Real-time active MR-tracking of metallic stylets in MR-guided radiation therapy

Wei Wang, Charles L. Dumoulin, Akila N. Viswanathan, Zion T.H. Tse, Alireza Mehrtash, Wolfgang Loew, Isaiah Norton, Junichi Tokuda, Ravi T. Seethamraju, Tina Kapur, Antonio L. Damato, Robert A. Cormack, Ehud J. Schmidt

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Purpose To develop an active MR-tracking system to guide placement of metallic devices for radiation therapy. Methods An actively tracked metallic stylet for brachytherapy was constructed by adding printed-circuit micro-coils to a commercial stylet. The coil design was optimized by electromagnetic simulation, and has a radio-frequency lobe pattern extending ∼5 mm beyond the strong B0 inhomogeneity region near the metal surface. An MR-tracking sequence with phase-field dithering was used to overcome residual effects of B0 and B1 inhomogeneities caused by the metal, as well as from inductive coupling to surrounding metallic stylets. The tracking system was integrated with a graphical workstation for real-time visualization. The 3 Tesla MRI catheter-insertion procedures were tested in phantoms and ex vivo animal tissue, and then performed in three patients during interstitial brachytherapy. Results The tracking system provided high-resolution (0.6 × 0.6 × 0.6 mm3) and rapid (16 to 40 frames per second, with three to one phase-field dithering directions) catheter localization in phantoms, animals, and three gynecologic cancer patients. Conclusion This is the first demonstration of active tracking of the shaft of metallic stylet in MR-guided brachytherapy. It holds the promise of assisting physicians to achieve better targeting and improving outcomes in interstitial brachytherapy. Magn Reson Med 73:1803-1811, 2015.

Original languageEnglish (US)
Pages (from-to)1803-1811
Number of pages9
JournalMagnetic resonance in medicine
Issue number5
StatePublished - May 1 2015
Externally publishedYes


  • active MR-tracking
  • metallic device
  • phase-field dithering
  • radiation therapy

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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