Session S81.5

Evidences of Possible Necrotic-Core Artifact around Dense Calcium in Virtual Histology Images

FJR Sales*, JLAA Falcao, BAA Falcao, PA Lemos, SS Furuie

University of São Paulo
São Paulo, Brazil

Virtual Histology (VH) is a new medical imaging technique, based on intravascular ultrasound (IVUS) backscattered radiofrequency analysis, that allows the assessment of in-vivo atherosclerotic plaque composition. For this, VH has been a potential useful tool for the evaluation of individuals with coronary disease. In its default output, VH provides a frame-by-frame assessment of the summed absolute and relative areas of all plaque components, which are divided into four classes - fibrous, fibro-fatty, necrotic core and dense calcium. We have developed some image processing tools based in java language on ImageJ platform to analyze the intra-plaque distribution, to improve our knowledge about the atherosclerotic disease. From our daily practice, we have observed that large components of dense calcium are frequently surrounded by pixels coded as necrotic-core tissue. To test the hypothesis of a possible artifactual relationship of these related components, an experiment and software tools were proposed. We assessed the plaque composition at baseline and compared with the values obtained after stent implantation. Since coronary stents are interpreted as dense calcium in IVUS and VH images, we use these implants to simulate the “addition” of calcium to the vessel wall in an attempt to check whether the increase in “calcium” content would be followed by an increase in necrotic-core area. To perform the analysis, the stented region was divided into 10 sub-segments, where the average composition was considered. In a preliminary evaluation, the average necrotic-core percentage of plaque in pre-PCI segments was 1.37 % and in the post-PCI was 5.87 % (a 4.2-fold increase in necrotic content). In nine of ten segments, the difference between the necrotic-core area pre-stent compared to post-stent images were superior to 5%, which is the estimated intrinsic repeatability error described for VH in the literature. Linear regression modeling disclosed a positive association between the difference of pre and post-stent dense calcium area (deltaCa) and the difference between pre and post-stent necrotic-core area (deltaNec): (deltaCa) = 1.0676*(deltaNec) + 0.0426, with an R²=0.749 (p<0.05). These findings are encouraging and further analyses are currently ongoing to obtain more robust and reliable results and better evaluate this possible artifactual effect in VH images.

(Abstract Control Number: 291)