title: Application of a novel Kalman filter based block matching method to ultrasound images for hand tendon displacement estimation.
abstract: OBJECTIVE
  Information about tendon displacement is important for allowing clinicians to not only quantify preoperative tendon injuries but also to identify any adhesive scaring between tendon and adjacent tissue. The Fisher-Tippett (FT) similarity measure has recently been shown to be more accurate than the Laplacian sum of absolute differences (SAD) and Gaussian sum of squared differences (SSD) similarity measures for tracking tendon displacement in ultrasound B-mode images. However, all of these similarity measures can easily be influenced by the quality of the ultrasound image, particularly its signal-to-noise ratio. Ultrasound images of injured hands are unfortunately often of poor quality due to the presence of adhesive scars. The present study investigated a novel Kalman-filter scheme for overcoming this problem.
  
  
  METHODS
  Three state-of-the-art tracking methods (FT, SAD, and SSD) were used to track the displacements of phantom and cadaver tendons, while FT was used to track human tendons. These three tracking methods were combined individually with the proposed Kalman-filter (K1) scheme and another Kalman-filter scheme used in a previous study to optimize the displacement trajectories of the phantom and cadaver tendons. The motion of the human extensor digitorum communis tendon was measured in the present study using the FT-K1 scheme.
  
  
  RESULTS
  The experimental results indicated that SSD exhibited better accuracy in the phantom experiments, whereas FT exhibited better performance for tracking real tendon motion in the cadaver experiments. All three tracking methods were influenced by the signal-to-noise ratio of the images. On the other hand, the K1 scheme was able to optimize the tracking trajectory of displacement in all experiments, even from a location with a poor image quality. The human experimental data indicated that the normal tendons were displaced more than the injured tendons, and that the motion ability of the injured tendon was restored after appropriate rehabilitation sessions.
  
  
  CONCLUSIONS
  The obtained results show the potential for applying the proposed FT-K1 method in clinical applications for evaluating the tendon injury level after metacarpal fractures and assessing the recovery of an injured tendon during rehabilitation.
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Lai
authors.affiliation: Department of Occupational Therapy, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Hsiao-I
authors.initials: HI
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan and Medical Imaging Research Center, Institute for Radiological Research, Chang Gung University and Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
authors.forename: Cho-Chiang
authors.initials: CC
authors.lastname: Shih
authors.affiliation: Department of Occupational Therapy, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Li-Chieh
authors.initials: LC
authors.lastname: Kuo
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Hsiu-Yun
authors.initials: HY
authors.lastname: Hsu
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Chih-Chung
authors.initials: CC
authors.lastname: Huang
mesh_terms: D006225:Hand; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D004204:Joint Dislocations / Q000000981:diagnostic imaging* / Q000503:physiopathology; D009068:Movement; D019047:Phantoms, Imaging; D011786:Quality Control; D059629:Signal-To-Noise Ratio; D013708:Tendon Injuries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013710:Tendons / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014463:Ultrasonography