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- Deyhle Jr, Richard
(författare)
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Cross-modal Imaging in Lung Research: From µCT dosimetry to synchrotron phase contrast microtomography biomechanical insights in preclinical lung injury models
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lung diseases continue to present a large burden to public health, especially in industrialized countries. For abetter understanding of the underlying patho-mechanisms in lung related diseases as well as for testing theefficacy of novel therapies, preclinical studies in animal models are indispensable. The significance of preclinical X-ray based micro-computed tomography (µCT) research lies in its ability to provide high-resolution, non-invasive lung imaging of small animals as the air inside the lung acts as a natural contrast and to image the lung parenchyma longitudinally to assess functional and morphological alterations and test efficacy of therapeutic interventions. This often requires requires imaging protocols that balance between sufficient image quality and clinically relevant radiation absorbed doses. A reproducible method for evaluation of absorbed radiation absorbed doses is desirable. Absorbed radiation absorbed doses were measured in a polymethyl methacrylate (PMMA) phantom using standard TLD and a novel type of OSLD made form household salt. Four imaging protocols from MILabs “xUHR-µCT” scanner were tested. A large discrepancy was observed from results compared to vendor-provided values. The results indicate a need for thorough empirical dose measurements prior to performing longitudinal studies. Four-dimensional imaging, allows for investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. It is of significant interest to have direct visualization and quantification of interstitial lung diseases at spatial resolutions beyond the capabilities of clinical and conventional absorption-based only CT. Thus far, the high intensity of synchrotron X-ray light sources offer a tool to investigate dynamic morphological and mechanistic features, enabling dynamic in-vivo microscopy. This investigation elucidates the direct effects of interventions targeting the pathophysiology of Acute Respiratory Distress Syndrome (ARDS) and Ventilator-Induced Lung Injury (VILI) on the terminal airways and alveolar microstructure within intact lungs. In such conditions, the relationship between microscopic strain within the mechanics of the alveolar structure and the broader mechanical characteristics and viscoelastic properties of the lungs remains poorly understood. A time-resolved synchrotron phase-contrast micro-computed tomography imaging acquisition protocol based on the synchronization between the mechanical ventilation and the cardiac activity was used to resolve the lung parenchyma motion with an effective isotropic voxel size of 6 µm. Quantitative maps of microscopic local lung tissue strain within aerated lung alveolar tissue under protective mechanical ventilation in anesthetized rats were obtained. This approach was used to assess the effect of alterations in lung tissue biomechanics induced by lung injury at 7 days after single-dose, intratracheal bleomycin instillation in combination with short-term high-tidal volume (VT) mechanical ventilation. Overall, this work address the aspects of radiation exposure to in experimental imaging of small animals and lays a foundation for a more nuanced understanding of lung injury and mechanical ventilation. In the future, it may result in a more effective and less injurious respiratory support for patients with acute lung injury or chronic lung diseases.
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| 2. |
- Löfhede, Johan, 1978
(författare)
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Classification of Burst and Suppression in the Neonatal EEG
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The brain requires a continuous supply of oxygen and even a short period of reduced oxygen supply risks severe and lifelong consequences for the affected individual. The delivery is a vulnerable period for a baby who may experience for example hypoxia (lack of oxygen) that can damage the brain. Babies who experience problems are placed in an intensive care unit where their vital signs are monitored, but there is no reliable way to monitor the brain directly. Monitoring the brain would provide valuable information about the processes going on in it and could influence the treatment and help to improve the quality of neonatal care. The scope of this project is to develop methods that eventually can be put together to form a monitoring system for the brain that can function as decision-support for the physician in charge of treating the patient.The specific technical problem that is the topic of this thesis is detection of burst and suppression in the electroencephalogram (EEG) signal. The thesis starts with a brief description of the brain, with a focus on where the EEG originates, what types of activity can be found in this signal and what they mean. The data that have been available for the project are described, followed by the signal processing methods that have been used for pre-processing, and the feature functions that can be used for extracting certain types of characteristics from the data are defined. The next section describes classification methodology and how it can be used for making decisions based on combinations of several features extracted from a signal. The classification methods Fisher’s Linear Discriminant, Neural Networks and Support Vector Machines are described and are finally compared with respect to their ability to discriminate between burst and suppression. An experiment with different combinations of features in the classification has also been carried out. The results show similar results for the three methods but it can be seen that the SVM is the best method with respect to handling multiple features.
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| 3. |
- Larsson, Emma, 1991
(författare)
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Towards a human body model for prediction of vehicle occupant kinematics in omni-directional pre-crash events
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the vehicle fleet becomes more equipped with crash avoidance systems, the proportion of crashes preceded by evasive manoeuvres is expected to increase. In an evasive manoeuvre, occupant position and posture can be influenced by the induced loading. Therefore, there is a need to predict the occupant response from evasive manoeuvres. During evasive manoeuvres, the occupant kinematics can also be affected by muscle activity, and as such, taking the effect from active muscles into account in simulations of occupant response to evasive manoeuvres is important. In this thesis, a method for activation of the neck and lumbar muscles in an active human body model, based on recorded muscle activity from volunteers, was enhanced and evaluated. The active human body model successfully predicted passenger kinematics in lane change, braking, and combined manoeuvres. As a step towards a model capable of predicting driver kinematics in evasive manoeuvres, the same method was adapted to control the shoulder muscles. The model with active shoulder muscles was evaluated in a simplified test setup. The active model successfully predicted peak elbow displacement for all loading directions. Based on the results from the included studies, an active muscle controller based on directionally dependent muscle activity data can successfully predict kinematics from reflex response to loading in a finite element human body model. These findings represent an important step towards developing an active human body model able to predict occupant kinematics and muscle forces in omni-directional pre-crash events.
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| 4. |
- Putra, I Putu Alit, 1992
(författare)
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An Average Female Head-Neck Finite Element Model with Reflexive Neck Muscles
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several factors potentially contribute to the risk of whiplash injuries; one of them is the neck muscle activities. Muscle activities in the neck have been shown to influence the head-neck kinematics during whiplash-like rear impacts. Thus, it is necessary to include the neck muscle responses when conducting a study of head-neck kinematics in a whiplash-like rear-impact condition. Therefore, as the first step, the development which focused on the implementation and optimization of a 50th percentile head-neck FE model with active reflexive neck muscles was conducted in the present thesis. The active muscles were implemented in the existing ViVA OpenHBM, and the work was divided into three studies. The first study concluded that both neck link angular position feedback (APF) and muscle length feedback (MLF) control strategies improved the head kinematics agreement compared to the passive model, but overall, the APF controller performed better. The second study showed that the optimum controller gains and parameters could be identified using optimizations. The final study evaluated different ways to combine APF and MLF controllers. Further study and optimizations are needed to understand the best way to implement and combine MLF controllers with APF controllers. The combined work increased the understanding of how to model active neck muscle controllers representing human reflexes during whiplash induced rear-impact. The optimization strategy used in the present thesis could be repeated in other head-neck models and in other regions of the human body in future work. In summary, an open-source head-neck FE model that represents a 50th percentile female in stature and mass with active reflexive neck muscle is now available and with future development will be used to study head-neck kinematics and its relation to whiplash injuries.
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