title: Optimizing accuracy and precision of micro-coil localization in active-MR tracking.
abstract: OBJECTIVE
  To examine whether a centroid peak detection algorithm and micro-transmit tracking improve the accuracy and precision of active-MR tracking when combined with previously published strategies of Hadamard Multiplexing and Phase-field Dithering.
  
  
  METHODS
  The dipole magnetic field of a solenoid tracking coil was modeled and MR spin excitation using both a uniform body coil and the tracking coil was simulated for 5329 orientations of the solenoid coil with respect to B0. A lumenless micro-coil was built onto a rotation platform and MR-tracking accuracy and precision were experimentally assessed for 576 orientations within a 1.5-T MRI scanner. Peak identification strategies (i.e. maximum pixel detection and the centroid pixel method) and transmit modes (body transmit and micro-transmit tracking) were employed and localization accuracy was assessed for each orientation in both simulation and experimentation.
  
  
  RESULTS
  The simultaneous use of the centroid pixel method, micro-transmit tracking, Phase-field Dithering, and Hadamard Multiplexing resulted in high MR tracking accuracy and precision: 0.52±0.41 mm and 0.34 mm respectively. Furthermore, all four methods combined offered a tracking error less than the size of the micro-coil, despite the lack of a signal source within the micro-coil.
  
  
  CONCLUSIONS
  Micro-transmit tracking and the centroid pixel method improve MR tracking accuracy and precision when combined with Phase-field Dithering and Hadamard Multiplexing compared to using Phase-field Dithering and Hadamard Multiplexing alone.
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC 5033, Cincinnati, OH 45229 USA; University of Cincinnati, 2901 Woodside Drive, Cincinnati, OH 45221 USA. Electronic address: barret.daniels@cchmc.org.
authors.forename: Barret Robert
authors.initials: BR
authors.lastname: Daniels
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC 5033, Cincinnati, OH 45229 USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Pratt
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC 5033, Cincinnati, OH 45229 USA; University of Cincinnati, 2901 Woodside Drive, Cincinnati, OH 45221 USA.
authors.forename: Randy
authors.initials: R
authors.lastname: Giaquinto
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC 5033, Cincinnati, OH 45229 USA; University of Cincinnati, 2901 Woodside Drive, Cincinnati, OH 45221 USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Dumoulin
mesh_terms: D000465:Algorithms; D060733:Electromagnetic Radiation; D004867:Equipment Design; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012984:Software
keywords: Active device tracking; Centroid pixel method; Interventional MRI; MR catheter tracking; MR tracking; Micro-transmit tracking