• 대한치과교정학회지
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• 제49권1호
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• pp.32-40
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• 2019

Objective: Precise identification of landmarks on posteroanterior (PA) cephalograms is necessary when evaluating lateral problems such as facial asymmetry. The aim of the present study was to investigate whether the use of lateral (LA) cephalograms can reduce errors in landmark identification on PA cephalograms. Methods: Five examiners identified 16 landmarks (Cg, N, ANS, GT, Me, RO, Lo, FM, Z, Or, Zyg, Cd, NC, Ms, M, and Ag) on 32 PA cephalograms with and without LA cephalograms at the same time. The positions of the landmarks were recorded and saved in the horizontal and vertical direction. The mean errors and standard deviation of landmarks location according to the use of LA cephalograms were compared for each landmark. Results: Relatively small errors were found for ANS, Me, Ms, and Ag, while relatively large errors were found for N, GT, Z, Or, and Cd. No significant difference was found between the horizontal and vertical errors for Z and Or, while large vertical errors were found for N, GT, and Cd. The value of identification error was lower when the landmarks were identified using LA cephalograms. Statistically significant error reductions were found at N and Cd with LA cephalograms, especially in the vertical direction. Conclusions: The use of LA cephalograms during identification of landmarks on PA cephalograms could help reduce identification errors.

• 대한치과교정학회지
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• 제49권1호
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• pp.41-48
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• 2019

Objective: This in-vivo study aimed to compare landmark identification errors in anteroposterior (AP) and posteroanterior (PA) cephalograms generated from cone-beam computed tomography (CBCT) scan data in order to examine the feasibility of using AP cephalograms in clinical settings. Methods: AP and PA cephalograms were generated from CBCT scans obtained from 25 adults. Four experienced and four inexperienced examiners were selected depending on their experience levels in analyzing frontal cephalograms. They identified six cephalometric landmarks on AP and PA cephalograms. The errors incurred in positioning the cephalometric landmarks on the AP and PA cephalograms were calculated by using the straight-line distance and the horizontal and vertical components as parameters. Results: Comparison of the landmark identification errors in CBCT-generated frontal cephalograms revealed that landmark-dependent differences were greater than experienceor projection-dependent differences. Comparisons of landmark identification errors in the horizontal and vertical directions revealed larger errors in identification of the crista galli and anterior nasal spine in the vertical direction and the menton in the horizontal direction, in comparison with the other landmarks. Comparison of landmark identification errors between the AP and PA projections in CBCT-generated images revealed a slightly higher error rate in the AP projections, with no inter-examiner differences. Statistical testing of the differences in landmark identification errors between AP and PA cephalograms showed no statistically significant differences for all landmarks. Conclusions: The reproducibility of CBCT-generated AP cephalograms is comparable to that of PA cephalograms; therefore, AP cephalograms can be generated reliably from CBCT scan data in clinical settings.

• Imaging Science in Dentistry
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• 제51권4호
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• pp.407-412
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• 2021

Purpose: The purpose of this study was to evaluate the accuracy of virtual 3-dimensional (3D) cephalograms constructed using the principle of biplanar radiography by comparing them with cone-beam computed tomography (CBCT) images. Materials and Methods: Thirty orthodontic patients were enrolled in this study. Frontal and lateral cephalograms were obtained with the use of a head posture aligner and reconstructed into 3D cephalograms using biplanar radiography software. Thirty-four measurements representing the height, width, depth, and oblique distance were computed in 3 dimensions, and compared with the measurements from the 3D images obtained by CBCT, using the paired t-test and Bland-Altman analysis. Results: Comparison of height, width, depth, and oblique measurements showed no statistically significant differences between the measurements obtained from 3D cephalograms and those from CBCT images (P>0.05). Bland-Altman plots also showed high agreement between the 3D cephalograms and CBCT images. Conclusion: Accurate 3D cephalograms can be constructed using the principle of biplanar radiography if frontal and lateral cephalograms can be obtained with a head posture aligner. Three-dimensional cephalograms generated using biplanar radiography can replace CBCT images taken for diagnostic purposes.

• 대한치과교정학회지
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• 제27권1호
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• pp.129-140
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• 1997

본 연구는 교정 임상에서 흔히 촬영되는 측모와 정모 두부방사선규격사진을 사용하여 3차원적인 두개안면 형태를 재현하였을 때 그 방법의 정확성을 고찰해 보고, 기존의 측모 두부방사선규격사진과 비교하여 어떠한 차이를 보이는지 알아보고자 하였다. 이를 위해 두개안면 골격모형의 3차원 두부방사선규격사진을 형성하고, 선 계측과 각도 계측을 시행하였다. 여기서 얻어진 계측치들을 실제 계측치 및 측모 두부방사선규격사진에서의 계측치와 비교하여 다음과 같은 결론을 얻었다. 1. 3차원 두부방사선규격사진의 선 계측 평균 오차는 $0.94{\pm}0.62mm$, 평균 확대율 $100.31{\pm}0.91%$ 이었으며 실제 계측치와 차이를 보이지 않았다(${\alpha}=0.1$). 2. 측모 두부방사선규격사진은 선 계측에서 평균 오차 $6.44{\pm}1.48mm$, 평균 확대율 $106.99{\pm}1.45%$로서 하악체를 제외한 모든 선 계측에서 확대를 보였다(P<0.005). 3. 3차원 두부방사선규격사진에서의 각도 계측은 평균 오차 $1.22{\pm}0.82^{\circ}$, 평균 확대율 $105.72{\pm}12.07%$ 로서 실제 계측치와 차이를 보이지 않았다(${\alpha}=0.1$). 4. 측모 두부방사선규격사진은 평균 오차 $1.70{\pm}0.94^{\circ}$, 평균 확대율 $106.35{\pm}15.70%$으로 실제 계측치와 차이를 보이지 않았다 (${\alpha}=0.1$).

• 대한치과교정학회지
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• 제39권5호
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• pp.289-299
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• 2009

본 연구는 3차원 콘빔CT 영상을 이용하여 2차원 정모두부방사선사진영상 형성 시 두부자세재현기(Head Posture Aligner, HPA)를 이용한 경우와 이용하지 않은 경우를 비교분석함으로써 HPA의 유용성을 평가하기 위하여 시행되었다. 성인 30명을 대상으로 먼저 일반적인 방법으로 콘빔CT 영상을 채득한 후 HPA를 이용하여 일정한 두부자세를 재현한 상태에서 또 하나의 콘빔CT 영상 및 정모두부방사선사진을 촬영하였다. 3차원 영상프로그램을 이용하여 HPA를 이용하지 않은 경우와 HPA를 이용한 경우 각각에서 2차원 정모두부방사선사진영상을 형성한 다음 각각의 투사도를 작성하고 실제로 HPA를 이용하여 촬영된 정모두부방사선사진 투사도와의 차이를 비교하였다. 거리 및 각도를 나타내는 여러 계측치를 비교분석한 결과 HPA를 이용하지 않은 경우에는 다수의 계측항목에서 실제 정모두부방사선사진과 유의한 차이를 보인 반면 HPA를 이용한 경우에는 모든 항목에서 통계적 유의차를 보이지 않았다. 아울러 실제 정모두부방사선사진과의 상관관계를 알아보기 위해 상관분석을 시행한 결과 HPA를 이용한 경우가 그렇지 않은 경우보다 모든 항목에서 높은 상관성을 보였다. 본 연구 결과는 3차원 콘빔CT 영상을 이용하여 2차원 정모두부방사선사진영상 형성 시 정확한 영상 획득을 위해서는 콘빔CT 촬영 시 HPA의 사용이 필요함을 시사하였다.

• 대한치과교정학회지
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• 제43권2호
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• pp.54-61
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• 2013

Objective: The purpose of this study was to evaluate the effectiveness of the use of Reference Ear Plug (REP) during cone-beam computed tomography (CBCT) scan for the generation of lateral cephalograms from CBCT scan data. Methods: Two CBCT scans were obtained from 33 adults. One CBCT scan was acquired using conventional methods, and the other scan was acquired with the use of REP. Virtual lateral cephalograms created from each CBCT image were traced and compared with tracings of the real cephalograms obtained from the same subject. Results: CBCT scan with REP resulted in a smaller discrepancy between real and virtual cephalograms. In comparing the real and virtual cephalograms, no measurements significantly differed from real cephalogram values in case of CBCT scan with REP, whereas many measurements significantly differed in the case of CBCT scan without REP. Conclusion: Measurements from CBCT-generated cephalograms are more similar to those from real cephalograms when REP are used during CBCT scan. Thus, the use of REP is suggested during CBCT scan to generate accurate virtual cephalograms from CBCT scan data.

• 대한치과교정학회지
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• 제48권5호
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• pp.292-303
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• 2018

Objective: Biplanar imaging systems allow for simultaneous acquisition of lateral and frontal cephalograms. The purpose of this study was to compare measurements recorded on three-dimensional (3D) cephalograms constructed from two-dimensional conventional radiographs and biplanar radiographs generated using a new biplanar imaging system with those recorded on cone-beam computed tomography (CBCT)-generated cephalograms in order to evaluate the accuracy of the 3D cephalograms generated using the biplanar imaging system. Methods: Three sets of lateral and frontal radiographs of 15 human dry skulls with prominent facial asymmetry were obtained using conventional radiography, the biplanar imaging system, and CBCT. To minimize errors in the construction of 3D cephalograms, fiducial markers were attached to anatomical landmarks prior to the acquisition of radiographs. Using the 3D $Ceph^{TM}$ program, 3D cephalograms were constructed from the images obtained using the biplanar imaging system (3D $ceph_{biplanar}$), conventional radiography (3D $ceph_{conv}$), and CBCT (3D $ceph_{cbct}$). A total of 34 measurements were obtained compared among the three image sets using paired t-tests and Bland-Altman plotting. Results: There were no statistically significant differences between the 3D $ceph_{biplanar}$ and 3D $ceph_{cbct}$ measurements. In addition, with the exception of one measurement, there were no significant differences between the 3D $ceph_{cbct}$ and 3D $ceph_{conv}$ measurements. However, the values obtained from 3D $ceph_{conv}$ showed larger deviations than those obtained from 3D $ceph_{biplanar}$. Conclusions: The results of this study suggest that the new biplanar imaging system enables the construction of accurate 3D cephalograms and could be a useful alternative to conventional radiography.

• Imaging Science in Dentistry
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• 제42권4호
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• pp.201-205
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• 2012

Purpose: This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for three-dimensional (3D) assessments. Materials and Methods: The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. Results: The linear measurements between the two imaging modalities were not statistically different (p>0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p>0.05) with the exception of the gonial angle, ANB difference, and facial convexity. Conclusion: Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.295-302
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• 2022

Purpose: Lateral cephalograms of orthodontic patients may contain incidental findings that could potentially lead to harm. Materials and Methods: The lateral cephalograms of 1765 consecutive 12- to 20-year-old patients, being considered for routine orthodontic treatment, were retrospectively reviewed. These patients were considered normal, because no abnormalities were found either in their medical history or on their clinical examination. Results: The overall prevalence of incidental findings was 18.8%, of which 10.3% were ponticulus posticus and 4.2% were bridging of the sella turcica. Although occipital spurs and ponticulus posticus were more prevalent in males, the size of the sella turcicas did not differ between sexes. Of the 1156 patients completing treatment about 2 years later, only one lateral cephalogram displayed progression of the ponticulus posticus in that time. Conclusion: The prevalence of incidental findings on lateral cephalograms of otherwise normal orthodontic 12- to 20-year-old patients was almost a fifth, of which ponticulus posticus, vertebral fusion, and enlarged parietal foramina were clinically significant.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제18권4호
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• pp.594-606
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• 1996

저자는 하악골의 측방 변위를 보이는 악안면 비대칭증례에서 이하두정방사선규격사진과 정모두부방사선규격사진을 이용하여 두개부 형태와 악안면부의 비대칭성과의 상호 관련성을 조사하여 다음과 같은 결론을 얻었다. 1. 이하두정방사선규격사진에서 하악골의 편위정도는 평균 $-3.12{\pm}3.80$ 이며 절대치의 평균은 $2.50{\pm}2.82$ 이였다. 2. 이하두정방사선규격사진에서 비편위측과 편위측에 대한 유의성 검정에서 통계적인 유의성은 없었으나(p>0.05), 그 차이의 평균은 전두부(Y10, Y9, Y8, Y7, Y6)에서는 편위측이 상대적으로 더 크고, 측두부(Y5, Y-1, Y-2, Y-3, Y-4, Y-5, Y-6)에서는 비편위측이 상대적으로 더 크게 나타났다. 3. 정모두부방사선규격사진에서 술전의 하악골의 평균 편위는 $1.3983{\pm}3.521$ 이며 절대치의 평균은 $3.95{\pm}2.85$ 이였다. 4. 정모두부방사선규격사진에서 수술에 의한 변화량 (PT2A-PT1A) 에 대한 재발량(PTLA-PT2A)의 상관관계분석에서 수술에 의한 이동량이 많을 수록 재발이 많은 것으로 나타났다(p<0.05). 5. 이하두정방사선규격사진에서 하악골 편위정도에 대하여 두개관 형태(비변위-변위차이)에 대한 상관관계분석에서 통계적인 유의성은 없었으나(P>0.05), 변위가 클수록 전두부에서는 비변위측이, 후두부에서는 변위측이 더 큰 경향을 보였다. 6. 정모두부방사선사진상에서 하악골의 변위 정도에 대한 두개관(비변위-변위)과의 상관관계 분석에서 Y4(P<0.05), Y3, Y2, Yl, 0, Y-1, Y-2, Y-4, Y-6(P<0,01), Y-5(p<0.001) 등의 위치에서 하악골의 변위 정도가 클수록 비변위측이 더 큰 것으로 나타났다. 7. 정모두부방사선사진상에서 하악골 재발에 대한 두개관(비변위-변위)과의 상관관계분석에서는 통계적인 유의성이 없었으나(P>0.05), 측두부에서는 비변위-변위 차이가 클수록 재발이 많은 경향을 보였다.