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Real‐time active MR‐tracking of metallic stylets in MR‐guided radiation therapy
Author(s) -
Wang Wei,
Dumoulin Charles L.,
Viswanathan Akila N.,
Tse Zion T.H.,
Mehrtash Alireza,
Loew Wolfgang,
Norton Isaiah,
Tokuda Junichi,
Seethamraju Ravi T.,
Kapur Tina,
Damato Antonio L.,
Cormack Robert A.,
Schmidt Ehud J.
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25300
Subject(s) - tracking (education) , nuclear medicine , magnetic resonance imaging , radiation therapy , nuclear magnetic resonance , medicine , radiology , physics , psychology , pedagogy
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 B 0 inhomogeneity region near the metal surface. An MR‐tracking sequence with phase‐field dithering was used to overcome residual effects of B 0 and B 1 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 mm 3 ) 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. © 2014 Wiley Periodicals, Inc.