New approaches to online estimation of electromagnetic tracking errors for laparoscopic ultrasonography

Abstract

Abstract. In abdominal surgery, a laparoscopic ultrasound transducer is commonly used to detect lesions such as metastases. The determination and visualization of position and orientation of its flexible tip in relation to the patient or other surgical instruments can be of great support for surgeons using the transducer intraoperatively. This difficult subject has recently been paid attention to by the scientific community. Electromagnetic tracking systems can be applied to track the flexible tip. However, current limitations of electromagnetic tracking are its accuracy and its sensibility, i.e. the magnetic field can be distorted by ferromagnetic material. This paper presents two novel methods for electromagnetic tracking error estimation. Based on optical tracking of the laparoscope as well as magneto-optic and visual tracking of the transducer, these methods automatically detect in 85 % of all cases, whether tracking is erroneous or not, and reduce tracking errors by up to 2.5 mm.

Electromagnetic Tracking in Medicine—A Review of Technology, Validation, and Applications

“…Additionally, reference ground truth to these poses is available, e.g., from an additional optical tracking system [31,45]. Based on these data, compensation is achieved by employing a certain mathematical method to assess the EM field within the workspace, then directly correlating the measured and the reference values using mathematical functions and subtracting the systematic error from the measurement.…”

“…The error compensation can be performed online during the use of the tracking system, based on another independent [31,32] Combination of EM and optical tracking systems Birkfellner et al [17] Using discrete LUT Meskers et al [107] Measurements averaged over time at reference points Perie et al [136] LUT based on plexi phantom Day et al [26] Employing a calibration phantom Interpolation Raab et al [148] First polynomial fit Thormann et al [177] Online correction by Hardy's multiquadric method Himberg et al [57] Multi-sensor data collection with LEGO Ikits et al [62] 4 th order polynomial fit Bryson et al [21] 4 th order polynomial fit Hagedorn et al [50] Delaunay tetrahedralization for rotations Kindratenko et al [71] 3-5 th order polynomial fit Nakamoto et al [124] 0-4 th order polynomial fit Traub et al [181] Interpolation on the top of LUT Fischer [35] Thin-Plate Spline Interpolation, Bernstein-polynoms Kelemen [67] Delaunay tetrahedralization and polynomial fit Extrapolation Kelemen [67] Extrapolation based on global polynomial fit…”

“…Note that in this case some authors proposed the generation of an error map in advance [177], others aim at the acquisition of this map intra-operatively [124,202]. The method of Feuerstein et al does not require an error map at all, but a calibration of the used instrument instead [31,32]. More typically, an offline calibration procedure is performed.…”

Magneto-Optical Tracking of Flexible Laparoscopic Ultrasound: Model-Based Online Detection and Correction of Magnetic Tracking Errors

“…Therefore, we also incorporate and calibrate a laparoscope camera that is localized by the OT. For the sake of completeness, we also briefly describe our ultrasound calibration techniques to determine the location of the ultrasound plane in OT coordinates, which is important for the final application [23], [24]. We also compare our results on error detection and correction to the findings of other groups [20], [21].…”

“…3). Furthermore, all tracking and video data streams need to be tagged with time stamps and synchronized; see our previous work incorporating temporal calibration [23], [24] for further details. Finally, our new error estimation methods require an exact modeling of the transducer axis as well as possible transducer tip movements.…”