffness of the plaque constituents.
动脉粥样硬化斑块破裂是大多数心肌梗死和急性冠状动脉综合征的原因。斑块破裂由斑块帽的机械故障引发，因此研究动脉中斑块的变形可以阐明导致心肌梗死的事件。血管内超声（IVUS）可提供血管的高分辨率体外和体内横截面图像。为了从IVUS图像序列中提取变形场，必须执行配准过程以关联图像对之间的物质点。本研究的目的是确定一种称为Warping的图像配准技术在从代表两种不同变形状态的成对IVUS图像确定斑块和冠状动脉应变方面的有效性。Warping技术利用图像对之间像素强度的逐点差异来生成一个分布式体力，该体力作用于使有限元模型变形。基于图像的Warping估计的应变分布与已知的正向有限元解（代表金标准，从中创建了位移图像）显示出极好的一致性。Warping技术对材料参数或材料模型的变化敏感性低，并且对图像中存在的噪声依赖性低。当用于Warping分析和正向分析的本构模型不同时，Warping分析也能够产生准确的应变分布。本研究结果表明，Warping与体内IVUS成像相结合将确定生理负荷导致的应变分布变化，并且可能作为一种诊断工具，通过确定斑块成分的相对刚度来预测斑块破裂的可能性。
