Faculty of Mechanical Engineering

The paper presents a case where an implant for a part of the sternum (with costal cartilages) affected by cancer was created and implanted by using the specific reverse modeling method and solid free-form fabrication. The method provides surgeons with a fast and reliable tool for tissue engineering and implantation and therefore improves the quality of life for patients. Digital images of healthy sternum samples were used to develop a reverse modeling algorithm that semi-automatically generates a necessary and sufficient simplification of the tissue geometry to be fabricated in an inexpensive and applicable manner. In this particular case, the redesign of the missing part of the sternum in CAD software took three designerhours. At the same time, the suitable simplification of the geometry affects the fabrication of simpler and less expensive casting molds. Furthermore, the core of the developed algorithm for the reverse modeling of sternum can be applied in the reverse modeling improvement of other tile (or plate-like) bones.

Workflow management systems manage business processes within an organization. In order to be successful, the systems must have ability for efficient management of resources which are used in processes. One of the shortcomings that have been noticed in the most of the workflow management systems is weak support for resource management. In this paper it is shown how to manage resources in MD system, which is developed on the Faculty of Mechanical Engineering Nis. This system tries to exceed shortcomings of the existing systems.

Geometrically accurate and anatomically correct threedimensional geometric models of human bones or bone sections are essential for successful pre-operative planning in orthopedic surgery. For such purposes, 3D polygonal models of bones are usually created based on Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) data. In cases where there is no CT or MRI scan, or part of bone is missing, such three-dimensional polygonal models are difficult to create. In these situations predictive bone models are commonly used. In this paper, the authors describe the developed a software system for creation of Human Bones Customized Polygonal models (HBCP) which is based on the use of the predictive parametric bone model. The software system enables creation of patient-specific polygonal models of bones, by using only a limited number of parameter values. Parameter values can be acquired from volumetric medical imaging methods (CT, MRI), or from two-dimensional imaging methods (i.e. X-ray). This paper introduces the new approach to the process of creation of human bones geometrical models which are based on the anatomical landmark points. Testing of the HBCP for the cases of femur bone samples has shown that created bone and bone region models are characterized by a good level of anatomical and morphometric accuracy compared to the results presented in similar researches. She is an author of over 70 scientific and professional papers. From 2008. Professor Arsić is the member of a multidisciplinary research team compose by mechanical engineers, orthopaedic surgeons, and radiologists whose scientific is 3D morphology and CAD design of the bones.

In order to create valid CAD (computer-aided design) model for planning orthopedic operations, rapid prototyping, designing of implants, etc., the accurate definition of geometry and topology of all regions of human tibia is essential. Therefore it is logical to base process of geometrical modeling of human tibia on its anatomical and morphological properties. This paper presents and compares the application of two modeling techniques for creating geometrical model of the human tibia. The techniques applied are developed considering the natural features of the human tibia bone, and not only standard CAD techniques for geometrical modeling which are common in standard engineering. The application of these methods can be extended to other bones in human body.

Uvod/Cilj. Rekonstrukcija nedostajuće, oštećene ili deformisane kosti donje vilice predstavlja izazov kako u funkcionalnom, tako i u estetskom pogledu. Cilj istraživanja bio je utvrđivanje potencijalnih razlika u vrednostima osnovnih linearnih morfometrijskih parametara (LMP) dobijenih direktnim i indirektnim merenjem istih humanih mandibula, uz istovremenu proveru preciznosti indirektne metode merenja koja se rutinski koristi u svakodnevnom kliničkom radu. Istraživanje je od značaja za definisanje parametarskog modela "standardne mandibule", odnosno virtuelnog modeliranja humane mandibule u budućim istraživanjima i kliničkoj praksi. Metode. Istraživanje je sprovedeno na 12 anatomskih osteoloških preparata adultnih humanih mandibula. Određivane su vrednosti 10 standardnih LMP koristeći standardne anatomske orijentacione tačke. Parametri su mereni na istim mandibulama manuelno i to direktno, uz pomoć kljunastog merila sa nonijusom i indirektno, softverskim alatom na dvodimenzionalnim (2D) rekonstrukcijama snimaka multislajsnih kompjuterskih tomografija (MSCT), uz međusobno poređenje vrednosti za isti LMP. Rezultati. Statistički značajne razli-ke upoređivanih vrednosti LMP-a, dobijenih različitim metodama merenja, bile su prisutne kod gnationinterdentalne distance (Gn-IdD) i gnation-kondilarne distance (Gn-KoD), obostrano. U oba slučaja, značajno više srednje vrednosti (sa procentualnom razlikom) uočene su pri direktnom u odnosu na indirektno merenje: Gn-IdD (21,57%; 29,2 mm vs 22,9 mm; p = 0,004); Gn-KoD leva strana (14,1%; 122,7 mm vs 105,4 cm; p = 0,001); Gn-KoD desna strana (11,87%; 124,7 mm vs 109,9 mm; p = 0,009). Zaključak. Uočene razlike u nepreciznosti indirektnog merenja, ukazuju na potrebu uvođenja odgovarajućeg korekcionog faktora za Gn-IdD i Gn-KoD prilikom definisanja parametarskog modela "standardne mandibule" na osnovu morfometrijskog merenja na 2D rekonstrukcijama MSCT snimaka. Dodatna ispitivanja na većem broju uzoraka, uz kvantifikovanje anatomskih varijacija u odnosu na pol, starost, stanje denticije i etničko poreklo, dodatno povećavaju preciznost merenja, a time i pouzdanost budućeg parametarskog modela humane mandibule.

In the majority of published research papers related to the application of CAD software in medicine, especially in the area of reverse engineering of the skeletal system, classical methods of CAD modeling were applied. The most methods are related on the standard features of CAD software, for creating valid surfaces, such as loft, blend, sweep, etc. Geometrical splines needed for the exact features are acquired and verified by statistical methods applied on numerous scanned specimens. A new method for computer modeling of the distal femur, especially for the femoral condyles, will be presented in this paper. The method applied on the geometrical modeling of the distal femur is based on morphological properties of the condyle of femur, rather than on the statistical approach, or some other standardized approach of the curves generation which were used for the most common tasks of surface modeling.

This study presents morphological analysis of 20 scans of femur samples from European (Serbian) adults from trochanteric region based on the customized computer aided reverse modeling procedure. Results indicated that trochanteric region is a separate morphological unit of proximal femur, named trochanteric wedge or canoe. This new perceiving of trochanteric region seems to provide a better understanding of trochanteric wedge volume and, therefore, better trochanter fractures treatment, operation planning, implant and endoprothesis design and selection. Also, it brings a new light to anatomy of proximal femur, its biomechanics and ossification.

One of the main issues that arise during preparation of models for subject specific finite element analysis (FEA) of long bones is the accuracy of material characterization. This paper tends to identify the most common sources of material characterization errors, which are sometimes also interconnected with bone geometry reconstruction errors, in order to help in creation of more accurate finite element models of long bones. Reconstruction of patient's bone geometry is usually based on medical images obtained by means of computational tomography (CT). Material characterization is performed either by segmentation of the model to characteristic zones that are assigned typical averaged material properties, or by local material mapping, based on bone density values estimated from CT numbers. Some of the main factors that influence material characterization accuracy are the choice of material model, the approach to material properties averaging, x-ray tube parameters, scanner calibra...

Paper outlines a feasibility study of using direct metal laser sintering (DMLS) for rapid tooling (RT) of tread ring of tyre vulcanization mould. Lead time and costs for rapid tooling with DMLS is acceptable for small mould segments (1/64 of tread ring). RT strategy that utilizes DMLS appeared to have significant advantages concerning lead time and costs as compared to conventional tooling of tyre mould including CNC-HSM engraving. Simplicity of tread ring tooling by DMLS makes new tyre development and test easier and faster.