Smooth Anatomical Models From 3D Imaging

3D imaging has become a standard tool in medical diagnostics and, while software is available to visualize volumetric data sets, we do not yet have software that can efficiently transform 3D scan data to solid models that are useful for engineering design and analysis. Why not? Currently, deriving solid models from 3D scans involves 3 steps: (1) segmentation: identification of voxels associated with the structure; (2) polygonization: computing a set of polygons that approximate the surface of the structure; and (3) repair: removing stray voxels and polygons, specifying connectivity, and establishing consistent orientation. Significant progress has been made on accurate, automated segmentation (recent work by Hu et al. (Image Segmentation and Registration for the Analysis of Joint Motion From 3D MRI,” Proc SPIE 6141, pp. 133–142, Medical Imaging: Visualization, Image-Guided Procedures, & Display, 2006), combining graph cuts with level sets is of particular interest) but effective polygonization cannot be guaranteed. In the worst case, manual repairs are needed to patch holes and remove stray elements. Even if a valid boundary representation (b-rep) model is obtained, accurate models contain so many polygons that modeling operations become unfeasible. Moreover, regardless of accuracy, the surface of a polyhedral model will never be truly smooth. In previous work (Storti, D., et al., Artifact vs. Anatomy: Dealing With Conflict of Geometric Modeling Descriptions,” SAE 2007 Transactions Journal of Passenger Cars: Electronic and Electrical Systems, Paper No. 2007-01-2450, Vol. 116, pp. 813–823, 2007), we proposed overcoming the barriers to creating solid models from 3D scans by employing a new solid modeling description, wavelet SDF-reps, that lies much closer to the native 3D scan format and eliminates polygonization. Here, we focus on the ability to produce models with smooth surfaces that are important for various biomedical simulations. For example, careful studies of joint function involve detailed modeling of ligament wrapping; i.e., connective tissue moving across bone surface as the joint configuration changes. Realistic behavior cannot be obtained if the ligament is snagging on or snapping across convex vertices of a polyhedral model. Similarly, haptic simulation of a catheter navigating through the circulatory system cannot be realistic if the catheter gets stuck in concave vertices of the anatomical model. How can the new modeling format address such issues? Wavelet SDF-reps take advantage of a by-product of the segmentation algorithm (Hue et al.) which converts the raw voxel intensity values to a grid of signed distance values. Applying an appropriate interpolant such as Daubechies wavelets (Daubechies, I., Wavelets, CBMS-NS Series in Applied Mathematics, SIAM Publications, Philadelphia, 1992) then produces an implicit or function-based (f-rep) solid model of the segmented structure. Wavelet SDF-reps are inherently multi-resolution and support significant data compression and medial axis computation. We illustrate the capability of wavelet SDF-reps to support smooth models and enable analysis of curvature features.

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Optimization of Curvilinear Needle Trajectories for Transforamenal Hippocampotomy

Operative Neurosurgery ◽

10.1227/neu.0000000000001361 ◽

2016 ◽

Vol 13 (1) ◽

pp. 15-22 ◽

Cited By ~ 5

Author(s):

David B. Comber ◽

E. Bryn Pitt ◽

Hunter B. Gilbert ◽

Matthew W. Powelson ◽

Emily Matijevich ◽

...

Keyword(s):

Magnetic Resonance ◽

Medial Axis ◽

Tumor Resection ◽

Percutaneous Treatment ◽

Thermal Therapy ◽

Foramen Ovale ◽

Worst Case ◽

Seizure Disorders ◽

Thermal Therapies ◽

Concentric Tube Robot

Abstract BACKGROUND: The recently developed magnetic resonance imaging–guided laser-induced thermal therapy offers a minimally invasive alternative to craniotomies performed for tumor resection or for amygdalohippocampectomy to control seizure disorders. Current laser-induced thermal therapies rely on linear stereotactic trajectories that mandate twist-drill entry into the skull and potentially long approaches traversing healthy brain. The use of robotically driven, telescoping, curved needles has the potential to reduce procedure invasiveness by tailoring trajectories to the curved shape of the ablated structure and by enabling access through natural orifices. OBJECTIVE: To investigate the feasibility of using a concentric tube robot to access the hippocampus through the foramen ovale to deliver thermal therapy and thereby provide a percutaneous treatment for epilepsy without drilling the skull. METHODS: The skull and both hippocampi were segmented from dual computed tomography/magnetic resonance image volumes for 10 patients. For each of the 20 hippocampi, a concentric tube robot was designed and optimized to traverse a trajectory from the foramen ovale to and through the hippocampus from head to tail. RESULTS: Across all 20 cases, the mean distances (errors) between the hippocampus medial axis and backbone of the needle were 0.55, 1.11, and 1.66 mm for the best, mean, and worst case, respectively. CONCLUSION: These curvilinear trajectories would provide accurate transforamenal delivery of an ablation probe to typical hippocampus volumes. This strategy has the potential both to decrease the invasiveness of the procedure and to increase the completeness of hippocampal ablation.

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Handling Blending Features in Form Feature Recognition Using Convex Decomposition

ASME 1994 International Computers in Engineering Conference and Exhibition ◽

10.1115/cie1994-0390 ◽

1994 ◽

Author(s):

Sreekumar Menon ◽

Yong Se Kim

Keyword(s):

Feature Recognition ◽

Boundary Representation ◽

Recognition Method ◽

Geometric Information ◽

Polyhedral Model ◽

Curved Boundary ◽

Convex Decomposition ◽

Geometric Objects ◽

Form Features ◽

Form Feature

Abstract Form features intrinsic to the product shape can be recognized using a convex decomposition called Alternating Sum of Volumes with Partitioning (ASVP). However, the domain of geometric objects to which ASVP decomposition can be applied had been limited to polyhedral solids due to the difficulty of convex hull construction for solids with curved boundary faces. We develop an approach to extend the geometric domain to solids having cylindrical and blending features. Blending surfaces are identified and removed from the boundary representation of the solid, and a polyhedral model of the unblended solid is generated while storing the cylindrical geometric information. From the ASVP decomposition of the polyhedral model, polyhedral form features are recognized. Form feature decomposition of the original solid is then obtained by reattaching the stored blending and cylindrical information to the form feature components of its polyhedral model. In this way, a larger domain of solids can be covered by the feature recognition method using ASVP decomposition. In this paper, handling of blending features in this approach is described.

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Application of Variational Geometry to the Analysis of Mechanical Tolerances

15th Design Automation Conference: Volume 1 — Computer-Aided and Computational Design ◽

10.1115/detc1989-0016 ◽

1989 ◽

Author(s):

P. M. Martino ◽

G. A. Gabriele

Keyword(s):

Mechanical Design ◽

Worst Case Analysis ◽

Prototype System ◽

Tolerance Design ◽

Worst Case ◽

Geometric Tolerances ◽

Solid Models ◽

The Cost ◽

Selection Of

Abstract The proper selection of tolerances is an important part of mechanical design that can have a significant impact on the cost and quality of the final product. Yet, despite their importance, current techniques for tolerance design are rather primitive and often based on experience and trial and error. Better tolerance design methods have been proposed but are seldom used because of the difficulty in formulating the necessary design equations for practical problems. In this paper we propose a technique for the automatic formulation of the design equations, or design functions, which is based on the use of solid models and variational geometry. A prototype system has been developed which can model conventional and statistical tolernaces, and a limited set of geometric tolerances. The prototype system is limited to the modeling of single parts, but can perform both a worst case analysis and a statistical analysis. Results on several simple parts with known characteristics are presented which demonstrate the accuracy of the system and the types of analysis it can perform. The paper concludes with a discussion of extensions to the prototype system to a broader range of geometry and the handling of assemblies.

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Digital Health

10.1093/oso/9780197503133.001.0001 ◽

2021 ◽

Author(s):

Eric D. Perakslis ◽

Martin Stanley ◽

Erin Brodwin

Keyword(s):

Health Care ◽

Side Effects ◽

Care Delivery ◽

Digital Health ◽

Detailed Examination ◽

Medical Diagnostics ◽

Medical Interventions ◽

Health Technologies ◽

Solid Models ◽

Medical Side

Digital health has been touted as a true transformation of health care, but all medical interventions have associated risks that must be understood and quantified. The Internet has brought many advancements, which quickly jumped from our computers into our pockets via powerful and completely connected mobile devices that are now being envisioned as devices for medical diagnostics and care delivery. As health care struggles with cost, inequity, value, and rapid virtualization, solid models of benefit-risk determination, new regulatory approaches for biomedical products, and clear risk-based conversations with all stakeholders are essential. Detailed examination of emerging digital health technologies has revealed 10 categories of digital side effects or “toxicities” that must be understood, prevented when possible, and managed when not. These toxicities include cyberthreat, loss of privacy, cyberchondria and cyber addiction, threats to physical security, charlatanism, overdiagnosis and overtreatment, medical/user error, and the plague of medical misinformation. For digital health to realize its promise, these toxicities must be understood, measured, warned against, and managed as concurrent side effects, in the same fashion as any other medical side effect.

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An approach to automatic boundary segmentation of solid models using virtual topology: toward reconstruction of design features

Journal of Computational Design and Engineering ◽

10.1093/jcde/qwaa030 ◽

2020 ◽

Vol 7 (3) ◽

pp. 367-385

Author(s):

Yingzhong Zhang ◽

Yufei Fu ◽

Jia Jia ◽

Xiaofang Luo

Keyword(s):

Design Feature ◽

Boundary Representation ◽

Virtual Topology ◽

Design Features ◽

Complex Part ◽

Novel Approach ◽

Solid Models ◽

Medium Level ◽

Feature Based ◽

Low Dimensional

Abstract Boundary segmentation of solid models is the geometric foundation to reconstruct design features. In this paper, based on the shape evolution analysis for the feature-based modeling process, a novel approach to the automatic boundary segmentation of solid models for reconstructing design features is proposed. The presented approach simulates the designer’s decomposing thinking on how to decompose an existing boundary representation model into a set of design features. First, the modeling traces of design features are formally represented as a set of feature vertex adjacent graphs that use low-dimensional vertex entities and their connection relations. Then, a set of Boolean segmentation loops is searched and extracted from the constructed feature vertex adjacent graphs, which segment the boundary of a solid model into a set of regions with different design feature semantics. In the search process, virtual topology operations are employed to simulate the topological changes resulting from Boolean operations in feature modeling processes. In addition, to realize effective search, search strategies and search algorithms are presented. The segmentation experiments and case study show that the presented approach is feasible and effective for the boundary segmentation of medium-level complex part models. The presented approach lays the foundation for the later reconstruction of design features.

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Integrating Design Process Knowledge With CAD Models

Volume 1: 21st Computers and Information in Engineering Conference ◽

10.1115/detc2001/cie-21247 ◽

2001 ◽

Author(s):

Erik E. Hayes ◽

William C. Regli

Keyword(s):

Design Process ◽

Computer Aided Design ◽

Search Space ◽

Temporal Changes ◽

Boundary Representation ◽

Process Knowledge ◽

Solid Models ◽

Design And Manufacturing ◽

Cad Models ◽

Manufacturing Problems

Abstract Solid models are static entities, often defined by boundary representation models as sets of enclosing surfaces. Constructive Solid Geometry and feature-based computer-aided design environments create procedural descriptions of 3D objects in forms of history or CSG trees. These representations are temporally fixed, i.e., they describe the state of an object at a point in time. This paper describes a method to represent and capture temporal evolution of solid models — what we call model process history. We define process history to be all states of a model — the search space of design process. This paper presents a representational formalism we call model process graphs (MPGs). We use MPGs to integrate a model’s description with a model of temporal changes that occur during the design process. We believe that MPG representations can have valuable application for many design and manufacturing problems. The paper describes our preliminary results to use MPGs to (1) create a record of design process; (2) store process-based design rationale; (3) represent in-process shapes for machined artifacts. We anticipate that similar structures will find application in other design and manufacturing problems where important process knowledge is embodied by temporal changes occurring in model evolution.

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Interval Method for Interrogation of Implicit Solid Models

Volume 2: 26th Design Automation Conference ◽

10.1115/detc2000/dac-14290 ◽

2000 ◽

Author(s):

Jack Chang ◽

Mark Ganter ◽

Duane Storti

Keyword(s):

Computer Aided Design ◽

Boundary Representation ◽

Free Form ◽

Solid Models ◽

Cad Cam ◽

Implicit Modeling ◽

Manufacturing Applications ◽

Determine Surface Area ◽

Implicit Solid ◽

Aided Design

Abstract Computer-aided design/manufacturing (CAD/CAM) systems intended to support automated design and manufacturing applications such as shape generation and solid free-form fabrication (SFF) must provide not only methods for creating and editing models of objects to be manufactured, but also methods for interrogating the models. Interrogation refers to any process that derives information from the model. Typical interrogation tasks include determine surface area, volume or inertial properties, computing surface points and normals for rendering, and computing slice descriptions for SFF. While currently available commercial modeling systems generally employ a boundary representation (B-rep) implementation of solid modeling, research efforts have considered implicit modeling schemes as a potential source of improved robustness. Implicit implementations are available for a broad range of modeling operations, but interrogation operations have been widely considered too costly for many applications. This paper describes a method based on interval analysis for interrogating implicit solid models that aims at achieving both robustness and efficiency.

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Interval Methods for B-Rep Model Verification and Rectification

Volume 2: 26th Design Automation Conference ◽

10.1115/detc2000/dac-14277 ◽

2000 ◽

Author(s):

Guoling Shen ◽

Takis Sakkalis ◽

Nicholas M. Patrikalakis

Keyword(s):

Interval Arithmetic ◽

Boundary Representation ◽

Model Verification ◽

Interval Methods ◽

Topological Structures ◽

Numerical Errors ◽

Solid Models ◽

Exact Boundary ◽

Geometric Consistency ◽

Model Conversion

Abstract Boundary representation (B-rep) models often have geometric specifications inconsistent with their topological structures due to numerical errors. In this paper, we verify the geometric consistency of B-rep models and evaluate existing inconsistencies of such models using interval arithmetic. Moreover, we convert conventional B-rep models into interval solid models to correct them. An interval solid is defined as a collection of non-degenerate boxes whose union covers the intended exact boundary and is guaranteed to be gap-free. An example illustrates our method for model conversion.

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