title: Feasibility of using real-time MRI to measure joint kinematics in 1.5T and open-bore 0.5T systems.
abstract: OBJECTIVE
  To test the feasibility and accuracy of measuring joint motion with real-time MRI in a 1.5T scanner and in a 0.5T open-bore scanner and to assess the dependence of measurement accuracy on movement speed.
  
  
  METHODS
  We developed an MRI-compatible motion phantom to evaluate the accuracy of tracking bone positions with real-time MRI for varying movement speeds. The measurement error was determined by comparing phantom positions estimated from real-time MRI to those measured using optical motion capture techniques. To assess the feasibility of measuring in vivo joint motion, we calculated 2D knee joint kinematics during knee extension in six subjects and compared them to previously reported measurements.
  
  
  RESULTS
  Measurement accuracy decreased as the phantom's movement speed increased. The measurement accuracy was within 2 mm for velocities up to 217 mm/s in the 1.5T scanner and 38 mm/s in the 0.5T scanner. We measured knee joint kinematics with small intraobserver variation (variance of 0.8 degrees for rotation and 3.6% of patellar width for translation).
  
  
  CONCLUSIONS
  Our results suggest that real-time MRI can be used to measure joint kinematics when 2 mm accuracy is sufficient. They can also be used to prescribe the speed of joint motion necessary to achieve certain measurement accuracy.
authors.affiliation: Department of Mechanical Engineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Christine E
authors.initials: CE
authors.lastname: Draper
authors.forename: Juan M
authors.initials: JM
authors.lastname: Santos
authors.forename: Lampros C
authors.initials: LC
authors.lastname: Kourtis
authors.forename: Thor F
authors.initials: TF
authors.lastname: Besier
authors.forename: Michael
authors.initials: M
authors.lastname: Fredericson
authors.forename: Gary S
authors.initials: GS
authors.lastname: Beaupre
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
authors.forename: Scott L
authors.initials: SL
authors.lastname: Delp
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003199:Computer Systems; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007596:Joints / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging