107 results on '"De Santis, Silvia"'
Search Results
102. Diffusion-MRI in neurodegenerative disorders
- Author
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Joseph Goveas a, Laurence O'Dwyer b, Mario Mascalchi c, d, Mirco Cosottini e, f, Stefano Diciotti g, Silvia De Santis h, Luca Passamonti i, Carlo Tessa j, Nicola Toschi k, l, m, Marco Giannelli n, Goveas, Joseph, O'Dwyer, Laurence, Mascalchi, Mario, Cosottini, Mirco, Diciotti, Stefano, De Santis, Silvia, Passamonti, Luca, Tessa, Carlo, Toschi, Nicola, and Giannelli, Marco
- Subjects
Pathology ,Radiology, Nuclear Medicine and Imaging ,Parkinson's disease ,Diffusion-MRI ,Contrast Media ,Disease ,Nuclear Medicine and Imaging ,Degenerative ataxias ,Amyotrophic lateral sclerosis ,Alzheimer's disease ,DTI ,Huntington's disease ,medicine.diagnostic_test ,diffusion ,Brain ,Settore MED/37 - Neuroradiologia ,Neurodegenerative Diseases ,neurodegenerative disorders ,Settore MED/26 - Neurologia ,Radiology ,Alzheimer’s disease ,Algorithms ,MRI ,Huntington’s disease ,medicine.medical_specialty ,Biophysics ,ataxias ,Biomedical Engineering ,Sensitivity and Specificity ,Settore MED/36 - Diagnostica per Immagini e Radioterapia ,Degenerative ataxia ,Image Interpretation, Computer-Assisted ,medicine ,Humans ,Amyotrophic lateral sclerosi ,Mechanism (biology) ,business.industry ,Reproducibility of Results ,Magnetic resonance imaging ,Parkinson’s disease ,medicine.disease ,Image Enhancement ,Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin) ,Review article ,Diffusion Magnetic Resonance Imaging ,Biophysic ,business ,Neuroscience ,Diffusion MRI - Abstract
The ability to image the whole brain through ever more subtle and specific methods/contrasts has come to play a key role in understanding the basis of brain abnormalities in several diseases. In magnetic resonance imaging (MRI), “diffusion” (i.e. the random, thermally-induced displacements of water molecules over time) represents an extraordinarily sensitive contrast mechanism, and the exquisite structural detail it affords has proven useful in a vast number of clinical as well as research applications. Since diffusion-MRI is a truly quantitative imaging technique, the indices it provides can serve as potential imaging biomarkers which could allow early detection of pathological alterations as well as tracking and possibly predicting subtle changes in follow-up examinations and clinical trials. Accordingly, diffusion-MRI has proven useful in obtaining information to better understand the microstructural changes and neurophysiological mechanisms underlying various neurodegenerative disorders. In this review article, we summarize and explore the main applications, findings, perspectives as well as challenges and future research of diffusion-MRI in various neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, Huntington’s disease and degenerative ataxias.
- Published
- 2015
103. Whole brain in vivo axonal diameter mapping in multiple sclerosis.
- Author
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De Santis S, Herranz E, Treaba CA, Barletta V, Mehndiratta A, Mainero C, and Toschi N
- Subjects
- Axons, Brain, Brain Mapping, Diffusion Magnetic Resonance Imaging, Humans, Multiple Sclerosis
- Abstract
Traditional techniques based on diffusion MR imaging suffer from extremely low specificity in separating disease-related alterations in white matter microstructure, which can involve multiple phenomena including axonal loss, demyelination and changes in axonal size. Multi-shell diffusion MRI is able to greatly increase specificity by concomitantly exploring multiple diffusion timescales. If multi-shell acquisition is combined with an exploration of different diffusion times, diffusion data allows the estimation of sophisticated compartmental models, which provide greatly enhanced specificity to the presence of different tissue sub-compartments, as well as estimates of intra-voxel axonal diameter distributions. In this paper, we apply a multiple-b-value, high angular resolution multi-shell diffusion MRI protocol with varying diffusion times to a cohort of multiple sclerosis (MS) patients and compare them to a population of healthy controls. By fitting the AxCaliber model, we are able to extract indices for axonal diameter across the whole brain. We show that MS is associated with widespread increases of axonal diameter and that our axonal diameter estimation provides the highest discrimination power for local alterations in normal-appearing white matter in MS compared to controls. AxCaliber has the potential to disentangle microstructural alterations in MS and holds great promises to become a sensitive and specific non-invasive biomarker of irreversible disease progression.
- Published
- 2019
- Full Text
- View/download PDF
104. Dynamics of White Matter Plasticity Underlying Working Memory Training: Multimodal Evidence from Diffusion MRI and Relaxometry.
- Author
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Metzler-Baddeley C, Foley S, de Santis S, Charron C, Hampshire A, Caeyenberghs K, and Jones DK
- Subjects
- Adult, Anisotropy, Brain diagnostic imaging, Female, Humans, Image Processing, Computer-Assisted, Male, Neuropsychological Tests, Verbal Learning, Young Adult, Cognition physiology, Diffusion Magnetic Resonance Imaging, Learning physiology, Memory, Short-Term physiology, White Matter diagnostic imaging
- Abstract
Adaptive working memory (WM) training may lead to cognitive benefits that are associated with white matter plasticity in parietofrontal networks, but the underlying mechanisms remain poorly understood. We investigated white matter microstructural changes after adaptive WM training relative to a nonadaptive comparison group. Microstructural changes were studied in the superior longitudinal fasciculus, the main parietofrontal connection, and the cingulum bundle as a comparison pathway. MRI-based metrics were the myelin water fraction and longitudinal relaxation rate R
1 from multicomponent relaxometry (captured with the mcDESPOT approach) as proxy metrics of myelin, the restricted volume fraction from the composite hindered and restricted model of diffusion as an estimate of axon morphology, and fractional anisotropy and radial diffusivity from diffusion tensor imaging. PCA was used for dimensionality reduction. Adaptive training was associated with benefits in a "WM capacity" component and increases in a microstructural component (increases in R1 , restricted volume fraction, fractional anisotropy, and reduced radial diffusivity) that predominantly loaded on changes in the right dorsolateral superior longitudinal fasciculus and the left parahippocampal cingulum. In contrast, nonadaptive comparison activities were associated with the opposite pattern of reductions in WM capacity and microstructure. No group differences were observed for the myelin water fraction metric suggesting that R1 was a more sensitive "myelin" index. These results demonstrate task complexity and location-specific white matter microstructural changes that are consistent with tissue alterations underlying myelination in response to training.- Published
- 2017
- Full Text
- View/download PDF
105. Early axonal damage in normal appearing white matter in multiple sclerosis: Novel insights from multi-shell diffusion MRI.
- Author
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De Santis S, Granberg T, Ouellette R, Treaba CA, Qiuyun Fan, Herranz E, Mainero C, and Toschi N
- Subjects
- Axons, Brain, Diffusion Magnetic Resonance Imaging, Diffusion Tensor Imaging, Humans, Multiple Sclerosis, White Matter
- Abstract
Conventional diffusion-weighted MR imaging techniques provide limited specificity in disentangling disease-related microstructural alterations involving changes in both axonal density and myelination. By simultaneously probing multiple diffusion regimens, multi-shell diffusion MRI is capable of increasing specificity to different tissue sub-compartments and hence separate different contributions to changes in diffusion-weighted signal attenuation. Advanced multi-shell diffusion models impose significant requirements on the amount of diffusion weighting (i.e. gradient coil performance) and angular resolution (i.e. in-scanner subject time), which commonly limits their applicability in a clinical setting. In this paper, we apply a high-b-value, high angular resolution multi-shell diffusion MRI protocol to a population of early multiple sclerosis (MS) patients and healthy controls. Through the Composite Hindered and Restricted Model of Diffusion (CHARMED) model, we extract indices for axonal density as well as parameters sensitive to myelin. We demonstrate increased sensitivity to microstructural changes in normal appearing white matter and in lesions in MS as compared to traditional models like DTI. These changes appear to be predominantly in axonal density, pointing towards the existence of axonal damage mechanisms in early MS.
- Published
- 2017
- Full Text
- View/download PDF
106. The CONNECT project: Combining macro- and micro-structure.
- Author
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Assaf Y, Alexander DC, Jones DK, Bizzi A, Behrens TE, Clark CA, Cohen Y, Dyrby TB, Huppi PS, Knoesche TR, Lebihan D, Parker GJ, Poupon C, Anaby D, Anwander A, Bar L, Barazany D, Blumenfeld-Katzir T, De-Santis S, Duclap D, Figini M, Fischi E, Guevara P, Hubbard P, Hofstetter S, Jbabdi S, Kunz N, Lazeyras F, Lebois A, Liptrot MG, Lundell H, Mangin JF, Dominguez DM, Morozov D, Schreiber J, Seunarine K, Nava S, Poupon C, Riffert T, Sasson E, Schmitt B, Shemesh N, Sotiropoulos SN, Tavor I, Zhang HG, and Zhou FL
- Subjects
- Humans, Models, Anatomic, Models, Neurological, Brain cytology, Brain physiology, Connectome methods, Diffusion Tensor Imaging methods, Image Enhancement methods, Nerve Net cytology, Nerve Net physiology
- Abstract
In recent years, diffusion MRI has become an extremely important tool for studying the morphology of living brain tissue, as it provides unique insights into both its macrostructure and microstructure. Recent applications of diffusion MRI aimed to characterize the structural connectome using tractography to infer connectivity between brain regions. In parallel to the development of tractography, additional diffusion MRI based frameworks (CHARMED, AxCaliber, ActiveAx) were developed enabling the extraction of a multitude of micro-structural parameters (axon diameter distribution, mean axonal diameter and axonal density). This unique insight into both tissue microstructure and connectivity has enormous potential value in understanding the structure and organization of the brain as well as providing unique insights to abnormalities that underpin disease states. The CONNECT (Consortium Of Neuroimagers for the Non-invasive Exploration of brain Connectivity and Tracts) project aimed to combine tractography and micro-structural measures of the living human brain in order to obtain a better estimate of the connectome, while also striving to extend validation of these measurements. This paper summarizes the project and describes the perspective of using micro-structural measures to study the connectome., (Copyright © 2013 Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
107. Molecular monitoring of hematologic malignancies: current and future issues.
- Author
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Lo Coco F, De Santis S, Esposito A, Divona M, and Diverio D
- Subjects
- Humans, Leukemia, Promyelocytic, Acute genetics, Leukemia, Promyelocytic, Acute mortality, Polymerase Chain Reaction, Prognosis, Recurrence, Reverse Transcriptase Polymerase Chain Reaction, Survival Rate, Hematologic Neoplasms genetics
- Abstract
Genetic markers associated with hematologic malignancies such as acute promyelocytic leukemia (APL) can be detected with high sensitivity and specificity using the reverse-transcription polymerase chain reaction (RT-PCR). This procedure can be applied to monitor minimal residual disease. In patients with APL, RT-PCR is now being used to detect molecular relapse, and a strong association has been found between outcome and the treatment of molecular as opposed to hematologic relapse. In APL, results from PCR assays are also being used to guide therapy. Prognostic groups can be defined using molecular and clinical characteristics of the disease as well as patient characteristics. In the future, PCR monitoring strategies may be adapted to the risk of relapse of individual patients. Patients at high risk of relapse may be monitored much more rigorously than patients at low risk of relapse. Although RT-PCR is in routine use as a clinical tool, the lack of standardization of techniques in different laboratories has resulted in some difficulties in interpretation of results. There is a real need for an international consensus on standardization of PCR techniques., (Copyright 2002, Elsevier Science (USA). All rights reserved.)
- Published
- 2002
- Full Text
- View/download PDF
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