title: Adaptive windowing in contrast-enhanced intravascular ultrasound imaging.
abstract: Intravascular ultrasound (IVUS) is one of the most commonly-used interventional imaging techniques and has seen recent innovations which attempt to characterize the risk posed by atherosclerotic plaques. One such development is the use of microbubble contrast agents to image vasa vasorum, fine vessels which supply oxygen and nutrients to the walls of coronary arteries and typically have diameters less than 200μm. The degree of vasa vasorum neovascularization within plaques is positively correlated with plaque vulnerability. Having recently presented a prototype dual-frequency transducer for contrast agent-specific intravascular imaging, here we describe signal processing approaches based on minimum variance (MV) beamforming and the phase coherence factor (PCF) for improving the spatial resolution and contrast-to-tissue ratio (CTR) in IVUS imaging. These approaches are examined through simulations, phantom studies, ex vivo studies in porcine arteries, and in vivo studies in chicken embryos. In phantom studies, PCF processing improved CTR by a mean of 4.2dB, while combined MV and PCF processing improved spatial resolution by 41.7%. Improvements of 2.2dB in CTR and 37.2% in resolution were observed in vivo. Applying these processing strategies can enhance image quality in conventional B-mode IVUS or in contrast-enhanced IVUS, where signal-to-noise ratio is relatively low and resolution is at a premium.
authors.affiliation: Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, CB7575 Chapel Hill, NC 27599, United States. Electronic address: brooks.lindsey@unc.edu.
authors.forename: Brooks D
authors.initials: BD
authors.lastname: Lindsey
authors.affiliation: Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, CB7575 Chapel Hill, NC 27599, United States.
authors.forename: K Heath
authors.initials: KH
authors.lastname: Martin
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University, 911 Oval Drive, 3282 Engineering Building III, Campus Box 7910, North Carolina State University, Raleigh, NC, United States; Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, CB7575 Chapel Hill, NC 27599, United States.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, CB7575 Chapel Hill, NC 27599, United States; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Marsico Hall, Chapel Hill, NC 27599, United States.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Dayton
mesh_terms: D000465:Algorithms; D000818:Animals; D050197:Atherosclerosis / Q000000981:diagnostic imaging*; D002642:Chick Embryo; D003198:Computer Simulation; D003287:Contrast Media; D003627:Data Interpretation, Statistical; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D015233:Models, Statistical; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013552:Swine; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*; D014651:Vasa Vasorum / Q000000981:diagnostic imaging*
chemical_list: D003287:Contrast Media
keywords: Adaptive beamforming; Contrast-enhanced ultrasound; High frequency ultrasound; Intravascular ultrasound; Phase coherence factor; Superharmonic