Procedure for Creating Personalized Geometrical Models of the Human Mandible and Corresponding Implants

The greatest challenge in engineering of human mandible implants lies in its customization for each patient individually, by adapting them to the patient's anatomical, morphological and physiological characteristics. This customization maximizes the efficiency of the patient's health recovery process. The application of anatomically shaped and personalized bone endoprosthesis, fixation plate and scaffold models bring great improvement to the clinical practice in maxillofacial surgery. It ensures that implant meets the biomechanical and dentofacial aesthetic requirements and, ultimately, reduces complications during recovery. In order to create such implants, novel procedure based on personalized models of mandible and its parts, and also plates and scaffold implants is presented in this paper. Design procedures for the creation of the personalized models are based on the application of Method of Anatomical Features, which has been already applied for the creation of geometrical models of human bones. This procedure improves pre-surgical planning, enables better execution of surgical intervention, and as a consequence improves patient recovery processes

Procedure for Creating Personalized Geometrical Models of the Human Mandible and Corresponding Implants

The greatest challenge in engineering of human mandible implants lies in its customization for each patient individually, by adapting them to the patient’s anatomical, morphological and physiological characteristics. This customization maximizes the efficiency of the patient‘s health recovery process. The application of anatomically shaped and personalized bone endoprosthesis, fixation plate and scaffold models bring great improvement to the clinical practice in maxillofacial surgery. It ensures that implant meets the biomechanical and dentofacial aesthetic requirements and, ultimately, reduces complications during recovery. In order to create such implants, novel procedure based on personalized models of mandible and its parts, and also plates and scaffold implants is presented in this paper. Design procedures for the creation of the personalized models are based on the application of Method of Anatomical Features, which has been already applied for the creation of geometrical models of human bones. This procedure improves pre-surgical planning, enables better execution of surgical intervention, and as a consequence improves patient recovery processes

GEOMETRICAL MODELS OF MANDIBLE FRACTURE AND PLATE IMPLANT

In the oral and maxillofacial surgery, there is a requirement to provide the best possible treatment for the patient with mandibular fractures. This treatment presumes application of reduction and fixation techniques for proper stabilization of the fracture site. The reduction of the bone fragments and their fixation is much better performed when geometry and morphology of the bone and osteofixation elements (e.g. plates) are properly defined. In this paper, a new healthcare procedure, which enables application of personalized plate implants for the fixation of the mandibular fractures, is presented. Geometrical models of mandible and plate implants, presented in this research, were created by means of the Method of Anatomical Features (MAF), which has been already applied to the creation of accurate geometrical models of various human bones, plates and fixators. By using such geometrically and anatomically accurate models, orthopedic and maxillofacial surgeons can better perform pre-operative tasks of simulating and planning the operation, as well as an intraoperative task of implanting the personalized plate into the patient body

A STATISTICAL FRAMEWORK FOR TESTING MODULARITY IN MULTIDIMENSIONAL DATA

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73227/1/j.1558-5646.2008.00476.x.pd

Towards automation of forensic facial reconstruction

Forensic facial reconstruction is a blend of art and science thus computerizing the process leads to numerous solutions. However, complete automation remains a challenge. This research concentrates on automating the first phase of forensic facial reconstruction which is automatic landmark detection by model fitting and extraction of feature points. Detection of landmarks is a challenging task since the skull orientation in a 3D scanned data cloud is generally arbitrary and unknown. To address the issue, well defined skull and mandible models with known geometric structure, features and orientation are (1) aligned and (2) fit to the scanned data. After model fitting is complete, landmarks can be extracted, within reasonable tolerance, from the dataset. Several methods exist for automatic registration (alignment); however, most suffer ambiguity or require interaction to manage symmetric 3D objects. A new alternative 3D model to data registration technique is introduced which works successfully for both symmetric and non-symmetric objects. It takes advantage of the fact that the model and data have similar shape and known geometric features. Therefore, a similar canonical frame of reference can be developed for both model and data. Once the canonical frame of reference is defined, the model can be easily aligned to data by a euclidian transformation of its coordinate system. Once aligned, the model is scaled and deformed globally to accommodate the overall size the object and bring the model in closer proximity to the data. Lastly, the model is deformed locally to better fit the scanned data. With fitting completed, landmark locations on the model can be utilized to isolate and select corresponding landmarks in the dataset. The registration, fitting and landmark detection techniques were applied to a set of six mandible and three skull body 3D scanned datasets. Results indicate the canonical axes formulation is a good candidate for automatic registration of complex 3D objects. The alternate approach posed for deformation and surface fitting of datasets also shows promise for landmark detection when using well constructed NURBS models. Recommendations are provided for addressing the algorithms limitations and to improve its overall performance

Visual analytics methods for shape analysis of biomedical images exemplified on rodent skull morphology

In morphometrics and its application fields like medicine and biology experts are interested in causal relations of variation in organismic shape to phylogenetic, ecological, geographical, epidemiological or disease factors - or put more succinctly by Fred L. Bookstein, morphometrics is "the study of covariances of biological form". In order to reveal causes for shape variability, targeted statistical analysis correlating shape features against external and internal factors is necessary but due to the complexity of the problem often not feasible in an automated way. Therefore, a visual analytics approach is proposed in this thesis that couples interactive visualizations with automated statistical analyses in order to stimulate generation and qualitative assessment of hypotheses on relevant shape features and their potentially affecting factors. To this end long established morphometric techniques are combined with recent shape modeling approaches from geometry processing and medical imaging, leading to novel visual analytics methods for shape analysis. When used in concert these methods facilitate targeted analysis of characteristic shape differences between groups, co-variation between different structures on the same anatomy and correlation of shape to extrinsic attributes. Here a special focus is put on accurate modeling and interactive rendering of image deformations at high spatial resolution, because that allows for faithful representation and communication of diminutive shape features, large shape differences and volumetric structures. The utility of the presented methods is demonstrated in case studies conducted together with a collaborating morphometrics expert. As exemplary model structure serves the rodent skull and its mandible that are assessed via computed tomography scans

Capturing the Multiscale Anatomical Shape Variability with Polyaffine Transformation Trees

International audienceMandible fractures are classified depending on their location. In clinical practice, locations are grouped into regions at different scales according to anatomical, functional and esthetic considerations. Implant design aims at defining the optimal implant for each patient. Emerging population-based techniques analyze the anatomical variability across a population and perform statistical analysis to identify an optimal set of implants. Current efforts are focused on finding clusters of patients with similar characteristics and designing one implant for each cluster. Ideally, the description of anatomical variability is directly connected to the clinical regions. This connection is what we present here, by introducing a new registration method that builds upon a tree of locally affine transformations that describes variability at different scales. We assess the accuracy of our method on 146 CT images of femurs. Two medical experts provide the ground truth by manually measuring six landmarks. We illustrate the clinical importance of our method by clustering 43 CT images of mandibles for implant design. The presented method does not require any application-specific input, which makes it attractive for the analysis of other multiscale anatomical structures. At the core of our new method lays the introduction of a new basis for stationary velocity fields. This basis has very close links to anatomical substructures. In the future, this method has the potential to discover the hidden and possibly sparse structure of the anatomy

Form and function of the craniomandibular complex in subterranean rodents

Rodents are the most speciose mammalian order and are represented in arboreal, semiaquatic, subterranean and terrestrial niches. To flourish in such environments, rodents must exhibit morphological traits that can reflect functions that are needed to survive. This thesis focuses on the functional morphology of digging subterranean rodents and in particular, African mole-rats (Bathyergidae). Species dependent, subterranean rodents dig using a number of different methods. This thesis concentrates on the morphological differences in the craniomandibular complex in scratch digging and chisel-tooth digging subterranean rodents. Scratch digging rodents use only their claws to remove softer soil whilst their chisel-tooth digging counterparts use their incisors in concert with their powerful masticatory muscles to remove harder soils.Chapter two looks at morphological traits associated with bite force and gape in African mole-rats (Bathyergidae). The study shows that chisel-tooth digging rodents have morphological traits that are associated with a larger bite force at wider gapes, which is probably achieved by having a temporalis with a greater mechanical advantage.Chapter three examines a selection of chisel-tooth digging, scratch digging and terrestrial rodents. It shows that the upper incisors of chisel-tooth digging rodents have a larger radius of curvature. Also, it shows that chisel-tooth digging rodent cranial shape converges in morphospace and covaries with the upper incisors, although these results were not significant when phylogeny was accounted for.Chapter four shows that, using finite element analysis, the cranium of a chisel-tooth digging mole-rat can create larger bite forces at wider gapes, compared to a scratch digging mole-rat. Using a novel method of combining geometric morphometrics with finite element analysis, this study also shows that the cranium of the chisel-tooth digging rodent deforms less, making it more efficient at performing chisel-tooth digging tasks.Overall, this thesis shows that the craniomandibular form of subterranean rodents can be strongly influenced by function. The digging method used by a subterranean rodent is therefore important to how they have evolved.[Thesis also includes article published in:Biological journal of the Linnean Societyhttp://onlinelibrary.wiley.com/doi/10.1111/bij.12691/fullDOI: 10.1111/bij.12691