Axonal diameter and density estimated with 7-Tesla hybrid diffusion imaging in transgenic Alzheimer rats
Year: 2016
Type: conference-paper
Abstract: Diffusion-weighted MR imaging (DWI) is a powerful tool to study brain tissue microstructure. DWI is sensitive to subtle changes in the white matter (WM), and can provide insight into abnormal brain changes in diseases such as Alzheimer’s disease (AD). In this study, we used 7-Tesla hybrid diffusion imaging (HYDI) to scan 3 transgenic rats (line TgF344-AD; that model the full clinico-pathological spectrum of the human disease) ex vivo at 10, 15 and 24 months. We acquired 300 DWI volumes across 5 q-sampling shells (b=1000, 3000, 4000, 8000, 12000 s/mm2). From the top three b-value shells with highest signal-to-noise ratios, we reconstructed markers of WM disease, including indices of axon density and diameter in the corpus callosum (CC) – directly quantifying processes that occur in AD. As expected, apparent anisotropy progressively decreased with age; there were also decreases in the intra- and extra-axonal MR signal along axons. Axonal diameters were larger in segments of the CC (splenium and body, but not genu), possibly indicating neuritic dystrophy – characterized by enlarged axons and dendrites as previously observed at the ultrastructural level (see Cohen et al., J. Neurosci. 2013). This was further supported by increases in MR signals trapped in glial cells, CSF and possibly other small compartments in WM structures. Finally, tractography detected fewer fibers in the CC at 10 versus 24 months of age. These novel findings offer great potential to provide technical and scientific insight into the biology of brain disease.
DOI: 10.1117/12.2216912
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
Funders: California Institute of Technology, National Institutes of Health, Beckman Institute, California Institute of Technology, National Institute on Aging, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Institute of Biomedical Imaging and Bioengineering, U.S. National Library of Medicine
Awards: G130320643, G1757829149, G2533166933, G3495954047, G3510044943, HARDI Mapping of Disease Effects on the Brain, G3642348494, Alzheimer's disease risk analyzed using population imaging genomics, G4741411087, Empowering Personalized Medicine: Integrating Imaging, Genetics, and Biomarkers, A Multidimensional Alzheimer's Disease Brain Atlas, Multidisciplinary Study of Social Behavior and Emotion in Frontotemporal Dementia, Multimodal microPET and microMRI Imaging Instrumentation, Peripheral TGF-beta Pathway Inhibitor Therapy in Alzheimer's Rats, ENIGMA Center for Worldwide Medicine, Imaging & Genomics, G6423720423, G9000210308
OpenAlex ID: W2313146511