Abstract
Objectives: The aims of this study were to explore how image compression affects density, fractal dimension, linear and angular measurements on digital panoramic images and assess inter and intra-observer repeatability of these measurements. Study Design: Sixty-one digital panoramic images in TIFF format (Tagged Image File Format) were compressed to JPEG (Joint Photographic Experts Group) images. Two observers measured gonial angle, antegonial angle, mandibular cortical width, coronal pulp width of maxillary and mandibular first molar, tooth length of maxillary and mandibular first molar on the left side of these images twice. Fractal dimension of the selected regions of interests were calculated and the density of each panoramic radiograph as a whole were also measured on TIFF and JPEG compressed images. Intra-observer and inter-observer consistency was evaluated with Cronbach’s alpha. Paired samples t-test and Kolmogorov-Smirnov test was used to evaluate the difference between the measurements of TIFF and JPEG compressed images. Results: The repeatability of angular measurements had the highest Cronbach’s alpha value (0.997). There was statistically significant difference for both of the observers in mandibular cortical width (MCW) measurements (1st ob. p: 0.002; 2nd ob. p: 0.003), density (p<0.001) and fractal dimension (p<0.001) between TIFF and JPEG images. There was statistically significant difference for the first observer in antegonial angle (1st ob p< 0.001) and maxillary molar coronal pulp width (1st ob. p<0.001) between JPEG and TIFF files. Conclusions: The repeatability of angular measurements is better than linear measurements. Mandibular cortical width, fractal dimension and density are affected from compression. Observer dependent factors might also cause statistically significant differences between the measurements in TIFF and JPEG images. Key words:Digital panoramic radiography, image compression, linear measurements, angular measurements, fractal dimension.
Highlights
Intraoral and extraoral dental radiography is an integral part of dental task
In this study gonial angle, antegonial angle, mandibular cortical width, coronal pulp widths of maxillary and mandibular first molar teeth, tooth lengths of maxillary and mandibular first molar, mean density of panoramic radiographs and fractal dimension were evaluated in TIFF and JPEG compressed images separately
Descriptive statistics of the Cronbach’s alpha values were grouped as angular measurements, vertical measurements, horizontal measurements for the two observers together and density and fractal dimension measurements of one observer are given in table 1
Summary
Intraoral and extraoral dental radiography is an integral part of dental task. Dental radiographs are used from diagnosis and treatment plan of various lesions and conditions within the jaws to follow up the success of treatments such as root canal therapy, implant applications, orthognathic surgery or periodontal therapy. The antegonial notch or angle is the depression along the jawline and it is the upward curving of the inferior border of the mandible anterior to the gonion. It lies at the junction of body and the ramus [3]. In this study gonial angle, antegonial angle, mandibular cortical width, coronal pulp widths of maxillary and mandibular first molar teeth, tooth lengths of maxillary and mandibular first molar, mean density of panoramic radiographs and fractal dimension were evaluated in TIFF and JPEG compressed images separately. It was aimed to assess the repeatability of these measurements and explore how image compression affects density, fractal dimension, linear and angular measurements performed on digital panoramic images
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