Automated Carotid IMT Measurement and Its Validation in Low Contrast Ultrasound Database of 885 Patient Indian Population Epidemiological Study: Results of AtheroEdge® Software

This chapter demonstrates the usage of an automated computer-based IMT measurement system called CALEX 3.0 (a class of patented AtheroEdge® software) on a low contrast and low-resolution image database acquired during an epidemiological study from India. The overall purpose of this chapter is to show that fully automated methods nowadays have accuracy and reproducibility suitable to epidemiological studies. The image contrast was very low resolution, with pixel density of 12.7 pixels/mm. The accuracy and reproducibility of the AtheroEdge® software system were compared with that of the manual tracings of a vascular surgeon—considered as a gold standard. We automatically measured the IMT value of 885 common carotid arteries in longitudinal B-Mode images. CALEX 3.0 consisted of a stage for the automatic recognition of the carotid artery and an IMT measurement modulus made of a fuzzy K-means classifier. Performance was assessed by measuring the system accuracy and reproducibility against manual tracings by experts. Results were very encouraging: CALEX 3.0 processed all the 885 images of the dataset (100% success). The average automated obtained IMT measurement by CALEX 3.0 was 0.407 ± 0.083 mm compared with 0.429 ± 0.052 mm for the manual tracings, which led to an IMT bias of 0.022 ± 0.081 mm. The IMT measurement accuracy (0.022 mm) was comparable to that obtained on high-resolution images and the reproducibility (0.081 mm) was very low and suitable to clinical application. The Figure-of-Merit defined as the percent agreement between the computer-estimated IMT and manually measured IMT for CALEX 3.0 was 94.7%. CALEX 3.0 had a 100% success in processing low contrast/low-resolution images. CALEX 3.0 is the first technique, which has led to high accuracy and reproducibility on low-resolution images acquired during an epidemiological study. We propose CALEX 3.0 as a generalized framework for IMT measurement on large datasets.