• 한국방사선학회논문지
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• 제17권4호
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• pp.515-521
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• 2023

치과 구내 촬영 시 사용하는 관전류 및 시간에 따라 환자가 받는 피폭선량은 달라진다. 영상의 질을 위해서는 많은 양의 관전류가 필요하지만, 환자에게 부여되는 방사선량은 그만큼 높아진다. 이에 본 연구에서는 시뮬레이션을 통한 치과 구내 촬영 시 사용하는 관전류에 따른 영상의 질 평가를 통해 영상의 질을 확보하면서 환자가 받는 피폭선량은 감소시킬 수 있는 최적의 관전류 양을 산출하였다. 치과 구내 촬영의 진단참고수준 가이드라인에 제시된 평균 관전류와 시간 및 관전압을 기본 촬영 조건으로 사용하고, 관전류만 변화시켰을 때 영상을 획득한 후 기본 영상과의 영상의 질 비교·분석을 통해 최적의 관전류 양을 산출하였다. 기본 조건은 63 kV, 6 mA, 0.29 s로 하고 관전류를 0.1, 0.5, 1, 2, 3, 4, 5 mA로 변경시켜 영상을 획득하였다. 획득한 영상은 ICY 프로그램을 사용하여 6 mA의 조건으로 촬영한 영상과 구조적 유사지수를 평가하였다. 그 결과 0.5 mA의 관전류 조건에서도 6 mA의 영상과 구조적 유사지수가 높은 것으로 평가되었다. 이러한 결과를 바탕으로 치과 구내 촬영 시 6 mA가 아닌 0.5 mA로 촬영한다면 환자에게 부여되는 피폭선량을 매우 감소시킬 수 있을 것으로 판단된다.

• Imaging Science in Dentistry
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• 제34권1호
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• pp.35-48
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• 2004

Purpose: To investigate the effect of rhBMP-2 on the healing of bone defect in the low calcium diet rat. Materials and Methods: To prepare the experimental model, control group was fed a normal diet and experimental group was fed a low calcium diet for 3 weeks. And then, 4 mm bicortical perforated bone defect was made on mandibular body of each rats. Experimental group was subdivided into two groups; experimental group 1 (rats given a low calcium diet before and after bone defect) and experimental group 2 (rats given a low calcium diet before and after bone defect with rhBMP-2 application). At 1, 3, 5 and 7 weeks after bone defect formation, the rats were terminated. The healing of bone defect was assessed by three-dimensional computerized tomography, soft x-ray radiography, and histopathological examination. Results : The wound healing of the bone defect for control group, experimental group 1, and experimental group 2 showed a increase from 3 weeks after bone defect formation. The experimental group 2 showed a more increase in healing amount than control group and experimental group 1 from 5 weeks after bone defect formation and the experimental group 2 showed a complete recovery of bone defect at 7 weeks after bone defect formation. Conclusion: The healing process of bone defect is accelerated by rhBMP-2 application in the low calcium diet rats.

• Imaging Science in Dentistry
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• 제36권1호
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• pp.63-68
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• 2006

Desmoplastic ameloblastoma is a rare histologic variant of ameloblastoma. It shows important differences in anatomic distribution, histologic appearance, and radiographic findings compared with the general type of ameloblastoma. It is histologically characterized by an abundance of densely collagenous stroma and radiographically a mixed radiolucent-radiopaque lesion. We present three cases of desmoplastic ameloblastoma. All the patients complained on buccal swelling with or without pain and the sites of occurrence were the anterior and the premolar region. Plain radiographs showed mixed radiopaque-radiolucent lesion with ill-defined or diffuse sclerotic margin and no external root resorption. Additionally, CT scans revealetl buccal expansion and relatively well-defined margin of the lesions. The clinical and radiographic features of the presented cases were compared with those of the desmoplastic ameloblastoma in the previous literatures.

• 한국전문물리치료학회지
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• 제7권3호
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• pp.1-18
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• 2000

The present study was performed to investigate the prevalence rate of idiopathic scoliosis and to determine the effect of exercise training on scoliotic angle in elementary school children. In this study, two out of five elementary schools in Seosan city were chosen by random sampling. Seven hundred sixty four students (from four grade to the sixth grade student) were selected in two schools. Screening tests were conducted to find idiopathic scoliosis. Among the 764 individuals, 139 subjects who showed positive sign in physical examination took whole spine radiography. Thirty six subjects who had a curve of 10 or greater and consented to participate in the exercise program were selected for the exercise program. The exercise program was performed four times a week for 5 months. The results of this study were as follows: 1) One hundred thirty nine subjects showed positive sign in the scoliosis screening test. 2) The overall prevalence of curve of $10^{\circ}or$ greater in X-ray finding was 8.15%. The prevalencies of curve of $10^{\circ}or$ greater in male and female were 7.1% and 9.2%, respectively. 3) Scoliosis curves were observed at thoracic area (48.4%), at thoracolumbar area (27.4%) and at lumbar area(24.4%). 4) Right side curve was 59.7%, and left side curve was 40.3%. 5) After the 5 month exercise program for scoliosis, the Cobb's angle was significantly decreased. 6) There was no significant difference of Cobb's angle change respect to sex, grades, and scoliosis curve site. Results shown here indicates that an early detection and early exercise for scoliosis can result in decreased the Cobb's angle in elementary school children.

• Imaging Science in Dentistry
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• 제32권1호
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• pp.19-25
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• 2002

Purpose: To evaluate the degree of accuracy of DentaScan reformatted images of the maxillary sinus and periapical, periodontal lesions and to clarify the usefulness of the reconstructed 3-dimensional images to the dental clinical aspects. Materials and Methods: 33 sides of maxillae of the hemi-sectioned Korean heads were used in this study. Periapical radiographs, computed tomography and DentaScan reformatted cross-sectional images were taken for the radiographic evaluation of the peiapical and peiodontal lesions of the maxillary teeth and inferior wall of maxillary sinus. Results : Compared the degree of accuracy and findings of dental and periapical pathoses on the intraoral radiographs and DentaScan reformatted images with the cross-sectioned specimens, the DentaScan reformatted cross-sectional images were more accurate and more effective than the intraoral radiography with a viewpoint of the detection of dental and periapical pathoses. Conclusion: Comparing the lesions of specimens with intraoral radiographies and DentaScan reformatted images, the dental and periodontal pathoses and topographical structures were more clearly observed in the DentaScan reformatted images, providing the possibility of more applications of reformatted images to clinical dentistry.

• Imaging Science in Dentistry
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• 제33권3호
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• pp.137-141
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• 2003

Purpose: To evaluate the precision of measurements taken of dental implants in bucco-lingually sectioned views of the maxilla by linear tomograms of the panorama and to assess the visibility of the inferior wall of the maxillary sinus. Materials and Methods : Eighty sites prepared with implants of gutta percha cone in the sockets of the upper premolars and molars of 10 dry skulls were radiographically examined using linear tomograms of panorama, and scanned coronally and axially by computed tomography. The differences in mm between the measurements in bucco-lingually sectioned images of maxillary alveolar bone and the true length and width of the implanted gutta percha cones were compared as mean values (mean) and standard deviations (SD) for each radiographic technique. Linear tomography of panorama was compared with computed tomography for visualization of the relationship between the inferior wall of maxillary sinus and the end of each implant. Results: The deviations between the actual implant length and the measured values taken from the linear tomograms (0.44±0.39 mm) was significantly less than the measured values from the multiplanar reconstructed images of the axially scanned computed tomogram (1.21 ± 0.90 mm). There was statistically significant difference (p < 0.05) between two techniques in the differences between the measurements and true implant length. The relationship of the inferior border of maxillary sinus with end of implant was worse identified with the linear tomogram of panorama (68%) than the multiplanar reconstructed image of axially scanned computed tomogram (99%). Conclusion: We could not find any differences in the accuracy of length measurement between the linear tomogram of panorama and computed tomogram, but computed tomogram allowed for a better visualization of the inferior wall of the maxillary sinus than the linear tomogram.

• Imaging Science in Dentistry
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• 제35권3호
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• pp.157-165
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• 2005

Purpose : To find out the proper compression ratios without degrading image quality and affecting lesion detectability on diagnostic images used in dentistry compressed with JPEG 2000 algorithm. Materials and Methods : Sixty Digora periapical images, sixty panoramic computed radiographic (CR) images, sixty computed tomographic (CT) images, and sixty magnetic resonance (MR) images were compressed into JPEG 2000 with ratios of 10 levels from 5:1 to 50:1. To evaluate the lesion detectability, the images were graded with 5 levels (1 : definitely absent; 2: probably absent; 3: equivocal; 4: probably present; 5: definitely present), and then receiver operating characteristic analysis was performed using the original image as a gold standard. Also to evaluate subjectively the image quality, the images were graded with 5 levels (1 definitely unacceptable; 2: probably unacceptable; 3: equivocal, 4: probably acceptable; 5· definitely acceptable), and then paired t-test was performed. Results : In Digora, CR panoramic and CT images, compressed images up to ratios of 15 : 1 showed nearly the same lesion detectability as original images, and in MR images, compressed images did up to ratios of 25 : 1. In Digora and CR panoramic Images, compressed images up to ratios of 5 : 1 showed little difference between the original and reconstructed images in subjective assessment of image quality In CT images, compressed images did up to ratios of 10: 1 and in MR images up to ratios of 15 : 1 Conclusion : We considered compression ratios up to 5 : 1 in Digora and CR panoramic images, up to 10 : 1 in CT images, up to 15 : 1 in MR images as clinically applicable compression ratios.

• Imaging Science in Dentistry
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• 제43권3호
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• pp.145-151
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• 2013

Purpose: This study was performed to evaluate and compare the radiopacity of dentin, enamel, and 8 restorative composites on conventional radiograph and digital images with different resolutions. Materials and Methods: Specimens were fabricated from 8 materials and human molars were longitudinally sectioned 1.0 mm thick to include both enamel and dentin. The specimens and tooth sections were imaged by conventional radiograph using #4 sized intraoral film and digital images were taken in high speed and high resolution modes using a phosphor storage plate. Densitometric evaluation of the enamel, dentin, restorative materials, a lead sheet, and an aluminum step wedge was performed on the radiographic images. For the evaluation, the Al equivalent (mm) for each material was calculated. The data were analyzed using one-way ANOVA and Tukey's test (p<0.05), considering the material factor and then the radiographic method factor, individually. Results: The high speed mode allowed the highest radiopacity, while the high resolution mode generated the lowest values. Furthermore, the high resolution mode was the most efficient method for radiographic differentiation between restorative composites and dentin. The conventional radiograph was the most effective in enabling differentiation between enamel and composites. The high speed mode was the least effective in enabling radiographic differentiation between the dental tissues and restorative composites. Conclusion: The high speed mode of digital imaging was not effective for differentiation between enamel and composites. This made it less effective than the high resolution mode and conventional radiographs. All of the composites evaluated showed radiopacity values that fit the ISO 4049 recommendations.

• 대한치과보철학회지
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• 제43권6호
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• pp.736-744
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• 2005

Statement of problem. Initial stability of implant is an important factor for predicting osseointegration. It requires a rapid, non-invasive, user-friendly technique to frequently assess the implant stability and the degree of osseointegration. Purpose. The aim of this study was to evaluate the correlation between the resonance frequency analysis (RFA) and the radiographic method for peri-implant bone change under in vitro conditions. Material and Method. Twenty implants of 3.75 mm in diameter(Neoplant, Neobiotech, Korea) were used. To simulate peri-implant bone change, 2 mm-deep $45^{\circ}$ range horizontal defect and 2 mm-deep $90^{\circ}$ range horizontal defect area were serially prepared perpendicular to the X-ray beam after conventional implant insertion. Customized film holding device was fabricated to standardize the projection geometry for serial radiographs of implants and direct digital image was obtained. ISQ values and gray values inside threads were measured before and after peri-implant bone defect preparation. Results. Within a limitation of this study, ISQ value of resonance frequency analysis was changed according to peri-implant bone change (p<0.05) and gray value of radiographic method was changed according to peri-implant bone change (p<0.05). There was no correlation between the ISQ value and the gray value for peri-implant bone change (p>0.05). But, in horizontal defect condition, relatively positive correlation were between ISQ and gray values(r=0.663). Conclusion. This results provided a possibility that peri-implant bone change may be evaluated by both RFA and radiographic method.

• 대한방사선기술학회지:방사선기술과학
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• 제29권3호
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• pp.133-139
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• 2006

디지털 X선영상으로 출력한 화상데이터를 Personal Computer로 가져와서 디지털 특성곡선, MTF, 위너스펙트럼을 계산할 수가 있다. 여기서는 디지털화상의 선예도를 후지타(藤田) 등의 이론에 의한 프리샘플링(presampling) Modualtion Transfer Function(MTF)을 산출하고 보정하는 방법에 대하여 검토하였다. 사용한 프로그램은 엑셀이며 슬릿의 촬영, 디지털 특성곡선, 합성 LSF법, 이산 퓨리어 변환, 고속 퓨리어 변환 등의 순서로 기술하였다. 이 방법의 커다란 장점은 퓨리어트랜스폼의 공식과 MTF 산출과정을 완전히 이해할 수 있다는 점과, 별도로 값비싼 프로그램이나 컴퓨터언어를 배우지 않았어도 MTF 결과를 산출할 수가 있다는 것이다. 그리고 워크시트 표시되는 엑셀의 장점을 그대로 살려 X선 영상계의 오류나 산출결과의 부적합성을 발견하기 쉽다는 점이다.