Abstract
PurposeSurgical navigation systems are generally only applied for targets in rigid areas. For non-rigid areas, real-time tumor tracking can be included to compensate for anatomical changes. The only clinically cleared system using a wireless electromagnetic tracking technique is the Calypso® System (Varian Medical Systems Inc., USA), designed for radiotherapy. It is limited to tracking maximally three wireless 5-degrees-of-freedom (DOF) transponders, all used for tumor tracking. For surgical navigation, a surgical tool has to be tracked as well. In this study, we evaluated whether accurate 6DOF tumor tracking is possible using only two 5DOF transponders, leaving one transponder to track a tool.MethodsTwo methods were defined to derive 6DOF information out of two 5DOF transponders. The first method uses the vector information of both transponders (TTV), and the second method combines the vector information of one transponder with the distance vector between the transponders (OTV). The accuracy of tracking a rotating object was assessed for each method mimicking clinically relevant and worst-case configurations. Accuracy was compared to using all three transponders to derive 6DOF (Default method). An optical tracking system was used as a reference for accuracy.ResultsThe TTV method performed best and was as accurate as the Default method for almost all transponder configurations (median errors < 0.5°, 95% confidence interval < 3°). Only when the angle between the transponders was less than 2°, the TTV method was inaccurate and the OTV method may be preferred. The accuracy of both methods was independent of the angle of rotation, and only the OTV method was sensitive to the plane of rotation.ConclusionThese results indicate that accurate 6DOF tumor tracking is possible using only two 5DOF transponders. This encourages further development of a wireless EM surgical navigation approach using a readily available clinical system.
Highlights
In surgical oncology, the primary goal is to completely remove the tumor while sparing as much surrounding healthy tissue as possible
The purpose of this study was to assess the feasibility of tumor tracking using two 5DOF wireless EM transponders, which is an important step in the development of wireless EM surgical navigation
The one transponder vector (OTV) method, on the other hand, did show differences between in-line and perpendicular rotation, where in general the jitter was higher for in-line rotations
Summary
The primary goal is to completely remove the tumor while sparing as much surrounding healthy tissue as possible. Surgical navigation systems can be used to assist the surgeon in making that translation, improving the accuracy of tumor localization and tumor border assessment [1,2,3,4] These systems register preoperative images to the actual surgical field, and by real-time projection of tracked surgical tools onto these images, the surgeons can navigate the targets. In non-rigid target areas such as the breast and the abdominal area, there are vast intraoperative deformations caused by breathing, organ deformation and surgical manipulation [2]. These deformations can cause large tumor motions, directly impacting the accuracy of these navigation systems.
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