Automated design of customized implants

Este artículo muestra un modelo que se postula como capaz para el diseño de un implante craneal personalizado directamente desde el proceso de toma de imágenes médica. La salida de este proceso de diseño se conseguirá en un formato capaz de ser reconocido por el sistema de manufactura. El sistema propuesto se ha creado a partir de la unión de dos prototipos informáticos desarrollados durante la presente investigación, y a través del estudio de las tecnologías relacionadas o circundantes. El núcleo del modelo en la tecnología basada en el conocimiento (KBS), que debe permitir de almacenar y gestionar datos médicos y de diseño para poder aplicar dichos conocimientos durante el proceso de diseño del implante. El objeto de este proyecto es el de obtener una herramienta para mejorar el proceso de diseño, la biocompatibilidad con el paciente y reducir los costes finales, y que pueda ser operado sin necesidad del conocimiento completo de todas sus fases por el usuario.This paper presents a model capable of design a customized cranial implant directly from a medical imaging process, whose output will be a file in a manufacture system recognizable format. The proposed system has been created by linking two computer prototypes developed during the present research and studying the inner and outer related technologies. The core of the model is the KBS (Knowledge Based System) technology, able to store and manage medical data, as well as designer knowledge, in order to use this information in the implant design process. The aim of this project is to obtain a tool to improve the design process, the biocompatibility with patient and reduce final costs, which can be operated without necessity of wide knowledge from the user

Novel finite element-based plate design for bridging mandibular defects:Reducing mechanical failure

Introduction: When the application of a free vascularised flap is not possible, a segmental mandibular defect is often reconstructed using a conventional reconstruction plate. Mechanical failure of such reconstructions is mostly caused by plate fracture and screw pull-out. This study aims to develop a reliable, mechanically superior, yet slender patient-specific reconstruction plate that reduces failure due to these causes. Patients and Methods: Eight patients were included in the study. Indications were as follows: fractured reconstruction plate (2), loosened screws (1) and primary reconstruction of a mandibular continuity defect (5). Failed conventional reconstructions were studied using finite element analysis (FEA). A 3D virtual surgical plan (3D-VSP) with a novel patient-specific (PS) titanium plate was developed for each patient. Postoperative CBCT scanning was performed to validate reconstruction accuracy. Results: All PS plates were placed accurately according to the 3D-VSP. Mean 3D screw entry point deviation was 1.54 mm (SD: 0.85, R: 0.10–3.19), and mean screw angular deviation was 5.76° (SD: 3.27, R: 1.26–16.62). FEA indicated decreased stress and screw pull-out inducing forces. No mechanical failures appeared (mean follow-up: 16 months, R: 7–29). Conclusion: Reconstructing mandibular continuity defects with bookshelf-reconstruction plates with FEA underpinning the design seems to reduce the risk of screw pull-out and plate fractures

THREE-DIMENSIONAL COMPUTER MODELLING AND STRESS-STRAIN ANALYSIS OF TEMPOROMANDIBULAR JOINT

The main purpose of the study is to build 3D model of temporomandibular joint and mandible using programs for modelling and design, research stress and strain in cartilage and bone of model depending on different contraction of chewing muscles (especially lateral pterygoid muscle). There were used such methods as computer tomography data, finite element method and analysis topography of lateral pterygoid muscle on cadavers. In results of study was obtained maximal stress in anterior and distal parts of articular disc between 1,4–3 MPa and 0,4–1 MPa. Thus, static loads of articular disc were different, depends on force of contraction lateral pterygoid muscle. Muscle disturbances (hyperfunctioning, atrophy etc.) should be considered in treatment of temporomandibular dysfunction and examined on magnetic resonance investigation if it is present in the same patient

Predictive modeling of the virtual Hemi-Fontan operation for second stage single ventricle palliation: Two patient-specific cases

Single ventricle hearts are congenital cardiovascular defects in which the heart has only one functional pumping chamber. The treatment for these conditions typically requires a three-staged operative process where Stage 1 is typically achieved by a shunt between the systemic and pulmonary arteries, and Stage 2 by connecting the superior venous return to the pulmonary circulation. Surgically, the Stage 2 circulation can be achieved through a procedure called the Hemi-Fontan, which reconstructs the right atrium and pulmonary artery to allow for an enlarged confluence with the superior vena cava. Based on pre-operative data obtained from two patients prior to Stage 2 surgery, we developed two patient-specific multi-scale computational models, each including the 3D geometrical model of the surgical junction constructed from magnetic resonance imaging, and a closed-loop systemic lumped-parameter network derived from clinical measurements. “Virtual” Hemi-Fontan surgery was performed on the 3D model with guidance from clinical surgeons, and a corresponding multi-scale simulation predicts the patient\u27s post-operative hemodynamic and physiologic conditions. For each patient, a post-operative active scenario with an increase in the heart rate (HR) and a decrease in the pulmonary and systemic vascular resistance (PVR and SVR) was also performed. Results between the baseline and this “active” state were compared to evaluate the hemodynamic and physiologic implications of changing conditions. Simulation results revealed a characteristic swirling vortex in the Hemi-Fontan in both patients, with flow hugging the wall along the SVC to Hemi-Fontan confluence. One patient model had higher levels of swirling, recirculation, and flow stagnation. However, in both models, the power loss within the surgical junction was less than 13% of the total power loss in the pulmonary circulation, and less than 2% of the total ventricular power. This implies little impact of the surgical junction geometry on the SVC pressure, cardiac output, and other systemic parameters. In contrast, varying HR, PVR, and SVR led to significant changes in theses clinically relevant global parameters. Adopting a work-flow of customized virtual planning of the Hemi-Fontan procedure with patient-specific data, this study demonstrates the ability of multi-scale modeling to reproduce patient specific flow conditions under differing physiological states. Results demonstrate that the same operation performed in two different patients can lead to different hemodynamic characteristics, and that modeling can be used to uncover physiologic changes associated with different clinical conditions

Minimization of Volumetric Errors in CAD Medical Models Using 64 Slice Spiral CT Scanner

Sixty four slice spiral Computed Tomography (CT) scanner is one of the advanced CT scanners to capture the large volume of tissues and improved longitudinal resolution. The CT images are used to develop a 3-Dimensional (3D) Computer Aided Design (CAD) medical model. While developing a 3D CAD medical model volumetric errors occur due to partial volume or volume averaging effect. In order to study, various CT image construction parameters were considered to minimize the volumetric errors in 3D CAD medical models, a human dry mandible has been selected as a phantom. A Taguchi technique was used to find optimal CT image construction parameters. A L9 orthogonal array was used to optimize the CT image construction parameters constituting slice thickness, slice increment and Field of View (FOV) while performing CT image construction. The resultant optimal parameters are scrutinized using analysis of variance (ANOVA) method for its influence on the CT image construction. In this work, it has been found that there is a volumetric error of a 3D CAD medical model (STL file) from CT images of a dry mandible was 1978 mm3 (6.11%).Mechanical Engineerin

Physical and statistical shape modelling in craniomaxillofacial surgery: a personalised approach for outcome prediction

Orthognathic surgery involves repositioning of the jaw bones to restore face function and shape for patients who require an operation as a result of a syndrome, due to growth disturbances in childhood or after trauma. As part of the preoperative assessment, three-dimensional medical imaging and computer-assisted surgical planning help to improve outcomes, and save time and cost. Computer-assisted surgical planning involves visualisation and manipulation of the patient anatomy and can be used to aid objective diagnosis, patient communication, outcome evaluation, and surgical simulation. Despite the benefits, the adoption of three-dimensional tools has remained limited beyond specialised hospitals and traditional two-dimensional cephalometric analysis is still the gold standard. This thesis presents a multidisciplinary approach to innovative surgical simulation involving clinical patient data, medical image analysis, engineering principles, and state-of-the-art machine learning and computer vision algorithms. Two novel three-dimensional computational models were developed to overcome the limitations of current computer-assisted surgical planning tools. First, a physical modelling approach – based on a probabilistic finite element model – provided patient-specific simulations and, through training and validation, population-specific parameters. The probabilistic model was equally accurate compared to two commercial programs whilst giving additional information regarding uncertainties relating to the material properties and the mismatch in bone position between planning and surgery. Second, a statistical modelling approach was developed that presents a paradigm shift in its modelling formulation and use. Specifically, a 3D morphable model was constructed from 5,000 non-patient and orthognathic patient faces for fully-automated diagnosis and surgical planning. Contrary to traditional physical models that are limited to a finite number of tests, the statistical model employs machine learning algorithms to provide the surgeon with a goal-driven patient-specific surgical plan. The findings in this thesis provide markers for future translational research and may accelerate the adoption of the next generation surgical planning tools to further supplement the clinical decision-making process and ultimately to improve patients’ quality of life

The characteristics of the CAT to CAD to rapid prototyping system

ThesisComputer Aided Design (CAD), Rapid Prototyping (RP) and Computer Aided Tomography (CAT) technologies were researched. The project entails a unique combination of the abovementioned technologies, which had to be mastered by the author, on local and international terms. Nine software packages were evaluated to determine the modus operandi, required input and final output results. Fifty Rapid Prototyping systems were investigated to determine the strong and weak areas of the various systems, which showed that prototype materials, machine cost and growing time play an essential role. Thirty Reverse Engineering systems were also researched. Six different RE methods were recorded with several commercial systems available. Nineteen case studies were completed by using several different Computer Aided Tomography (CAT) and Magnetic Resonance Imaging (MRI) centers. Each scanning centre has different apparatus and is discussed in detail in the various case studies. The focus of this project is the data transfer of two dimensional CAT scanning data to threedimensional prototypes by using Reverse Engineering (RE) and Rapid Prototyping (RP). It is therefore of cardinal importance that one is familiar and understands the various fields of interest namely Reverse Engineering, Computer Aided Tomography and Rapid Prototyping. Each of these fields will be discussed in detail, with the latest developments in these fields covered as well. Case studies and research performed in the medical field should gain the medical industry's confidence. Constant marketing and publications will ensure that the technology is applied and transferred to the industry. Commercialisation of the technology is of utmost importanc