4,775 research outputs found
A Review of Innovations in Rhegmatogenous Retinal Detachment Surgical Techniques.
Rhegmatogenous retinal detachment (RRD) requires surgical intervention for its repair. There are variable techniques used for this purpose, and they are all being continuously refined. In this review, we detail the recent innovations in surgical management of RRD and proliferative vitreoretinopathy (PVR)
Area-preserving mapping of 3D ultrasound carotid artery images using density-equalizing reference map
Carotid atherosclerosis is a focal disease at the bifurcations of the carotid
artery. To quantitatively monitor the local changes in the
vessel-wall-plus-plaque thickness (VWT) and compare the VWT distributions for
different patients or for the same patients at different ultrasound scanning
sessions, a mapping technique is required to adjust for the geometric
variability of different carotid artery models. In this work, we propose a
novel method called density-equalizing reference map (DERM) for mapping 3D
carotid surfaces to a standardized 2D carotid template, with an emphasis on
preserving the local geometry of the carotid surface by minimizing the local
area distortion. The initial map was generated by a previously described
arc-length scaling (ALS) mapping method, which projects a 3D carotid surface
onto a 2D non-convex L-shaped domain. A smooth and area-preserving flattened
map was subsequently constructed by deforming the ALS map using the proposed
algorithm that combines the density-equalizing map and the reference map
techniques. This combination allows, for the first time, one-to-one mapping
from a 3D surface to a standardized non-convex planar domain in an
area-preserving manner. Evaluations using 20 carotid surface models show that
the proposed method reduced the area distortion of the flattening maps by over
80% as compared to the ALS mapping method
A variational approach for viewpoint-based visibility maximization
We present a variational method for unfolding of the cortex based on a user-chosen point of view as an alternative to more traditional global flattening methods, which incur more distortion around the region of interest. Our approach involves three novel contributions. The first is an energy function and its corresponding gradient flow to measure the average visibility of a region of interest of a surface from a given viewpoint. The second is an additional energy function and flow designed to preserve the 3D topology of the evolving surface. This latter contribution receives significant focus in this thesis as it is crucial to obtain the desired unfolding effect derived from the first energy functional and flow. Without it, the resulting topology changes render the unconstrained evolution uninteresting for the purpose of cortical visualization, exploration, and inspection. The third is a method that dramatically improves the computational speed of the 3D topology-preservation approach by creating a tree structure of the triangulated surface and using a recursion technique.Ph.D.Committee Chair: Allen R. Tannenbaum; Committee Member: Anthony J. Yezzi; Committee Member: Gregory Turk; Committee Member: Joel R. Jackson; Committee Member: Patricio A. Vel
Three-dimensional reconstruction and visualization of the cerebral cortex in primates
We present a prototype interactive application for the direct analysis in three dimensions of the cerebral cortex in primates. The paper provides an overview of the current prototype system and presents the techniques used for reconstructing the cortex shape from data derived from histological sections as well as for rendering it at interactive rates. Results are evaluated by discussing the analysis of the right hemisphere of the brain of a macaque monkey used for neuroanatomical tract-tracing experiments.147-15
Non-rigid registration of 2-D/3-D dynamic data with feature alignment
In this work, we are computing the matching between 2D manifolds and 3D manifolds with temporal constraints, that is we are computing the matching among a time sequence of 2D/3D manifolds. It is solved by mapping all the manifolds to a common domain, then build their matching by composing the forward mapping and the inverse mapping. At first, we solve the matching problem between 2D manifolds with temporal constraints by using mesh-based registration method. We propose a surface parameterization method to compute the mapping between the 2D manifold and the common 2D planar domain. We can compute the matching among the time sequence of deforming geometry data through this common domain. Compared with previous work, our method is independent of the quality of mesh elements and more efficient for the time sequence data. Then we develop a global intensity-based registration method to solve the matching problem between 3D manifolds with temporal constraints. Our method is based on a 4D(3D+T) free-from B-spline deformation model which has both spatial and temporal smoothness. Compared with previous 4D image registration techniques, our method avoids some local minimum. Thus it can be solved faster and achieve better accuracy of landmark point predication. We demonstrate the efficiency of these works on the real applications. The first one is applied to the dynamic face registering and texture mapping. The second one is applied to lung tumor motion tracking in the medical image analysis. In our future work, we are developing more efficient mesh-based 4D registration method. It can be applied to tumor motion estimation and tracking, which can be used to calculate the read dose delivered to the lung and surrounding tissues. Thus this can support the online treatment of lung cancer radiotherapy
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