title: Magnetic microbubble-mediated ultrasound-MRI registration based on robust optical flow model.
abstract: BACKGROUND
  As a dual-modality contrast agent, magnetic microbubbles (MMBs) can not only improve contrast of ultrasound (US) image, but can also serve as a contrast agent of magnetic resonance image (MRI). With the help of MMBs, a new registration method between US image and MRI is presented.
  
  
  METHODS
  In this method, MMBs were used in both ultrasound and magnetic resonance imaging process to enhance the most important information of interest. In order to reduce the influence of the speckle noise to registration, semi-automatic segmentations of US image and MRI were carried out by using active contour model. After that, a robust optical flow model between US image segmentation (floating image) and MRI segmentation (reference image) was built, and the vector flow field was estimated by using the Coarse-to-fine Gaussian pyramid and graduated non-convexity (GNC) schemes.
  
  
  RESULTS
  Qualitative and quantitative analyses of multiple group comparison experiments showed that registration results using all methods tested in this paper without MMBs were unsatisfactory. On the contrary, the proposed method combined with MMBs led to the best registration results.
  
  
  CONCLUSIONS
  The proposed algorithm combined with MMBs contends with larger deformation and performs well not only for local deformation but also for global deformation. The comparison experiments also demonstrated that ultrasound-MRI registration using the above-mentioned method might be a promising method for obtaining more accurate image information.
authors.forename: Mo
authors.initials: M
authors.lastname: Hou
authors.forename: Chunxiao
authors.initials: C
authors.lastname: Chen
authors.forename: Dalin
authors.initials: D
authors.lastname: Tang
authors.forename: Shouhua
authors.initials: S
authors.lastname: Luo
authors.forename: Fang
authors.initials: F
authors.lastname: Yang
authors.forename: Ning
authors.initials: N
authors.lastname: Gu
mesh_terms: D000465:Algorithms; D003287:Contrast Media; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D059346:Magnets; D045423:Microbubbles; D008962:Models, Theoretical; D055620:Optical Phenomena; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D014463:Ultrasonography
chemical_list: D003287:Contrast Media