Development and application of stent-based image guided navigation system for oral and maxillofacial surgery

Purpose : The purpose of this study was to develop a stent-based image guided surgery system and to apply it to oral and maxillofacial surgeries for anatomically complex sites. Materials and Methods : We devised a patient-specific stent for patient-to-image registration and navigation. Threedimensional positions of the reference probe and the tool probe were tracked by an optical camera system and the relative position of the handpiece drill tip to the reference probe was monitored continuously on the monitor of a PC. Using 8 landmarks for measuring accuracy, the spatial discrepancy between CT image coordinate and physical coordinate was calculated for testing the normality. Results : The accuracy over 8 anatomical landmarks showed an overall mean of 0.56±0.16 mm. The developed system was applied to a surgery for a vertical alveolar bone augmentation in right mandibular posterior area and possible interior alveolar nerve injury case of an impacted third molar. The developed system provided continuous monitoring of invisible anatomical structures during operation and 3D information for operation sites. The clinical challenge showed sufficient accuracy and availability of anatomically complex operation sites. Conclusion : The developed system showed sufficient accuracy and availability in oral and maxillofacial surgeries for anatomically complex sites. (Korean J Oral Maxillofac Radiol 2009; 39 : 149-56)grant of the Korea healthcare technology R & D Project Ministry for Health. Welfare & Family Affairs. Republic of Korea(A08-4491-AL2023-08N1-00030B)

압전 엑츄에이터의 위상최적설계 이슈 : 물질 보간 개념

Thesis(doctors) --서울대학교 대학원 :기계항공공학부, 2008.8.Docto

Evolution strategy of population in the multiscale multiresolution genetic algorithm

Thesis (master`s)--서울대학교 대학원 :기계항공공학부,2004.Maste

An integrated system for simulation and image-guidance for orthognathic surgery

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 방사선응용생명과학 전공, 2013. 8. 이원진.Accurate orthognathic surgery planning and planning transfer in the operation theatre are important factors for a successful surgery outcome with appropriate esthetical and functional improvements. However, conventional surgery has inherent limitations because the surgery planning is performed based on 2-dimensional cephalograms and the surgery operation depends on the experience and skill of surgeons. Moreover, 3-dimensional natural head position (NHP) information was not contained in not only the cephalogram but also CT data. To overcome these limitations, a new integrated system covering from virtual surgery planning to surgery guide system for orthognathic surgery has been developed. A new method for 3-dimensional simulation of NHP was also developed using POSIT algorithm. An accuracy evaluation was performed for the NHP simulation and the surgery guide system. In the virtual surgery planning system, realistic virtual osteotomy was performed on a 3-dimensional surface model reconstructed from the CT data using a haptic device. After designation of the landmarks on the surface model for a bone relocation procedure, bone segment was relocated by a combination of rotational and translational movements for each axis. The simulation of bone segment relocation was done according to the conventional surgery planning method. Movements of the designated landmarks were calculated for each relocation step and the final positions of the landmarks were compared with the conventional surgery plan to verify the simulation result. Relocated final position of the bone segment was recorded for the surgery guide system. For the NHP simulation, a photograph of subject was taken after attaching ceramic sphere markers on the subjects maxillofacial area. CT data of the subject was also acquired while the ceramic markers were attached on the same positions. The POSIT algorithm was performed to acquire the relationship between the photograph coordinate system and the CT coordinate system. The 2-dimensional and 3-dimensional marker positions were acquired from the photograph and the CT data, respectively, and these positions were used for the POSIT algorithm calculation. The transformation matrix between the two coordinate systems was acquired as a result of the transformation calculation. Acquired transformation was applied to the CT data of the subject and the CT data was reoriented to the NHP. A Phantom was designed for an accuracy evaluation of the NHP simulation. Discrepancy between the simulated orientation and a virtual NHP of the phantom was determined as an accuracy of the simulation. The result of the accuracy evaluation of the NHP simulation showed clinically acceptable errors (degree) with 0.05±0.19 in roll, -0.56±0.37 in pitch and -0.01±0.29 in yaw. Intra-observer and inter-observer variation was evaluated for the NHP simulation and showed good agreement between measurements (p-value = 0.05). The surgery guide system tracked the maxilla bone segment intra-operatively using a 3-dimensional optical tracking system. Specially designed registration body was fabricated to improve the efficiency of the surgery. The point-to-point registration method was implemented to acquire the relationship between the optical tracking system coordinate system and the CT coordinate system. With the help of newly developed registration body, the registration procedure could be performed preoperatively. After the registration was completed, real-time maxilla bone segment position was tracked by the system. The result of the surgery planning which was previously acquired from the virtual surgery planning system was imported into the surgery guide system. During the tracking procedure, discrepancy between the planned position and the real-time intraoperative position of the maxilla bone segment was shown in 3-dimensional virtual environment. The discrepancy information of the points of interests on the bone segment was also quantitatively calculated. An accuracy of the surgery guide system was evaluated and compared with the conventional surgery guide method. The mean error was 0.47 ± 0.22 mm for the developed method and 1.05 ± 0.49 mm for the conventional method. The error of the developed method was significantly lower than the conventional method for all direction of movements. The accuracy of the surgery guide system was also evaluated in more clinical condition using the result of the model surgery. The CT data of the patients dental casts was acquired with the registration assembly. Registration between the CT coordinate system and the articulator coordinate system was performed, and the surface model of the dental cast was reoriented to the articulator coordinate system. The maxilla bone segment was relocated according to the model surgery result and tracked by the surgery guide system. Discrepancy of the landmark positions between the virtual surgery planned position and the actual position according to the model surgery was calculated and used for the evaluation of the system accuracy. Total of 7 cases of experiment was done and 5 measurements were implemented on 8 landmarks for each case. Total average of the absolute error ranged from 0.06 to 0.87 mm and the RMS error was 0.54±0.21 mm. The evaluation results showed clinically acceptable accuracy. In this study, integrated system for orthognathic surgery was developed. The system contained the virtual surgery planning system, the NHP simulation and the surgery guide system. The developed system helped the surgeons to predict the result of orthognathic surgery preoperatively and verify the exact intraoperative transfer of the surgery planning. In conclusion, this system was compatible with the clinical environment and increased the efficiency and the accuracy of the orthognathic surgery from the surgery planning to the surgery operation. The developed system is expected to be adopted in routine clinical situation and could be useful for the overall improvements of facial deformities after surgery.Abstract ⅰ Contents ⅵ List of tables ⅸ List of figures ⅹ Introdction 1 Materials and Methods 7 1. Virtual surgery planning system 7 1) Virtual osteotomy 7 2) Bone segment relocation 8 3) Virtual surgery procedure 10 4) Collision detection 11 2. Natural head position simulation 13 1) POSIT algorithm 13 2) Data acquisition 15 3) Application of POSIT algorithm 15 4) Phantom for accuracy evaluation 16 5) Simulation of Natural head position 18 6) Accuracy evaluation 18 3. Surgery guide system 25 1) Model surgery and surgical splint 25 2) Tracking device 26 3) Registration body 26 4) Registration procedure 27 5) Acquisition of initial maxilla position 29 6) Maxilla relocation and tracking 30 7) Transformation for maxilla tracking 30 8) Real-time maxilla tracking 32 9) Accuracy evaluation: simple-condition experiment 33 10) Accuracy evaluation: clinical situation experiment 35 Results 47 1. Virtual surgery planning system 47 2. Natural head position simulation 51 3. Surgery guide system 56 Discussion 63 1. Virtual surgery planning system 63 2. Natural head position simulation 65 3. Surgery guide system 66 References 74 Abstract in Korean 83Docto

턱관절 움직임 분석을 위한 턱 움직임 추적 및 재현 시스템의 개발

Thesis(masters) --서울대학교 대학원 :협동과정 방사선응용생명과학전공, 2009.2.Maste

한국 시장에서 상영한 한국영화와 외국영화의 3단계 성과와 군집행동(Herding behavior)현상의 분석

This article analyzes film performances in the Korean movie market utilizing three-stage models that incorporate available information in three different stages of the movie life cycle, i.e., at the time of its release, at the end of the first week, and at the end of its life cycle. Based on the premise that the performance of a movie is affected principally by factors of scale, evaluation, and competition, we attempted to ascertain the effects on these factors on performances, and how they differ in different stages. Also, by analyzing domestic and foreign movies released in Korea separately, we were able to compare the different effects of the three factors on the performances of the two categories of movies. Additionally, our movie performance models incorporated herding behavior among the customers. Our results demonstrate that herding is prominently observed after the first week only for domestic movies. In general, the scale factor has been shown to be most important for movie performances in all stages. For foreign films, it is particularly critical for the first week and total performances. Whereas the evaluation factor influences domestic film performance more strongly at the screen choice stage, it affects the performance of foreign films more strongly in the later stages of the life cycle. As compared to foreign films, domestic film performance appears to be more sensitive to the competition factor. We also discuss the effects of covariates such as genre and symbolicity on movie performance

정보 가능 시기별 경로 분석을 기반으로

학위논문(석사) - 한국과학기술원 : 경영공학전공, 2006.2, [ iv, 64 p. ]한국 영화 시장은 멀티 플렉스 극장 중심으로 영화관이 재편된 1999년 이후 급격히 성장하고 있다. 영화 시장이 커져감에 따라 상업적으로 높은 흥행성적을 기록한 영화들이 생겨났지만 한편으로는 상업적으로 실패하여 투자사에 막대한 손실을 입히는 영화들 또한 이전보다 많아졌다. 본 논문에서는 영화의 흥행 성공에 영향을 끼치는 주 요인들을 밝혀냄으로써 영화 관객수를 예측하는 모형을 도출하였다. 2004년 5월에서 2005년 8월 사이 국내에서 개봉된 영화들을 대상으로 실증분석함으로써 모형이 추정되었다. 추정 결과 국내 영화와 외국 영화 사이에 주 요인들은 유사하지만 외국 영화의 경우 더 많은 정보들을 얻을 수 있어 예측모형에 차이를 보였다. 외국 영화의 경우 국내 영화에 비하여 모형의 설명력과 예측력이 더 높은 것으로 나타났다. 국내 영화에 대해서는 스타 파워, 제작비, 관람객 평점, 스크린 수, 첫 주 관객 수가 중요한 것으로 나타났다. 반면 외국 영화에 대해서는 제작국가의 첫 주 성적, 장르가 첫 주 관객수와 더불어 중요한 것으로 나타났다. 모형을 통한 예측 결과는 Benchmark 모형들에 의한 예측 결과에 비하여 높은 결과를 보여 실무적으로 이용 가능성이 높을 것으로 예상된다.한국과학기술원 : 경영공학전공

가시계층과 렌더링에서의 응용

학위논문(박사) - 한국과학기술원 : 전산학과, 1997.8, [ vii, 101 p. ]It is one of the greatest challenges to improve rendering efficiency. An important issue in rendering is to develop a geometric data structure which provides efficient visibility operations, because the most of the rendering time is spent for performing them. In this thesis, we present new data structures, called {\it visibility layers},to efficiently handle the visibility operations originated from a given area light source. Our structures maintain scene polygons in a sequence of layers according to their visibility from the source. The polygons in a layer do not obscure each other with respect to the source. From this property, a balanced 3D BSP tree can be constructed to accelerate visibility queries for the layer. Moreover, the shadow volumes cast by the polygons in the layer can be efficiently merged into a composite shadow volume. Since the shadow volume is a simple polyhedron, its boundary can be represented as a planar graph. The balanced BSP tree together with this graph allow ray coherence and output-sensitive clipping for fast visibility operations. We then generalize the visibility layers to accelerate visibility operations not originated from the source. Finally, we explore the applications of the visibility layers to advanced rendering such as shadow generation with area light sources, ray tracing, radiosity and walkthrough. Our experiments indicate that the visibility layers greatly improve the efficiency of the rendering applications.한국과학기술원 : 전산학과