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

Towards a CAD-based automatic procedure for patient specific cutting guides to assist sternal osteotomies in pectus arcuatum surgical correction

Abstract Pectus Arcuatum, a rare congenital chest wall deformity, is characterized by the protrusion and early ossification of sternal angle thus configuring as a mixed form of excavatum and carinatum features. Surgical correction of pectus arcuatum always includes one or more horizontal sternal osteotomies, consisting in performing a V-shaped horizontal cutting of the sternum (resection prism) by means of an oscillating power saw. The angle between the saw and the sternal body in the V-shaped cut is determined according to the peculiarity of the specific sternal arch. The choice of the right angle, decided by the surgeon on the basis of her/his experience, is crucial for a successful intervention. The availability of a patient-specific surgical guide conveying the correct cutting angles can considerably improve the chances of success and, at the same time, reduce the intervention time. The present paper aims to propose a new CAD-based approach to design and produce custom-made surgical guides, manufactured by using additive manufacturing techniques, to assist the sternal osteotomy. Starting from CT images, the procedure allows to determine correct resection prism and to shape the surgical guide accordingly taking into account additive manufacturing capabilities. Virtually tested against three case studies the procedure demonstrated its effectiveness. Highlights Patient-specific surgical guide improves the chances of success in sternal osteotomy. A CAD-based approach to design and produce custom-made surgical guides is proposed. The proposed framework entails both a series of automatic and user-guided tasks

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

Anticollusion watermarking of 3D meshes by prewarping

A novel pre-warping technique for 3D meshes is presented to prevent collusion attacks on fingerprinted 3D models. By extending a similar technique originally proposed for still images, the surface of watermarked 3D meshes is randomly and imperceptibly pre-distorted to protect embedded fingerprints against collusion attacks. The peculiar problems set by the 3D nature of the data are investigated and solved by preserving the perceptual quality of warped meshes. The proposed approach is independent of the chosen fingerprinting system. The proposed algorithm can be implemented inside a watermarking chain, as an independent block, before performing features extraction and watermark embedding. It follows that the detection algorithm is not influenced by the anti-collusion block. The application of different collusion strategies has revealed the difficulty for colluders to inhibit watermark detection while ensuring an acceptable quality of the attacked mode

Computer Aided Design Tool for GT Ventilation System Ductworks

The proper design of a ventilation system (VS) is an important requirement in the Gas Turbine (GT) and energy production industry in general. In fact, ventilation systems are designed to provide a continuous source of cooling air so as to: remove heat and maintain the air temperature in the compartment below the operating limit; prevent the accumulation of hazardous gases; preserve a constant and uniform airflow through the ducts, independently from the environmental conditions; avoid accidental dust and sand contamination in gas turbines, especially when these are located in regions prone to sandstorm conditions. When compared to typical Heating, Ventilating and Air Conditioning (HVAC) systems, the design of VSs results particularly challenging since many requirements, generally involving different engineering aspects such as fluid-dynamic, acoustic and structural, have to be fulfilled. Generally speaking, a VS is composed by a number of elements such as linear ducts, expansion joints, transition duct sections, elbows, outlets to the atmosphere, supports, saddles and brackets. Shape and dimensions of these elements may significantly vary depending on the kind of application. Basically, the elements may have circular/oval or rectangular/square section. In the first case, they are manufactured by employing calendaring process followed by welding. Otherwise, the component is realized by cutting and welding metal sheets. Elements are coupled by using bolted flanges or welded joints in order to obtain the entire VS ductwork

Comparing two 3D measurement techniques for documenting painted wooden panels surface deformations on a real test case: "mystical Marriage of Saint Catherine" by Renaissance artist Piero di Cosimo

Ancient wooden panel paintings are an essential part of our cultural heritage. Wood as artworks support has always been very popular and painted panels are largely diffuse in many churches and museums. However, depending on conservation conditions, the wooden panels shape may vary and if not properly controlled may lead to some sever damage to the artworks. This paper presents the results of a study on the measurement of paintings surface deformation carried out using two different three-dimensional acquisition devices both making use of structured light. The main goal was to highlight and measure the reliability of such 3D measuring techniques to evaluate deviations from planarity due to the curving and warping of the wood and to document spatial deformation suffered by the painting and monitoring its conservation status