2,444 research outputs found

    A Framework of Vertebra Segmentation Using the Active Shape Model-Based Approach

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    We propose a medical image segmentation approach based on the Active Shape Model theory. We apply this method for cervical vertebra detection. The main advantage of this approach is the application of a statistical model created after a training stage. Thus, the knowledge and interaction of the domain expert intervene in this approach. Our application allows the use of two different models, that is, a global one (with several vertebrae) and a local one (with a single vertebra). Two modes of segmentation are also proposed: manual and semiautomatic. For the manual mode, only two points are selected by the user on a given image. The first point needs to be close to the lower anterior corner of the last vertebra and the second near the upper anterior corner of the first vertebra. These two points are required to initialize the segmentation process. We propose to use the Harris corner detector combined with three successive filters to carry out the semiautomatic process. The results obtained on a large set of X-ray images are very promising

    Characterization of the Response of the Cadaveric Human Spine to Loading in a Six-Degree-of-Freedom Spine Testing Apparatus

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    Chronic back pain has historically been treated through spinal decompression and fusion often accompanied by fixation devices. Concerns regarding the effect of rigid fixation on the surrounding tissue and vertebral levels adjacent to fusion have given rise to a new paradigm based on restoring healthy or natural motion of the operated level. This paradigm revolves around the design and implementation of so-called motion preservation devices. In vitro testing has been and will continue to be an integral step in the design and evaluation process for both rigid fixation and motion preservation devices. However, the metrics commonly used to asses the efficacy of a rigid fixation device are insufficient for the assessment of motion preservation devices. In addition, motion preservation device metrics have not been rigorously defined or characterized in the healthy human spine. The kinematic response of the human cadaveric spine to loading in a six-degree-of-freedom spine testing apparatus can be expressed in terms of Euler angles and the helical axis of motion while the viscoelastic response can be expressed in terms of the energy dissipated by each specimen during a single cycle of testing. Beyond conventional metrics, a new, noninvasive method based on applying test kinematics to a three-dimensional rigid-body model of the spine is developed and used to investigate articulation of the facet joints. Articulation is investigated based on a distance map between adjacent articular surfaces and quantified through the calculation of a parameter describing the proportion of the facet contact area. Statistically significant differences were found between the facet contact area parameter at full extension and full flexion at every level of the lumbar spine during in vitro testing (p<0.037). Additionally, significant differences were found between the mean helical axis locations of some of the levels. A significant difference was found between the anterior/posterior location of the helical axis during flexion and Extension at the L1-L2 level (p=0.003). The sensitivity of these parameters in describing differences in lumbar kinematics between levels and between different portions of the range-of-motion lends credence to their efficacy in evaluating the quality of motion achieved after implantation of a motion preservation device

    The effectiveness of a 4-week yoga intervention on the activation and timing of transverse abdominis and lumbar multifidus, pain and functional disability among healthy and low back pain participants

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    Low back pain (LBP) poses a significant long-term health problem and requires the exploration of complementary alternative medicines, such as yoga. LBP patients often present with a delay in the onset of contraction of core musculature, which is necessary to stabilize the spine in dynamic movements. The aim of this study was two-fold. First, it was to determine the effectiveness of a 4-week yoga intervention on the timing of muscle activation and activation ratio of the transversus abdominis (TrA) and lumbar multifidus (LM) muscles among all participants. Second, it was to determine the effectiveness of a 4-week yoga intervention on the visual analogue pain scale (VAS) and functional disability levels as measured by the Oswestry disability index (ODI) among LBP participants. A controlled laboratory study was conducted in healthy participants (n=10) and those with LBP (n=14) between the ages of 18-30. All participants underwent a 30-minute bi-weekly 4-week yoga intervention for LBP taught by a certified yoga teacher. The primary outcome measures were the ODI, VAS, and TrA and LM muscle activation and timing. All outcomes were measured before and after the 4-week intervention. Statistical analyses of the results were performed using 2x2 analysis of variance for group comparison of the outcomes measures, and t-tests were used for intra-group comparison of the LBP participants. The pain scores were not significantly different between conditions (p=.239), but there was a strong effect size (0.87). The ODI scores were statistically significant (p=.049) but does not show clinical significance due to the weak effect size and confidence interval that crossed 0 (CI -0.55-0.94). There were no significant differences between the groups for muscle timing or thickness after 4 weeks of yoga for either TrA (p=.101) or LM (p=.437). A 4-week yoga intervention may provide benefits to participants with and without LBP for decreasing pain and functional disability however a larger and longer duration study may be required to provide more definite evidence

    Biokinematic analysis of human body

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    Thesis (Doctoral)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2011Includes bibliographical references (leaves: 118-123)Text in English; Abstract: Turkish and Englishxiii, 123 leavesThis thesis concentrates on the development of rigid body geometries by using method of intersections, where simple geometric shapes representing revolute (R) and prismatic (P) joint motions are intersected by means of desired space or subspace requirements to create specific rigid body geometries in predefined octahedral fixed frame. Using the methodical approach, space and subspace motions are clearly visualized by the help of resulting geometrical entities that have physical constraints with respect to the fixed working volume. Also, this work focuses on one of the main areas of the fundamental mechanism and machine science, which is the structural synthesis of robot manipulators by inserting recurrent screws into the theory. After the transformation unit screw equations are presented, physical representations and kinematic representations of kinematic pairs with recurrent screws are given and the new universal mobility formulations for mechanisms and manipulators are introduced. Moreover the study deals with the synthesis of mechanisms by using quaternion and dual quaternion algebra to derive the objective function. Three different methods as interpolation approximation, least squares approximation and Chebyshev approximation is introduced in the function generation synthesis procedures of spherical four bar mechanism in six precision points. Separate examples are given for each section and the results are tabulated. Comparisons between the methods are also given. As an application part of the thesis, the most important elements of the human body and skeletal system is investigated by means of their kinematic structures and degrees of freedom. At the end of each section, an example is given as a mechanism or manipulator that can represent the behavior of the related element in the human body

    Hearing and morphological specializations of the mojarra (<i>Eucinostomus argenteus</i>)

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    The air-filled swimbladder acts as an acoustic amplifier for some fish by converting sound pressure into particle motion, which is transmitted to the inner ear. Here, we describe in detail the specialized connection between the swimbladder and ear in the mojarra, as well as a modified cone on the anal fin in which the posterior end of the swimbladder sits. Hearing tests show the mojarra has better hearing sensitivity than other species of fish without a connection. However, mojarras do not seem to use this adaptation for communication. Furthermore, the inclined position of the swimbladder may help the fish to catch their prey more easily, as the swimbladder will be horizontal when they are picking up benthic prey

    Surgical treatment of degenerative lumbosacral stenosis in the dog : a critical appraisal

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    Dissertação de Mestrado Integrado em Medicina VeterináriaDegenerative lumbosacral stenosis (DLSS) is the compression of the cauda equina caused by protrusion of supportive tissues into the vertebral canal. Young adult, male, and large-breed dogs seem to be predisposed to this condition, although it can also affect cats. When medical treatment fails to provide adequate relief of clinical signs associated with DLSS, surgical treatment is often performed. Although several surgical modalities to treat DLSS have been reported, definitive criteria for surgical technique preference are currently lacking. Critical appraisal is the process of systematically examining research evidence to judge its trustworthiness, its value and relevance in a particular context. Therefore it is essential to make informed decisions in clinical practice. The main objective of this study was to critically appraise the literature reporting the results of surgical treatment of DLSS; to identify gaps in current knowledge and ensure there is justification for future research on the subject; and to propose study characteristics that would enrich the conduct and reporting of these studies. A critical appraisal tool that examined the conduct and reporting of each study was designed. After a systematic search and screening of the literature, 17 papers were critically appraised. Results showed that 94% of included studies did not clearly report inclusion and exclusion criteria and in 71% it was unclear whether consecutive inclusion of participants was applied. 94% of studies reported age, breed, and sex of the participants, and 65% did not report duration and prevalence of clinical signs. In 76% of studies, the condition was not measured in a standard and reliable way. Identification of the condition was performed using radiography in 88% of studies, CT in 29%, and MRI in 53%. It was considered that 47% of included studies did not clearly describe the intervention. Objective outcome measures were used in 35% of studies and clinical practical guidance was provided by all included studies. Although case series rank relatively low in the evidence hierarchy and have several limitations, results demonstrate that there is room for improvement of the conduct and reporting quality of case series so that rigorous data can be generated and analysed, to inform research design, guide clinical practice, and improve veterinary healthcare delivery.RESUMO - A estenose lombossagrada degenerativa é a compressão da cauda equina causada pela protusão de tecidos de suporte no canal vertebral. Apesar de também poder afetar gatos, cães de raça grande, machos e jovens adultos parecem ter predisposição para esta doença. Quando o tratamento médico não promove o alívio dos sinais clínicos associados à estenose lombossagrada degenerativa, o tratamento cirúrgico é uma escolha frequente. Apesar de já terem sido descritas diversas técnicas cirúrgicas para o tratamento de estenose lombossagrada degenerativa, não há critérios definitivos para a escolha de uma ou outra técnica. A análise crítica é o exame sistemático da evidência científica para verificar a sua fiabilidade, o seu valor e relevância em determinado contexto. É, portanto, essencial para a tomada de decisões fundadas em prática clínica. Os principais objetivos deste estudo foram os de apreciar criticamente a literatura que relata os resultados do tratamento cirúrgico de estenose lombossagrada degenerativa, de identificar lacunas no conhecimento e justificar a necessidade de mais investigação acerca do tema e ainda propôr elementos que poderão valorizar a execução e o relato de informação destes estudos. Foi construída uma ferramenta de análise crítica que examina a execução e o relato de informação de cada estudo e, após uma pesquisa sistemática e seleção da literatura, 17 artigos foram analisados criticamente. Os resultados mostraram que 94% dos estudos incluídos não relataram claramente critérios de inclusão e exclusão e em 71% não foi claro se a inclusão dos participantes foi feita de forma consecutiva. 94% dos estudos relatou a idade, a raça e o sexo dos participantes e 65% não relatou a duração e prevalência dos sinais clínicos. Em 76% dos estudos, a doença não foi medida de forma padronizada e repetível. O diagnóstico da doença foi auxiliado por radiografia em 88% dos estudos, tomografia computorizada em 29%, e ressonância magnética em 53%. Foi considerado que 47% dos estudos incluídos não descreveram claramente a intervenção cirúrgica. Em 35% dos estudos foram usadas medidas objetivas para avaliação dos resultados e todos os estudos incluídos forneceram orientação clínica prática ao leitor. Apesar de se situarem numa posição relativamente baixa na hierarquia da evidência e possuírem diversas limitações, os resultados demonstram que há lugar para melhorar a execução e o relato de informação em séries de caso, de forma a que se possam gerar e analisar dados rigorosos, para informar a investigação científica, guiar a prática clínica e, acima de tudo, melhorar a prestação de cuidados de saúde em medicina veterinária.N/

    Delineation of the primary tumour Clinical Target Volumes (CTV-P) in laryngeal, hypopharyngeal, oropharyngeal and oral cavity squamous cell carcinoma : AIRO, CACA, DAHANCA, EORTC, GEORCC, GORTEC, HKNPCSG, HNCIG, IAG-KHT, LPRHHT, NCIC CTG, NCRI, NRG Oncology, PHNS, SBRT, SOMERA, SRO, SSHNO, TROG consensus guidelines

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    Purpose: Few studies have reported large inter-observer variations in target volume selection and delineation in patients treated with radiotherapy for head and neck squamous cell carcinoma. Consensus guidelines have been published for the neck nodes (see Gregoire et al., 2003, 2014), but such recommendations are lacking for primary tumour delineation. For the latter, two main schools of thoughts are prevailing, one based on geometric expansion of the Gross Tumour Volume (GTV) as promoted by DAHANCA, and the other one based on anatomical expansion of the GTV using compartmentalization of head and neck anatomy. Method: For each anatomic location within the larynx, hypopharynx, oropharynx and oral cavity, and for each T-stage, the DAHANCA proposal has been comprehensively reviewed and edited to include anatomic knowledge into the geometric Clinical Target Volume (CTV) delineation concept. A first proposal was put forward by the leading authors of this publication (VG and CG) and discussed with opinion leaders in head and neck radiation oncology from Europe, Asia, Australia/New Zealand, North America and South America to reach a worldwide consensus. Results: This consensus proposes two CTVs for the primary tumour, the so called CTV-P1 and CVT-P2, corresponding to a high and lower tumour burden, and which should be associated with a high and a lower dose prescription, respectively. Conclusion: Implementation of these guidelines in the daily practice of radiation oncology should contribute to reduce treatment variations from clinicians to clinicians, facilitate the conduct of multi institutional clinical trials, and contribute to improved care of patients with head and neck carcinoma. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

    An Investigation of Subaxial Cervical Spine Trauma and Surgical Treatment through Biomechanical Simulation and Kinematic Analysis

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    In vitro biomechanical investigations can help to identify changes in subaxial cervical spine (C3-C7) stability following injury, and determine the efficacy of surgical treatments through controlled joint simulation experiments and kinematic analyses. However, with the large spectrum of cervical spine trauma, a large fraction of the potential injuries have not been examined biomechanically. This includes a lack of studies investigating prevalent flexion-distraction injuries. Therefore, the overall objective of this thesis was to investigate the changes in subaxial cervical spine kinematic stability with simulated flexion-distraction injuries and current surgical instrumentation approaches using both established and novel biomechanical techniques. Three in vitro experiments were performed with a custom-designed spinal loading simulator. The first evaluated sequential disruption of the posterior ligaments with and without a simulated facet fracture (n=7). In these specimens, posterior lateral mass screw fixation provided more stability than anterior cervical discectomy and fusion with plating (ACDFP). A second study examined a unilateral facet perch injury by reproducing a flexion-distraction injury mechanism with the simulator (n=9). The resulting soft tissue damage was quantified through meticulous dissection of each specimen, which identified the most commonly injured structures across all specimens as both facet capsules, ¾ of the annulus, and ½ of the ligamentum flavum. This information was used to develop and validate a standardized injury model (SIM) in new specimens (n=10). A final study examined the ACDFP surgical factor of graft size height (bony spacer replacing the intervertebral disc to promote fusion) for the SIM and two other injuries (n=7). Results were motion and injury dependent, which suggests that both these factors must be considered in the surgical decision. Two additional investigations were completed. The first examined mathematical techniques to generate a large number of accurate finite helical axes from six-DOF rigid body tracker output to describe changes in cervical spine kinematic stability. The second explored the effect of boundary conditions and PID control settings on the ability of the current simulator design to reproduce desired loading techniques. Ultimately, it is hoped that these results, and the protocols developed for future investigations, will provide valuable biomechanical evidence for standardized treatment algorithms

    Quantitative Molecular MRI of Intervertebral Disc Degeneration

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    Degeneration of the intervertebral disc (IVD) is the most common cause of back-related disability among North American adults. Low-back-pain and associated disability costs the United States more than 100 billion dollars annually in health care expenditures and reduced productivity. The mechanism of IVD degeneration, especially its biomolecular aspect, is poorly understood in an in vivo setting. Thus there is increasingly a need for the non-invasive diagnosis and quantification of IVD degeneration. MRI is a non-invasive imaging modality capable of producing contrast sensitive to biomolecules. Therefore, the primary objective of this dissertation research project is to develop MRI techniques capable of non-invasive quantification of IVD biomolecular composition in vivo. We further developed three MRI techniques specifically for IVD imaging. Magnetization transfer (MT) MRI, T1ρ MRI and sodium MRI were first separately validated of their specificities for IVD biomolecular components. In doing so, we concluded that MT MRI is sensitive to IVD collagen content, T1ρ MRI is indicative of IVD osmotic pressure, and sodium MRI is sensitive to IVD proteoglycan (PG) content. Next, we applied all three techniques to human subjects in vivo. Due to the inherently low signal-to-noise ratio (SNR) efficiency of sodium MRI, we engineered a custom radio-frequency (RF) surface coil for sodium MRI of human lumbar spine on a 7 T MRI scanner. Cross-correlation of the MT MRI, T1ρ MRI and sodium MRI data with the corresponding Pfirrmann grade revealed that the relative collagen density of IVD increases with degeneration, the IVD osmotic pressure decreases with degeneration, and the IVD PG content decreases with degeneration. By establishing that in vivo MT MRI, T1ρ MRI and sodium MRI can be used to quantify multiple IVD biomolecular characteristics non-invasively, we open up the possibility to conduct longitudinal studies on human subjects as they undergo IVD degeneration. The combination of MT MRI, T1ρ MRI and sodium MRI provides scientists and clinicians with the diagnostic tool to improve our understanding of IVD degeneration, which could benefit future treatment and prognosis of IVD degeneration
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