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Dickerson B.C.,Biomedical Imaging Center | Eichenbaum H.,Boston University
Neuropsychopharmacology | Year: 2010

The ability to encode and retrieve our daily personal experiences, called episodic memory, is supported by the circuitry of the medial temporal lobe (MTL), including the hippocampus, which interacts extensively with a number of specific distributed cortical and subcortical structures. In both animals and humans, evidence from anatomical, neuropsychological, and physiological studies indicates that cortical components of this system have key functions in several aspects of perception and cognition, whereas the MTL structures mediate the organization and persistence of the network of memories whose details are stored in those cortical areas. Structures within the MTL, and particularly the hippocampus, have distinct functions in combining information from multiple cortical streams, supporting our ability to encode and retrieve details of events that compose episodic memories. Conversely, selective damage in the hippocampus, MTL, and other structures of the large-scale memory system, or deterioration of these areas in several diseases and disorders, compromises episodic memory. A growing body of evidence is converging on a functional organization of the cortical, subcortical, and MTL structures that support the fundamental features of episodic memory in humans and animals. © 2010 Nature Publishing Group All rights reserved. Source

Gutchess A.,Brandeis University | Gutchess A.,Biomedical Imaging Center
Science | Year: 2014

Cognitive neuroscience has revealed aging of the human brain to be rich in reorganization and change. Neuroimaging results have recast our framework around cognitive aging from one of decline to one emphasizing plasticity. Current methods use neurostimulation approaches to manipulate brain function, providing a direct test of the ways that the brain differently contributes to task performance for younger and older adults. Emerging research into emotional, social, and motivational domains provides some evidence for preservation with age, suggesting potential avenues of plasticity, alongside additional evidence for reorganization. Thus, we begin to see that aging of the brain, amidst interrelated behavioral and biological changes, is as complex and idiosyncratic as the brain itself, qualitatively changing over the life span. Copyright © 2014 by the American Association for the Advancement of Science; all rights reserved. Source

Clough R.E.,Biomedical Imaging Center | Nienaber C.A.,University of Rostock
Nature Reviews Cardiology | Year: 2015

Acute aortic syndrome (AAS) encompasses a group of severe, life-threatening disorders of the aorta, including acute aortic dissection, intramural haematoma (IMH), and penetrating aortic ulcer (PAU). The concept of AAS was developed to enable the early identification and definitive treatment of patients with chest pain from an aortic origin. Aortic dissection is the most common form of AAS, followed by IMH and PAU. Congenital cardiovascular defects, genetic syndromes, and nonsyndromic genetic variants have all been linked with the development of AAS. The diagnosis of AAS in the clinic can be made using imaging modalities such as CT, echocardiography, and MRI. The initial management of patients with AAS is focussed on the control of blood pressure to reduce aortic wall stress. A multidisciplinary team is required to assess each patient and decide whether endovascular or open surgical treatment, or further medical management is indicated. The optimal treatment of patients with AAS remains a challenging clinical dilemma, and further studies are required to fully characterize conditions within the AAS spectrum and to design individualized, patient-centred treatment plans. © 2015 Macmillan Publishers Limited. All rights reserved. Source

PURPOSE: The purpose of this study was to estimate perfusion metrics in healthy and cirrhotic liver with pharmacokinetic modeling of high–temporal resolution reconstruction of continuously acquired free-breathing gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid–enhanced acquisition in patients undergoing clinically indicated liver magnetic resonance imaging.SUBJECTS AND METHODS: In this Health Insurance Portability and Accountability Act–compliant prospective study, 9 cirrhotic and 10 noncirrhotic patients underwent clinical magnetic resonance imaging, which included continuously acquired radial stack-of-stars 3-dimensional gradient recalled echo sequence with golden-angle ordering scheme in free breathing during contrast injection. A total of 1904 radial spokes were acquired continuously in 318 to 340 seconds. High–temporal resolution data sets were formed by grouping 13 spokes per frame for temporal resolution of 2.2 to 2.4 seconds, which were reconstructed using the golden-angle radial sparse parallel technique that combines compressed sensing and parallel imaging. High–temporal resolution reconstructions were evaluated by a board-certified radiologist to generate gadolinium concentration-time curves in the aorta (arterial input function), portal vein (venous input function), and liver, which were fitted to dual-input dual-compartment model to estimate liver perfusion metrics that were compared between cirrhotic and noncirrhotic livers.RESULTS: The cirrhotic livers had significantly lower total plasma flow (70.1 ± 10.1 versus 103.1 ± 24.3 mL/min per 100 mL; P < 0.05), lower portal venous flow (33.4 ± 17.7 versus 89.9 ± 20.8 mL/min per 100 mL; P < 0.05), and higher arterial perfusion fraction (52.0% ± 23.4% versus 12.4% ± 7.1%; P < 0.05). The mean transit time was higher in the cirrhotic livers (24.4 ± 4.7 versus 15.7 ± 3.4 seconds; P < 0.05), and the hepatocellular uptake rate was lower (3.03 ± 2.1 versus 6.53 ± 2.4 100/min; P < 0.05).CONCLUSIONS: Liver perfusion metrics can be estimated from free-breathing dynamic acquisition performed for every clinical examination without additional contrast injection or time. This is a novel paradigm for dynamic liver imaging. © 2014 by Lippincott Williams & Wilkins Source

Mormino E.C.,Harvard University | Mormino E.C.,Biomedical Imaging Center
Neuropsychology Review | Year: 2014

Aberrant accumulation of beta-amyloid (Aβ) is thought to be an early event in a biological cascade that eventually leads to Alzheimer’s disease (AD). Along these lines, many clinically normal (CN) older individuals have evidence of beta-amyloid (Aβ) accumulation, which may be indicative of preclinical AD. However, relationships between Aβ and “downstream” AD markers are often inconsistent across studies. These inconsistencies may be due to the presence of other age-related processes that also influence AD markers, as well as additional risk factors that interact with Aβ to influence downstream changes. For instance, it is possible that the effect of Aβ is modified by neurodegeneration, genetics, sex-differences and cognitive reserve. Thus, a multivariate approach to determining risk of AD within CN participants may be more appropriate than reliance on Aβ status alone. An understanding of how additional risk factors interact with Aβ to influence an individual’s trajectory towards AD is essential for characterizing preclinical AD and has implications for prevention trials. © 2014, Springer Science+Business Media New York. Source

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