This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

Non-invasive electrical imaging of the heart aims to quantitatively reconstruct information about the electrical activity of the heart from multiple thoracic ECG signals. The computational framework required to produce such electrical images of the heart from non-invasive torso surface signals is presented. It is shown reliable electrical images of the heart can be obtained under a controlled environment. This has been demonstrated using an anatomically realistic boundary element porcine torso model. The procedures required to create a subject specific model using a small number of control points and to create a specific heart model from three-dimensional ultrasound images using a linear fitting procedure are presented. From discrete ECG electrodes a continuous representation of the potential field over the entire torso surface can also be produced using this linear fitting procedure. The construction of the transfer matrices for the two predominant electrocardiographic sources (epicardial potentials and myocardial activation times) are described in detail. The transfer matrices are used to compute activation times within the heart and epicardial potentials on the heart surface. Myocardial activation times are computed using an algorithm based on the Critical Point Theorem while epicardial potentials are computed using standard Tikhonov and Truncated SVD spatially regularised methods as well as Greensite's spatial and temporal regularisation method. The regularisation parameters for the epicardial potentials are determined using a variety of methods (e.g., CRESO criterion, L-curve, zero-crossing). The potential and activation based formulations are compared in a comprehensive inverse simulation study. To try and capture the dynamic and variable nature of cardiac electrical activity, the study is performed with three different types of cardiac sources with a realistic porcine model. These simulations investigate the effect on the computed solutions of individual and combinations of modelling errors. These errors include corruption in the torso surface signals, changes in material properties and geometric distortion. In general, the activation based formulation is preferred over the epicardial potential formulations, with Greensite's method found to be the best method for reconstructing epicardial potentials. Under optimal conditions, the activation approach could reconstruct the activation times to within RMS. Both potential and activation based formulations were found to be relatively insensitive to changes in material properties such as lung conductivities and activation function shapes. When examining individual errors, the geometry and positions of the torso and heart had the greatest effects on the inverse solutions. The relative heart position needed to be determined to within to obtain results within of the solutions obtained under control conditions. When the modelling errors are combined to produce errors which can be expected in a clinical or experimental situation the activation based solutions were consistently more accurate than potential based solutions. The next necessary step in this project is the detailed validation of the results against in-vivo data. This step is necessary before such algorithms can be reliably used to aid in the assessment of heart function in a clinical environment.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

Non-invasive electrical imaging of the heart aims to quantitatively reconstruct information about the electrical activity of the heart from multiple thoracic ECG signals. The computational framework required to produce such electrical images of the heart from non-invasive torso surface signals is presented. It is shown reliable electrical images of the heart can be obtained under a controlled environment. This has been demonstrated using an anatomically realistic boundary element porcine torso model. The procedures required to create a subject specific model using a small number of control points and to create a specific heart model from three-dimensional ultrasound images using a linear fitting procedure are presented. From discrete ECG electrodes a continuous representation of the potential field over the entire torso surface can also be produced using this linear fitting procedure. The construction of the transfer matrices for the two predominant electrocardiographic sources (epicardial potentials and myocardial activation times) are described in detail. The transfer matrices are used to compute activation times within the heart and epicardial potentials on the heart surface. Myocardial activation times are computed using an algorithm based on the Critical Point Theorem while epicardial potentials are computed using standard Tikhonov and Truncated SVD spatially regularised methods as well as Greensite's spatial and temporal regularisation method. The regularisation parameters for the epicardial potentials are determined using a variety of methods (e.g., CRESO criterion, L-curve, zero-crossing). The potential and activation based formulations are compared in a comprehensive inverse simulation study. To try and capture the dynamic and variable nature of cardiac electrical activity, the study is performed with three different types of cardiac sources with a realistic porcine model. These simulations investigate the effect on the computed solutions of individual and combinations of modelling errors. These errors include corruption in the torso surface signals, changes in material properties and geometric distortion. In general, the activation based formulation is preferred over the epicardial potential formulations, with Greensite's method found to be the best method for reconstructing epicardial potentials. Under optimal conditions, the activation approach could reconstruct the activation times to within RMS. Both potential and activation based formulations were found to be relatively insensitive to changes in material properties such as lung conductivities and activation function shapes. When examining individual errors, the geometry and positions of the torso and heart had the greatest effects on the inverse solutions. The relative heart position needed to be determined to within to obtain results within of the solutions obtained under control conditions. When the modelling errors are combined to produce errors which can be expected in a clinical or experimental situation the activation based solutions were consistently more accurate than potential based solutions. The next necessary step in this project is the detailed validation of the results against in-vivo data. This step is necessary before such algorithms can be reliably used to aid in the assessment of heart function in a clinical environment.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

Non-invasive electrical imaging of the heart aims to quantitatively reconstruct information about the electrical activity of the heart from multiple thoracic ECG signals. The computational framework required to produce such electrical images of the heart from non-invasive torso surface signals is presented. It is shown reliable electrical images of the heart can be obtained under a controlled environment. This has been demonstrated using an anatomically realistic boundary element porcine torso model. The procedures required to create a subject specific model using a small number of control points and to create a specific heart model from three-dimensional ultrasound images using a linear fitting procedure are presented. From discrete ECG electrodes a continuous representation of the potential field over the entire torso surface can also be produced using this linear fitting procedure. The construction of the transfer matrices for the two predominant electrocardiographic sources (epicardial potentials and myocardial activation times) are described in detail. The transfer matrices are used to compute activation times within the heart and epicardial potentials on the heart surface. Myocardial activation times are computed using an algorithm based on the Critical Point Theorem while epicardial potentials are computed using standard Tikhonov and Truncated SVD spatially regularised methods as well as Greensite's spatial and temporal regularisation method. The regularisation parameters for the epicardial potentials are determined using a variety of methods (e.g., CRESO criterion, L-curve, zero-crossing). The potential and activation based formulations are compared in a comprehensive inverse simulation study. To try and capture the dynamic and variable nature of cardiac electrical activity, the study is performed with three different types of cardiac sources with a realistic porcine model. These simulations investigate the effect on the computed solutions of individual and combinations of modelling errors. These errors include corruption in the torso surface signals, changes in material properties and geometric distortion. In general, the activation based formulation is preferred over the epicardial potential formulations, with Greensite's method found to be the best method for reconstructing epicardial potentials. Under optimal conditions, the activation approach could reconstruct the activation times to within RMS. Both potential and activation based formulations were found to be relatively insensitive to changes in material properties such as lung conductivities and activation function shapes. When examining individual errors, the geometry and positions of the torso and heart had the greatest effects on the inverse solutions. The relative heart position needed to be determined to within to obtain results within of the solutions obtained under control conditions. When the modelling errors are combined to produce errors which can be expected in a clinical or experimental situation the activation based solutions were consistently more accurate than potential based solutions. The next necessary step in this project is the detailed validation of the results against in-vivo data. This step is necessary before such algorithms can be reliably used to aid in the assessment of heart function in a clinical environment.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

Non-invasive electrical imaging of the heart aims to quantitatively reconstruct information about the electrical activity of the heart from multiple thoracic ECG signals. The computational framework required to produce such electrical images of the heart from non-invasive torso surface signals is presented. It is shown reliable electrical images of the heart can be obtained under a controlled environment. This has been demonstrated using an anatomically realistic boundary element porcine torso model. The procedures required to create a subject specific model using a small number of control points and to create a specific heart model from three-dimensional ultrasound images using a linear fitting procedure are presented. From discrete ECG electrodes a continuous representation of the potential field over the entire torso surface can also be produced using this linear fitting procedure. The construction of the transfer matrices for the two predominant electrocardiographic sources (epicardial potentials and myocardial activation times) are described in detail. The transfer matrices are used to compute activation times within the heart and epicardial potentials on the heart surface. Myocardial activation times are computed using an algorithm based on the Critical Point Theorem while epicardial potentials are computed using standard Tikhonov and Truncated SVD spatially regularised methods as well as Greensite's spatial and temporal regularisation method. The regularisation parameters for the epicardial potentials are determined using a variety of methods (e.g., CRESO criterion, L-curve, zero-crossing). The potential and activation based formulations are compared in a comprehensive inverse simulation study. To try and capture the dynamic and variable nature of cardiac electrical activity, the study is performed with three different types of cardiac sources with a realistic porcine model. These simulations investigate the effect on the computed solutions of individual and combinations of modelling errors. These errors include corruption in the torso surface signals, changes in material properties and geometric distortion. In general, the activation based formulation is preferred over the epicardial potential formulations, with Greensite's method found to be the best method for reconstructing epicardial potentials. Under optimal conditions, the activation approach could reconstruct the activation times to within RMS. Both potential and activation based formulations were found to be relatively insensitive to changes in material properties such as lung conductivities and activation function shapes. When examining individual errors, the geometry and positions of the torso and heart had the greatest effects on the inverse solutions. The relative heart position needed to be determined to within to obtain results within of the solutions obtained under control conditions. When the modelling errors are combined to produce errors which can be expected in a clinical or experimental situation the activation based solutions were consistently more accurate than potential based solutions. The next necessary step in this project is the detailed validation of the results against in-vivo data. This step is necessary before such algorithms can be reliably used to aid in the assessment of heart function in a clinical environment.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

Non-invasive electrical imaging of the heart aims to quantitatively reconstruct information about the electrical activity of the heart from multiple thoracic ECG signals. The computational framework required to produce such electrical images of the heart from non-invasive torso surface signals is presented. It is shown reliable electrical images of the heart can be obtained under a controlled environment. This has been demonstrated using an anatomically realistic boundary element porcine torso model. The procedures required to create a subject specific model using a small number of control points and to create a specific heart model from three-dimensional ultrasound images using a linear fitting procedure are presented. From discrete ECG electrodes a continuous representation of the potential field over the entire torso surface can also be produced using this linear fitting procedure. The construction of the transfer matrices for the two predominant electrocardiographic sources (epicardial potentials and myocardial activation times) are described in detail. The transfer matrices are used to compute activation times within the heart and epicardial potentials on the heart surface. Myocardial activation times are computed using an algorithm based on the Critical Point Theorem while epicardial potentials are computed using standard Tikhonov and Truncated SVD spatially regularised methods as well as Greensite's spatial and temporal regularisation method. The regularisation parameters for the epicardial potentials are determined using a variety of methods (e.g., CRESO criterion, L-curve, zero-crossing). The potential and activation based formulations are compared in a comprehensive inverse simulation study. To try and capture the dynamic and variable nature of cardiac electrical activity, the study is performed with three different types of cardiac sources with a realistic porcine model. These simulations investigate the effect on the computed solutions of individual and combinations of modelling errors. These errors include corruption in the torso surface signals, changes in material properties and geometric distortion. In general, the activation based formulation is preferred over the epicardial potential formulations, with Greensite's method found to be the best method for reconstructing epicardial potentials. Under optimal conditions, the activation approach could reconstruct the activation times to within RMS. Both potential and activation based formulations were found to be relatively insensitive to changes in material properties such as lung conductivities and activation function shapes. When examining individual errors, the geometry and positions of the torso and heart had the greatest effects on the inverse solutions. The relative heart position needed to be determined to within to obtain results within of the solutions obtained under control conditions. When the modelling errors are combined to produce errors which can be expected in a clinical or experimental situation the activation based solutions were consistently more accurate than potential based solutions. The next necessary step in this project is the detailed validation of the results against in-vivo data. This step is necessary before such algorithms can be reliably used to aid in the assessment of heart function in a clinical environment.