title: Clinical feasibility of a magnetic resonance tracking system to guide the position of the scan plane during physiologic joint motion.
abstract: OBJECTIVE
  Unrestricted physiologic joint motion results in multidirectional displacement of the anatomic structures. When performing real-time magnetic resonance (MR) imaging of such a joint motion, continuous adjustment of the scan plane position may be required. The purpose of this study was to evaluate the clinical feasibility of a method to guide the scan plane position during dynamic-motion MR imaging of freely moving joints.
  
  
  METHODS
  The location of a small tracker device (dedicated hardware) placed on the patient's skin overlying a joint was determined by an ultrashort MR sequence and used to automatically adjust the scan plane position prior to each dynamic-motion MR image. Using a vertically open MR unit, this MR tracking system was applied in ten dynamic-motion MR examinations to evaluate flexion/extension manoeuvres in the weight-bearing knee joint, and in ten dynamic-motion MR examinations of the shoulder joint to evaluate manoeuvres such as internal/external rotation of the humerus, stress testing of the glenohumeral joint and abduction/adduction manoeuvres. Average number of manoeuvre repetitions, total number of images and percentage of useful images per manoeuvre were calculated. Imaging time per scan plane for each manoeuvre was recorded.
  
  
  RESULTS
  Average repetition of manoeuvres varied between 1.6 and 5.8, with an average number of 7 to 18 images per manoeuvre. Average percentage of useful images varied between 61% and 89%. Total imaging time per scan plane ranged between 1 min 10 s and 4 min 51 s.
  
  
  CONCLUSIONS
  The MR tracking system to guide the slice position for each consecutive dynamic-motion MR image of the freely but slowly moving shoulder or knee joint was feasible for clinical use, providing a high percentage of useful images for each manoeuvre within a clinically acceptable time frame.
authors.affiliation: Department of Radiology, Ziekenhuizen Oost-Limburg, Genk, Belgium. jan.vandevenne@zol.be
authors.forename: J
authors.initials: J
authors.lastname: Vandevenne
authors.forename: A
authors.initials: A
authors.lastname: Pearle
authors.forename: P
authors.initials: P
authors.lastname: Lang
authors.forename: K Butts
authors.initials: KB
authors.lastname: Pauly
authors.forename: G
authors.initials: G
authors.lastname: Bergman
mesh_terms: D000328:Adult; D004867:Equipment Design; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007593:Joint Instability / Q000175:diagnosis; D007596:Joints / Q000502:physiology; D007719:Knee Joint / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000502:physiology*