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Papers by Alejandro F Frangi
# Springer Science+Business Media, LLC 2012 Abstract Subtraction of Ictal SPECT Co-registered to ... more # Springer Science+Business Media, LLC 2012 Abstract Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epi-lepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate
European Journal of Echocardiography, 2010
Interface Focus, 2011
Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools ... more Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost ...
IEEE Transactions on Medical Imaging, 2013
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2019
European Heart Journal
Introduction Left ventricular (LV) myocardial fibrosis is posited to result in left atrial (LA) c... more Introduction Left ventricular (LV) myocardial fibrosis is posited to result in left atrial (LA) changes via LV remodelling and diastolic dysfunction, though the association remains poorly characterised. Native myocardial T1 mapping is a non-invasive modality that quantifies diffuse myocardial fibrosis. This study examines the relationship between LV fibrosis (quantified by native T1 times) and LA function, drawing upon data from the UK Biobank. Methods 40,818 participants underwent cardiovascular magnetic resonance (CMR) using steady-state free precession imaging at 1.5 Tesla. Native T1-mapping was performed using the Shortened Modified Look-Locker Inversion recovery technique (ShMOLLI), with global myocardial T1 estimated by an automatic segmentation framework. Nine parameters of LA phasic function were calculated (representing global, reservoir, conduit and booster components) from normalised LA volume-time curves. LV parameters (LV Mass, end-diastolic volume and ejection fraction...
IEEE Transactions on Biomedical Engineering, 2008
Biomechanics and Modeling in Mechanobiology, 2016
IEEE Transactions on Medical Imaging, 2005
Abstract. In this paper we introduce the concept of statistical deformation mod-els (SDM) which a... more Abstract. In this paper we introduce the concept of statistical deformation mod-els (SDM) which allow the construction of average models of the anatomy and their variability. SDMs are built by performing a statistical analysis of the defor-mations required to map anatomical features in one subject into the corresponding features in another subject. The concept of SDMs is similar to active shape mod-els (ASM) which capture statistical information about shapes across a population but offers several new advantages over ASMs: Firstly, SDMs can be constructed directly from images such as MR or CT without the need for segmentation which is usually a prerequisite for the construction of active shape models. Instead a non-rigid registration algorithm is used to compute the deformations required to establish correspondences between the reference subject and the subjects in the population class under investigation. Secondly, SDMs allow the construction of an atlas of the average anatomy as we...
Studies in Health Technology and Informatics, 2006
The aim of the @neurIST project is to create an IT infrastructure for the management of all proce... more The aim of the @neurIST project is to create an IT infrastructure for the management of all processes linked to research, diagnosis and treatment development for complex and multi-factorial diseases. The IT infrastructure will be developed for one such disease, cerebral aneurysm and subarachnoid haemorrhage, but its core technologies will be transferable to meet the needs of other medical areas. Since the IT infrastructure for @neurIST will need to encompass data repositories, computational analysis services and information systems handling multi-scale, multi-modal information at distributed sites, the natural basis for the IT infrastructure is a Grid Service middleware. The project will adopt a service-oriented architecture because it aims to provide a system addressing the needs of medical researchers, clinicians and health care specialists (and their IT providers/systems) and medical supplier/consulting industries.
Studies in Health Technology and Informatics, 2005
In this work we present a Grid-based optimization approach performed on a set of parameters that ... more In this work we present a Grid-based optimization approach performed on a set of parameters that affects both the geometric and grey-level appearance properties of a three-dimensional model-based algorithm for cardiac MRI segmentation. The search for optimal values was assessed by a Monte Carlo procedure using computational Grid technology. A series of segmentation runs were conducted on an evaluation database comprising 30 studies at two phases of the cardiac cycle (60 datasets), using three shape models constructed by different methods. For each of these model-patient combinations, six parameters were optimized in two steps: those which affect the grey-level properties of the algorithm first and those relating to the geometrical properties, secondly. Two post-processing tasks (one for each stage) collected and processed (in total) more than 70000 retrieved result files. Qualitative and quantitative validation of the fitting results indicates that the segmentation performance was g...
A novel anisotropic diffusion filter is proposed in this work with application to cardiac ultraso... more A novel anisotropic diffusion filter is proposed in this work with application to cardiac ultrasonic images. It includes probabilistic models which describe the probability density function (PDF) of tissues and adapts the diffusion tensor to the image iteratively. For this purpose, a preliminary study is performed in order to select the probability models that best fit the stastitical behavior of each tissue class in cardiac ultrasonic images. Then, the parameters of the diffusion tensor are defined taking into account the statistical properties of the image at each voxel. When the structure tensor of the probability of belonging to each tissue is included in the diffusion tensor definition, a better boundaries estimates can be obtained instead of calculating directly the boundaries from the image. This is the main contribution of this work. Additionally, the proposed method follows the statistical properties of the image in each iteration. This is considered as a second contributio...
Studies in Health Technology and Informatics, 2008
This paper presents an overview of computerised decision support for clinical practice. The conce... more This paper presents an overview of computerised decision support for clinical practice. The concept of computer-interpretable guidelines is introduced in the context of the @neurIST project, which aims at supporting the research and treatment of asymptomatic unruptured cerebral aneurysms by bringing together heterogeneous data, computing and complex processing services. The architecture is generic enough to adapt it to the treatment of other diseases beyond cerebral aneurysms. The paper reviews the generic requirements of the @neurIST system and presents the innovative work in distributing executable clinical guidelines.
BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneu-rys... more BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneu-rysms can be constructed by using image-based vascular models and CFD techniques. This work evaluates the impact of the choice of imaging technique on these simulations. MATERIALS AND METHODS: Ten aneurysms, imaged with 3DRA and CTA, were analyzed to assess the reproducibility of geometric and hemodynamic variables across the 2 modalities. RESULTS: Compared with 3DRA models, we found that CTA models often had larger aneurysm necks (P .05) and that most of the smallest vessels (between 0.7 and 1.0 mm in diameter) could not be reconstructed successfully with CTA. With respect to the values measured in the 3DRA models, the flow rate differed by 14.1 2.8 % (mean SE) just proximal to the aneurysm and 33.9 7.6 % at the aneurysm neck. The mean WSS on the aneurysm differed by 44.2 6.0%. Even when normalized to the parent vessel WSS, a difference of 31.4 9.9 % remained, with the normalized WSS in mo...
A method to construct a Purkinje system automatically for a particular subject is presented. The ... more A method to construct a Purkinje system automatically for a particular subject is presented. The system is grown using a rule-based algorithm controlled by stochastic Introduction The specialized electrical cardiac conduction system (CCS) coordinates the excitation and consequently the contraction of the ventricles. The electrical impulse, initiated in the sino-atrial node, reaches the Hisbundle and rapidly propagates through the whole Purkinje system. Then, the electrical impulse enters the myocardium through the Purkinje-myocardium junctions (PMJ) distributed throughout the ventricular subendocardium. Therefore, including the His-Purkinje system in a computational model of the heart is fundamental to obtain realistic electrophysiological simulations. The CCS was well characterized by Tawara in 1906 [1], who described the atrioventricular (AV) conduction axis. Nonetheless there is still a lot of controversy about its origin, development and morphology. Despite the advances on medic...
# Springer Science+Business Media, LLC 2012 Abstract Subtraction of Ictal SPECT Co-registered to ... more # Springer Science+Business Media, LLC 2012 Abstract Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epi-lepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate
European Journal of Echocardiography, 2010
Interface Focus, 2011
Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools ... more Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost ...
IEEE Transactions on Medical Imaging, 2013
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2019
European Heart Journal
Introduction Left ventricular (LV) myocardial fibrosis is posited to result in left atrial (LA) c... more Introduction Left ventricular (LV) myocardial fibrosis is posited to result in left atrial (LA) changes via LV remodelling and diastolic dysfunction, though the association remains poorly characterised. Native myocardial T1 mapping is a non-invasive modality that quantifies diffuse myocardial fibrosis. This study examines the relationship between LV fibrosis (quantified by native T1 times) and LA function, drawing upon data from the UK Biobank. Methods 40,818 participants underwent cardiovascular magnetic resonance (CMR) using steady-state free precession imaging at 1.5 Tesla. Native T1-mapping was performed using the Shortened Modified Look-Locker Inversion recovery technique (ShMOLLI), with global myocardial T1 estimated by an automatic segmentation framework. Nine parameters of LA phasic function were calculated (representing global, reservoir, conduit and booster components) from normalised LA volume-time curves. LV parameters (LV Mass, end-diastolic volume and ejection fraction...
IEEE Transactions on Biomedical Engineering, 2008
Biomechanics and Modeling in Mechanobiology, 2016
IEEE Transactions on Medical Imaging, 2005
Abstract. In this paper we introduce the concept of statistical deformation mod-els (SDM) which a... more Abstract. In this paper we introduce the concept of statistical deformation mod-els (SDM) which allow the construction of average models of the anatomy and their variability. SDMs are built by performing a statistical analysis of the defor-mations required to map anatomical features in one subject into the corresponding features in another subject. The concept of SDMs is similar to active shape mod-els (ASM) which capture statistical information about shapes across a population but offers several new advantages over ASMs: Firstly, SDMs can be constructed directly from images such as MR or CT without the need for segmentation which is usually a prerequisite for the construction of active shape models. Instead a non-rigid registration algorithm is used to compute the deformations required to establish correspondences between the reference subject and the subjects in the population class under investigation. Secondly, SDMs allow the construction of an atlas of the average anatomy as we...
Studies in Health Technology and Informatics, 2006
The aim of the @neurIST project is to create an IT infrastructure for the management of all proce... more The aim of the @neurIST project is to create an IT infrastructure for the management of all processes linked to research, diagnosis and treatment development for complex and multi-factorial diseases. The IT infrastructure will be developed for one such disease, cerebral aneurysm and subarachnoid haemorrhage, but its core technologies will be transferable to meet the needs of other medical areas. Since the IT infrastructure for @neurIST will need to encompass data repositories, computational analysis services and information systems handling multi-scale, multi-modal information at distributed sites, the natural basis for the IT infrastructure is a Grid Service middleware. The project will adopt a service-oriented architecture because it aims to provide a system addressing the needs of medical researchers, clinicians and health care specialists (and their IT providers/systems) and medical supplier/consulting industries.
Studies in Health Technology and Informatics, 2005
In this work we present a Grid-based optimization approach performed on a set of parameters that ... more In this work we present a Grid-based optimization approach performed on a set of parameters that affects both the geometric and grey-level appearance properties of a three-dimensional model-based algorithm for cardiac MRI segmentation. The search for optimal values was assessed by a Monte Carlo procedure using computational Grid technology. A series of segmentation runs were conducted on an evaluation database comprising 30 studies at two phases of the cardiac cycle (60 datasets), using three shape models constructed by different methods. For each of these model-patient combinations, six parameters were optimized in two steps: those which affect the grey-level properties of the algorithm first and those relating to the geometrical properties, secondly. Two post-processing tasks (one for each stage) collected and processed (in total) more than 70000 retrieved result files. Qualitative and quantitative validation of the fitting results indicates that the segmentation performance was g...
A novel anisotropic diffusion filter is proposed in this work with application to cardiac ultraso... more A novel anisotropic diffusion filter is proposed in this work with application to cardiac ultrasonic images. It includes probabilistic models which describe the probability density function (PDF) of tissues and adapts the diffusion tensor to the image iteratively. For this purpose, a preliminary study is performed in order to select the probability models that best fit the stastitical behavior of each tissue class in cardiac ultrasonic images. Then, the parameters of the diffusion tensor are defined taking into account the statistical properties of the image at each voxel. When the structure tensor of the probability of belonging to each tissue is included in the diffusion tensor definition, a better boundaries estimates can be obtained instead of calculating directly the boundaries from the image. This is the main contribution of this work. Additionally, the proposed method follows the statistical properties of the image in each iteration. This is considered as a second contributio...
Studies in Health Technology and Informatics, 2008
This paper presents an overview of computerised decision support for clinical practice. The conce... more This paper presents an overview of computerised decision support for clinical practice. The concept of computer-interpretable guidelines is introduced in the context of the @neurIST project, which aims at supporting the research and treatment of asymptomatic unruptured cerebral aneurysms by bringing together heterogeneous data, computing and complex processing services. The architecture is generic enough to adapt it to the treatment of other diseases beyond cerebral aneurysms. The paper reviews the generic requirements of the @neurIST system and presents the innovative work in distributing executable clinical guidelines.
BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneu-rys... more BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneu-rysms can be constructed by using image-based vascular models and CFD techniques. This work evaluates the impact of the choice of imaging technique on these simulations. MATERIALS AND METHODS: Ten aneurysms, imaged with 3DRA and CTA, were analyzed to assess the reproducibility of geometric and hemodynamic variables across the 2 modalities. RESULTS: Compared with 3DRA models, we found that CTA models often had larger aneurysm necks (P .05) and that most of the smallest vessels (between 0.7 and 1.0 mm in diameter) could not be reconstructed successfully with CTA. With respect to the values measured in the 3DRA models, the flow rate differed by 14.1 2.8 % (mean SE) just proximal to the aneurysm and 33.9 7.6 % at the aneurysm neck. The mean WSS on the aneurysm differed by 44.2 6.0%. Even when normalized to the parent vessel WSS, a difference of 31.4 9.9 % remained, with the normalized WSS in mo...
A method to construct a Purkinje system automatically for a particular subject is presented. The ... more A method to construct a Purkinje system automatically for a particular subject is presented. The system is grown using a rule-based algorithm controlled by stochastic Introduction The specialized electrical cardiac conduction system (CCS) coordinates the excitation and consequently the contraction of the ventricles. The electrical impulse, initiated in the sino-atrial node, reaches the Hisbundle and rapidly propagates through the whole Purkinje system. Then, the electrical impulse enters the myocardium through the Purkinje-myocardium junctions (PMJ) distributed throughout the ventricular subendocardium. Therefore, including the His-Purkinje system in a computational model of the heart is fundamental to obtain realistic electrophysiological simulations. The CCS was well characterized by Tawara in 1906 [1], who described the atrioventricular (AV) conduction axis. Nonetheless there is still a lot of controversy about its origin, development and morphology. Despite the advances on medic...