title: Enhanced characterization of calcified areas in intravascular ultrasound virtual histology images by quantification of the acoustic shadow: validation against computed tomography coronary angiography.
abstract: We enhance intravascular ultrasound virtual histology (VH) tissue characterization by fully automatic quantification of the acoustic shadow behind calcified plaque. VH is unable to characterize atherosclerosis located behind calcifications. In this study, the quantified acoustic shadows are considered calcified to approximate the real dense calcium (DC) plaque volume. In total, 57 patients with 108 coronary lesions were included. A novel post-processing step is applied on the VH images to quantify the acoustic shadow and enhance the VH results. The VH and enhanced VH results are compared to quantitative computed tomography angiography (QTA) plaque characterization as reference standard. The correlation of the plaque types between enhanced VH and QTA differs significantly from the correlation with unenhanced VH. For DC, the correlation improved from 0.733 to 0.818. Instead of an underestimation of DC in VH with a bias of 8.5 mm(3), there was a smaller overestimation of 1.1 mm(3) in the enhanced VH. Although tissue characterization within the acoustic shadow in VH is difficult, the novel algorithm improved the DC tissue characterization. This algorithm contributes to accurate assessment of calcium on VH and could be applied in clinical studies.
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands. a.broersen@lumc.nl.
authors.forename: Alexander
authors.initials: A
authors.lastname: Broersen
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, Postal zone 2300 RC, 2333 ZA, Leiden, The Netherlands.|The Interuniversity Cardiology Institute of the Netherlands, Utrecht, The Netherlands.
authors.forename: Michiel A
authors.initials: MA
authors.lastname: de Graaf
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Eggermont
authors.affiliation: Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Ron
authors.initials: R
authors.lastname: Wolterbeek
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.|Medis Medical Imaging Systems bv, Leiden, The Netherlands.
authors.forename: Pieter H
authors.initials: PH
authors.lastname: Kitslaar
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jouke
authors.initials: J
authors.lastname: Dijkstra
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, Postal zone 2300 RC, 2333 ZA, Leiden, The Netherlands.
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.|Medis Medical Imaging Systems bv, Leiden, The Netherlands.
authors.forename: Johan H C
authors.initials: JH
authors.lastname: Reiber
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, Postal zone 2300 RC, 2333 ZA, Leiden, The Netherlands.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Scholte
mesh_terms: D000465:Algorithms; D001331:Automation; D000072226:Computed Tomography Angiography; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D005355:Fibrosis; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D061330:Multidetector Computed Tomography; D009336:Necrosis; D058226:Plaque, Atherosclerotic; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018084:Ultrasonography, Interventional; D061205:Vascular Calcification / Q000000981:diagnostic imaging*
keywords: Acoustic shadow; Plaque constitution; Quantitative CT angiography; Tissue characterization