## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Name**} & \multicolumn{2}{c}{**Middle Turbinate**} & \multicolumn{2}{c}{**Maxillary Sinus**} & \multicolumn{2}{c}{**Post. Ethmoid**} & \multicolumn{2}{c}{**Sphenoid Sinus**} & \multicolumn{2}{c}{**Frontal Sinus**} & \multicolumn{2}{c}{**Total**} \\ \cline{2-13}  & & **M** & **S** & **M** & **S** & **M** & **S** & **M** & **S** & **M** & **S** \\ \hline
1 & KYK & 9 & 8 & 10 & 10 & 8 & 10 & 9 & 8 & 10 & 9 & 9.2 & 9.0 \\
2 & CYS & 9 & 10 & 10 & 10 & 5 & 10 & 8 & 10 & 7 & 10 & 7.8 & 10 \\
3 & YSY & 10 & 9 & 10 & 10 & 8 & 9 & 10 & 10 & 10 & 9.6 & 9.6 \\
4 & PWY & 8 & 7 & 10 & 10 & 9 & 8 & 10 & 9 & 9 & 10 & 9.2 & 8.8 \\
5 & KDH & 9 & 8 & 10 & 10 & 9 & 9 & 10 & 10 & 10 & 9.6 & 9.4 \\
6 & KYS & 9 & 9 & 10 & 10 & 6 & 8 & 10 & 10 & 8 & 8 & 8.6 & 9.0 \\
7 & KDS & 8 & 8 & 10 & 10 & 8 & 9 & 9 & 8 & 10 & 10 & 9.0 & 9.0 \\
8 & CCH & 10 & 10 & 10 & 10 & 7 & 9 & 10 & 10 & 9 & 9 & 9.2 & 9.6 \\
9 & KYH & 10 & 7 & 10 & 10 & 7 & 8 & 9 & 9 & 10 & 9 & 9.2 & 8.6 \\
10 & ISH & 10 & 10 & 10 & 10 & 10 & 10 & 10 & 9 & 10 & 9.8 & 10 \\
11 & KJB & 10 & 10 & 10 & 10 & 10 & 10 & 9 & 10 & 10 & 9 & 9.8 & 9.8 \\ \hline \multirow{2}{*}{Mean} & \multicolumn{2}{c}{9.27 \(\pm\)} & \multicolumn{2}{c}{8.73 \(\pm\)} & \multirow{2}{*}{\(10\pm 0\)} & \multicolumn{2}{c}{7.91 \(\pm\)} & \multicolumn{2}{c}{9.09 \(\pm\)} & \multicolumn{2}{c}{9.45 \(\pm\)} & \multicolumn{2}{c}{9.45 \(\pm\)} & \multicolumn{2}{c}{9.27 \(\pm\)} & \multicolumn{2}{c}{9.45 \(\pm\)} & \multicolumn{2}{c}{9.18 \(\pm\)} & \multicolumn{2}{c}{9.35 \(\pm\)} \\  & & 0.79 & 1.19 & 1.58 & 0.83 & 0.69 & 0.82 & 1.01 & 0.69 & 0.58 & 0.49 \\ \hline \multicolumn{2}{c}{\(p\)-value} & \multicolumn{2}{c}{0.283} & \multicolumn{2}{c}{1.000} & \multicolumn{2}{c}{0.058} & \multicolumn{2}{c}{0.852} & \multicolumn{2}{c}{0.826} & \multicolumn{2}{c}{0.715} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Visual analogue scale accuracies when surgeon pointed out important structures in the nasal cavity using the developed (Medigator®, Gmeditec, Incheon, Korea) and the commercialized (Scopis® Hybrid Navigation System, Stryker, Kalamazoo, MI, USA) systems. and the image space. In general, the error of the IGS system for use in ESS surgery is less than 2 mm [34,35]. Previous studies have shown that the accuracy of registration is highly correlated with the surgical accuracy of IGS [36,37]. Some researchers proposed three metrics to evaluate the accuracy of the registration: (1) fiducial localization error (FLE), which is error in the location of the fiducials; (2) fiducial registration error (FRE), which is the root mean squared (RMS) distance between corresponding fiducials used in registration; and (3) target registration error (TRE), which is the RMS distance corresponding fiducials which are not used in registration [38,39]. To date, there is no standardized criterion for evaluating the accuracy of the registration. Therefore, previous studies evaluated the accuracy of registration with their own customized methods [8,40,41]. In a previous study, a skin-attached skull phantom with 26 titanium screws was fabricated to evaluate the TREs of five registration methods [8]. The TRE values (mean \(\pm\) standard deviation) were 0.94 \(\pm\) 0.06 mm for point-to-point registration using invasive fiducials, 1.41 \(\pm\) 0.04 mm for non-invasive point-to-point registration using the metal balls on a headset, 1.59 \(\pm\) 0.14 mm for the surface registration, and 5.15 \(\pm\) 0.66 mm and 4.37 \(\pm\) 0.73 mm for point-to-point registration using four and five anatomic landmarks, respectively [8]. Another study reported TRE values in the range of 0.71 to 3.51 mm for point-to-point registration using a customized plastic phantom [41]. [PERSON] et al. measured an accuracy of 1.82 \(\pm\) 1.42 mm after performing the point-to-point registration using fiducials [42].