Accuracy assessment of wireless transponder tracking in the operating room environment
To evaluate the applicability of the Calypso® wireless transponder tracking system (Varian Medical Systems Inc., USA) for real-time tumor motion tracking during surgical procedures on tumors in non-rigid target areas. An accuracy assessment was performed for an extended electromagnetic field of view (FoV) of 27.5 × 27.5 × 22.5 cm (which included the standard FoV of 14 × 14 × 19 cm) in which 5DOF wireless Beacon® transponders can be tracked.
Using a custom-made measurement setup, we assessed single transponder relative accuracy, absolute accuracy and jitter throughout the extended FoV at 1440 locations interspaced with 2.5 cm in each orthogonal direction. The NDI Polaris Spectra optical tracking system (OTS) was used as a reference. Measurements were taken in a room without surrounding distorting factors and repeated in an operating room (OR). In the OR, the influence of a carbon fiber and regular stainless steel OR tabletop was investigated.
The calibration of the OTS and transponder system resulted in an average root-mean-square error (RMSE) vector of 0.03 cm. For both the standard and extended FoV, all accuracy measures were dependent on transponder to tracking array (TA) distances and the absolute accuracy was also dependent on TA to OR tabletop distances. This latter influence was reproducible, and after calibrating this, the residual error was below 0.1 cm RMSE within the entire standard FoV. Within the extended FoV, this residual RMSE did not exceed 0.1 cm for transponder to TA distances up to 25 cm.
This study shows that transponder tracking is promising for accurate tumor tracking in the operating room. This applies when using the standard FoV, but also when using the extended FoV up to 25 cm above the TA, substantially increasing flexibility.
KeywordsAccuracy assessment Electromagnetic tracking Surgical navigation Wireless tracking Surgical oncology Abdominal surgery
We would like to thank Ton Vlasveld for his help in fabricating the measurement setup and Professor Jan-Jakob Sonke for his insightful input. We would like to thank Koningin Wilhelmina Fonds - Alpe d’HuZes (NKI 2014-6596) for their funding.
This study was funded by KWF-Alpe d’HuZes (NKI 2014-6596)
Compliance with ethical standards
Conflict of interest
The Netherlands Cancer Institute that facilitated this research has a research agreement with Varian Medical Systems. Varian was not involved in the design or execution of the study.
Human and animal rights
This article does not contain any studies with human participants or animals performed by any of the authors.
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