Articles by Gregory M. Szilagyi in JoVE
Lesão Explorer: Um guiada por vídeo, protocolo padronizado para Volumetrics MRI derivados precisos e confiáveis na doença de Alzheimer e idosos normais Joel Ramirez1, Christopher J.M. Scott1, Alicia A. McNeely1, Courtney Berezuk1, Fuqiang Gao1, Gregory M. Szilagyi1,2, Sandra E. Black1,2 1LC Campbell Cognitive Neurology Research Unit, Heart & Stroke Foundation Canadian Partnership for Stroke Recovery, Brain Sciences Research Program, Sunnybrook Health Sciences Centre, 2Department of Medicine (Neurology), Institute of Medical Science, University of Toronto Lesão Explorer (LE) é, de um gasoduto semi-automáticas de processamento de imagem desenvolvido para obter o tecido cerebral regional e volumetria das lesões hiperintensas subcorticais de ressonância magnética estrutural da doença de Alzheimer e idosos normal. Para garantir um alto nível de precisão e confiabilidade, o que se segue é, um protocolo padronizado guiada por vídeo para procedimentos manuais de LE.
Other articles by Gregory M. Szilagyi on PubMed
Imaging Genetics in Multiple Sclerosis: a Volumetric and Diffusion Tensor MRI Study of APOE Îµ4 NeuroImage. Oct, 2011 | Pubmed ID: 21723395 Evidence linking the Îµ4 allele of APOE to more severe brain MRI abnormalities in multiple sclerosis (MS) has been conflicting and limited to studies of lesion load and whole brain atrophy. The purpose of the present study was to determine whether the Îµ4 allele of APOE is associated with more extensive brain pathology in MS using structural and diffusion tensor MRI. Using a case-control design, 43 MS patients with the Îµ4 allele and 47 Îµ4 negative MS patients underwent structural and diffusion tensor imaging (DTI) at 3T. Hypo- and hyperintense lesion volumes, whole brain and medial temporal volumes, and DTI parameters (fractional anisotropy (FA) and mean diffusivity (MD)) in normal-appearing brain tissue and lesions were compared between the groups. Îµ4+ and Îµ4- MS patients were well-matched on demographic characteristics, disease variables, and proportions receiving disease-modifying therapy. Îµ4+ and Îµ4- patients did not differ on any MRI or DTI measure. This study refutes a role for the Îµ4 allele in MRI abnormalities in MS, particularly those linking Îµ4 to greater T1 hypointense lesion volume and brain atrophy. Previous work on this putative gene-MRI relationship is extended by comparing DTI measures within lesions and normal-appearing brain tissue. A lack of differences in medial temporal regions, areas that have been linked to Îµ4-associated changes in health and disease, further supports the conclusion that that Îµ4 is not associated with more subtle MRI markers of brain pathology in MS.
Object Alternation: a Novel Probe of Medial Frontal Function in Frontotemporal Dementia Alzheimer Disease and Associated Disorders. Oct-Dec, 2013 | Pubmed ID: 23604006 We studied behavioral variant frontotemporal dementia (bvFTD) using object alternation (OA) as a novel probe of cognition. This task was adopted from animal models and is sensitive to ventrolateral-orbitofrontal and medial frontal function in humans. OA was administered to bvFTD patients, normal controls, and a dementia control group with Alzheimer disease (AD). Two other frontal lobe measures adopted from animal models were administered: delayed response (DR) and delayed alternation (DA). Brain volumes were measured using the semiautomatic brain region extraction method. Compared with the normal controls, bvFTD patients were significantly impaired on OA and DR. For OA and DR, sensitivities and specificities were 100% and 51.5% (cutoff=22.5 errors) and 9.5% and 98% (cutoff=1.5 errors), respectively. Negative predictive value (NPV) for OA was 100% at all prevalence rates. Comparing AD with bvFTD, there were no significant differences on OA, DR, or DA. Nevertheless, positive predictive value (PPV) and NPV were good at all prevalence rates for OA (cutoff=36.5 errors) and DA (cutoff=6 errors); PPV was good for DR (cutoff=9 errors). Error scores above cutoffs favored diagnosis of AD. Performance on OA was significantly related to medial frontal gray matter atrophy. OA, together with DR and DA, may facilitate assessment of bvFTD as a novel probe of medial frontal function.
Region-Based Partial Volume Correction Techniques for PET Imaging: Sinogram Implementation and Robustness International Journal of Molecular Imaging. 2013 | Pubmed ID: 24455241 Background/Purpose. Limited spatial resolution of positron emission tomography (PET) requires partial volume correction (PVC). Region-based PVC methods are based on geometric transfer matrix implemented either in image-space (GTM) or sinogram-space (GTMo), both with similar performance. Although GTMo is slower, it more closely simulates the 3D PET image acquisition, accounts for local variations of point spread function, and can be implemented for iterative reconstructions. A recent image-based symmetric GTM (sGTM) has shown improvement in noise characteristics and robustness to misregistration over GTM. This study implements the sGTM method in sinogram space (sGTMo), validates it, and evaluates its performance. Methods. Two 3D sphere and brain digital phantoms and a physical sphere phantom were used. All four region-based PVC methods (GTM, GTMo, sGTM, and sGTMo) were implemented and their performance was evaluated. Results. All four PVC methods had similar accuracies. Both noise propagation and robustness of the sGTMo method were similar to those of sGTM method while they were better than those of GTMo method especially for smaller objects. Conclusion. The sGTMo was implemented and validated. The performance of the sGTMo in terms of noise characteristics and robustness to misregistration is similar to that of the sGTM method and improved compared to the GTMo method.