title: Real-time MR navigation and localization of an intravascular catheter with ferromagnetic components.
abstract: OBJECTIVE
  To develop an intravascular catheter with ferromagnetic components that is navigated with MR gradient forces and imaged with dedicated MR sequences in real time.
  
  
  METHODS
  The orientation of a device with ferromagnetic components can be controlled by gradient forces. In this work, a 3D input device for interactive real-time control of the force gradient was combined with a dedicated real-time MR pulse sequence. The pulse sequence offered acquisition of FLASH images, force gradient and localization of the ferromagnetic tip with three projections. The technique for localization is a combination of off-set resonance excitation and gradient rephasing. According to the position of the ferromagnetic components from the projections, the imaging slice is automatically aligned with the ferromagnetic component. The navigation methods and localization techniques were assessed in phantom and animal studies.
  
  
  RESULTS
  At a reaction time of 24 ms and a frame rate of one image per second, the orientation of a ferromagnetic catheter could be navigated in a complex vascular phantom. The magnetic force generated by a gradient of 28 mT/m could reach up to 100+/-20 microN. The localization of the ferromagnetic tip could be performed with an uncertainty of 1 mm in phantom studies and 4 mm in animal studies.
  
  
  CONCLUSIONS
  The use of a deflectable catheter with a ferromagnetic tip to target the blood vessels and localize the position of device provides a novel method to use the MR system to image the anatomy and steer an interventional device which helps to increase the precision and speed of endovascular procedures.
authors.affiliation: German Cancer Research Center (DKFZ), Medical Physics in Radiology (E020), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.forename: Axel Joachim
authors.initials: AJ
authors.lastname: Krafft
authors.forename: Reiner
authors.initials: R
authors.lastname: Umathum
authors.forename: Florian
authors.initials: F
authors.lastname: Maier
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Semmler
authors.forename: Michael
authors.initials: M
authors.lastname: Bock
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000378:metabolism / Q000473:pathology; D002405:Catheterization, Central Venous; D057785:Catheters; D004867:Equipment Design; D005260:Female; D005290:Ferric Compounds / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008954:Models, Biological; D013552:Swine; D013997:Time Factors
chemical_list: D005290:Ferric Compounds; C001215:ferrite