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Papers by Marcel Jackowski

Schizophrenia Research, 2008

cerebral tissue composition. WMH are associated with brain tract disruption and have been related... more cerebral tissue composition. WMH are associated with brain tract disruption and have been related to several psychiatric conditions including bipolar disorder, late-onset depression, suicidality in unipolar depression and substance misuse. There have been conflicting findings regarding the frequency of WMH in schizophrenia for both early-onset (EOS) and late-onset (LOS) cases. We conducted a metaanalysis of the presence of these lesions in schizophrenia aiming to improve the statistical power through collapsing the data. Methods: A systematic review of the literature was performed searching for studies that have systematically assessed the presence and/or extent of WMH in both EOS and LOS patients compared to controls. Analysis of the pooled data was conducted using the Mantel-Haenszel statistics. Results: Initially Sixteen studies were identified. However, only eight studies involving EOS were homogenous enough to be included in the meta-analysis (378 patients and 471 controls). Studies of WMH in LOS varied greatly in methodology and a meta-analysis was not, therefore, possible. No difference was observed in the prevalence of WMH between EOS subjects and controls (OR = 0.92, CI 95% = 0.62-1.38, p = 0.698). The test of heterogeneity of odds ratio did not reveal differences among the enrolled studies. Conclusions: EOS is not associated with increased rates of WMH. Further studies with larger samples and standardized methods are needed to better evaluate the role of these lesions in LOS.

Journal of the American Heart Association, Jan 2, 2018

Late gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In thi... more Late gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In this study, we introduce the tractographic propagation angle (PA), a metric of myofiber curvature (degrees/unit distance) derived from diffusion tensor imaging (DTI), and compare its use to LGE and invasive scar assessment by endocardial voltage mapping. DTI was performed on 7 healthy human volunteers, 5 patients with myocardial infarction, 6 normal mice, and 7 mice with myocardial infarction. LGE to delineate the infarct and border zones was performed with a 2-dimensional inversion recovery gradient-echo sequence. Ex vivo DTI was performed on 5 normal human and 5 normal sheep hearts. Endocardial electroanatomic mapping and subsequent ex vivo DTI was performed on 5 infarcted sheep hearts. PA in the normal human hearts varied smoothly and was generally <4. The mean PA in the infarct zone was significantly elevated (10.34±1.02 versus 4.05±0.45,<0.05). Regions with a PA ≤4 consistently h...

Radiology, 2016

To develop a clinically feasible whole-heart free-breathing diffusion-tensor (DT) magnetic resona... more To develop a clinically feasible whole-heart free-breathing diffusion-tensor (DT) magnetic resonance (MR) imaging approach with an imaging time of approximately 15 minutes to enable three-dimensional (3D) tractography.

ABSTRACT An increasing demand for sophisticated tools to characterize the integrity and functiona... more ABSTRACT An increasing demand for sophisticated tools to characterize the integrity and functional state of vascular networks from different imaging modalities has emerged. Currently available tools are time-consuming and limited in their ability to assess the state of vascular architectures, There is a need for developing robust and fast computer-based techniques for extracting vessel trajectories as well as estimate their diameters. To investigate a technique based on the well-known Hough Transform (HT) to dynamically estimate the trajectory and vessel diameter without resorting to time-consuming multiscale techniques [1]. We have proposed a semi-automated method to detect and track vessel trajectories in MRA. The novelty of this study is the use of HT to define the seed point for tracking and detecting the vessel scale without resorting to multiscale analysis technique. In spite of presence of noise, a mean diameter can be established. Future work will focus on automatic bifurcation handling using analysis of curvature of the vessel profile at the cross-section.

Determination of axonal pathways provides an invaluable means to study the connectivity of the hu... more Determination of axonal pathways provides an invaluable means to study the connectivity of the human brain and its functional network. Diffusion tensor imaging (DTI) is unique in its ability to capture the restricted diffusion of water molecules which can be used to infer the directionality of tissue components. In this paper, we introduce a white matter tractography method based on anisotropic wavefront propagation in diffusion tensor images. A front propagates in the white matter with a speed profile governed by the isocontour of the diffusion tensor ellipsoid. By using the ellipsoid, we avoid possible misclassification of the principal eigenvector in oblate regions. The wavefront evolution is described by an anisotropic version of the static Hamilton-Jacobi equation, which is solved by a sweeping method in order to obtain correct arrival times. Pathways of connection are determined by tracing minimum-cost trajectories using the characteristic vector field of the resulting partial differential equation. A validity index is described to rate the goodness of the resulting pathways with respect to the directionality of the tensor field. Connectivity results using normal human DTI brain images are illustrated and discussed. We also compared our method with a similar level set-based tractography technique, and found that the anisotropic evolution increased the validity index of the obtained pathways by 18%.

Vascular disease is characterized by any condition that affects the circulatory system. Recently,... more Vascular disease is characterized by any condition that affects the circulatory system. Recently, a demand for sophisticated software tools that can characterize the integrity and functional state of vascular networks from different vascular imaging modalities has appeared. Such tools face significant challenges such as: large datasets, similarity in intensity distributions of other organs and structures, and the presence of complex vessel geometry and branching patterns. Towards that goal, this paper presents a new approach to automatically track vascular networks from CTA and MRA images. Our methodology is based on the Hough transform to dynamically estimate the centerline and vessel diameter along the vessel trajectory. Furthermore, the vessel architecture and orientation is determined by the analysis of the Hessian matrix of the CTA or MRA intensity distribution. Results are shown using both synthetic vessel datasets and real human CTA and MRA images. The tracking algorithm yielded high reproducibility rates, robustness to different noise levels, associated with simplicity of execution, which demonstrates the feasibility of our approach.

Background / Purpose: Several theoretical models consider that white matter (WM) abnormalities ha... more Background / Purpose: Several theoretical models consider that white matter (WM) abnormalities have a central role in the pathophysiology of schizophrenia, and brain imaging studies have found WM abnormalities in individuals with both recent-onset and chronic psychosis. However, no study to date has investigated whether these changes are stable or state-dependent, i.e., varying according to the acute versus remitted phase of the disorder. In this study, we aim to evaluate the WM microstructure using diffusion tensor imaging (DTI) in a group of patients with non-affective first-episode psychosis (FEP) at the acute psychotic state and after symptomatic remission. Main conclusion: Our findings suggest that some WM changes present in the very beginning of FEP could reverse following symptom remission. It may be possible that such changes affecting brain areas related to the integration of perceptual information, could partially underpin the emergence of symptoms in FEP.

Digital Imaging and Communications In Medicine (DICOM) is a well-established standard regarding s... more Digital Imaging and Communications In Medicine (DICOM) is a well-established standard regarding storage, printing, and transmission of medical images. However, there are no security methods that preserve metadata confidentiality, nor image authenticity. This work assesses three steganographic methods-least significant bit insertion (LSB), division into blocks, mean change modified method (MCMM)-and verify their feasibility for clinical use in medical imaging. Integrating MCMM in DICOM standard would provide increased information security in medical imaging, deterring fraud, privacy invasion, while preserving diagnostic information.

2013 IEEE International Conference on Image Processing, 2013

Multiple Sclerosis International, 2011

The corpus callosum is the largest fiber bundle in the central nervous system and it takes part i... more The corpus callosum is the largest fiber bundle in the central nervous system and it takes part in several cognitive pathways. It can be affected by multiple sclerosis (MS) early in the disease. DTI is capable of infering the microstructural organization of the white matter. The vectorial analysis of the DTI offers the more specific indices of axial diffusivity (AD) and radial diffusivity (RD), which have shown to be useful to discriminate myelin damage from axon loss, respectively. This study presents DTI results (mean diffusivity (MD), fractional anisotropy (FA), RD, and AD) of 23 relapsing-remitting MS patients and its correlation with cognitive performance. There were 47.8% of cognitive impaired patients (MS CI). We found signs of demyelination, reflected by increased RD, and incipient axon loss, reflected by AD increase, which was slightly higher in the MS CI. The cognitive changes correlated with the DTI parameters, suggesting that loss of complexity in CC connections can impa...

Page 1. 2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, Oct... more Page 1. 2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, October 24-28, 2011 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-04-5 NSECT IMAGES ...

Abnormalities in fronto-limbic-striatal white matter (WM) have been reported in bipolar disorder ... more Abnormalities in fronto-limbic-striatal white matter (WM) have been reported in bipolar disorder (BD), but results have been inconsistent across studies. Furthermore, there have been no detailed investigations as to whether acute mood states contribute to microstructural changes in WM tracts. In order to compare fiber density and structural integrity within WM tracts between BD depression and remission, whole-brain fractional anisotropy (FA) and mean diffusivity (MD) were assessed in 37 bipolar I disorder (BD-I) patients (16 depressed and 21 remitted), and 26 healthy individuals with diffusion tensor imaging. Significantly decreased FA and increased MD in bilateral prefronto-limbic-striatal white matter and right inferior fronto-occipital, superior and inferior longitudinal fasciculi were shown in all BD-I patients versus controls, as well as in depressed BD-I patients compared to both controls and remitted BD-I patients. Depressed BD-I patients also exhibited increased FA in the ventromedial prefrontal cortex. Remitted BD-I patients did not differ from controls in FA or MD. These findings suggest that BD-I depression may be associated with acute microstructural WM changes.

Schizophrenia Research, 2008

cerebral tissue composition. WMH are associated with brain tract disruption and have been related... more cerebral tissue composition. WMH are associated with brain tract disruption and have been related to several psychiatric conditions including bipolar disorder, late-onset depression, suicidality in unipolar depression and substance misuse. There have been conflicting findings regarding the frequency of WMH in schizophrenia for both early-onset (EOS) and late-onset (LOS) cases. We conducted a metaanalysis of the presence of these lesions in schizophrenia aiming to improve the statistical power through collapsing the data. Methods: A systematic review of the literature was performed searching for studies that have systematically assessed the presence and/or extent of WMH in both EOS and LOS patients compared to controls. Analysis of the pooled data was conducted using the Mantel-Haenszel statistics. Results: Initially Sixteen studies were identified. However, only eight studies involving EOS were homogenous enough to be included in the meta-analysis (378 patients and 471 controls). Studies of WMH in LOS varied greatly in methodology and a meta-analysis was not, therefore, possible. No difference was observed in the prevalence of WMH between EOS subjects and controls (OR = 0.92, CI 95% = 0.62-1.38, p = 0.698). The test of heterogeneity of odds ratio did not reveal differences among the enrolled studies. Conclusions: EOS is not associated with increased rates of WMH. Further studies with larger samples and standardized methods are needed to better evaluate the role of these lesions in LOS.

Journal of the American Heart Association, Jan 2, 2018

Late gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In thi... more Late gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In this study, we introduce the tractographic propagation angle (PA), a metric of myofiber curvature (degrees/unit distance) derived from diffusion tensor imaging (DTI), and compare its use to LGE and invasive scar assessment by endocardial voltage mapping. DTI was performed on 7 healthy human volunteers, 5 patients with myocardial infarction, 6 normal mice, and 7 mice with myocardial infarction. LGE to delineate the infarct and border zones was performed with a 2-dimensional inversion recovery gradient-echo sequence. Ex vivo DTI was performed on 5 normal human and 5 normal sheep hearts. Endocardial electroanatomic mapping and subsequent ex vivo DTI was performed on 5 infarcted sheep hearts. PA in the normal human hearts varied smoothly and was generally <4. The mean PA in the infarct zone was significantly elevated (10.34±1.02 versus 4.05±0.45,<0.05). Regions with a PA ≤4 consistently h...

Radiology, 2016

To develop a clinically feasible whole-heart free-breathing diffusion-tensor (DT) magnetic resona... more To develop a clinically feasible whole-heart free-breathing diffusion-tensor (DT) magnetic resonance (MR) imaging approach with an imaging time of approximately 15 minutes to enable three-dimensional (3D) tractography.

ABSTRACT An increasing demand for sophisticated tools to characterize the integrity and functiona... more ABSTRACT An increasing demand for sophisticated tools to characterize the integrity and functional state of vascular networks from different imaging modalities has emerged. Currently available tools are time-consuming and limited in their ability to assess the state of vascular architectures, There is a need for developing robust and fast computer-based techniques for extracting vessel trajectories as well as estimate their diameters. To investigate a technique based on the well-known Hough Transform (HT) to dynamically estimate the trajectory and vessel diameter without resorting to time-consuming multiscale techniques [1]. We have proposed a semi-automated method to detect and track vessel trajectories in MRA. The novelty of this study is the use of HT to define the seed point for tracking and detecting the vessel scale without resorting to multiscale analysis technique. In spite of presence of noise, a mean diameter can be established. Future work will focus on automatic bifurcation handling using analysis of curvature of the vessel profile at the cross-section.

Determination of axonal pathways provides an invaluable means to study the connectivity of the hu... more Determination of axonal pathways provides an invaluable means to study the connectivity of the human brain and its functional network. Diffusion tensor imaging (DTI) is unique in its ability to capture the restricted diffusion of water molecules which can be used to infer the directionality of tissue components. In this paper, we introduce a white matter tractography method based on anisotropic wavefront propagation in diffusion tensor images. A front propagates in the white matter with a speed profile governed by the isocontour of the diffusion tensor ellipsoid. By using the ellipsoid, we avoid possible misclassification of the principal eigenvector in oblate regions. The wavefront evolution is described by an anisotropic version of the static Hamilton-Jacobi equation, which is solved by a sweeping method in order to obtain correct arrival times. Pathways of connection are determined by tracing minimum-cost trajectories using the characteristic vector field of the resulting partial differential equation. A validity index is described to rate the goodness of the resulting pathways with respect to the directionality of the tensor field. Connectivity results using normal human DTI brain images are illustrated and discussed. We also compared our method with a similar level set-based tractography technique, and found that the anisotropic evolution increased the validity index of the obtained pathways by 18%.

Vascular disease is characterized by any condition that affects the circulatory system. Recently,... more Vascular disease is characterized by any condition that affects the circulatory system. Recently, a demand for sophisticated software tools that can characterize the integrity and functional state of vascular networks from different vascular imaging modalities has appeared. Such tools face significant challenges such as: large datasets, similarity in intensity distributions of other organs and structures, and the presence of complex vessel geometry and branching patterns. Towards that goal, this paper presents a new approach to automatically track vascular networks from CTA and MRA images. Our methodology is based on the Hough transform to dynamically estimate the centerline and vessel diameter along the vessel trajectory. Furthermore, the vessel architecture and orientation is determined by the analysis of the Hessian matrix of the CTA or MRA intensity distribution. Results are shown using both synthetic vessel datasets and real human CTA and MRA images. The tracking algorithm yielded high reproducibility rates, robustness to different noise levels, associated with simplicity of execution, which demonstrates the feasibility of our approach.

Background / Purpose: Several theoretical models consider that white matter (WM) abnormalities ha... more Background / Purpose: Several theoretical models consider that white matter (WM) abnormalities have a central role in the pathophysiology of schizophrenia, and brain imaging studies have found WM abnormalities in individuals with both recent-onset and chronic psychosis. However, no study to date has investigated whether these changes are stable or state-dependent, i.e., varying according to the acute versus remitted phase of the disorder. In this study, we aim to evaluate the WM microstructure using diffusion tensor imaging (DTI) in a group of patients with non-affective first-episode psychosis (FEP) at the acute psychotic state and after symptomatic remission. Main conclusion: Our findings suggest that some WM changes present in the very beginning of FEP could reverse following symptom remission. It may be possible that such changes affecting brain areas related to the integration of perceptual information, could partially underpin the emergence of symptoms in FEP.

Digital Imaging and Communications In Medicine (DICOM) is a well-established standard regarding s... more Digital Imaging and Communications In Medicine (DICOM) is a well-established standard regarding storage, printing, and transmission of medical images. However, there are no security methods that preserve metadata confidentiality, nor image authenticity. This work assesses three steganographic methods-least significant bit insertion (LSB), division into blocks, mean change modified method (MCMM)-and verify their feasibility for clinical use in medical imaging. Integrating MCMM in DICOM standard would provide increased information security in medical imaging, deterring fraud, privacy invasion, while preserving diagnostic information.

2013 IEEE International Conference on Image Processing, 2013

Multiple Sclerosis International, 2011

The corpus callosum is the largest fiber bundle in the central nervous system and it takes part i... more The corpus callosum is the largest fiber bundle in the central nervous system and it takes part in several cognitive pathways. It can be affected by multiple sclerosis (MS) early in the disease. DTI is capable of infering the microstructural organization of the white matter. The vectorial analysis of the DTI offers the more specific indices of axial diffusivity (AD) and radial diffusivity (RD), which have shown to be useful to discriminate myelin damage from axon loss, respectively. This study presents DTI results (mean diffusivity (MD), fractional anisotropy (FA), RD, and AD) of 23 relapsing-remitting MS patients and its correlation with cognitive performance. There were 47.8% of cognitive impaired patients (MS CI). We found signs of demyelination, reflected by increased RD, and incipient axon loss, reflected by AD increase, which was slightly higher in the MS CI. The cognitive changes correlated with the DTI parameters, suggesting that loss of complexity in CC connections can impa...

Page 1. 2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, Oct... more Page 1. 2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, October 24-28, 2011 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-04-5 NSECT IMAGES ...

Abnormalities in fronto-limbic-striatal white matter (WM) have been reported in bipolar disorder ... more Abnormalities in fronto-limbic-striatal white matter (WM) have been reported in bipolar disorder (BD), but results have been inconsistent across studies. Furthermore, there have been no detailed investigations as to whether acute mood states contribute to microstructural changes in WM tracts. In order to compare fiber density and structural integrity within WM tracts between BD depression and remission, whole-brain fractional anisotropy (FA) and mean diffusivity (MD) were assessed in 37 bipolar I disorder (BD-I) patients (16 depressed and 21 remitted), and 26 healthy individuals with diffusion tensor imaging. Significantly decreased FA and increased MD in bilateral prefronto-limbic-striatal white matter and right inferior fronto-occipital, superior and inferior longitudinal fasciculi were shown in all BD-I patients versus controls, as well as in depressed BD-I patients compared to both controls and remitted BD-I patients. Depressed BD-I patients also exhibited increased FA in the ventromedial prefrontal cortex. Remitted BD-I patients did not differ from controls in FA or MD. These findings suggest that BD-I depression may be associated with acute microstructural WM changes.