Accuracy of a wireless localization system for radiotherapy

James M. Balter, J. Nelson Wright, Laurence J. Newell, Barry Friemel, Steven Dimmer, Yuki Cheng, John Wong, Edward Vertatschitsch, Timothy P. Mate

Research output: Contribution to journalArticlepeer-review

231 Scopus citations


Purpose: A system has been developed for patient positioning based on real-time localization of implanted electromagnetic transponders (beacons). This study demonstrated the accuracy of the system before clinical trials. Methods and Materials: We describe the overall system. The localization component consists of beacons and a source array. A rigid phantom was constructed to place the beacons at known offsets from a localization array. Tests were performed at distances of 80 and 270 mm from the array and at positions in the array plane of up to 8 cm offset. Tests were performed in air and saline to assess the effect of tissue conductivity and with multiple transponders to evaluate crosstalk. Tracking was tested using a dynamic phantom creating a circular path at varying speeds. Results: Submillimeter accuracy was maintained throughout all experiments. Precision was greater proximal to the source plane (σx = 0.006 mm, σy = 0.01 mm, σz = 0.006 mm), but continued to be submillimeter at the end of the designed tracking range at 270 mm from the array (σx = 0.27 mm, σy = 0.36 mm, σz = 0.48 mm). The introduction of saline and the use of multiple beacons did not affect accuracy. Submillimeter accuracy was maintained using the dynamic phantom at speeds of up to 3 cm/s. Conclusion: This system has demonstrated the accuracy needed for localization and monitoring of position during treatment.

Original languageEnglish (US)
Pages (from-to)933-937
Number of pages5
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number3
StatePublished - Mar 1 2005
Externally publishedYes


  • Electromagnetic localization
  • Target localization
  • Tracking

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research


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