• Korean Journal of Digital Imaging in Medicine
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• v.3 no.1
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• pp.100-105
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• 1997

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.111-117
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• 2004

Most of digital subtraction methods in dental radiography are based on registration using manual landmarks. We have developed an automatic registration method without using the manual selection of landmarks. By restricting a geometrical matching of images to a region of interest (ROl), we compare the cross-correlation coefficient only between the ROIs. The affine or perspective transform parameters satisfying maximum of cross-correlation between the local regions are searched iteratively by a fast searching strategy. The parameters are searched on the 1/4 scale image coarsely and then, the fine registration is performed on the original scale image. The developed method can match the images corrupted by Gaussian noise with the same accuracy for the images without any transform simulation. The registration accuracy of the perspective method shows a 17% improvement over the manual method. The application of the developed method to radiography of dental implants provides an automatic noise robust registration with high accuracy in almost real time.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.73-80
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• 2004

In this paper, we propose a medical image processing method for detection of periodontal disease. The proposed method is the method of an automatic image alignment and detection of minute changes, to overcome defects in the conventional subtraction radiography by digital image processing technique, that is necessary for getting subtraction image and ROI(Region of Interest) focused on a selection method using the structured features in target images. And the method services accuracy, consistency and objective information or data to results. In result, easily and visually we can identify minute differences in the affected parts whether they have problems or not, and using application system.

• Imaging Science in Dentistry
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• v.47 no.3
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• pp.215-217
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• 2017

• Imaging Science in Dentistry
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• v.47 no.2
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• pp.99-107
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• 2017

Purpose: Erosions and osteophytes are radiographic characteristics that are found in different stages of temporomandibular joint (TMJ) osteoarthritis. This study assessed the effectiveness of digital subtraction radiography (DSR) in diagnosing simulated osteophytes and erosions in the TMJ. Materials and Methods: Five intact, dry human skulls were used to assess the effectiveness of DSR in detecting osteophytes. Four cortical bone chips of varying thicknesses (0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm) were placed at the medial, central, and lateral aspects of the condyle anterior surface. Two defects of varying depth (1.0 mm and 1.5 mm) were created on the lateral, central, and medial poles of the condyles of 2 skulls to simulate erosions. Panoramic images of the condyles were acquired before and after artificially creating the changes. Digital subtraction was performed with Emago dental image archiving software. Five observers familiar with the interpretation of TMJ radiographs evaluated the images. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of the imaging methods. Results: The area under the ROC curve (Az) value for the overall diagnostic accuracy of DSR in detecting osteophytic changes was 0.931. The Az value for the overall diagnostic accuracy of panoramic imaging was 0.695. The accuracy of DSR in detecting erosive changes was 0.854 and 0.696 for panoramic imaging. DSR was remarkably more accurate than panoramic imaging in detecting simulated osteophytic and erosive changes. Conclusion: The accuracy of panoramic imaging in detecting degenerative changes was significantly lower than the accuracy of DSR (P<.05). DSR improved the accuracy of detection using panoramic images.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.961-974
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• 2005

Various biological approaches to the promotion of periodontal regeneration have been used. These can be divided into the use of growth and differentiation factors, application of extracellular matrix proteins and attachment factors and use of mediators of bone metabolism. The purpose of this study was to evaluate the effect of enamel matrix protein and platelet-rich plasma on the treatment of intrabony defect, with bovine-derived bone powder in humans by digital subtraction radiography. 12 teeth(experimental I group) were treated with enamel matrix protein combined with bovine-derived bone powder and 12 teeth(experimental II group) were treated with platelet-rich plasma combined with bovine-derived bone powder. The change of bone density was assessed by digital subtraction radiography in this study. The change of mineral content was assessed in the method that two radiography were put into computer program to be overlapped and the previous image was subtracted by the later one. Both groups were statistically analyzed by Wilcoxon signed Ranks Test and Mann-whitney Test using SPSS program for windows(5% significance level). The results were as follows: 1. The radiolucency in 3 months after surgery was significantly increased than 1 month after surgery in both groups(experimental I and II groups)(p<0.05). 2. The radiopacity in 6 months after surgery was significantly increased than 3 months after surgery in both groups(experimental I and II groups) (p<0.05). 3. In experimental I group, there was no significant difference between 1 month and 6 months after surgery. 4. In experimental II group. the radiopacity in 6 months after surgery was significantly increased than 1 month after surgery(p<0.05). 5. There was no significant difference between experimental I and II group at 1 month and 3 months after surgery, but the radiopacity in experimental II group was significantly increased at 6 months after surgery(p<0.05). In conclusion, platelet-rich plasma can enhance bone density than enamel matrix protein until 6 months after surgery.

• Imaging Science in Dentistry
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• v.32 no.3
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• pp.147-151
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• 2002

Purpose: To compare the standard deviation of gray levels on digital subtracted images obtained by different dental subtraction programs. Materials and Methods: Paired periapical films were taken at the lower premolar and molar areas of the phantoms involving human mandible. The bite registration group used Rinn XCP equipment and bite registration material, based on polyvinyl siloxane, for standardization. The no bite registration group used only Rinn XCP equipment. The periapical film images were digitized at 1200 dpi resolution and 256 gray levels by a flat bed scanner with transparency unit. Dental digital subtraction programs used for this study were Subtractor (Biomedisys Co., Korea) and Emago (Oral Diagnostic Systems, The Netherlands). To measure the similarities between the subtracted images, the standard deviations of the gray levels were obtained using a histogram of subtracted images, which were then analyzed statistically. Results: Subtracted images obtained by using the Emago program without manual selection of corresponding points showed the lowest standard deviation of gray levels (p<0.01). And the standard deviation of gray levels was lower in subtracted images in the group of a bite registration than in the group of no use of bite registration (p < 0.01). Conclusion: Digital radiographic subtraction without manual selection of reference points was found to be a convenient and superior method.

• Imaging Science in Dentistry
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• v.32 no.2
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• pp.107-111
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• 2002

Purpose : To compare the accuracy of digital subtraction images acquired by two different methods different in positioning four reference points for geometrical standardization. Materials and Methods : A total of 36 digital radiographic images of 6 volunteers were taken at the areas of the incisor, premolar, and molar of both the maxilla and mandible using the Digora system. Each image was moved 4 mm vertically and horizontally. Four oral and maxillofacial radiologists performed digital subtraction radiography between the paired images before and after movement using Emago (Oral Diagnostic Systems, Amsterdam, The Netherlands) and Sunny (Biomedisys Co., Seoul, Korea). The standard deviation of the internal gray value in Region of Interest (ROI) was statistically analyzed between the two programs using the paired t-test. Results : The standard deviation of pixel gray values from the digital subtraction images using the Sunny program were lower than that of the Emago program (p<0.05). All observers showed significant differences between each other when the Sunny program was used (p<0.05), but one observer showed a significantly higher score than other observers when they used Emago (p<0.05). The standard deviations of premolar area from both Sunny and Emago programs were significantly higher than those of anterior and molar regions (p<0.05). Conclusion: The subtracted images using the Sunny program were more accurate and sensitive than those taken using the Emago program.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.2
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• pp.15-25
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• 1997

This study was performed to prepare the quantitative method of judging the sensitive prognosis of chronic apical periodontitis as early as possible. The subjects were 25 cases with periapical radiolucencies of which were treated with endodontic treatment. Serial radiographs were taken by standardized method longitudinally. The density slice function of digital radiographic system were employed for quantitative and longitudinal assessment of the radiolucent area and the condensing osteitis simultaneously. Obtained results were as follows: 1. The amount of bone repair after endodontic treatment could be detected quantitatively by the density slice function of digital radiographic system. 2. Within the 6-week period after root canal filling, the prognosis could be evaluated by assessment both radiolucent area and condensing osteitis on digital radiographic system. 3. The pattern of bone repair showed peripheral type in most cases from the 6th week after root canal filling. 4. In longitudinal change, bone repair showed two patterns; the succeeding reduction of radiolucent area showing the increase of condensing osteitis in size till 6th week and following by static state or reduction tendency and the reduction following the initial increase of both areas. 5. Cases with pulpitis by trauma showed initial increase of condensing osteitis at 2nd week, marked reduction of radiolucent area and condensing osteitis at 6th week, and approximately normal bone state at 8th week after root canal filling.

• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.173-186
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• 2002

The purpose of this study was to evaluate effect of platelet rich plasma on the treatment of Grade II furcation involvement, with Demineralized Freeze-Dried Bone(Dembone(R)) and bioabsorable membrane(BioMesh(R)) in humans by digital subtraction radiography. 12 teeth(control group) were treated with Demineralized Freeze-Dried Bone(Dembone(R)) and bioabsorable membrane(BioMesh(R)), and 12 teeth(test group) were treated with Demineralized Freeze-Dried Bone(Dembone(R)), bioabsorable membrane(BioMesh(R)) and Platelet Rich Plasma. The change of bone density was assessed by digital subtraction radiography in this study. The change of mineral content by as much as 5%(vol) could be perceived in the subtracted images. The change of mineral content was assessed in the method that two radiographs are put into computer program to be overlapped and the previous image is subtracted by the later one. Both groups were statistically analyzed by Wilcoxon signed Ranks Test and Mann-whitney Test using SPSS program (5% significance level). The results were as follows: 1. In test group, the radiopacity in 3 months after surgery were significantly increased than 1 month after surgery(p<0.05). However. there were no significant difference between 1 month after surgery and 3 months after surgery in control group(p>0.05). 2. In test and control group, the radiopacity in 6 months after surgery were significantly increased than 1 month after surgery(p<0.05) 3. In test and control group, the radiopacity in 6 months after surgery were significantly increased than 3 months after surgery(p<0.05). 4. There were no significant difference between test group and control group at 1 month, 3 months after surgery, but radiopacity in test group were significantly increased than control group at 6 months after surgery(p<0.05). In conclusion, Platelet Rich Plasma can enhance bone density.