Jan Kretschmer

Interactive Patient-Specific Vascular Modeling with Sweep Surfaces

The precise modeling of vascular structures plays a key role in medical imaging applications, such as diagnosis, therapy planning and blood flow simulations. For the simulation of blood flow in particular, high-precision models are required to produce accurate results. It is thus common practice to perform extensive manual data polishing on vascular segmentations prior to simulation. This usually involves a complex tool chain which is highly impractical for clinical on-site application. To close this gap in current blood flow simulation pipelines, we present a novel technique for interactive vascular modeling which is based on implicit sweep surfaces. Our method is able to generate and correct smooth high-quality models based on geometric centerline descriptions on the fly. It supports complex vascular free-form contours and consequently allows for an accurate and fast modeling of pathological structures such as aneurysms or stenoses. We extend the concept of implicit sweep surfaces to achieve increased robustness and applicability as required in the medical field. We finally compare our method to existing techniques and provide case studies that confirm its contribution to current simulation pipelines.

ADR--Anatomy-Driven Reformation.

Dedicated visualization methods are among the most important tools of modern computer-aided medical applications. Reformation methods such as Multiplanar Reformation or Curved Planar Reformation have evolved as useful tools that facilitate diagnostic and therapeutic work. In this paper, we present a novel approach that can be seen as a generalization of Multiplanar Reformation to curved surfaces. The main concept is to generate reformatted medical volumes driven by the individual anatomical geometry of a specific patient. This process generates flat views of anatomical structures that facilitate many tasks such as diagnosis, navigation and annotation. Our reformation framework is based on a non-linear as-rigid-as-possible volumetric deformation scheme that uses generic triangular surface meshes as input. To manage inevitable distortions during reformation, we introduce importance maps which allow controlling the error distribution and improving the overall visual quality in areas of elevated interest. Our method seamlessly integrates with well-established concepts such as the slice-based inspection of medical datasets and we believe it can improve the overall efficiency of many medical workflows. To demonstrate this, we additionally present an integrated visualization system and discuss several use cases that substantiate its benefits.

Reliable Adaptive Modelling of Vascular Structures with Non-Circular Cross-Sections

Accurate visualizations of complex vascular structures are essential for medical applications, such as diagnosis, therapy planning and medical education. Vascular trees are usually described using centerlines, since they capture both the topology and the geometry of the vasculature in an intuitive manner. State‐of‐the‐art vessel segmentation algorithms deliver vascular outlines as free‐form contours along the centerline, since this allows capturing anatomical pathologies. However, existing methods for generating surface representations from centerlines can only cope with circular outlines. We present a novel model‐based technique that is capable of generating intersection‐free surfaces from centerlines with complex outlines. Vascular segments are described by local signed distance functions and combined using Boolean operations. An octree‐based surface generation strategy automatically computes watertight, scale‐adaptive meshes with a controllable quality. In contrast to other approaches, our method generates a reliable representation that guarantees to capture all vessels regardless of their size.

Bilateral Depth Filtering for Enhanced Vessel Reformation

Curved Planar Reformation is a powerful visualization technique for the diagnosis of vascular diseases. It allows an accurate centerline-driven investigation of vessel lumen while providing valuable anatomical context. Extended methods like Multipath Curved Planar Reformation, Centerline Reformation or Curved Surface Reformation provide additional flexibility by condensing entire vascular systems into rotatable views. Unfortunately, all these methods produce depth discontinuities because they operate in a projective fashion. While large discontinuities provide valuable hints about distinct anatomical contexts, small discontinuities, which frequently arise, have distracting effects on the visualization result and do not contribute significant information. In this paper we present a bilateral filtering technique which allows to selectively remove depth discontinuities without affecting discontinuities that carry information. The presented approach significantly improves the quality of vessel reformations, can be applied at interactive frame rates and is orthogonal to existing methods.