title: Real-time ultrasound-tagging to track the 2D motion of the common carotid artery wall in vivo.
abstract: OBJECTIVE
  Tracking the motion of biological tissues represents an important issue in the field of medical ultrasound imaging. However, the longitudinal component of the motion (i.e., perpendicular to the beam axis) remains more challenging to extract due to the rather coarse resolution cell of ultrasound scanners along this direction. The aim of this study is to introduce a real-time beamforming strategy dedicated to acquire tagged images featuring a distinct pattern in the objective to ease the tracking.
  
  
  METHODS
  Under the conditions of the Fraunhofer approximation, a specific apodization function was applied to the received raw channel data, in real-time during image acquisition, in order to introduce a periodic oscillations pattern along the longitudinal direction of the radio frequency signal. Analytic signals were then extracted from the tagged images, and subpixel motion tracking of the intima-media complex was subsequently performed offline, by means of a previously introduced bidimensional analytic phase-based estimator.
  
  
  RESULTS
  The authors' framework was applied in vivo on the common carotid artery from 20 young healthy volunteers and 6 elderly patients with high atherosclerosis risk. Cine-loops of tagged images were acquired during three cardiac cycles. Evaluated against reference trajectories manually generated by three experienced analysts, the mean absolute tracking error was 98 ± 84 μm and 55 ± 44 μm in the longitudinal and axial directions, respectively. These errors corresponded to 28% ± 23% and 13% ± 9% of the longitudinal and axial amplitude of the assessed motion, respectively.
  
  
  CONCLUSIONS
  The proposed framework enables tagged ultrasound images of in vivo tissues to be acquired in real-time. Such unconventional beamforming strategy contributes to improve tracking accuracy and could potentially benefit to the interpretation and diagnosis of biomedical images.
authors: Biomedical Imaging Group Rotterdam, Departments of Radiology and Medical Informatics, Erasmus MC, Rotterdam 3000 CA, The Netherlands.
authors: Guillaume
authors: G
authors: Zahnd
authors: Université de Lyon, CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université Lyon 1, Lyon 69100, France.
authors: Sébastien
authors: S
authors: Salles
authors: Université de Lyon, CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université Lyon 1, Lyon 69100, France.
authors: Hervé
authors: H
authors: Liebgott
authors: Université de Lyon, CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université Lyon 1, Lyon 69100, France.
authors: Didier
authors: D
authors: Vray
authors: Department of Radiology, Louis Pradel Hospital, Lyon 69500, France.
authors: André
authors: A
authors: Sérusclat
authors: Department of Endocrinology, Louis Pradel Hospital, Hospices Civils de Lyon, Université Lyon 1, Lyon 69100, France and INSERM UMR 1060, Lyon 69500, France.
authors: Philippe
authors: P
authors: Moulin
mesh_terms: D000328:Adult; D000368:Aged; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging* / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009068:Movement; D013997:Time Factors; D014463:Ultrasonography