Contrast enhancement of orthopantomograms to improve tooth segmentation using U-Nets

Abstract

Panoramic radiographs of teeth, also called orthopantomograms, play an important role in different tasks, from the diagnosis of diseases to the identification of persons in forensic dentistry. The segmentation of teeth from these radiographs can be used as a preliminary step for tasks such as counting, measure the similarity between two orthopantomograms and recognition of a person's teeth. These types of radiographs suffer from low contrast which can make it difficult to segment the teeth. In this paper we propose a methodology in which a contrast enhancement technique is used on orthopantomograms, and then used in the segmentation task using U-Nets. In the experiments, different image contrast enhancement methods were evaluated, obtaining better values in the F1-score metric compared to using no pre-processing before segmentation using U-nets. Finally, a correlation analysis of different metrics of image quality enhancement evaluation was performed, showing that contrast is positively correlated with the precision and accuracy of the segmentation obtained by U-nets.