title: Bone motion analysis from dynamic MRI: acquisition and tracking.
abstract: OBJECTIVE
  For diagnosis, preoperative planning and postoperative guides, an accurate estimate of joint kinematics is required. It is important to acquire joint motion actively with real-time protocols.
  
  
  METHODS
  We bring together MRI developments and new image processing methods in order to automatically extract active bone kinematics from multi-slice real-time dynamic MRI. We introduce a tracking algorithm based on 2D/3D registration and a procedure to validate the technique by using both dynamic and sequential MRI, providing a gold standard bone position measurement.
  
  
  RESULTS
  We present our technique for optimizing jointly the tracking method and the acquisition protocol to overcome the trade-off in acquisition time and tracking accuracy. As a case study, we apply this methodology on a human hip joint.
  
  
  CONCLUSIONS
  The final protocol (bFFE, TR/TE 3.5/1.1 ms, Flip angle 80 degrees , pixel size 4.7 x 2.6 mm, partial Fourier reduction factor of 0.65 in read direction, SENSE acceleration factor of 2, frame rate = 6.7 frames/s) provides sufficient morphological data for bone tracking to be carried out with an accuracy of 3 degrees in terms of joint angle.
authors.affiliation: MIRALab - University of Geneva, 24 rue general Dufour CH-1211 Geneva, Switzerland. benjamin@miralab.unige.ch
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gilles
authors.forename: Rosalind
authors.initials: R
authors.lastname: Perrin
authors.forename: Nadia
authors.initials: N
authors.lastname: Magnenat-Thalmann
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vallee
mesh_terms: D000465:Algorithms; D005269:Femur / Q000033:anatomy & histology / Q000502:physiology*; D006621:Hip Joint / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010384:Pelvic Bones / Q000033:anatomy & histology / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity