DIMENSIONALITY REDUCTION IN SMALLPOX HISTOPATHOLOGICAL IMAGES USING AUTOENCODER AND KERNEL PCA

Histopathological images of smallpox-infected tissue are complex and high-dimensional, which poses challenges for analysis and diagnosis. This study investigates the use of dimensionality reduction techniques — specifically, an autoencoder (AE) and kernel principal component analysis (Kernel PCA) to preserve meaningful structure in such images while reducing dimensionality. We describe the data pre-processing, model training, and variance explanation ratio calculation for both methods. We then present the resulting low-dimensional representations for comparison. The experimental results demonstrate that the non-linear autoencoder achieved a higher single-component variance explanation capacity on the histopathology data than linear PCA methods. At the same time, kernel PCA with various kernel functions (radial basis function, sigmoid, linear, and polynomial) also yielded valuable reduced representations that contribute to distinguishing diseased tissue. Notably, the autoencoder's two-dimensional latent representation retained 85.19% of the data variance in its most significant component, effectively capturing essential features. Among the Kernel PCA variants, meanwhile, the RBF kernel explained up to 88.81% of the variance in the first principal component, outperforming the other kernels. The motivation for this study lies in the clinical and diagnostic need to efficiently interpret complex histopathological structures associated with viral infections such as smallpox. Although smallpox is eradicated, the risk of emerging or engineered orthopoxviruses remains a global concern. Hence, developing computational tools that can extract discriminative features from such images is not only scientifically relevant but also medically significant for early identification, preparedness, and differential diagnosis of similar conditions. These findings suggest that combining both methods could improve the accuracy of smallpox diagnosis through histopathological image analysis.