# Morphological Foot Model for Temperature Pattern Analysis Proposed for Diabetic Foot Disorders
## 3 Results and Discussion
### Statistical Analysis
Figure 6: IR images for all the subjects were registered to the respective models: (**a**) female and (**c**) male. The images corresponding to the right foot were flipped and registered to the left foot for both groups of subjects: (**b**) female and (**d**) male. Furthermore, in some studies, the mean temperature of the complete plantar surface is used for assessment [15] or even selected spots [14; 47]. In addition to the contralateral pixel-wise comparison, the average temperature for each foot was calculated and the difference, left minus right foot, was recorded for each individual. Afterwards, the mean difference across subjects was calculated at each time point and displayed in Table 7.  
As can be noticed, the mean temperature difference is larger for the male group as compared to the female, although not statistical significance was detected according to [PERSON]'s test. Furthermore, the largest temperature difference for the female group of subjects was around 0.8 \({}^{\circ}\)C at T15, whereas for the male group, the largest difference was 1.6 \({}^{\circ}\)C at T0. In order to facilitate the visualization of the changes observed, the individual temperature differences at each time point are plotted in Figure 8. For some individuals in both groups, negative values were detected, this indicates that the right foot was hotter than the left one. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Time Point** & **Female (\({}^{\circ}\)C)** & **Male (\({}^{\circ}\)C)** \\ \hline T0 & 0.155 \(\pm\) 0.175 & 0.337 \(\pm\) 0.715 \\ T5 & 0.127 \(\pm\) 0.261 & 0.357 \(\pm\) 0.642 \\ T10 & 0.170 \(\pm\) 0.328 & 0.332 \(\pm\) 0.622 \\ T15 & 0.205 \(\pm\) 0.205 & 0.394 \(\pm\) 0.546 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Mean temperature difference at each time point for the female and male subjects. Figure 7: Statistically significant \(p\) values map, for each gender, at each time point, T0, T5, T10 and T15. The upper row corresponds to the female subjects (**a–d**), whereas the lower to the male subjects, (**e–h**), respectively. Another source of controversy is the establishment of the threshold at which an acute situation is detected. As mentioned above, 2.2 \({}^{\circ}\)C is usually consider as the standard threshold at the clinical settings for DFU [7,17,18]. Furthermore, this threshold seems to be independent of the ambient temperature, the time of the day, and the walking activity of the subject [47]. However, in patients affected by diabetic foot infection, a plantar foot asymmetry of 1.35 \({}^{\circ}\)C suffices to seek urgent treatment [16]. As demonstrated here, some healthy subjects presented a mean temperature difference above this threshold. Therefore, the heterogeneity among subjects must be considered, and the establishment of a personalized threshold and treatment are mandatory. In fact, it is plausible that using the mean values solely to assess the foot asymmetry in a single measurement may not provide enough information. As previously reported, the above-threshold asymmetry must be confirmed longitudinally to improve its validity [47]. Once the model has been extracted, the methodology presented here would allow us to monitor the same patient longitudinally as long as required. Furthermore, the images acquired in time can be easily compared pixel-wise, facilitating the localization of areas, within the entire plantar aspects of both feet, which may present an anomaly. In this particular case, the comparison between left and right feet for the female group, was performed in 129.7 \(\pm\) 14.1 s for 36 input images using a standard processor. For the male group, which consisted of 52 images, the analysis was performed in 127.4 \(\pm\) 4.4 s. Each individual analysis, in which eight input images are used (T0, T5, T10, T15), was 125.5 \(\pm\) 1.4 s. The spatial registration to the corresponding model depends on the number of images to be registered as well as the processor used.