A noniterative approach to the problem of visually lossless compression of dental images is proposed for an image coder based on the discrete cosine transform (DCT) and partition scheme optimization. This approach considers the following peculiarities of the problem. It is necessary to carry out lossy compression of dental images to achieve large compression ratios (CRs). Since dental images are viewed and analyzed by specialists, it is important to preserve useful diagnostic information preventing appearance of any visible artifacts due to lossy compression. At last, dental images may contain noise having complex statistical and spectral properties. In this paper, we have analyzed and utilized dependences of three quality metrics (Peak signal-to-noise ratio, PSNR; eak Signal-to-Noise Ratio using Human Visual System and Masking (PSNR-HVS-M); and feature similarity, FSIM) on the quantization step (QS), which controls a compression ratio for the so-called advanced DCT coder (ADCTC). The threshold values of distortion visibility for these metrics have been considered. Finally, the recent results on detectable changes in noise intensity have been incorporated in the QS setting. A visual comparison of original and compressed images allows to conclude that the introduced distortions are practically undetectable for the proposed approach; meanwhile, the provided CR lies within the interval.
Background and aimsPrevalence of atopic diseases is progressively increasing in children with unclear clinical picture in oral cavity. This study aimed to find correlation between the total antioxidant and periodontal status in the saliva of periodontally compromised with atopy.Materials and methodsThe groups consisted of patients of atopic diseases and gingivitis (ADG), of atopic diseases without gingivitis (AD), and healthy controls (HC). The level of gingival inflammation was evaluated using the sulcus bleeding index (SBI) reported by Mühlemann and Son. Glutathione (GSH), malondialdehyde (MDA), and superoxide dismutase (SOD) were estimated in saliva.ResultsThe mean salivary MDA levels of group HC was significantly lower compared with group ADG and AD (P < 0.05). Similarly, in the case of salivary GSH, marker levels revealed a significant decrease (P < 0.05) when mean values in the control group (5.12 ± 0.66 µmol/L) were compared with the ADG (2.31 ± 0.44 µmol/L) and AD groups (2.69 ± 0.56 µmol/L). The SOD activity was significantly lower in the ADG and AD groups compared with HC.DiscussionAs there was no significant difference in the level of SOD concentration between groups, we suggest that antioxidant imbalance is primarily explained by atopic disease.ConclusionThe results showed changes in antioxidant balance in children with atopy.
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