• Imaging Science in Dentistry
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• v.32 no.3
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• pp.123-127
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• 2002

Purpose : To determine whether subtraction images utilizing contrast media can improve the diagnostic performance of proximal caries diagnosis compared to conventional periapical radiographic images. Materials and Methods: Thirty-six teeth with 57 proximal surfaces were radiographied using a size #2 RVG-ui sensor (Trophy Radiology, Marne-la-Vallee, France). The teeth immersed in water-soluble contrast media and subtraction images were taken. Each tooth was then sectioned for histologic examination. The digital radiographic images and subtraction images were examined and interpreted by three dentists for proximal caries. The results of the proximal caries diagnosis were then verified with the results of the histologic examination. Results: The proximal caries sensitivity using digital subtraction radiography was significantly higher than simply examining a single digital radiograph. The sensitivity of the proximal dentinal carious lesion when analyzed with the subtraction radiograph and the radiograph together was higher than with the subtraction radiograph or the radiograph alone. Conclusion: The use of subtraction radiography with contrast media may be useful for detecting proximal dentinal carious lesions.

• Imaging Science in Dentistry
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• v.31 no.1
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• pp.51-55
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• 2001

Purpose : This study was performed to compare the diagnostic ability of conventional intraoral radiographs with that of digital subtraction image and to assess the quantifying ability of digital subtraction image for simulated apical root resorption Materials and Methods : Conventional intraoral radiographs and digital images of ten sound maxillary central incisors and those with simulated apical root resorption were taken with varying horizontal and vertical angulations of the x-ray beam. The diagnostic accuracy to detect the lesion was evaluated on conventional intraoral radiographs and digital subtraction images by ROC analysis. The amount of simulated apical root resorption was also estimated on the reconstruction images by Emago/sup (R)/ and compared with actual amount of tooth loss using paired t-test. Results: The diagnostic accuracy of conventional intraoral radiographs to detect the apical root resorption was low (ROC area = 0.6446), and the sensitivity and the specificity of digital subtraction images were 100%, respectively. The calculated amounts of apical root resorption showed no statistically significant difference with the actual amounts of the lesion (p>0.05). Conclusion: Digital subtraction radiography is powerful tool to detect the small apical root resorption, and quantitative analysis of small amounts of the lesion can be evaluated by digital subtraction radiography.

• Imaging Science in Dentistry
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• v.31 no.1
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• pp.23-34
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• 2001

Purpose : To develop a new subtraction program for registering digital periapical images based on the correspondence of anatomic structures. Materials and Methods: The digital periapical images were obtained by Digora system with Rinn XCP equipment after translation of 1-16 mm, and rotation of 2-20° at the premolar and molar areas of the human dried mandible. The new subtraction program, NIH Image program and Emago/Advanced program were compared by the peak-signal-to noise ratio (PSNR). Results : The new subtraction program was superior to NIH Images program and Emagol Advanced program up to 16 mm translation and horizontal angulation up to 4°. Conclusion: The new subtraction program can be used for subtracting digital periapical images.

• Journal of Periodontal and Implant Science
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• v.25 no.1
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• pp.67-75
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• 1995

The progress of periodontal disease and the wound healing process after treatment result in alveolar bone bone change. So, detection of it is very important in the diagnosis and the radiograph of periodontal disease. Various effects have been made to assess the subtle alveolar bone change and digital subtraction radiography (DSR) has been reported to be the best method in evaluating it qualitatively and quantitatively. The present study was performed to estimate the detectable alveolar bone change qualitatively with digital subtraction radiography. For the in vitro study, 10 intraoral standard radiographs were taken from porcine dry mandible which a rectangular cortical bone chip of 0.1mm to 1.0mm thickness with 0.1mm increment was attached on the buccal surface. The radiographs without and with bone plates were reviewed at the same time by 10 observers and requested to detect the presence of cortical bone plates. Digital Subtraction radiograph was reviewed subsequently by using the DSR system(digital converter-256 grey-levels,DT 2851,Data Translation Co., U.S.A;IBM 386 ; CCD camera, FOTOVIX, Tamrom Co., Japan). The detectable thickness of cortical bone plate was O.4mm on the intraoral radiograph and 0.2mm on the subtaction images. For the human study, radiographs were taken from patients by using intraoral film holding device and aluminum reference wedge before and 3 month after bone graft and 1 week after osteoplasty. The grey level change was estimated in the subtraction images and calculated to aluminum equivalent thickness. The grey level of the grafted site was higher that that of healthy controls. Average grey levels of change on healthy controls were O.48mm aluminum equivalent. However, the amount of changes in grafted sites were 1.87mm aluminum thickness equivalent and in the site of osteoplasty were -1.49mm aluminum thickness equivalent. In conclusion, digital subtraction radiography was more effective in detecting as subtle change of alveolar bone than intraoral standard radiography. With the aid of quantitative analysis of digital subtraction radiography, alveolar bone resorption of apposition can be estimated during diagnosis and treatment of periodontally diseased patients.

• Journal of radiological science and technology
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• v.42 no.5
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• pp.351-356
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• 2019

This study aimed to determine whether there was a difference in measurements between North American Symptomatic Carotid Endarterectomy Trial(NASCET) and Warfarin-Aspirin Symptomatic Intracranial Disease(WASID) methods that measure the middle cerebral artery stenosis in Digital Subtraction Angiography (DSA) and Magnetic Resonance Angiography (MRA). It involved 24 patients who had completed both DSA and MRA among patients with Middle Cerebral Artery (MCA) stenosis. The Middle Cerebral Artery (MCA) stenosis was measured using the NASCET and WASID methods through a retrospective analysis. For the NASCET and WASID methods, they performed measurements on normal blood vessels located far from and close to the stenosis, respectively. The mean value and standard deviation of the Digital Subtraction Angiography (DSA) measured by the NASCET method were 59.23% and 13.27%. On the other hand, those of the Digital Subtraction Angiography (DSA) measured by the WASID method were 66.64% and 12.47%. And, the mean value and standard deviation of the Magnetic Resonance Angiography (MRA) measured by the NASCET method were 49.82% and 12.06%. By contrast, those of the Magnetic Resonance Angiography (MRA) measured by the WASID method were 56.63% and 10.67%. All the p-values obtained by the Pearson and Spearman correlation tests in the Digital Subtraction Angiography (DSA) and the Magnetic Resonance Angiography (MRA) were <0.01. In conclusion, this study suggests that both the NASCET and WASID methods to measure the middle cerebral artery stenosis in the Digital Subtraction Angiography (DSA) and the Magnetic Resonance Angiography (MRA) can be used if they are not used interchangeably.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.2
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• pp.417-422
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• 1999

Purpose : The aim of this study was to assess the validity of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error. Materials and Methods : Twenty periapical radiographs were used as baseline images and they were copied to exclude the influence of exposure geomety and contrast differences. These subsequent images were linearly displaced by 0.1-0.5 mm in the x-. y- and xy-directions, rotated by 0.5-3° and distorted by angular contraction of 1-5° in x- and y-axis before subtraction. The standard deviations of gray levels in the subtraction images were obtained and paired t-tests were performed. Pearson correlation coefficients(r) were calculated between the standard deviations and the superimposition errors. Results : Linear displacement showed high correlation coefficients of 0.997, 0.997 and 0.995 in x-. y- and xy-axis respectively. Statistically significant different standard deviation existed among all linearly displaced groups(p<0.05). Distortion showed relatively low correlation coefficients of 0.982 and 0.959 in x- and y-axis. The standard deviations between the two distortion groups were statistically significant different(p<0.05). Conclusion : Standard deviation of gray level distribution in digital subtraction images is satisfactory but not perfect similarity measure to assess the superimposition errors.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.797-809
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• 1998

The purposes of this study were to develop the computer program for the contrast and geometric correction in digital subtration radiography with the IDL (Interactive Data Language) and compare the results with this program for the correction of the non-standardized radiographs to those of standardized radiographs and those with "Emago" software, the commercial program for the correction. The procedures were written for the contrast correction and subtraction with the geometric correction, using IDL. 32 pairs of periapical radiographs of premolar and molar portion of two dry human mandibles were taken at two different occasions with XCP film holder(nonstandardized films) and another 32 pairs with customized XCP film holder(standardized films). Subtraction of standardized film pairs was performed. Subtraction after the contrast and geometric correction of non-standardized films was performed using the newly developed program and Emago software. Standard deviations of grey levels of the subtracted images by the newly developed program were compared with those of the standardized group and Emago-corrected group. Standard deviations of grey levels of new program-corrected group were much smaller than those of the Emago-corrected group (p<0.001) and slightly larger than those of standardized group (p<0.05). However, the difference was very minute. This study indicates that the newly developed program written with IDL may substitute the mechanical standardization for digital subtraction radiography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.305-316
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• 1994

The comparative detectability of the artificial defects among conventional radiographs, digital images and digital subtraction images was evaluated. The artificial defects were made within spogy bone of 24 unilateral mandibles of adult dogs. The results were as follows: 1. With normal exposure time, the detectability of digital subtraction radiographs was 90.3% which was statistically significant superior to those of conventional radiographs(78.0%) and digital images(75.9%) (p<0.05). 2. With half-exposure time, the detectability of conventional radiographs, digital images and digital subtraction radiographs was 68.4%, 67.3% and 69.9% respectively. There was no statistical significant difference among the detectability of these methods(p>0.05). 3. All radiographic images with normal exposure time showed statistically significant superior detectability to those with half-exposure time(p<0.05). 4. The detectability of digital subtraction radiographs was not linearly related to the standard deviation of the grey levels of reference line(p<0.05).

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.595-604
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• 1993

Since $Gr{\"{o}}nadhl$ et al introduced a digital subtraction radiography into periodontal dignosis in 1983, many reports using this system has aimed to assess the peroiodontal disease activity and the alveolar bone changes after periodontal treatment. The present study was performed to evaluate the usefulness of digital subtraction radiography for asessing an alveolar bone changes in 3 months after periodontal flap surgery. Serial intraral raiographs were taken from 5 normal subjects and 6 periodontally diseased patients using customized bite blocks attached to film holder in fxation device and digitized by image processing system(consisting of IBM 386, digital frame grabber, CCD camera, Image-pro II software). And the reference parameters were measured by pixel unit and compared with respective radiographs. The serial radiographs showed a little and statistically insignificant difference in reference paramenters. The conventional intraoral radiographs, the subtraction images and the clor enhanced subtraction images were reviewed by 4 examiners and the examiner's agreement rates were compared. The subtraction images and its color enhanced images showed higher examiner's agreement rate than the conventional radiographs. And the propotions of sites diagnosed with bone loss or gain after periodontal surgery were highter in the subtraction images and its color enhanced images than in the conventional radiographs. Especially, in color enhanced images, the unber of bone agin sites tended to increase according to post-surgery periods. These results indicate that projection geometry could be standardized with the divice used in this study, and the subtraction radiography may be useful to assess an alveolar bone changes after periodntal flap surgery.

• Journal of Biomedical Engineering Research
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• v.6 no.2
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• pp.29-32
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• 1985

We have developed a real time digital subtraction a giographic system(RTDSA) and specified it's performance characteristics. Our RTDSA has large-capacity frame memories and a post-processing computer which enables various advanced digital image processing techniques.