• Imaging Science in Dentistry
• /
• 제35권1호
• /
• pp.25-31
• /
• 2005

Purpose : To evaluate the stability of the segmental occlusal plane and anatomical line as the reference line for measuring the mesiodistal tooth angulation in panoramic radiography and to determine the mean angle and the range of the mesiodistal tooth angulation in Korean population with normal occlusions. Materials and Methods : Twenty nine subjects (15 men, 14 women) with normal occlusion were selected. A total of 29 panoramic radiograms were taken at normal head position and then 10 images of 5 subjects selected were repeatedly taken with repositioning 2 times at each of the head down (V-shaped occlusion) and up (horizontal occlusion) for evaluation of stability of adopted reference lines by using PM2002CC (Planmeca, Finland). The images were traced with adoption of two test reference lines and the long axes of the teeth. The mesial angles formed by each reference line and the long axes of the teeth were measured and analyzed. Results : With anatomical reference line, the mesiodistal tooth angulations of the molars showed the significant difference by over 5 degree between the normal and each changed head position. With segmented occlusal reference line, deviations of mesiodistal tooth angulations by the two changed head positions were less than 1 degree. The means, standard deviations, and maximum and minimum values of mesiodistal tooth angulations to segmental occlusal reference line on panoramic radiography were determined. Conclusion : It would appear that mesiodistal tooth angulations to segmental occlusal plane as reference line in panograms are predictable as standards of normal occlusion and useful for evaluation of tooth arrangement between adjacent teeth.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제33권4호
• /
• pp.346-351
• /
• 2011

Purpose: The purpose of this study was to measure the angular differences between the horizontal reference planes on the CBCT generated PA cephalogram and the modified interpupillary plane, which was usually used in the clinical examination, and to evaluate the validity of the horizontal reference planes. Methods: The CBCT generated PA cephalogram was used to measure the angles between the FH, Lo and IP planes. The subjects consisted of 42 patients with facial asymmetry (males: 21, females: 21, mean-age: 21.6 years). The control groups were also assessed (males: 10, females: 10, mean-age: 23.8 years). The distance of the interpupil was measured on the soft-tissue volume rendered image. The angular differences were statistically analyzed using the $Mann-Whitney$ $U$ $test$ for inter-group comparisons and the $Friedman$ $test$ for intra-group comparisions. Results: The angle between the FH plane and IP plane (the angle of the FH-IP line) showed a statistically significant difference between the two groups ($p$ <0.05). There was no statistical differences between each angle (angle of the FH-IP line, angle of the FH-Lo line, angle of the Lo-IP line) on the intra-group comparision ($p$ >0.05). Conclusion: The angle between the Lo line and IP line (angle of the Lo-IP line) showed no statistically significant difference in both the control and asymmetry groups. Therefore, the Lo line could be used as a horizontal reference plane in CBCT generated PA cephalograms.

• 한국정보통신학회논문지
• /
• 제20권10호
• /
• pp.1973-1979
• /
• 2016

기술이 발전하면서 카메라를 통해 3D 측정을 하는 방법은 계속 발전되어왔고 최근에는 여러 주기의 fringe pattern을 이용한 측정 방법을 쓰고 있다. 본 논문에서는 여러 주기의 fringe pattern을 이용한 3D 측정 방법에 대한 기존 방법의 문제점을 제시하고, 이에 대한 해결 방안으로 기준면의 절대위상과 물체의 위상차를 이용한 물체의 절대위상을 구하는 방법을 제안한다. 이를 이용하면 새로운 물체에 대해서 매번 여러 주기의 fringe pattern을 조사하지 않고 물체의 절대위상을 얻을 수 있다. 따라서 제안하는 방법을 이용하면, 측정단계에서 취득하는 영상의 개수가 적기 때문에 보다 빠른 속도로 3D 측정을 할 수 있다. 실험을 통하여 제안하는 방법의 유용성을 보였다.

• 소음진동
• /
• 제7권2호
• /
• pp.255-260
• /
• 1997

This paper describes 3-dimensional volume array of 4 microphones including a reference microphone which is capable of imaging wideband noise source position in 2-dimensional image plane. The cross correlation function and corresponding imaging function between a reference microphone and other microphone, are derived as a function of noise source position. The magnitude of the imaging function gives noise source mapping in image plane. Since the image plane is selective from a rectangular and a cylindrical plane, noise source position information such as range and bearing relative to the array is identified very much easily. Simulation results for typical source configurations confirms the applicability of the proposed array in noise control field.

• Imaging Science in Dentistry
• /
• 제41권2호
• /
• pp.79-84
• /
• 2011

Purpose : The aim of the present study was to investigate the disagreement of cephalometric analysis depending on the reference determination of midsagittal plane on three-dimensional computed tomography. Materials and Methods : A total of 102 young women with class III dentofacial deformity were evaluated using three-dimensional computed tomography. The cranial and facial midsagittal planes were defined and the amounts of jaw deviation were calculated. The amounts of jaw deviation were compared with paired t-test (2-tailed) and Bland-Altman plot was drawn. Results : The landmark tracing were reproducible ($r{\ge}.978$). The jaws relative to the cranial midsagittal plane were 10-17 times more significantly deviated than to the facial midsagittal plane (P<.001). Bland-Altman plot demonstrated that the differences between the amounts of jaw deviation from two midsagittal planes were not normally distributed versus the average of the amounts of jaw deviation from two midsagittal planes. Conclusion : The cephalometric analyses of facial asymmetry were significantly inconsistent depending on the reference determination of midsagittal plane. The reference for midsagittal plane should be carefully determined in three-dimensional cephalometric analysis of facial asymmetry of patients with class III dentofacial deformity.

• Imaging Science in Dentistry
• /
• 제49권2호
• /
• pp.159-169
• /
• 2019

Purpose: Cone-beam computed tomography (CBCT) is widely used for 3-dimensional assessments of cranio-maxillo-facial relationships, especially in patients undergoing orthognathic surgery. We have introduced, for reference in CBCT cephalometry, an anatomical mid-sagittal plane (MSP) identified by the nasion, the midpoint between the posterior clinoid processes of the sella turcica, and the basion. The MSP is an updated version of the median plane previously used at our institution for 2D posterior-anterior cephalometry. This study was conducted to test the accuracy of the CBCT measures compared to those obtained using standard posterior-anterior cephalometry. Materials and Methods: Two operators measured the inter-zygomatic distance on 15 CBCT scans using the MSP as a reference plane, and the CBCT measurements were compared with measurements made on patients' posterior-anterior cephalograms. The statistical analysis evaluated the absolute and percentage differences between the 3D and 2D measurements. Results: As demonstrated by the absolute mean difference (roughly 1 mm) and the percentage difference (less than 3%), the MSP showed good accuracy on CBCT compared to the 2D plane, especially for measurements of the left side. However, the CBCT measurements showed a high standard deviation, indicating major variability and low precision. Conclusion: The anatomical MSP can be used as a reliable reference plane for transverse measurements in 3D cephalometry in cases of symmetrical or asymmetrical malocclusion. In patients who suffer from distortions of the skull base, the identification of landmarks might be difficult and the MSP could be unreliable. Becoming familiar with the relevant software could reduce errors and improve reliability.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2008년도 춘계학술대회 논문집
• /
• pp.455-456
• /
• 2008

• 한국산학기술학회논문지
• /
• 제10권5호
• /
• pp.909-916
• /
• 2009

본 연구는 위상천이 영사식 모아레 측정기의 기준 위상 측정단계에서 기준 위상의 검출 정확도를 높이기 위한 방안으로, 일반적인 N-bucket 방법이 아닌, 줄무늬 패턴 투사 영상의 직접적인 영상처리를 기반으로, 노이즈가 포함된 영상으로부터 기준 위상을 자동으로 검출하고 보정하는 방법을 다룬다. 일반적으로 기준위상을 정확히 구하기 위해서는 상대적으로 노이즈가 원천적으로 적은 고정밀도의 교정 시편과 이에 맞는 세분화된 교정방법이 필요하다. 하지만, 고가의 시편 제작비용 절감과 고정도 교정을 위한 교정시간의 단축을 위해, 상대적으로 일반 정밀도등급의 제작된 시편으로부터 획득된 영상을 이용하여, 효율적인 기준위상 교정 방법을 제안한다. 투사된 평행 라인 띠가 시편에서 반사되어 카메라로 입력되는 영상으로부터, 영상처리 라인마스크를 이용하여 격자 라인들의 중심점을 정밀하게 추출하고, 각 라인들에서 추출된 샘플링점 기반의 최소자승법을 이용하여, 라인 특징치인 기울기와 절편을 추출함으로써 실제 관측되는 격자 라인의 중심선을 획득하였으며, 획득된 중심선들을 이용하여 N-bucket 알고리즘에 적용할 수 있도록 위상을 추출한 후, 기준위상을 자동으로 생성하였다. 본 연구를 통하여 고가의 시편 제작 없이 빠르게 자동으로 기준위상을 추출할 수 있었다.

• 대한치과교정학회지
• /
• 제48권4호
• /
• pp.236-244
• /
• 2018

Objective: The aim of this study is to compare the adaptation of a straight wire between brackets positioned at the mid-lingual surface and those placed gingivally by using a three-dimensional simulation software. Methods: This cross-sectional study was performed using OrthoAid, an in-house software. The subjects were 36 adolescents with normal Class I occlusion. For each dental cast, two bracket positioning approaches, namely the middle and gingival, were examined. In the middle group, the reference points were placed on the mid-lingual surface of each tooth, while in the gingival group, the reference points were positioned lingually on the anterior teeth. A 4th degree polynomial was adopted, and the in-plane and off-plane root mean squares (RMSs) of the distances between the reference points and the fitted polynomial curve were calculated using the software. Statistical analysis was performed using the paired-samples t-test (${\alpha}=0.05$). Results: The mean in-plane RMS of the polynomial curve to the bracket distance in the gingival group was significantly lower than that in the middle group (p < 0.001). The off-plane RMS was higher in the gingivally positioned brackets in the maxilla than in the middle group (p < 0.001). However, the off-plane RMS in mandible was not statistically significantly different between the two groups (p = 0.274). Conclusions: The results demonstrated that the gingival placement of lingual brackets on the anterior teeth could decrease the distance between a tooth and the straight wire.

• 한국정보통신학회논문지
• /
• 제13권8호
• /
• pp.1659-1665
• /
• 2009

본 논문에서는 집적영상기술을 이용한 광학적 3D 영상 상관기의 구현 방법을 제안한다. 제안하는 방법에서는 참조 3D 물체와 신호 3D 물체의 요소 영상들이 렌즈 배열을 통하여 얻어지고 이 요소 영상들을 디스플레이 패널에 다시 표시하여 출력 평면에서 광학적으로 고해상도 출력 평면 영상을 얻는다. 이렇게 얻어진 참조 및 신호 물체의 출력 평면 영상에 대하여 상호 상관관계를 수행하여 3D 물체를 인식한다. 제안한 방법은 기존 방법과 비교하여 높은 해상도의 출력 평면 영상을 사용하기 때문에 정확한 3D 물체 인식이 가능하며, 실시간 3D 물체 인식 시스템을 광학적으로 구현할 수 있다. 제안하는 방법의 유용함을 보이기 위하여 광학 실험을 수행하고 그 결과를 보고한다.