title: Measurement accuracy of different active tracking sequences for interventional MRI.
abstract: OBJECTIVE
  To compare the spatial accuracy of three typical active tracking sequences using a new, unique phantom design.
  
  
  METHODS
  Three different tracking sequences (Single Echo, Dual Echo and Hadamard Multiplexed) were compared with each other in a phantom study with respect to their positional accuracy. A custom-built phantom was constructed to conduct the experiments with precise framework conditions which facilitated sufficient measurement accuracy. An electrophysiology catheter incorporating four micro-coils was used as an interventional device. Tracking profiles were acquired in all three spatial dimensions and validated against the distances that were measured by a Vernier caliper in combination with a three-dimensional reference scan.
  
  
  RESULTS
  The Bland-Altman plots demonstrated that all three sequences show < 1.5 mm positional error. The measurement accuracy of Single Echo and Double Echo are prone to off-resonances, whereas Hadamard Encoding is immune to it.
  
  
  CONCLUSIONS
  The developed phantom enabled the performance of objective measurements of the accuracy of different active tracking sequences. The proposed setup allows for objectively contrasting different methods for interventional procedures.
authors.affiliation: Center for Applied Medical Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Baltimore, Maryland, USA; Institute of Radiology, University of Würzburg, Würzburg, Germany; Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wech
authors.forename: Steven M
authors.initials: SM
authors.lastname: Shea
authors.forename: Julien
authors.initials: J
authors.lastname: Barbot
authors.forename: Kamal
authors.initials: K
authors.lastname: Vij
authors.forename: Li
authors.initials: L
authors.lastname: Pan
authors.forename: Christine H
authors.initials: CH
authors.lastname: Lorenz
authors.forename: Sunil
authors.initials: S
authors.lastname: Patil
mesh_terms: D000465:Algorithms; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: active tracking; electrophysiological procedures; interventional MRI