# Texture-Based Analysis of \({}^{\bf 18}\)F-Labeled Amyloid PET Brain Images
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Image Feature** & \multicolumn{2}{c}{**Frontal**} & \multicolumn{2}{c}{**Occipital**} & \multicolumn{2}{c}{**Parietal**} & \multicolumn{2}{c}{**Temporal**} & \multicolumn{2}{c}{**PCC**} & \multicolumn{2}{c}{**Anterior**} \\  & **L** & **R** & **L** & **R** & **L** & **R** & **L** & **R** & **L** & **R** & **L** & **R** \\ \hline SUVR & **0.971** & **0.935** & **0.880** & **0.851** & **0.920** & **0.924** & **0.989** & **0.978** & **0.964** & **0.945** & **0.964** & **0.956** \\ Energy & 0.644 & 0.625 & **0.942** & **0.873** & 0.582 & 0.345 & **0.789** & **0.807** & **0.927** & **0.949** & 0.567 & **0.796** \\ Contrast & **0.280** & **0.222** & **0.105** & **0.138** & 0.396 & 0.404 & **0.276** & **0.222** & **0.225** & **0.124** & 0.538 & 0.502 \\ Entropy & **0.258** & **0.295** & **0.091** & **0.138** & 0.375 & 0.538 & **0.273** & **0.185** & **0.076** & **0.025** &describe quantitatively the grey-to-white matter contrast present in A\(\beta-\) images compared to its decrease in A\(\beta+\) cases. Statistical testing revealed that the SUVR is still the best feature when discriminating between A\(\beta+\) and A\(\beta-\) PET images, showing significant differences in all regions and study groups except in 3 VOIs of the [18]FBP group. Cut-offs have been previously defined for different amyloid-binding radiotracers [5; 12; 13; 14] and the SUV is also used in clinical practice for quantifying PET images. However, all HFs showed significant differences in at least 3 VOIs in every study group. An exception is correlation, which is found to not be a useful image feature in our study. Even though grey and white matter present similar voxel intensities in positive amyloid PET images, neighboring voxels do not necessarily need to be linearly correlated in either case, especially given that A\(\beta\) plaques are present as diffuse deposits [2]. On the contrary, other features like homogeneity that show good performance describe the general similarity of neighboring voxel intensities and show greater differences between A\(\beta+\) and A\(\beta-\) cases as demonstrated by ROC analyses. Comparing the findings of the present study to those by [PERSON] et al. [22], the authors reported results that state that energy and entropy best discriminate between the studied groups. While these features generally show statistically significant differences in our study, energy in the [18]FMM group is also one of the three HFs that are not significant when extracted from the global VOI. However, the authors grouped the patients by clinicopathological features and not by A\(\beta\) positivity. Moreover, in their study, SUVR showed no statistically significant differences between the groups and HFs performed better, unlike the results presented in this study. AUC values of ROC curves from features using the global VOI were generally larger than 0.7. Again, correlation is not sufficiently capable of discriminating between A\(\beta+\) and A\(\beta-\). All other features showed overall good performance in ROC analyses of regional VOIs indicating their discriminatory capability and describing correctly the visually identified grey-to-white matter contrast patterns. Overall, an association between the statistically significant group differences in Mann-Whitney U-tests and higher AUC values can be observed. Compared to [PERSON] et al. [22], the AUC values are generally higher in this study. The authors reported their highest AUC value as 0.695 (energy of the PCC), while in our study it is 0.989 (SUVR of the left temporal VOI). On the other hand, [PERSON] et al. [23] obtained AUC values < 0.75 with HFs in a cross-sectional study group. However, the authors employed a different segmentation method and did not analyze cortical brain regions. Moreover, ROC analyses show the relationship between the features and A\(\beta\) positivity. As mentioned previously, A\(\beta+\) PET images are characterized by a more homogeneous uptake pattern between grey and white matter.