A new method to measure necrotic core and calcium content in coronary plaques using intravascular ultrasound radiofrequency-based analysis

Although previous intravascular ultrasound (IVUS) radiofrequency-based analysis data showed acceptable reproducibility for plaque composition, measurements are not easily obtained, particularly that of lumen contour, because of the limited IVUS resolution. The purpose of this study was to compare a new measurement method (Shin’s method) and the conventional measurement method for necrotic core and calcium content in atherosclerotic lesions using Virtual Histology-intravascular ultrasound (VH-IVUS). Fifty-seven patients with unstable angina who underwent elective percutaneous coronary intervention were included. Shin’s method focuses on catheter contour, instead of lumen contour, and vessel contour. Patients ages ranged from 46 to 88 years, and 34 were men. A total of 1,401 frames from 59 culprit lesions were assessed. There were no significant differences in the mean area and volume of necrotic core and dense calcium between the two methods. Correlation coefficients (R) were ≥0.99 for all above mentioned parameters (P < 0.001). Between methods, the absolute differences in mean area and volume of necrotic core were 0.02 ± 0.02 mm² and 0.34 ± 0.29 mm³, respectively, while for mean area and volume of dense calcium, the absolute differences were 0.04 ± 0.07 mm² and 0.36 ± 0.52 mm³, respectively. The reproducibility of Shin’s method was excellent. For area of the necrotic core and dense calcium, the means of the differences between the two measurements were nearly zero, and the reproducibility coefficients were within 1% of the means of the two measurements. Mean analysis time for both measurements was 26.8 ± 6.7 min/segment in the conventional method and 3.3 ± 0.6 min/segment in Shin’s method. Shin’s method for measurement of necrotic core and dense calcium using VH-IVUS demonstrated a good correlation with the conventional method and excellent reproducibility. Also, Shin’s method required a significantly shorter analysis time than the conventional method. Therefore, Shin’s method could replace the conventional method for necrotic core and calcium measurement in atherosclerotic lesions, and it might be useful in the catheterization laboratory for online clinical decision.