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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A temporal 3D-registration framework for computer-integrated surgery

Backman, Ronald Bruce January 1999 (has links)
Traditionally, volumetric modalities such as CT and MRI have provided static snapshots of anatomy enabling insight into the progression of disease and to the severity of injury. Recently, 3D-registration algorithms, originating in the neurosurgical field, have been used to merge these images resulting in richer visualizations. However, in situations where trauma patients are unable to be moved or are at risk of infection, there have been comparatively few advances. This thesis presents a 3D-registration framework that supports longitudinal study of morphologic changes in surface images of the upper body based on an optical technique - structured light imaging. The framework incorporates soft-tissue deformation modeling to allow coordinate frame determination and specific point tracking required for applications of Computer-Integrated Surgery. The framework is implemented in three stages using a coarse-fine approach that separately addresses the different sources of registration error commonly found in temporal registration applications. The coarse stage defines seven thoracic fiducials that form a rigid body. A special anthropomorphic stand is designed and used to enforce a rigid body assumption. Experimental results show the fiducials to have precision of approximately 2 mm. The medium stage incorporates the novel use of ultraviolet light as a surface registration technique. UV is used to avoid error caused when the projected light stripes interfere with the marker material - a common problem with external landmarks and optical assessment systems. A semi-automatic algorithm for identifying the centre of the fiducials is given and shown to be highly accurate - to within 1 pixel precision compared to the visually assessed centre. The movement of these fiducials is also modelled at the extremes of the respiratory cycle with individual fiducials moving from 5-17 mm. A least-squares algorithm is implemented to bring surfaces together based on their fiducial locations and rigid-body motion. This algorithm results in RMS error of approximately 1.17 +/- 0.45 mm. The fine stage involves finding fixed point correspondences in changed regions between a base surface and a comparison surface acquired at a different time given the rigid body registration from the previous stages. Five algorithmic variants are assessed using two simulations of thoracic swelling. The results do not show statistical significance between variants but do indicate visually some promising results. An application of this framework could be the near real-time guidance of the FAROArm, a precision measuring instrument commonly used in Computer-Integrated Surgery, to these points. This would facilitate the collection of functional information of clinical interest while maintaining positional congruence with data acquired at a different time point.
2

Statistical models of appearance for functional analysis of cardiac MRI /

Andreopoulos, Alexander. January 2005 (has links)
Thesis (M.Sc.)--York University, 2005. Graduate Programme in Computer Science. / Typescript. Includes bibliographical references (leaves 160-166). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11736
3

An intelligent approach to automatic medical model reconstruction fromserial planar CT images

關福延, Kwan, Folk-year. January 2002 (has links)
published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy
4

Three-dimensional assessment of facial deformities and their surgical outcomes

Jayaratne, Yasas Shri Nalaka January 2011 (has links)
Data on the three?dimensional (3?D) morphology of normal faces and facial deformities as well as objective techniques for evaluating postoperative changes are currently unavailable. With the advent of stereophotography and cone?beam CT (CBCT), it is possible to acquire 3?D images of soft and hard tissues of the maxillofacial complex. A series of studies were conducted aimed at 1) establishing 3?D facial anthropometric norms for Hong Kong young adults, 2) determining 3?D facial anthropometric features in skeletal Class II and III deformities, 3) characterizing the oropharyngeal space in Class II and III skeletal deformities, 4) exploring clinical applications of 3?D colour maps, 5) establishing a non?invasive technique for estimating serial volume changes and 6) creating virtual craniofacial models by fusing 3?D photographs and CBCT images. Study 1: A stereophotographic system was used to capture 3?D images of 103 Hong Kong Chinese young adults with normal balanced faces. An anthropometric analysis protocol with linear, angular and proportional measurements was developed to establish a normative database and quantify dysmorphology. The Hong Kong Chinese norms were distinct from Caucasians, especially with regard to ocular and nasal measurements. Facial height and nasolabial measurements differed significantly between Hong Kong males and females. Study 2: Anthropometric analyses of 3?D facial images from 41 skeletal Class II and 43 Class III subjects were performed. The Class II subjects had increased lower facial height compared with Class III, who had longer total facial heights and narrower faces. While Class II deformity primarily resulted from mandibular deficiency with a normal maxilla, Class III presented as combined midfacial hypoplasia and mandibular hyperplasia. Study 3: Anthropometric characteristics of the oropharygeal space in skeletal Class II and III were evaluated using 62 CBCT scans. The retroglossal (RG) and retropalatal (RP) volumes and average cross sectional areas were significantly larger in Class III than Class II skeletal deformity. The RP compartment was larger but less uniform than the RG compartment in both Classes. Study 4: 3?D photographs or CBCT images acquired at two different time points were superimposed using a common unaffected area. 3?D colour maps were generated depicting distance differences between superimposed images in a graphical format. These maps were used as an objective tool for treatment planning and assessing outcomes after orthognathic surgery, bimaxillary distraction and facial trauma. Study 5: 3?D photogrammetry was employed for planning soft tissue expansion (STE) and transplantation of a vascularised scapular flap in hemifacial microsomia. This technique facilitated the identification of extent and degree of tissue deficiency, selection of the appropriate tissue expander, monitoring volumetric changes during STE and estimation of the free flap dimensions. Study 6: 3?D facial photographs and CBCT scans of 29 subjects were merged to create virtual craniofacial models with natural surface texture. Accuracy was assessed with 3?D colour maps and Root Mean Square (RMS) error. The CBCT and 3?D photographic data were integrated while minimizing average RMS error to 0.441mm. These virtual composite craniofacial models permitted concurrent 3?D assessment of bone and soft tissue. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy
5

An Automated System for Design and Analysis of Total Hip Implants: A Method of Modeling the Proximal Endosteal Canal Using 3-D CT Data

Manasas, Mark A. 01 April 1999 (has links)
The clinical success of Total Hip Arthroplasty is enhanced by matching hip implant geometry to femoral geometry. Traditionally, the shapes of hip implant designs have been based on data collected from patient populations using X-ray, CT Scan, digitized sliced bone, and other physical methods. The morphology of interest and the frame of reference often vary across researchers and the resulting numeric data are difficult to use in a Computer Aided Design package to build an implant model. This goal of this thesis was to develop procedures and automated programs for the design and evaluation of femoral hip implants using CT data. The procedures bridge the gap between patient specific "custom" prosthesis design and the so-called "averaged femur" implant designs. By automating the measurement, orientation and averaging of any user selected grouping of femora, these programs allow construction of an average femur template for small subsets of a population or populations. The programs allow grouping of femora using either dimensional attributes and/or patient attributes such as pathology, ethnic background, etc. The average femur template created for each group can then be used as the design boundary for a discrete implant size. Additional functionality is also provided for comparing average femur templates to their constitutive femora and for comparison of average femur templates against each other. To illustrate that the goals of this theses were realized, an example of the use of the system for a population of 192 Japanese is included in this thesis. The criteria for evaluation of the average femur templates was the gap or interference of the template to that of each constitutive femur along the medial and lateral endosteal contours. Testing 24 template sizes, the average of the worst fitting template to femur combination for each size resulted in a gap or interference of less than 2mm in the metaphysis and less than 4mm proximally.
6

Application of ultrasonography in early pregnancy

Chen, Min, January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
7

Application of three-dimensional ultrasonography in obstetrics

Yang, Fang, 杨芳 January 2012 (has links)
Three-dimensional (3D) sonography is regarded as a further development of ultrasound imaging technology and its application has greatly increased in recent years. This thesis summarizes the original research findings of the application of 3D ultrasonography for biometry measurement, morphology screening, prenatal diagnosis of abnormalities, ultrasound training and the application of 3D volumetry in the early diagnosis of homozygous α-thalassemia and birth weight prediction in term pregnancy. In a study involving 50 singleton pregnancies at 17-34 weeks' gestation, fetal biometric measurements obtained by an inexperienced operator using both two-dimensional (2D) and 3D ultrasound were reproducible and showed good agreement with those obtained by an experienced operator (all intraclass correlation coefficients were ≥ 0.991). The use of 3D ultrasound by an inexperienced operator allowed faster measurement of fetal biometric parameters than the use of 2D ultrasound, and also seemed to facilitate the acquisition of higher-quality images for the measurement of abdominal circumference. In basic central nervous system and cardiac screening examination, for the inexperienced operator, 3D/four-dimensional(4D) volume acquisition yielded a quicker but less optimal anatomic examination of the fetal central nervous system and heart structures compared to 2D. The diagnostic accuracy of 3D ultrasonography in central nervous system abnormalities was also investigated. The results illustrated that 3D agreed with 2D ultrasonography in the prenatal diagnosis of intracranial malformations. Homozygous α0-thalassemia is very common in South-east Asia and its prenatal diagnosis is essential due to increased fetal and maternal mortality and morbidity. Placental volume/CRL quotient measured by 3D volumetry was significantly higher in pregnancies with α0-thalassemia major cases, and 1.49 may be regarded as a cut-off for early prediction of α0-thalassemia major. In a cross-sectional study of 290 Hong Kong Chinese women with a singleton pregnancy at 37-42 weeks of gestation, the birth weight prediction models based on 3D thigh volume and conventional 2D biometric measurements were developed. It was found that with 3D thigh model, the precision of birth weight prediction to within 5 and 10% of actual birth weight in a Chinese population at term gestation could be achieved. Previous studies have shown that there is a difference in the learning curve of fetal biometry measurement by 2D ultrasound among trainees. Whether there is any difference in the learning curve between 2D and 3D ultrasound is unknown. The study included three trainees and each of them performed 90 scans in biometry measurements. By using cumulative sum analysis graphs, it could be shown that there was no difference in the learning curve between 2D and 3D ultrasound. In conclusion, the above studies have demonstrated that the use of 3D ultrasound has diversified and provided much additional information in selected indications. / published_or_final_version / Obstetrics and Gynaecology / Doctoral / Doctor of Philosophy
8

Comparison of septal defects in 2-D and 3-D echocardiography using active contour models

Lassige, Timothy A. 05 1900 (has links)
No description available.
9

Three-dimensional motion capture for the DIET breast cancer imaging system : a thesis presented for the degree of Doctor of Philosophy in Mechanical Engineering at the University of Canterbury, Christchurch, New Zealand /

Brown, Richard January 1900 (has links)
Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "June 2008." Includes bibliographical references (p. [135]-138). Also available via the World Wide Web.
10

Analysis tools for brachytheraphy seed reconstruction /

Lam, Steve Troluong. January 2002 (has links)
Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 98-107).

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