# Digital Histology by Phase Imaging Specific Biomarkers for Human Tumoral Tissues Discrimination
## 4 Discussion  
The results shown in the previous sections allow an estimation of the diagnostic potentiality of the novel phase contrast parameters proposed. The main difference between conventional or digital histology is based on the collection of phase information of the optical signal and the subsequent implementation of phase contrast parameters. This fact allows the use of fresh tissue slices that do not require fixation or staining, unlike conventional samples. This procedure decreases artifacts and processing time. Phase contrast images were obtained with a phase microscopy setup. Potentially relevant structures can be appreciated in Figures 1-3. They correspond to liver, colon, and kidney, either healthy or tumoral, and with different magnifications at 10\(\times\), 20\(\times\), and 40\(\times\). Each image was processed to calculate the proposed phase contrast parameters: anisotropy factor, scattering coefficient, fractal dimension, outer scale, and refractive index variance. These results are shown in Tables 1-3, for each tissue type, state, and magnification, and for selected cases in Figures 4 and 5. These results are a first approach to discrimination significance. For instance, in the case of liver at 10\(\times\) (Table 1), refractive index variance and fractal dimension seem to have potentially usable differences. On the contrary, scattering coefficient, anisotropy of scattering, or outer scale do not seem to be useful, as they have values \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Magnification** & **F** & _p-Value_ \\ \hline Anisotropy factor & 10\(\times\) & 33.0444 & 0.0000047223 \\  & 20\(\times\) & 0.00000087686 & 0.9993 \\  & 40\(\times\) & 4.1214 & 0.0527 \\ Scattering coefficient & 10\(\times\) & 17.8232 & 0.00026167 \\  & 20\(\times\) & 4.1114 & 0.0530 \\  & 40\(\times\) & 0.7272 & 0.4016 \\ Fractal dimension & 10\(\times\) & 25.8860 & 0.000026657 \\  & 20\(\times\) & 25.5593 & 0.000029020 \\  & 40\(\times\) & 0.0058 & 0.9399 \\ Outer scale & 10\(\times\) & 2.2104 & 0.1491 \\  & 20\(\times\) & 2.2326 & 0.1476 \\  & 40\(\times\) & 3.8885 & 0.0593 \\ Refractive index variance & 10\(\times\) & 0.0780 & 0.7822 \\  & 20\(\times\) & 0.0322 & 0.8590 \\  & 40\(\times\) & 9.9905 & 0.0040 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of the ANOVA analysis for phase contrast parameters when comparing healthy and tumoral kidney samples, for different magnifications. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Magnification** & **F** & _p-Value_ \\ \hline Anisotropy factor & 10\(\times\) & 0.9263 & 0.3401 \\  & 20\(\times\) & 9.8824 & 0.0027 \\  & 40\(\times\) & 4.6820 & 0.0349 \\ Scattering coefficient & 10\(\times\) & 0.2152 & 0.6446 \\  & 20\(\times\) & 10.3137 & 0.0022 \\  & 40\(\times\) & 0.2728 & 0.6036 \\ Fractal dimension & 10\(\times\) & 13.5217 & 0.00054414 \\  & 20\(\times\) & 0.0378 & 0.8466 \\  & 40\(\times\) & 0.0107 & 0.9181 \\ Outer scale & 10\(\times\) & 0.6673 & 0.4176 \\  & 20\(\times\) & 1.5712 & 0.2155 \\  & 40\(\times\) & 7.4722 & 0.0086 \\ Refractive index variance & 10\(\times\) & 13.0546 & 0.00066435 \\  & 20\(\times\) & 0.1451 & 0.7047 \\  & 40\(\times\) & 1.2440 & 0.2696 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of the ANOVA analysis for phase contrast parameters when comparing healthy and tumoral colon samples, for different magnifications. that overlap healthy and tumoral samples. The differences seem to be relevant for the scattering coefficient parameter in Table 1 for 20\(\times\) compared with the rest of the phase contrast parameters. It is difficult to establish an a priori good differentiation parameter in the case of 40\(\times\) magnification. These tendencies indicate that the validity of the parameters depends on the magnification factor. It is an expected result, considering that almost all the parameters are spatially sensitive. A similar analysis can be made in Table 2, which is devoted to colon tissues, or for Table 3, which contains kidney samples.