  Electromagnetic (EM) tracking enables localization of surgical instruments
within the magnetic field emitted by an EM field generator (FG). Usually, the
larger a FG is, the larger its tracking volume is. However, the company NDI
(Northern Digital Inc., Waterloo, ON, Canada) recently introduced the Planar
10-11 FG, which combines a compact construction (97mm x 112mm x 31mm) with a
relatively large, cylindrical tracking volume (diameter: 340mm, height: 340mm).
Using the standardized assessment protocol of Hummel et al., the FG was tested
with regard to its tracking accuracy and to its robustness with respect to
external sources of disturbance. The mean positional error (5cm distance metric
according to Hummel protocol) was 0.59mm, with a mean jitter of 0.26mm in the
standard setup. The mean orientational error was found to be 0.10{\deg}. The
highest positional error (4.82mm) due to metallic sources of disturbance was
caused by the steel SST 303. In contrast, steel SST 416 caused the lowest
positional error (0.10mm). Overall, the Planar 10-11 FG tends to achieve better
tracking accuracy results compared to other NDI FGs. Due to its compact
construction and portability, the FG could contribute to increased clinical use
of EM tracking systems.
