Non-Calcified Coronary Artery Plaque Characterization by Dual-Energy Computed Tomography

Abstract

Background: Inversion of dual-energy computed tomography (DECT) data for obtaining the electron density and effective atomic number of substances has been a work in progress for the past forty years. It has been the practice to characterize the material in terms of Hounsfield Unit (HU) values obtained by two different energies. Objectives: Since HU values are equipment-dependent quantities, it is necessary to develop a method that characterizes the substance in terms of certain physical quantities that are equipment independent. Materials and Methods: The process that we adopt is to find a calibration method by which all equipment-dependent quantities are eliminated and we directly deal with quantities that are representative of the sample, namely its electron density and effective atomic number. We collect the DECT data from 21 samples of non-calcified coronary artery plaques in human cadavers. Results: With our standardized inversion method, we have obtained the electron density and effective atomic number of these samples. With physical models of lipids and proteins, it becomes possible to conclude that non-calcified plaque samples can have calcium dispersed in the lipid part of the plaque in trace amounts that cannot be observed by light based microscopy or by CT images alone. Conclusion: This characterization, may give a new insight in characterization of non-calcified coronary artery plaque and in medical diagnostics.