Compositional volumetry of non-calcified coronary plaques by multislice computed tomography: an ex vivo feasibility study

Non-invasive quantitative compositional analysis of coronary plaque would be a major advantage to study coronary artery disease. This study explores the application to use the Hounsfield units (HU) distribution of coronary plaques imaged by multislice computed tomography-coronary angiography (MSCT-CA).A dedicated computer-assisted method was developed to measure the HU distribution within a coronary plaque by MSCT-CA. To test the feasibility of the method, an ex vivo left anterior descending (LAD) coronary specimen, excised during autopsy, was imaged both by non-enhanced and enhanced MSCT-CA. Quantitative histology was used as a reference. To test the feasibility of the new volumetric analytic method, the MSCT-CA data were compared with volumetric histopathology. The coronary specimen, with a heterogeneously distributed plaque composition without large areas of calcification, was histologically sampled at five different locations, 5 mm apart, where at each location 15 sections were taken at 100 microm intervals, resulting in 75 individual histology sections. Tri-chrome Masson staining was used for histology quantification of three plaque/tissue components: smooth muscle cells (SMC), collagen and calcium. MSCT plaque composition was defined as "lower-HU" or "higher-HU" plaque and "calcium" based on the HU distribution. Comparison of the MSCT defined tissue components against histology showed a good relationship without significant differences.This ex vivo study shows the feasibility of using the Hounsfield unit distribution to perform compositional coronary plaque volumetry by MSCT-CA. The results are encouraging.