Additional sampling directions improve detection range of wireless radiofrequency probes

Purpruse: While MRI is enhancing our knowledge about the structure and function of the human inbrain subject motion. remains a problem many clinical applications. Recently, the use of wireless radiofrequency markers with three one-dimensional (1D) navigators for prospective correction was dernonetrated. This method is restricted in the range of motion that can be corrected, however, because of limited information in the 1D readouts. Methods: Here, the limitation of techniques for disambiguating marker locations was investigated. It was shown that including more sampling directions extends the tracking range for head rotations. The efficiency of trading readout resolution for speed was explored. Results: Tracking of head rotations was demonstrated from 19.2 to 34.4 degrees, -2.7 to 10.0 degrees, and -60.9 to 70.9 degrees in the x-, y-, and z-directions. respectively. In the presence of excessive head motion, the deviation of marker estimates from SPIV'S was reduced by 17.1% over existing three-prorection methods. This was achieved by using an additional seven directions, extending the time needed for readouts by a factor of 3.3. Much of this increase may be circumvented by reducing resolution, without compromising accuracy. Conclusion: Including additional sampling directions extends the range in which markers can be used. for patients who move a lot. Magn Resort Med 76:913-918, 2016. (C.) 2015 The Authors, Magnetic Resonance lit Medicine ptiblisilecl by Wiley Periodicals, litc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms cif the Creative Conlmearis Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited,