Application of a novel automatic method for determining the bilateral symmetry midline of the facial skeleton based on invariant moments

© 2020 by the authors. Assuming a symmetric pattern plays a fundamental role in the diagnosis and surgical treatment of facial asymmetry, for reconstructive craniofacial surgery, knowing the precise location of the facial midline is important since for most reconstructive procedures the intact side of the face serves as a template for the malformed side. However, the location of the midline is still a subjective procedure, despite its importance. This study aimed to automatically locate the bilateral symmetry midline of the facial skeleton based on an invariant moment technique using pseudo-Zernike moments. A total of 367 skull images were evaluated using the proposed technique. The technique was found to be reliable and provided good accuracy in the symmetry planes. This new technique will be utilized for subsequent studies to evaluate diverse craniofacial reconstruction techniques

The Role of Transient Vibration of the Skull on Concussion

Concussion is a traumatic brain injury usually caused by a direct or indirect blow to the head that affects brain function. The maximum mechanical impedance of the brain tissue occurs at 450±50 Hz and may be affected by the skull resonant frequencies. After an impact to the head, vibration resonance of the skull damages the underlying cortex. The skull deforms and vibrates, like a bell for 3 to 5 milliseconds, bruising the cortex. Furthermore, the deceleration forces the frontal and temporal cortex against the skull, eliminating a layer of cerebrospinal fluid. When the skull vibrates, the force spreads directly to the cortex, with no layer of cerebrospinal fluid to reflect the wave or cushion its force. To date, there is few researches investigating the effect of transient vibration of the skull. Therefore, the overall goal of the proposed research is to gain better understanding of the role of transient vibration of the skull on concussion. This goal will be achieved by addressing three research objectives. First, a MRI skull and brain segmentation automatic technique is developed. Due to bones’ weak magnetic resonance signal, MRI scans struggle with differentiating bone tissue from other structures. One of the most important components for a successful segmentation is high-quality ground truth labels. Therefore, we introduce a deep learning framework for skull segmentation purpose where the ground truth labels are created from CT imaging using the standard tessellation language (STL). Furthermore, the brain region will be important for a future work, thus, we explore a new initialization concept of the convolutional neural network (CNN) by orthogonal moments to improve brain segmentation in MRI. Second, the creation of a novel 2D and 3D Automatic Method to Align the Facial Skeleton is introduced. An important aspect for further impact analysis is the ability to precisely simulate the same point of impact on multiple bone models. To perform this task, the skull must be precisely aligned in all anatomical planes. Therefore, we introduce a 2D/3D technique to align the facial skeleton that was initially developed for automatically calculating the craniofacial symmetry midline. In the 2D version, the entire concept of using cephalometric landmarks and manual image grid alignment to construct the training dataset was introduced. Then, this concept was extended to a 3D version where coronal and transverse planes are aligned using CNN approach. As the alignment in the sagittal plane is still undefined, a new alignment based on these techniques will be created to align the sagittal plane using Frankfort plane as a framework. Finally, the resonant frequencies of multiple skulls are assessed to determine how the skull resonant frequency vibrations propagate into the brain tissue. After applying material properties and mesh to the skull, modal analysis is performed to assess the skull natural frequencies. Finally, theories will be raised regarding the relation between the skull geometry, such as shape and thickness, and vibration with brain tissue injury, which may result in concussive injury

Three-Dimensional Cephalometric Landmarking and Frankfort Horizontal Plane Construction: Reproducibility of Conventional and Novel Landmarks

In some dentofacial deformity patients, especially patients undergoing surgical orthodontic treatments, Computed Tomography (CT) scans are useful to assess complex asymmetry or to plan orthognathic surgery. This assessment would be made easier for orthodontists and surgeons with a three-dimensional (3D) cephalometric analysis, which would require the localization of landmarks and the construction of reference planes. The objectives of this study were to assess manual landmarking repeatability and reproducibility (R&R) of a set of 3D landmarks and to evaluate R&R of vertical cephalometric measurements using two Frankfort Horizontal (FH) planes as references for horizontal 3D imaging reorientation. Thirty-three landmarks, divided into “conventional”, “foraminal” and “dental”, were manually located twice by three experienced operators on 20 randomly-selected CT scans of orthognathic surgery patients. R&R confidence intervals (CI) of each landmark in the -x, -y and -z directions were computed according to the ISO 5725 standard. These landmarks were then used to construct 2 FH planes: a conventional FH plane (orbitale left, porion right and left) and a newly proposed FH plane (midinternal acoustic foramen, orbitale right and left). R&R of vertical cephalometric measurements were computed using these 2 FH planes as horizontal references for CT reorientation. Landmarks showing a 95% CI of repeatability and/or reproducibility > 2 mm were found exclusively in the “conventional” landmarks group. Vertical measurements showed excellent R&R (95% CI < 1 mm) with either FH plane as horizontal reference. However, the 2 FH planes were not found to be parallel (absolute angular difference of 2.41°, SD 1.27°). Overall, “dental” and “foraminal” landmarks were more reliable than the “conventional” landmarks. Despite the poor reliability of the landmarks orbitale and porion, the construction of the conventional FH plane provided a reliable horizontal reference for 3D craniofacial CT scan reorientation

Effective 3D Geometric Matching for Data Restoration and Its Forensic Application

3D geometric matching is the technique to detect the similar patterns among multiple objects. It is an important and fundamental problem and can facilitate many tasks in computer graphics and vision, including shape comparison and retrieval, data fusion, scene understanding and object recognition, and data restoration. For example, 3D scans of an object from different angles are matched and stitched together to form the complete geometry. In medical image analysis, the motion of deforming organs is modeled and predicted by matching a series of CT images. This problem is challenging and remains unsolved, especially when the similar patterns are 1) small and lack geometric saliency; 2) incomplete due to the occlusion of the scanning and damage of the data. We study the reliable matching algorithm that can tackle the above difficulties and its application in data restoration. Data restoration is the problem to restore the fragmented or damaged model to its original complete state. It is a new area and has direct applications in many scientific fields such as Forensics and Archeology. In this dissertation, we study novel effective geometric matching algorithms, including curve matching, surface matching, pairwise matching, multi-piece matching and template matching. We demonstrate its applications in an integrated digital pipeline of skull reassembly, skull completion, and facial reconstruction, which is developed to facilitate the state-of-the-art forensic skull/facial reconstruction processing pipeline in law enforcement

Craniofacial gracilisation within Homo sapiens and its relationship to masticatory loading

It is frequently proposed that differences in craniofacial form are selectively and plastically driven by dietary differences, with species that consume mechanically challenging items having adaptations that increase bite force and optimise gape capacities, while also reducing strains experienced under masticatory loading. Paleoanthropologists commonly describe the crania of ancestral Homo species (such as Homo ergaster) as more robust that the crania of modern Homo sapiens. Interestingly, one area of increased robusticity in H. ergaster is the zygoma region, a key structure of the masticatory apparatus. Whether this zygoma region morphology is more optimal for consuming a mechanically challenging diet (relative to the morphology of H. sapiens) has yet to be investigated, nor have the global impacts of having a more robust zygoma region on craniofacial strains.This thesis uses finite elements analysis to investigate the impact of simulating different masticatory loads, and changes in zygoma region morphology on craniofacial strains in a H. sapiens cranium. This involved constructing a H. sapiens cranial finite element model and subsequently using virtual anatomy techniques to create a hypothetical model containing H. ergaster-like zygoma regions. By comparing craniofacial strains, the efficiency of the jaw-elevator muscles, and bite force predictions in both models, the functional significance of the H. ergaster-like zygoma region is explored.It is demonstrated that the zygoma region morphology of H. ergaster may be an adaptation to increase bite force and to reduce strains locally during bites at large gapes, however its importance in lowering strains during all masticatory loading scenarios remains questionable. It is therefore concluded that the gracile zygoma region of H. sapiens may be less of direct product of a release on selective pressures maintaining traits that reduce craniofacial strains, but consequential to less frequently performing bites at large gapes and reduced selective pressures on having large jaw-elevator musculature

3D skull models: a new craniometric approach

Mestrado em Sistemas de InformaçãoEsta dissertação apresenta uma nova abordagem para realizar análises craniométricas com base em modelos 3D de crânios. Atualmente o procedimento usado pelos antropólogos assenta no recurso a craniometria tradicional, i.e. medições manuais, o que implica variados problemas tais como dificuldade em assegurar repetibilidade das medições, erros na mesmas e possível dano nos crânios inerente ao seu manuseamento. A abordagem proposta passa por fazer a aquisição dos crânios recorrendo a um scanner 3D de luz estruturada (realizada por terceiros) e posterior análise recorrendo a uma aplicação especificamente desenvolvida para tal, e na qual assenta o trabalho descrito neste documento. Vários métodos serão abordados, tais como análise de malhas 3D, estudos de normais e curvaturas, obtenção de pontos de interesse e respectivas medidas e, por fim, serão apresentadas conclusões sobre o trabalho, bem como sugestões de trabalho futuro.This dissertation presents a new approach to conduct craniometric analysis based on 3D models of skulls. Nowadays procedures used by anthropologists are based in traditional methods, i.e. manual measurements, which may imply a set of problems such as difficulty in ensuring repeatability of the measurements, measurement errors and can skull damage inherent to the handling. The new approach lies on the acquisition of the skulls using a structured 3D light scanner (done by a third party entity) and subsequent analysis using an application specifically designed for that purpose. Is on the latter that this work is based. Several methods are going to be addressed, such as analysis of 3D meshes, studies of normal vectors and curvatures, obtainment of points of interest (landmark points) and measurements. Finally, conclusions about the developed methods, results and future work

Estimating Symmetry/Asymmetry in the Human Torso: A Novel Computational Method

Asymmetry in human body has largely been based on bilateral traits and/or subjective estimates, with potential usage in fields such as medicine, rehabilitation and apparel product design. In case of apparel, asymmetry in human body has been measured primarily by estimating differential linear measurement of bilateral traits. However, the characteristics of asymmetry can be better understood and be useful for clinicians and designers if it is quantified by considering the whole 3D surface. To address the prevailing issues in measuring asymmetry objectively, this research attempts to develop a novel method to quantify asymmetry that is robust, effective and non-invasive in operation. The method discussed here uses 3D scans of human torso to estimate asymmetry as a numerical index. Furthermore, using skeletal landmarks, twist and tilt measurements of the torsos are computed numerically. Together, these three measures can characterize the asymmetric/symmetric nature of a human torso. The approach taken in this research uses cross sections of torso to estimate local plane of symmetry that equi-divides a given cross section on the basis of its area, and connecting those planes to form a global surface that divides the torso volumetrically. The computational approach in estimating the area of cross section is based on the Green's theorem. The developed method was validated by both testing it on a known geometric model and by comparing the estimated index with subjective ratings by experts. This method has potential applications in various fields requiring characterizing asymmetry i.e., in case of scoliosis patients as diagnostic tool or an evaluation metric for rehabilitation efficiency, for body builders, and fashion models as an evaluation tool.Design, Housing and Merchandisin

Advanced Applications of Rapid Prototyping Technology in Modern Engineering

Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems