Methods for medical applications

The object of this paper is testing the performance of a new device for 3D oral scanning: a two channel PTOF (pulsed time-of-flight) laser scanner, designed for dental and industrial applications in the measurement range of zero to a few centimetres. The application on short distances (0-10 cm) has entailed the improvement of performance parameters such as single shot precision, average precision and walk error up to mm-level and to μm-level respectively. The single-shot precision (σ-value) has resulted to range from 43 to 63 ps (9-10 mm), having considered the measurement range (6.5-10 mm) corresponding to 1-2 V signal; this result agrees well with estimates made from simulations. The average precision has resulted to be dependent on the number of measurements and can reach a value equal to ±25 μm, whenever the measurements frequency is sufficiently high. For example, if the required scanning speed is 1000 points/s and the required average precision is ±25 μm, then a pulses frequency of 30-50 MHz is needed, considering signal amplitude varying between 1-2 V. On the whole, the performance of this new device, based on PTOF has proven to be adequate to its employment in the field of restorative dentistry. © 2013 Elsevier Ltd.

Keywords: CAD/CAM , Intraoral scanner , Laser range-finding techniques , Pulsed time of flight , Restorative dentistry

Intra-oral scanning technology is a very fast-growing field in dentistry since it responds to the need of an accurate three-dimensional mapping of the mouth, as required in a large number of procedures such as restorative dentistry and orthodontics. Nowadays, more than 10 intra-oral scanning devices for restorative dentistry have been developed all over the world even if only some of those devices are currently available on the market. All the existing intraoral scanners try to face with problems and disadvantages of traditional impression fabrication process and are based on different non-contact optical technologies and principles. The aim of this publication is to provide an extensive review of existing intraoral scanners for restorative dentistry evaluating their working principles, features and performances. © 2013 Elsevier Ltd.

Keywords: Confocal microscopy , Digital dental impressions , Intraoral scanner , Optical coherence tomography , Triangulation

The artifacts that appear on maxillofacial X-ray CT images are mainly caused by the presence of metallic prosthetic appliances (such as amalgam or gold fillings). They cause problems in the three dimensional virtual reconstruction and in the eventual physical reproduction by rapid prototyping systems. At present the classification of different artifact types, metallic presences or artifacts induced by them, is often left to the experience and sensitivity of the operator. The purpose of this paper is to solve this problem automatically, by using an expert system based on fuzzy logic. Decisional networks were created and tested, using the Hounsfield scale values of each CT image pixel, for the membership functions. Three cases study were considered to evaluate the novel method. The CT images were processed and cleaned automatically leaving the decisional phase to the computer. The data from the three cases study show that the proposed methodology is accurate. The results of this study allow to get correct virtual and physical models in medical applications. © 2012 Springer-Verlag France.

Keywords: CT images , Expert system , Fuzzy logic , Metallic artifacts

In this work, a new technique for symmetry line detection for non-erected postures, which can not be investigated with the other methods presented in the literature, is proposed. It evaluates the symmetry line by means an adaptive process in which a first attempt is modified step by step until the solution converges to the best estimation. The method here proposed is validated by analysing four different non-erected postures in which the spine does not lie onto sagittal plane, by the comparison with the traditional approach to symmetry line detection, having as reference the cutaneous marking. Results are analysed and critically discussed. © 2012 Springer-Verlag France.

Keywords: Anatomical landmarks , Back shape analysis , Posture prediction , Rasterstereography , Symmetry line

This paper proposes a new method for the identification of the symmetry plane of the human face, working from 3D high-density scanned data. The method being proposed is an original variant of a typical mirroring and registration method. This method is validated by analysing some specifically designed test cases. The obtained results show that the method is quite insensitive to local asymmetries, whether they be near or far from the symmetry plane, and is also repeatable and slightly conditioned by the acquisition process. © 2012 Springer-Verlag France.

Keywords: Asymmetry , Mirroring , Rasterstereography , Registration , Symmetry plane

The methods for symmetry line detection presented in the literature are typically suited to analyse symmetric upright postures, both standing and seated. The proposed method focuses on the symmetry line detection in subjects assuming asymmetric postures in which this line falls far outside the sagittal plane. The proposed approach evaluates the symmetry line by means of an autoregressive process in order to determine the set of planes suited to slice the back coherently with its geometric spatial configuration. The method is analysed assuming the cutaneous marking as reference and it is compared with a previous one, also developed by these authors. Results are analysed and critically discussed. © 2013 Taylor & Francis.

Keywords: anatomical landmarks , back shape analysis , posture prediction , rasterstereography , symmetry line

It was reported that next to style, comfort is the second key aspect in purchasing footwear. One of the most important components of footwear is the shoe sole, whose design is based on many factors such as foot shape/size, perceived comfort and materials. The present paper focuses on the parametric analysis of a shoe sole to improve the perceived comfort. The sensitivity of geometric and material design factors on comfort degree was investigated by combining real experimental tests and CAD-FEM simulations. The correlation between perceived comfort and physical responses, such as plantar pressures, was estimated by conducting real tests. Four different conditions were analyzed: subjects wearing three commercially available shoes and in a barefoot condition. For each condition, subjects expressed their perceived comfort score. By adopting plantar sensors, the plantar pressures were also monitored. Once given such a correlation, a parametric FEM model of the footwear was developed. In order to better simulate contact at the plantar surface, a detailed FEM model of the foot was also generated from CT scan images. Lastly, a fractional factorial design array was applied to study the sensitivity of different sets of design factors on comfort degree. The findings of this research showed that the sole thickness and its material highly influence perceived comfort. In particular, softer materials and thicker soles contribute to increasing the degree of comfort. © 2012 IPEM.

Keywords: CAD-FEM modeling , Comfort assessment , Fractional factorial design , Numerical-physical correlation , Pressure map , Shoe sole

Aim of this work is to compare two different total knee prostheses that differ mainly in the shape of the polyethylene (PE) component inserted between the femoral and tibial plates. The best solution between them has been originally reshaped in order to reduce stress peaks. The study procedure has been divided into the following steps. First step is the digitalisation of the shape of the prostheses by means of a 3D laser scanner. The morphology of two prototypes of the prostheses has been acquired by elaborating multiple Moirè fringe patterns projected on their surfaces. Second step consisted on the manipulation of these data in a CAD module, that is the interpolation of raw data into NURBS surfaces, reducing singularities due to the typical scattering of the acquiring system. Third step has been the setting up of FEM simulations to evaluate the prostheses behaviour under benchmark loading conditions given in literature. The CAD model of the prostheses has been meshed into solid finite elements. Different flexion angles configurations have been analysed, the load being applied along the femoral axis. FEM analyses have returned stress fields in the PE insert and, in particular, in the stabilizing cam which function is to avoid dislocation. Last step has been the integrated use of CAD and FEM to modify the shape of the stabilizing cam of the best prosthesis, in order to reduce the stress peaks in the original prosthesis without affecting kinematics of the joint. Good results have been obtained both in terms of stress and contact pressure peaks reduction. © 2012 Springer-Verlag.

Keywords: Contact analysis , FEM simulation , Total knee replacement

This article concerns the design of lower limb prosthesis, both belowand above knee. It describes a newcomputer-based design framework and a digital model of the patient around which the prosthesis is designed and tested in a completely virtual environment. The virtual model of the patient is the backbone of the whole system, and it is based on a biomechanical generalpurpose model customized with the patient's characteristics (e.g. anthropometric measures). The software platform adopts computer-aided and knowledge-guided approaches with the goal of replacing the current development process, mainly hand made, with a virtual one. It provides the prosthetics with a set of tools to design, configure and test the prosthesis and comprehends two main environments: the prosthesis modelling laboratory and the virtual testing laboratory. The first permits the three-dimensional model of the prosthesis to be configured and generated, while the second allows the prosthetics to virtually set up the artificial leg and simulate the patient's postures and movements, validating its functionality and configuration. General architecture and modelling/simulation tools for the platform are described as well as main aspects and results of the experimentation. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

Keywords: Digital patient , Human modelling , Lower limb prosthesis , Virtual prototyping

This paper presents an environment, named Virtual Testing Lab-VTL, where the orthopedic technicians can test the prosthesis replicating the traditional procedures. It is part of an innovative design framework centered on digital models of the whole patient or of his/her anatomical districts, which constitute the backbone of the whole prosthesis design process. The virtual lab permits to realize a complete amputee's digital model, an avatar, by which it is possible to execute prosthesis set up and evaluate its functionality simulating postures and movements. First, we describe the state of art of techniques used, i.e., virtual humans and motion capture systems. Then, the application of virtual humans for the prosthesis design and simulation is presented as well as preliminary results. © 2013 CAD Solutions, LLC.

Keywords: Prosthesis design , Virtual human , Virtual testing

This paper concerns a research project that aims at developing an innovative platform to design lower limb prosthesis. The platform is centered on the virtual model of the amputee and is based on a computer-aided and knowledge-guided approach. In particular, the paper focuses on the module, named Socket Modeling Assistant-SMA, conceived to design the socket, the most critical component of the whole prosthesis. The underlining idea is to experiment low-cost devices, such the Leap Motion, to manipulate the 3D virtual model of the socket using hands as traditional done by the prosthetist. The goal is to make available a modeling tool that permits to replicate/emulate manual operations usually performed by the prosthetist during the traditional development process. First, we first describe the traditional socket development process; then the SMA software architecture and the guidelines used to develop the interaction algorithms (integrated within SMA) that exploit the Leap Motion and Falcon devices. Finally preliminary tests and results will be illustrated. © 2013 ACM.

Keywords: 3D modeling , hand tracking , haptic interaction , lower limb prosthesis

Lower limb prostheses for above or below knee amputees are still designed and produced almost completely in a manual way, deeply relying on the experience and manual skills of orthopaedic technicians. This paper presents the main features characterising the prototype of a virtual environment developed to assist the technicians designing and testing the prosthesis. To reach the ambitious goal of replacing the manual process with a complete virtual one several issues have been considered and addressed: the capture and formalisation of process knowledge of orthopaedic technicians, the acquisition of patient's information and digital data, the development of an integrated solution to design and test standard and custom-fit components and the simulation of the gait of a virtual human wearing the virtual prosthesis. The architecture of the prosthesis design platform as well as the modelling and simulation tools are described. Finally, the experimentation phase and related results are presented and discussed. © 2013 Copyright Taylor and Francis Group, LLC.

Keywords: design environment , digital human modelling , lower limb , prosthesis

In this paper, we propose a knowledge-based approach to design lower limb prostheses; in particular, we focus on the 3D modelling of the socket, the most critical component. First, the architecture of a dedicated design framework is described, detailing features of the main design steps. Then, the paper discusses the acquisition and formalisation of the knowledge related both to the prosthesis manufacturing process and to the considered component. Finally, we present the computer-aided module, named socket modelling assistant-SMA, we specifically developed to design the socket. It is a virtual laboratory where the socket virtual prototype is generated directly on the digital model of patient's residual limb. It guides and supports the designer during each step in an automatic and/or semi-automatic way applying design rules and procedures. The modelling steps and available interactive tools that emulate orthopaedic technician's operations are described. Results of the experimentation phase are described. At current state of the prototype development, they are encouraging and have permitted to preliminarily validate the proposed approach and envisage future improvements. Copyright © 2013 Inderscience Enterprises Ltd.

Keywords: 3D socket modelling , Knowledge-based design , Lower limb prosthesis , Virtual prototyping

In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT) and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces) through the digitalization of both patients' mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: Dental CBCT images , Optical scanning , Orthodontic model , Sensor fusion , Tooth segmentation

Recent developments in digital imaging techniques have allowed a wide spread of three-dimensional methodologies based on capturing anatomical tissues by different approaches, such as cone-beam computed tomography, three-dimensional photography and surface scanning. In oral rehabilitation, an objective method to predict surgical and orthodontic outcomes should be based on anatomical data belonging to soft facial tissue, facial skeleton and dentition (maxillofacial triad). However, none of the available imaging techniques can accurately capture the complete triad. This article presents a multi-modal framework, which allows image fusion of different digital techniques to create a three-dimensional virtual maxillofacial model, which integrates photorealistic face, facial skeleton and dentition. The methodology is based on combining structured light surface scanning and cone-beam computed tomography data processing. The fusion procedure provides multi-modal representations by aligning different tissues on the basis of common anatomical constraints. © IMechE 2012.

Keywords: Computer assisted , Cone-beam computed tomography scanning , Maxillofacial modelling , Multi-modal image fusion , Optical scanning , Three-dimensional medical imaging

The energy generation inside the human body represents a crucial aspect for powering implantable measuring circuits. In this work, a system for the electromagnetic energy harvesting, implantable in a total knee prosthesis (TKP) and capable of generating electricity from the knee movement, is presented. The energy harvesting system (EHS) is composed of two series of NdFeB magnets, located on each condyle, and a coil placed in a pivot of the tibial tray. The operating principles, design considerations and performed simulations are shown. Simulation results demonstrate that it is possible to generate an alternating voltage of maximum 600 mV. The proposed generator eliminates the batteries inside the human body and the use of techniques for the inductive power supply. The structural changes with respect to commercial prosthesis are minimal. Furthermore, the proposed energy harvester allows to generate electricity without changing or hindering the patient natural movement. Copyright © 2013 Inderscience Enterprises Ltd.

Keywords: Electromechanical generator , Human energy harvesting , TKP , Total knee prosthesis

Aims. To measure the friction force generated during sliding mechanics with conventional, self-ligating (Damon 3 mx, Smart Clip, and Time 3) and low-friction (Synergy) brackets using different archwire diameters and ligating systems in the presence of apical and buccal malalignments of the canine. Methods. An experimental setup reproducing the right buccal segment of the maxillary arch was designed to measure the friction force generated at the bracket/wire and wire/ligature interfaces of different brackets. A complete factorial plan was drawn up and a three-way analysis of variance (ANOVA) was carried out to investigate whether the following factors affect the values of friction force: (i) degree of malalignment, (ii) diameter of the orthodontic wire, and (iii) bracket/ligature combination. Tukey post hoc test was also conducted to evaluate any statistically significant differences between the bracket/ligature combinations analyzed. Results. ANOVA showed that all the above factors affect the friction force values. The friction force released during sliding mechanics with conventional brackets is about 5-6times higher than that released with the other investigated brackets. A quasilinear increase of the frictional forces was observed for increasing amounts of apical and buccal malalignments. Conclusion. The Synergy bracket with silicone ligature placed around the inner tie-wings appears to yield the best performance. © 2013 Vito Crincoli et al.

Nanoindentation has recently emerged as a powerful tool for measuring nano- and microscale mechanical properties in tissues and other biomaterials. This technique has been used to measure the mechanical properties of microstructural features in cells, biopolymer networks, and complex biomaterials. Despite the wide use of the nanoindentation, the residual stress effect in the determination of soft samples elastic properties is still poorly explored. By using parametric finite element analysis and atomic force spectroscopy, we determined the relationships between residual stress and indenter geometry and how it can affect the structural response of polymeric spherical shells flattened on a hard surface. © 2013 AIP Publishing LLC.

The present paper describes the design features, potential indications and a clinical application of a newly designed device for jaw motion rehabilitation, the Spring-Bite. This device is characterized by a first class lever mechanism, which allows performing passive jaw motion rehabilitation at constant load without an active participation by the patient. Spring-Bite was developed for the management of temporomandibular joint (TMJ) hypomobility and its application may be much useful in the post-operatory phases of TMJ or orthognathic surgeries as well as in patients with reduced muscular force.

In this paper we report the application of CAD/CAM based technologies for the innovative development of customized surgical devices to assist the mandibular rehabilitation in both primary surgery (resection and reconstruction) and secondary surgery (only reconstruction). Design and manufacturing of such customized surgical device are conducted according to the virtual pre-operative planning of the surgeon and with the aim to transferring this planning into the operating theatre. In the case of primary surgery, a cutting guide is developed to assist the resection step while a bone plate is developed to assist the reconstruction step. Instead, in the case of secondary surgery, in addition to the bone plate to support the reconstruction, also a repositioning guide is designed to bring back to the original position the resected stumps according to the original shape of the mandible. Finally, the components of the surgical devices are manufactured by DMLS in alloys suitable for biomedical applications. © 2012 Springer-Verlag France.

Keywords: 3D Reconstruction , Computed tomography , Computer aided design , Direct metal laser sintering , Rapid prototyping