DICOM-based intravascular ultrasound signal intensity analysis: an Echoplaque Medical Imaging Bench study

Most intravascular ultrasound (IVUS) data are stored digitally using the Digital Imaging and Communications in Medicine (DICOM) standard. This allows random access to studies and improves on the major limitation of conventional grayscale IVUS.

We harvested 129 coronary arteries from 43 autopsied cases. Grayscale IVUS and virtual histology-IVUS imaging were performed beginning 30 mm distal to the ostium of each coronary artery. Grayscale IVUS was processed; and the signal intensity was determined from DICOM-stored images using a new Medical Imaging Bench system (Echoplaque-MIB). We compared 436 regions of interest. The accuracy rate was expressed using the interpolation method and 95% confidence interval (CI).

Patients' mean age was 49±9 years and 82% were men. Four patients succumbed to sudden cardiac death and 39 to noncardiac death. Grayscale IVUS signal intensity of dense calcium was 215±21.1 (95% CI: 207-223), that of fibrotic plaque was 75±17.8 (95% CI: 72-79), and that of fibrofatty plaque was 55±11.3 (95% CI: 52-59); however, the signal intensity of the necrotic core was between fibrotic plaque and dense calcium of 161±27.4 (95% CI: 153-168). Using the interpolation method, the cutoff values were as follows: fibrofatty plaque 0-65, fibrotic plaque 66-105, necrotic core 106-187, and dense calcium of at least 188. Overall, MIB grayscale had a 78.1% sensitivity and a 91.9% specificity versus histopathology.

Plaque characterization using DICOM-based grayscale IVUS signal intensity analysis may improve on the major limitation of conventional grayscale IVUS: its inability to assess plaque composition.