# Digital Histology by Phase Imaging Specific Biomarkers for Human Tumoral Tissues Discrimination
## 4 Discussion
A dependency on magnification and phase contrast parameters can be qualitatively stated. Figure 4 shows the cases of fractal dimension of liver tissue at 40x and refractive index variance of kidney tissue at 20\(\times\). There is practically no area free from overlapping, so differentiation is expected to be complex. On the contrary, Figure 5 shows a refractive index variance of colon tissue at 10\(\times\) and scattering coefficient of liver tissue at 20\(\times\). In these examples, areas of no overlapping exist. This fact enormously facilitates the differentiation. Although these analyses provide qualitative results, a deeper statistical analysis is made by using ANOVA, in order to better assess the potentiality of the phase contrast parameters. The results are shown in Tables 4-6, for the different samples of interest, liver, colon, and kidney. In these tables, a high Snedecor F value or, equivalently, a low \(p\)-value indicate that healthy and tumoral groups are statistically significant to the degree expressed by the \(p\)-value. The criterion of a \(p\)-value less than 0.005 is established to be considered statistically significant. With this criterion, for the liver case in Table 4, the scattering coefficient at 20\(\times\), the fractal dimension at 10\(\times\), and the refractive index variance at 10\(\times\) would be significant. Particularly in the case of the scattering coefficient at 20\(\times\), the significance would be greater. Interestingly, there are not significant parameters at 40\(\times\) magnification for this tissue type, and two out of three belong to the 10\(\times\) magnification. This fact stresses the relevance of the magnification factor of the images. This factor is intuitively related with the proposed phase contrast parameters, as they rely on spatially varying structures that are altered at different magnifications. In the case of colon samples, as shown in Table 5, the significant phase contrast parameters would be the anisotropy factor at 20\(\times\), the scattering coefficient at 20\(\times\), the fractal dimension at 10\(\times\), the outer scale at 40\(\times\), and the refractive index variance at 10\(\times\). Interestingly, these parameters are the same as those that affected liver tissue, but adding the anisotropy factor at 20\(\times\) and the outer scale at 40\(\times\). Nevertheless, the best significance results are for the fractal dimension at 10\(\times\) and the refractive index variance at 10\(\times\). These parameters do not coincide with the previous maximum significance parameter for liver tissue, which was the scattering coefficient at 20\(\times\). This fact implies that there is a tissue type dependency in the selection of the optimum phase contrast parameter. According to the morphstructural differences of Figures 1-3, it is also an expected result. In the case of kidney, statistically significant parameters are the anisotropy factor at 10\(\times\), scattering coefficient at 10\(\times\), fractal dimensions at 10\(\times\) and 20\(\times\), and refractive index variance at 40\(\times\). When compared with colon, there is a coincidence in the case of fractal dimension at 10\(\times\), which was also present in liver. The other significant parameters are different, with changes in magnification with respect to colon, and lack of significance of the outer scale. Again, the rationale has to do with the structural difference of each tissue type and its relationship with the magnification factor. These results show a promising applicability of phase contrast parameters in digital histology on fresh tissue samples. In particular, for the tissue samples under analysis, there is a coincidence of significance in the fractal dimension at 10\(\times\) magnification. Other parameters, such as scattering coefficient at 20\(\times\) or refractive index variance at 10\(\times\), present significance in at least two tissue types.