BACKGROUND Single-ventricle patients with interrupted inferior vena cava (IVC) can develop pulmonary arterio-venous malformations due to abnormal hepatic flow distribution (HFD). However, preoperatively determining the hepatic baffle design that optimizes HFD is far from trivial. In this study, we combine virtual surgery and numerical simulations to identify potential surgical strategies for patients with interrupted IVC. METHODS Five patients with interrupted IVC and severe PAVMs were enrolled. Their in vivo anatomies were reconstructed from MRI (n=4) and CT (n=1), and alternate virtual-surgery options (intra/extra-cardiac, Y-grafts, hepato-to-azygous and azygous-to-hepatic shunts) were generated for each. HFD was assessed for all options using a fully validated computational flow solver. RESULTS For patients with a single superior vena cava (SVC, n=3), intra/extra-cardiac connections proved dangerous, as even a small left or right offset led to a highly preferential HFD to the associated lung. Best results were obtained with either a Y-graft spanning the Kawashima to split the flow, or hepato-to-azygous shunts to promote mixing. For patients with bilateral SVCs (n=2), results depended on the balance between the left and right superior inflows. When those were equal, connecting the hepatic baffle between the SVCs performed well, but other options should be pursued otherwise. CONCLUSION This study demonstrates how virtual-surgery environments can benefit the clinical community, especially for rare and complex cases such as single-ventricle patients with interrupted IVC. Furthermore, the sensitivity of the optimal baffle design to the superior inflows underscores the need to characterize both pre-operative anatomy and flows to identify the best suited option.

The generation of inbetween frames that interpolate a given set of key frames is a major component in the production of a 2D feature animation. Our objective is to considerably reduce the cost of the inbetweening phase by offering an intuitive and effective interactive environment that automates inbetweening when possible while allowing the artist to guide, complement, or override the results. Tight inbetweens, which interpolate similar key frames, are particularly time-consuming and tedious to draw. Therefore, we focus on automating these high-precision and expensive portions of the process. We have designed a set of user-guided semi-automatic techniques that fit well with current practice and minimize the number of required artist-gestures. We present a novel technique for stroke interpolation from only two keys which combines a stroke motion constructed from logarithmic spiral vertex trajectories with a stroke deformation based on curvature averaging and twisting warps. We discuss our system in the context of a feature animation production environment and evaluate our approach with real production data.

The first version of an anatomy editing/surgical planning tool (SURGEM) targeting anatomical complexity and patient-specific computational fluid dynamics (CFD) analysis is presented. Novel three-dimensional (3D) shape editing concepts and human-shape interaction technologies have been integrated to facilitate interactive surgical morphology alterations, grid generation and CFD analysis. In order to implement "manual hemodynamic optimization" at the surgery planning phase for patients with congenital heart defects, these tools are applied to design and evaluate possible modifications of patient-specific anatomies. In this context, anatomies involve complex geometric topologies and tortuous 3D blood flow pathways with multiple inlets and outlets. These tools make it possible to freely deform the lumen surface and to bend and position baffles through real-time, direct manipulation of the 3D models with both hands, thus eliminating the tedious and time-consuming phase of entering the desired geometry using traditional computer-aided design (CAD) systems. The 3D models of the modified anatomies are seamlessly exported and meshed for patient-specific CFD analysis. Free-formed anatomical modifications are quantified using an in-house skeletization based cross-sectional geometry analysis tool. Hemodynamic performance of the systematically modified anatomies is compared with the original anatomy using CFD. CFD results showed the relative importance of the various surgically created features such as pouch size, vena cave to pulmonary artery (PA) flare and PA stenosis. An interactive surgical-patch size estimator is also introduced. The combined design/analysis cycle time is used for comparing and optimizing surgical plans and improvements are tabulated. The reduced cost of patient-specific shape design and analysis process, made it possible to envision large clinical studies to assess the validity of predictive patient-specific CFD simulations. In this paper, model anatomical design studies are performed on a total of eight different complex patient specific anatomies. Using SURGEM, more than 30 new anatomical designs (or candidate configurations) are created, and the corresponding user times presented. CFD performances for eight of these candidate configurations are also presented.

We present Smart Scribbles-a new scribble-based interface for user-guided segmentation of digital sketchy drawings. In contrast to previous approaches based on simple selection strategies, Smart Scribbles exploits richer geometric and temporal information, resulting in a more intuitive segmentation interface. We introduce a novel energy minimization formulation in which both geometric and temporal information from digital input devices is used to define stroke-to-stroke and scribble-to-stroke relationships. Although the minimization of this energy is, in general, a NP-hard problem, we use a simple heuristic that leads to a good approximation and permits an interactive system able to produce accurate labelings even for cluttered sketchy drawings. We demonstrate the power of our technique in several practical scenarios such as sketch editing, as-rigid-as-possible deformation and registration, and on-the-fly labeling based on pre-classified guidelines.

Homeomorphisms between curves and between surfaces are fundamental to many applications of 3D modeling, graphics, and animation. They define how to map a texture from one object to another, how to morph between two shapes, and how to measure the discrepancy between shapes or the variability in a class of shapes. Previously proposed maps between two surfaces, S and S′, suffer from two drawbacks: (1) it is difficult to formally define a relation between S and S′ which guarantees that the map will be bijective and (2) mapping a point x of S to a point x′ of S′ and then mapping x′ back to S does in general not yield x, making the map asymmetric. We propose a new map, called ball-map, that is symmetric. We define simple and precise conditions for the ball-map to be a homeomorphism. We show that these conditions apply when the minimum feature size of each surface exceeds their Hausdorff distance. The ball-map, BM S,S′, between two such manifolds, S and S′, maps each point x of S to a point x′ = BM s,s′(x) of S′. BM S′,S is the inverse of BM S,S′, hence BM is symmetric. We also show that, when S and S′ are Ck (n - 1)-manifolds in ℝn, BM S,S′ is a Ck-1 diffeomorphism and defines a Ck-1 ambient isotopy that smoothly morphs between S to S′. In practice, the ball-map yields an excellent map for transferring parameterizations and textures between ball compatible curves or surfaces. Furthermore, it may be used to define a morph, during which each point x of S travels to the corresponding point x′ of S′ along a broken line that is normal to S at x and to S′ at x′.