Distributed quantitative evaluation of 3D patient specific arterial models

In this paper we describe a new system for the 3D reconstruction and distribution on the net of models for vessels structures. The system is specifically designed to support measurements of medical interest. We describe 2D and 3D segmentation methods implemented and the procedure used to build interactive VRML97 models. The experimental section presents a comparison between segmentation methods, and a first application to surgical planning for endovascular repair of Abdominal Aortic Aneurysms

Catheter insertion simulation with co-registered direct volume rendering and haptic feedback

We have developed an experimental catheter insertion simulation system supporting head-tracked stereoscopic viewing of volumetric anatomic reconstructions registered with direct haptic 3D interaction. The system takes as input data acquired with standard medical imaging modalities and regards it as a visual and haptic environment whose parameters are interactively defined using look-up tables. The system's display, positioned like a surgical table, provide a realistic impression of looking down at the patient. Measuring head motion via a six degrees-of-freedom head tracker, good positions to observe the anatomy and identify the catheter insertion point are quickly established with simple head motion. By generating appropriate stereoscopic images and co-registering physical and virtual spaces beforehand, volumes appear at fixed physical positions and it is possible to control catheter insertion via direct interaction with a PHANToM haptic device. During the insertion procedure, the system provides perception of the effort of penetration and deviation inside the traversed tissues. Semi-transparent volumetric rendering augment the sensory feedback with the visual indication of the inserted catheter position inside the body.96-9

Catheter insertion simulation with combined visual and haptic feedback

We have developed an experimental catheter insertion system supporting head-tracked stereoscopic viewing of volumetric reconstruction registered with direct haptic 3D interaction. The system takes as input patient data acquired with standard medical imaging modalities and regards it as a visual and haptic environment whose parameters are defined using look-up tables. By means of a mirror, the screen seems to be positioned like a surgical table providing the impression of looking down at the patient in a natural way. Co-registering physical and virtual spaces beforehand means that the patient appears at a fixed physical positionj on the surgical table and inside the workspace of the PHANToM device which controls catheter insertion. During the insertion procedure the system provides perception of the force of penetration and positional deviation of the inserted catheter

Web based 3D quantitative measurements of abdominal aortic aneurysms

We tested a novel approach for the quantitative remote analysis of abdominal aortic aneurysms by reconstructing their 3D geometry and topological structure (i.e. centereline path) and put them on the web as VRML97 models including specialized code enabling the user to perform guided inspection and measurements useful for surgical planning

Anatomical shape reconstruction and manufacturing: solving topological changes of lumen vessel trough geometric approach

Over the last years there has been an increasing growth of interest in Rapid Prototyping (RP) techniques applied to various fields of medicine. RP makes it possible, in vascular surgery, to produce accurate anatomic replicas of patient vessels. These replicas can help the customization of surgical invasive interventions such as in situ stent-graft insertion in carotid region. The main goal of this work is to obtain high quality in lumen reconstruction and manufacturing replicas by RP technique. This goal is achieved through the complete control of each phase of the generating process. We present a semi-automatic method for carotid lumen reconstruction based on Boundary Representation (BRep). All parameters influencing the quality of the shape reconstruction are presented and discussed: shape acquisition, shape reconstruction and shape manufacturing. The shape acquisition starts by extracting the points belonging to the boundary of the lumen vessel, from Computer Tomography (CT) images. These points, parameterised in a vector, are the input data of the shape reconstruction algorithm based on B-Spline interpolation. The B-Spline type for representing curves and surfaces were chosen because of their properties of continuity and local control. In the shape reconstruction stage we had to face problems due to the topological change on the vessel structure. For vessel regions where there are not changes of topology, we use the closed B-Spline curves (belonging to adjacent acquisition planes) as generating curves to build a B-Spline surface. For vessel regions with at least a change of topology (ex. bifurcation region) our algorithm split automatically the involved curves to obtain three rectangular B-Spline patches. Such patches are joined together to obtain the bifurcation vessel lumen. The set of lumen surfaces is then inserted in a Boundary Representation in order to get a valid solid. To analyse the quality of the reconstructed shapes, the final object is compared with the acquisition image. This solid is correctly tessellated in triangles to produce the data format used by the RP devices (STL)

Oxamate salts as novel agents for the restoration of marble and limestone substrates : case study of ammonium N-phenyloxamate

The ammonium salt of N-phenyloxamic acid (AmPhOxam) was synthesised, characterised by FT-IR, FT-Raman, UV-Vis, 1H-NMR spectroscopic methods and single crystal X-ray diffraction, and evaluated as a protective and consolidating agent for calcareous stone substrates under mild conditions. Hydro-alcoholic solutions of AmPhOxam were tested for the treatment of naturally weathered white marble and biomicritic limestone. Mercury intrusion porosimetry, FT-NIR spectroscopy measurements and SEM microscopy showed the formation of a superficial protective layer of crystals of the corresponding monohydrated calcium salt, CaPhOxam, on both treated stones.Publisher PDFPeer reviewe

Computational vascular fluid dynamics: problems, models and methods

In the cardiovascular system, morphology and functionality are closely related. Altered flow conditions play an important role in the development of arterial disease. In turn, these flow conditions are modified by arterial wall changes. A detailed understanding of the local hemodynamic environment, the influence of wall modifications on flow patterns and the long-term adaptations of the vascular wall after surgical procedures can have useful clinical applications, especially in view of reconstruction and revascularization operations. Some of these alterations are not well-understood, making it quite difficult to foresee short- and long-term evolution of the atherosclerotic disease and to plan an aggressive approach. Computational fluid dynamics (CFD) allows the carrying out of simulations at low cost and in completely controlled conditions. Three different issues are relevant to this subject and are addressed in this paper: (1) the definition of suitable mathematical models; (2) pre-processing of clinical data; and (3) the development of appropriate numerical technique

Reconstruction and web distribution of measurable arterial models

In this paper a novel framework for the segmentation, 3D reconstruction and web distribution of vessel structures specifically tailored to the assessment of abdominal aortic aneurysms for endovascular surgery planning is presented. Deformable models are used for segmentation, while VRML97 and ECMA scripting are used to obtain models that are not only viewable from any VRML97 enabled browser, but that also allow users to perform, directly from standard web browsers, guided measurements of geometrical parameters, relevant to surgical planning.79-93Pubblicat

Web distribution of patient specific measurable arterial models

In this communication a novel framework for the segmentation, 3D reconstruction and web distribution of vessel structures is presented. Deformable models are used for segmentation, VRML and ECMA scripting are used to obtain 3D models that are not only viewable from any VRML97 enabled browser, but that also allow users to interact with the model, to navigate along the vessel lumen and to perform guided measurements of distances and angles. The segmented data are automatically converted in VRML97 worlds hiding scripting code that enables the measurement of the geometrical parameters relevant for surgical planning directly from standard web browsers