3D MODELLING AND RAPID PROTOTYPING FOR CARDIOVASCULAR SURGICAL PLANNING – TWO CASE STUDIES

In the last years, cardiovascular diagnosis, surgical planning and intervention have taken advantages from 3D modelling and rapid prototyping techniques. The starting data for the whole process is represented by medical imagery, in particular, but not exclusively, computed tomography (CT) or multi-slice CT (MCT) and magnetic resonance imaging (MRI). On the medical imagery, regions of interest, i.e. heart chambers, valves, aorta, coronary vessels, etc., are segmented and converted into 3D models, which can be finally converted in physical replicas through 3D printing procedure. In this work, an overview on modern approaches for automatic and semiautomatic segmentation of medical imagery for 3D surface model generation is provided. The issue of accuracy check of surface models is also addressed, together with the critical aspects of converting digital models into physical replicas through 3D printing techniques. A patient-specific 3D modelling and printing procedure (Figure 1), for surgical planning in case of complex heart diseases was developed. The procedure was applied to two case studies, for which MCT scans of the chest are available. In the article, a detailed description on the implemented patient-specific modelling procedure is provided, along with a general discussion on the potentiality and future developments of personalized 3D modelling and printing for surgical planning and surgeons practice

Patient-specific 3D modelling of heart and cardiac structures workflow: an overview of methodologies

Cardiovascular diagnosis, surgical planning and intervention are among the most interested in recent developments in the field of 3D acquisition, modelling and rapid prototyping techniques. In case of complex heart disease, to provide an accurate planning of the intervention and to support surgical planning and intervention, an increasing number of Hospitals make use of physical 3D models of the cardiac structure, including heart, obtained using additive manufacturing starting from the 3D model retrieved with medical imagery. The present work aims in providing an overview on most recent approaches and methodologies for creating physical prototypes of patient-specific heart and cardiac structures, with particular reference to most critical phases such as segmentation and aspects concerning converting digital models into physical replicas through rapid prototyping techniques. First, recent techniques for image enhancement to highlight anatomical structures of interest are presented together with the current state of the art of semi-automatic image segmentation. Then, most suitable techniques for prototyping the retrieved 3D model are investigated so as to draft some hints for creating prototypes useful for planning the medical intervention

Improvements on a MMI-based method for automatic texture mapping of 3D dense models

Maximization of Mutual Information routines proved to be suitable for registration of multimodal images. Here a method is proposed to select, in a set of candidates, the image which has a closer resemblance with a given external one. Such algorithm is intended to serve within a wider scope procedure for the automatic texturing of 3D models, where the initial 2D-3D registration problem is shifted to a 2D-2D registration challenge. In order to improve its performance a number of variations in the way the Mutual Information is computed are introduced and a method to judge its reliability is proposed

Comparison of Mesh Simplification tools in a 3D Watermarking framework

Given a to-be-watermarked 3D model, a transformed domain analy-sis is needed to guarantee a robust embedding without compromising the visual quality of the result. A multiresolution remeshing of the model allows to repre-sent the 3D surface in a transformed domain suitable for embedding a robust and imperceptible watermark signal. Simplification of polygonal meshes is the basic step for a multiresolution remeshing of a 3D model; this step is needed to obtain the model approximation (coarse version) from which a refinement framework (i.e. 3D wavelet analysis, spectral analysis, \u2026) able to represent the model at multiple resolution levels, can be performed. The simplification algo-rithm should satisfy some requirements to be used in a watermarking system: the repeatability of the simplification, and the robustness of it to noise or, more generally, to slight modifications of the full resolution mesh. The performance of a number of software packages for mesh simplification, including both commercial and academic offerings, are compared in this survey. We defined a benchmark for testing the different software in the watermarking scenario and reported a comprehensive analysis of the software performances based on the geometric distortions measurement of the simplified versions

Computer Aided Design Tool for GT Ventilation System Ductworks

The design of gas turbine ventilation systems (VSs) is a lengthy and tedious process, often requiring weeks to refine a single design concept and by additional time to manufacture it. This is particularly true when dealing with structural design since the typical approach followed by main worldwide manufacturing companies is to outsource finite elements analysis and, often, the 3d modelling phase itself. Moreover, the structural design process is iterative: the modeling and finite elements analysis steps are repeated several times whenever a new VS has to be produced. Accordingly, speeding-up the structural design phase is today a crucial issue for gas turbine sector. Keeping the above objective in mind, the present paper proposes a CAD-based tool, implemented in a commercial 3D CAD software package (SolidWorks), supporting and partly automating the complex structural VS design process. The solution suggested in this work consists of the design and implementation of a SolidWorks add-in, called DuctWorks, developed by using C# programming language. Differently from commercially available solutions, the proposed tool is specifically thought keeping in mind the necessity of performing a final structural assessment, which is of utmost importance given the considerable dimensions and stresses this kind of VS are subject to in the specific field of GT and energy production industry. Tested against a set of case studies, DuctWorks proved to be effective in allowing designers to accelerate the ventilation systems design process with excellent results when compared with the traditional design process

Copyright Protection of Digital Images of Cultural Heritage

This Chapter is dedicated to present digital watermarking technology and mainly to propose how it can be used to protect digital documents (copyright protection). In the field of Cultural Heritage (CH), the protection of images is a crucial issue, stated the importance of their diffusion, both with dissemination aims and in order to attract visitors to real museums. Digital marking techniques are a key application for the protection of Cultural Heritage digital images. In the following, digital marking techniques are presented, with particular attention to the \u201cperceptual\u201d invisibility of the mark (in order to not deteriorate the image itself) and \u201crobustness\u201d (the strength of the mark, that is its resistance to be removed). Examples concerning art-works of the Polo Museale Fiorentino are shown

Identification of pictorial materials by means of optimized multispectral reflectance image processing

Image spectroscopy may allow identifying the materials present on a painting surface in a non-invasive way. The proposed method aims at optimizing, and thus reducing, the number of filters employed, while still providing a robust method, that achieves similar performances as traditional ones, which in turn employ a large number of filters. Moreover, we targeted the identification of the pigments present on the outer layer of a painting independently from their thickness, the underlying background or support, the binder employed, their aging and acquisition set-up. In order to achieve this objective, a relevant number of swatches have been prepared, on different supports and with different thicknesses and binding mediums. Spectral reflectance curves of such chemically known pictorial layers have been recorded by means of a spectrometer and a spectrophotometer. A novel Principal Component Analysis (PCA) based approach has been devised to select the most relevant wavebands, i.e. those that allow the most effective discrimination among (quasi)metameric colours, which are thus not to be distinguished with the naked eye or with an RGB camera. Comparisons of results using the 13 filters available on the filter wheel and of a selection of only 3 and 4 filters, support the idea of the simplified version investigated in this paper being a viable alternative