Abstract
Accurate plaque cap thickness quantification and cap stress/strain calculations are of fundamental importance for vulnerable plaque research. To overcome uncertainties due to intravascular ultrasound (IVUS) resolution limitation, IVUS and optical coherence tomography (OCT) coronary plaque image data were combined together to obtain accurate and reliable cap thickness data, stress/strain calculations, and reliable plaque progression predictions. IVUS, OCT, and angiography baseline and follow-up data were collected from nine patients (mean age: 69; m: 5) at Cardiovascular Research Foundation with informed consent obtained. IVUS and OCT slices were coregistered and merged to form IVUS + OCT (IO) slices. A total of 114 matched slices (IVUS and OCT, baseline and follow-up) were obtained, and 3D thin-layer models were constructed to obtain stress and strain values. A generalized linear mixed model (GLMM) and least squares support vector machine (LSSVM) method were used to predict cap thickness change using nine morphological and mechanical risk factors. Prediction accuracies by all combinations (511) of those predictors with both IVUS and IO data were compared to identify optimal predictor(s) with their best accuracies. For the nine patients, the average of minimum cap thickness from IVUS was 0.17 mm, which was 26.08% lower than that from IO data (average = 0.23 mm). Patient variations of the individual errors ranged from ‒58.11 to 20.37%. For maximum cap stress between IO and IVUS, patient variations of the individual errors ranged from ‒30.40 to 46.17%. Patient variations of the individual errors of maximum cap strain values ranged from ‒19.90 to 17.65%. For the GLMM method, the optimal combination predictor using IO data had AUC (area under the ROC curve) = 0.926 and highest accuracy = 90.8%, vs. AUC = 0.783 and accuracy = 74.6% using IVUS data. For the LSSVM method, the best combination predictor using IO data had AUC = 0.838 and accuracy = 75.7%, vs. AUC = 0.780 and accuracy = 69.6% using IVUS data. This preliminary study demonstrated improved plaque cap progression prediction accuracy using accurate cap thickness data from IO slices and the differences in cap thickness, stress/strain values, and prediction results between IVUS and IO data. Large-scale studies are needed to verify our findings.
Highlights
Cardiovascular disease is a serious threat to human life and health
intravascular ultrasound (IVUS), optical coherence tomography (OCT), and angiography data including three epicardial coronary vessels were collected at Cardiovascular Research Foundation (CRF) from patients with coronary heart diseases between April 2017 and November 2018 using the protocol approved by the local institute, and informed consent forms were obtained from the patients
Cap thickness was selected as the measure for plaque progression
Summary
Cardiovascular disease is a serious threat to human life and health. Atherosclerotic plaques often rupture without warning, leading to acute cardiovascular syndrome. Quantification of fibrous cap thickness and cap stress/strain conditions plays an important role in plaque progression prediction and vulnerability assessment, which in turn has clinical importance in monitoring disease development and patient management. In most available patient follow-up data (followup time around 1 year), plaque vessel wall thickness changes were mostly under 100 μm in a year (Yang et al, 2010). A modelling approach combining IVUS and OCT was introduced by Guo et al (2019) for cap thickness quantification, more accurate cap stress/strain calculations, and plaque progression prediction. We should be able to trust cap thickness change measured by OCT and use that to obtain some reliable progression prediction results
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