## 4 Discussion  
The current study aimed to assess the reliability of the novel SIBPAIR method, and the intra-rater, inter-rater, and inter-session reliability of the overall SIBPAIR-based measurement protocol for foot morphological parameters, in terms of ICC and SEM. The SIBPAIR method was found to have very high reliability with very small SEM values (Table 1). The overall SIBPAIR-based measurement protocol was also shown to have very high intra-rater, inter-rater, and inter-session reliability with small SEM. The current results indicate that following the experimental protocol the SIBPAIR method implemented on the FAST machine was capable of producing accurate and reliable measurements regardless of the rater's experience or time of measurement. These outcomes will be useful for foot assessment and subsequent applications, such as design and manufacture of customized orthoses or shoes. The SIBPAIR method identifies the 2D coordinates of the color-coded pins on the image of the impression. These coordinates are then combined with the camera parameters and the known physical distribution of the pins in the measurement area to reconstruct the 3D coordinates of the pins, and thus the 3D surface of the foot sole. Given a foot impression, the SIBPAIR method showed a very high reliability with ICC values greater than 0.95, indicating that the 2D image analysis, the 3D surface reconstruction, and the morphological parameters calculated were highly repeatable when the measurement image was taken at different poses within a range allowed by the movable tablet-supporting arm. The SIBPAIR method also showed low SEM values for the morphological parameters measured, without significant differences between trials. Standard error of measurement is a measure of how much the measurements are spread around the \"true\" outcome. The high ICC and low SEM suggest that the SIBPAIR method is a reliable and accurate method for foot morphological measurements, and that the repeatability of the outcome measurements in real-life applications will require using the measurement protocol involving the subject positioning and rater operation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Foot** & **Session** & **Mean (SD)** & **ICC** & **SEM** & _p-Value_ \\
**Parameters** & First & 255.4 (13.3) & & & & \\   FL (mm) & Second & 254.2 (12.7) & 0.98 & 2.6 & 0.82 \\   FW (mm) & First & 102.5 (5.1) & & & \\  & Second & 102.4 (5.0) & 0.91 & 2.2 & 0.74 \\   AI & First & 0.30 (0.04) & & & \\  & Second & 0.30 (0.04) & & & \\   SAI & First & 1.03 (0.23) & & & \\  & Second & 1.04 (0.21) & & & \\  & First & 55.5 (14.0) & 0.91 & 6.4 & 0.49 \\   CSI & Second & 96.0 (41.8) & 0.97 & 10.4 & 0.65 \\   AH (mm) & First & 0.04 (0.02) & & & \\   NAH & Second & 0.04 (0.02) & & & \\   HVA & First & 10.8 (4.4) & & & \\  (degrees) & Second & 10.9 (4.0) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Means (standard deviations, SD) of the foot parameters, as well as inter-session ICC and SEM (n = 30). Following the measurement protocol, the SIBPAIR method showed high intra-rater, inter-rater, and inter-session reliability with ICC values greater than 0.90 and low SEM, indicating that rater experience and time of measurement did not affect the reliability of the measurement of most morphological parameters. These results were much better than those from most previously published methods, especially for parameters that are 3D in nature and not directly defined on 2D footprint or pressure distributions. For example, AH and NAH measured using scales were reported to have moderate (ICC = 0.565 and 0.563) to high (ICC = 0.71) reliability [17; 45]. In the current study, the HVA was the only parameter with an ICC slightly less than 0.90 (ICC > 0.84). These results indicate that the SIBPAIR method has high reliability for studies of groups of patients in a clinical trial, and is also acceptable for assessment of individuals, except for the HVA. As suggested by [PERSON] et al.