Effects of contrast limited adaptive histogram equalization (CLAHE) on manual and automated tracing of lateral cephalometric radiographs

Abstract

Objective: The aim of this study is to compare the difference between original lateral cephalometric radiographs (LCRs) and Contrast Limited Adaptive Histogram Equalization (CLAHE) LCRs in two examiners and WebCeph. Methods: A total of 200 LCRs were selected, and CLAHE (tile size: 20*20) was applied to the original LCRs. 27 LCR landmarks were manually determined by two examiners and, the selected LCR's determined automatically using the WebCeph program. Absolute differences between the original LCRs and CLAHE-LCRs were calculated in the x-y axes and Euclidean distance. The Kruskal Wallis test was used for comparisons between the examiners and WebCeph. The Wilcoxon Signed Rank Test was used to evaluate the x and y axes within each group. Results: The best accuracy values were seen in examiner 1 along the x-y axes and Euclidean distance, while the worst accuracy values were seen in WebCeph. The mean differences according to the methods were higher along the y-axis than along the x-axis for both examiners (except PNS, Me') and WebCeph (except Po, Co). The mean Euclidean distances were above 2 mm only in Co, PNS at Examiner 1, PNS, Po, Ba, Co, Go, Pog, U1RT, Me', Pog at Examiner 2, and WebCeph in all measurements. However, the differences in Euclidean distances were less than 4 mm for both examiners and WebCeph. Conclusion: CLAHE-LCRs require more adjustments for landmark determination in WebCeph than the in the manual system.