Abstract 383: Patient-Specific Coronary Models Combining Intravascular Ultrasound and Optical Coherence Tomography Lead to More Accurate Plaque Cap Thickness and Stress/Strain Quantifications

Abstract

Accurate cap thickness and stress/strain quantifications are of fundamental importance for vulnerable plaque research. An innovative modeling approach combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) is introduced for more accurate patient-specific coronary morphology and stress/strain calculations. In vivo IVUS and OCT coronary plaque data were acquired from two patients with informed consent obtained. IVUS and OCT images were segmented, co-registered, and merged to form the IVUS+OCT data set, with OCT providing accurate cap thickness. Biplane angiography provided 3D vessel curvature. Due to IVUS resolution (150 μm), original virtual histology (VH) IVUS data often had lipid core exposed to lumen since it sets cap thickness as zero when cap thickness <150 μm. VH-IVUS data were processed with minimum cap thickness set as 50 and 180 μm to generate IVUS50 and IVUS180 data sets for modeling use. 3D fluid-structure interaction models based on IVUS+OCT, IVUS50 and IVUS180 data sets were constructed to investigate the impact of OCT cap thickness improvement on stress/strain calculations. Figure 1 is a brief summary of results from 27 slices with cap covering lipid cores from 2 patients. Mean cap thickness (unit: mm) from Patient 1 was 0.353 (OCT), 0.201 (IVUS50), and 0.329 (IVUS180), respectively. Patient 2 mean cap thickness was 0.320 (OCT), 0.224 (IVUS50), and 0.285 (IVUS180). IVUS50 underestimated cap thickness (27 slices) by 34.5%, compared to OCT cap values. IVUS50 overestimated mean cap stress (27 slices) by 45.8%, compared to OCT cap stress (96.4 vs. 66.1 kPa). IVUS50 maximum cap stress was 59.2% higher than that from IVUS+OCT model (564.2 vs. 354.5 kPa). Differences between IVUS and IVUS+OCT models for mean cap strain and flow shear stress were modest (cap strain: <12%; FSS <2%). Conclusion: IVUS+OCT data and models could provide more accurate cap thickness and stress/strain calculations which will serve as basis for plaque research.