• The korean journal of orthodontics
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• v.27 no.4 s.63
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• pp.633-641
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• 1997

Spatial change of craniofacial structures from growth or orthopedic force is usually evaluated by cephalometric superimpositions at different points in time.As the evaluation cu be changed according to cephalometric superimposition method,selettion for correct superimposition method is very important.Double registration of nineteen pairs of female lateral head films,their growth period is average 3.7 years and age is overage 10.7 years,were performed by two observers.Comparisions was made between two methods and the results revealed the following, 1. NS line and ACB superimpositions ate not markedly different in reliability due to almost same registration error of them. 2. The investigation was undertaken to examine interobserver difference.In NS line method, there is no significance in all measurements. In ACB method,significant difference was revealed in 4 measurements of 7 measurements was 3. In the investigation of intermethod difference, there is no significance between NS line and ACB superimpositions

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.900-913
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• 1998

Despite of technical difficulties, the combination of occlusal projection and densitometric digital analysis may ultimately provide a means of detection of subtle bone loss at the facial and lingual side of dental implant (Oblique occlusal view is more useful for $ITI^{(R)}$ dental implant due to its contour of shoulder as like tulip flower). In this study, conventional periapical projections of x-ray beam had shown more high sensitivity to detect the bony defects than oblique occlusal projections in alveolar crest obscured by dental implants or not, even if the difference was not statistically significant. Unlike conventional periapical projections. occusal projections combined with densitometric digital analysis technique may provide a means for detection of subtle bone change at the all around of implants without obscuring effect by implant itself. Although the results from this in vitro study were performed under limited circumstances, these results might afford more possibility and versatile modality of diagnosis options to clinician in the implant practice.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.371-379
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• 1994

본 연구는 비규격화시켜 촬영한 두장의 방사선 사진을 일반 영상처리 프로그램으로 기하학적 보정을 하여 디지탈 공제 촬영술을 시행한 결과를 개인별로 제작된 필름유지장치를 이용하여 규격화 시켜 촬영한 두장의 방사선사진을 디지탈 공제 촬영술을 시행한 결과와 비교하여 일반 영상처리 프로그램의 임상적 유용성을 평가해보고자 시행하였다. 19명의 자원자를 대상으로 하여, 각 환자에서 4매의 하악구치부 치근단 사진을 촬영하였다. 그중 2매는 XCP 필름 유지장치만으로 평행촬영법으로 촬영하였고, 나머지 2매는 교합제에 인상재를 부가하여 개인별로 제작된 XCP필름 유지장치를 이용하여 표준화시켜 역시 평행촬영법으로 촬영하였다. 기하학적 보정은 "Adobe Photoshop"과 "NIH Image" 프로그램으로 시행하였다. 특히 "Adobe Photoshop"의 임의영상회전 기능과 "IH Image"의 공제시술시 중첩된 사진을 투명하게 보여주는 기능, 병진기능을 활용하였다. 두 사진의 유사성을 측정하기 위해 공제된 사진의 계조도의 표준편차를 구하였다. 표준화군의 평균 표준편차가 기하학적 보정군의 평균 표준편차보다 약간 낮았으나, 통계적으로 유의성이 있는 차이를 보이지는 않았다. 위의 결과로 미루어보아, 하악구치부 에서 XCP필름 유지장치로 평행촬영한 비표준화방사선사진을 "Adobe Photoshop"과 "NIH Image" 프로그램을 이용하여 기하학적 보정을 할 수 있으리라 사료된다.

• The korean journal of orthodontics
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• v.38 no.6
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• pp.427-436
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• 2008

Objective: The purpose of this study is to compare landmark position between cephalometric radiography and midsagittal plane projected images from 3 dimensional (3D) CT. Methods: Cephalometric radiographs and CT scans were taken from 20 patients for treatment of mandibular prognathism. After selection of land-marks, CT images were projected to the midsagittal plane and magnified to 110% according to the magnifying power of radiographs. These 2 images were superimposed with frontal and occipital bone. Common coordinate system was established on the base of FH plane. The coordinate value of each landmark was compared by paired t test and mean and standard deviation of difference was calculated. Results: The difference was from $-0.14{\pm}0.65$ to $-2.12{\pm}2.89\;mm$ in X axis, from $0.34{\pm}0.78$ to $-2.36{\pm}2.55\;mm$ ($6.79{\pm}3.04\;mm$) in Y axis. There was no significant difference only 9 in X axis, and 7 in Y axis out of 20 landmarks. This might be caused by error from the difference of head positioning, by masking the subtle end structures, identification error from the superimposition and error from the different definition.

• Journal of Digital Convergence
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• v.16 no.12
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• pp.441-447
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• 2018

This study aims to develop digital techniques that enable repeated practice of dental radiography using augmented reality technology. A three-dimensional object was fabricated by superimposing a photograph of an adult model and a computed tomography image of a manikin phantom. The system was structured using 106 radiographs such that one of these saved radiographs is opened when the user attempts to take a radiograph on a mobile device. This system enabled users to repeatedly practice at the pre-clinical stage without exposure to radiation. We attempt to contribute to enhancing dental hygienists' competency in dental radiography using these techniques. However, a system that enables the user to actually take a radiograph based on face recognition would be more useful in terms of practice, so additional studies are needed on the topic.

• The korean journal of orthodontics
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• v.40 no.2
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• pp.77-86
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• 2010

Objective: The purposes of this study were to evaluate the reproducibility and reliability of head posture obtained by registering outer canthus as a soft tissue landmark with the Outer Canthus Indicator (OCI). Methods: Twenty-one adults with normal facial morphology were enrolled in this study (mean age $27.5\;{\pm}\;1.72$ years). To register initial head posture, height of the outer canthus from the ear rod plane was measured using OCI. Head posture was reproduced by moving the head upwards and downwards until the outer canthus was in a straight line with the indicator set at a registered height. After the head posture is reproduced by two operators after two days, lateral photographs were taken. Computerized photometric analyses of the photographs were performed. Results: The head rotations around the transverse axis were $0.69\;{\pm}\;0.43^{\circ}$, $0.98\;{\pm}\;0.65^{\circ}$ from each of the two operators. Standard errors were $0.09^{\circ}$ and $0.14^{\circ}$ each, which were similar to results from past research findings. There were no significant differences between the data from the two operators (p > 0.05). There were no correlations between the head rotation around the horizontal and vertical axes (p > 0.05). Conclusions: The present study suggests that OCI-registered head posture may minimize errors from vertical head rotation in cephalometry and photometry.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.1
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• pp.37-43
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• 1991

Cephalometric prediction tracing is the preoperative double checking procedure which can predict bony and soft tissue change. Soft tissue profile prediction is routinely performed according to the known ratios of the soft to hard tissue movement which can vary considerably in each individual. Besides interindividual variation of the ratios of the soft to hard tissue change, actual results of the postoperative soft tissue profile can reflect other important modifying factors if it is compared with prediction tracing used. The purpose of this study is to compare soft tissue prediction tracing used with postoperative tracing and to find intervening modifying factor via serial tracing. Review of 30 prediction tracing showed that the most important factor contributing to prodiction tracing inaccuracy was the skeletal and dental relapse. And, some factors which may be responsible for prediction tracing inaccuracy were discussed.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.1
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• pp.7-13
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• 1991

An anatomic radiolucency called medial sigmoid depression can be observed on a number of panoramic and mandibular oblique lateral views in the ramus just below and anterior to the mandibular sigmoid notch. The radiolucency may be unilateral or bilateral. Seventy-eight mandibles of dry skulls were visually examined and radiographed by panoramic machine. The observable incidence, the location center, and the mean size of the medial sigmoid depression were studied. Additionally, the radiographic incidence of the depression was determined using 500 panoramic radiographs. Normal anatomic radiolucent areas in the jaws are encountered often in the radiographs taken for the usual dental practice purpose. Some of these radiolucencies can be misdiagnosed as pathologic entities. But in most cases, the size, location, and appearance of the radiolucent area, and the presence or absence of symptoms can lead one to the correct diagnosis before surgery is undertaken. And this can be secured if diagnosticians are aware of the common and varied appearances of the normal anatomic radiolucencies A depression in the ramus just below and slightly anterior to the most inferior aspect of mandibular sigmoid notch shows occasionally foramen-like or notch-like radiolucency on some panoramic and oblique lateral views. This radiolucency was named medial sigmoid depression by Langlais et a1. in 1983. Since there're no reports about this medial sigmoid depression after that, (The author retrieved the Mediline from 1983 to 1990: Cambridge scientific abstracts, (7200 Wisconsin Ave Bethesda MD 20814 U.S.A.) National Library of Medicine) the author studied the size and the location of the depression of the mandible specimens, and determined the relationship between the observable anatomic incidence and its reproducibility on the radiographs.

• Progress in Medical Physics
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• v.14 no.3
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• pp.196-202
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• 2003

In 3-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), many studies on reducing setup error have been conducted in order to focus the irradiation on the tumors while sparing normal tissues as much as possible. As one of these efforts, we developed an image enhancement and registration tool for simulators and portal images that analyze setup errors in a quantitative manner. For setup verification, we used simulator (films and EC-L films (Kodak, USA) as portal images. In addition, digital-captured images during simulation, and digitally-reconstructed radiographs (DRR) can be used as reference images in the software, which is coded using IDL5.4 (Research Systems Inc., USA). To improve the poor contrast of portal images, histogram-equalization, and adaptive histogram equalization, CLAHE (contrast limited adaptive histogram equalization) was implemented in the software. For image registration between simulator and portal images, contours drawn on the simulator image were transferred into the portal image, and then aligned onto the same anatomical structures on the portal image. In conclusion, applying CLAHE considerably improved the contrast of portal images and also enabled the analysis of setup errors in a quantitative manner.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.222-232
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• 2014

Purpose: This study aims to investigate if 2D analysis method is applicable to analysis of CBCT by comparing measuring points of CBCT with those of Adjusted 2D Lateral Cephalogram (Adj-Ceph) with magnification adjusted to 100% and finding out at which landmarks the difference in position appear. Materials and methods: CBCT data and Adj-Ceph (100% magnification) data from 50 adult patients have been extracted as research objects, and the horizontal (Y axis) and vertical (Z axis) coordinates of landmarks were compared. Landmarks have been categorized into 4 groups by the position and whether they are bilaterally overlapped. Paired t-test was used to compare differences between Adj-Ceph and CBCT. Results: Significant difference was found at 11 landmarks including Group B (S, Ar, Ba, PNS), Group C (Po, Or, Hinge axis, Go) and Group D (U1RP, U6CP, L6CP) in the horizontal (Y) axis while all the landmarks in vertical (Z) axis showed significant difference (P<.05). As a result of landmark difference analysis, a meaningful difference with more than 1 mm at 13 landmarks were indentifed in the horizontal axis. In the vertical axis, significant difference over 1 mm was detected from every landmark except Sella. Conclusion: Using the conventional lateral cephalometric measurements on CBCT is insufficient. A new 3D analysis or a modified 2D analysis adjusted on 19 landmarks of the vertical axis and 13 of the horizontal axis are needed when implementing CBCT diagnosis.