Impact of ROI size on fractal dimension values in radiographs using a novel ROI selection method

Objective: This study aimed to evaluate the effect of various sizes of regions of interest (ROIs) on fractal dimension (FD) in the evaluation of trabecular bone structure in dental radiographic images. Materials and methods: This study included 12 sheep hemimandibles. One set of digital images was obtained from each hemimandible using either periapical radiography, panoramic radiography, or cone-beam computed tomography (CBCT). Fractal analysis (FA) was conducted using ImageJ 1.3 software with the box-counting method on small, medium, and large ROIs obtained from each image, using a novel ROI selection method. Comparisons of FD values obtained from the three different ROI sizes were conducted within each radiographic image using repeated-measures ANOVA. Post hoc pairwise comparisons were performed with Bonferroni correction. Data were analyzed using Jamovi 1.6.23. Statistical significance was accepted as p < 0.05. Results: In periapical radiography, the FD values ​​obtained in small, medium, and large ROI sizes were 1.60 ± 0.02, 1.60 ± 0.01, and 1.65 ± 0.01, respectively (p < 0.001). In panoramic radiography, they were 1.45 ± 0.04, 1.71 ± 0.02, and 1.59 ± 0.01, respectively (p < 0.001), and in CBCT, they were 0.76 ± 0.07, 1.21 ± 0.04, and 1.48 ± 0.04, respectively (p < 0.001). Conclusions: The study demonstrates that FD is affected by the ROI size.