Hossein Moein Taghavi
Life Science Research Professional, Rad/Neuroimaging and Neurointervention
All Publications
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Elevated tau in the piriform cortex in Alzheimer's but not Parkinson's disease using PET-MR.
Alzheimer's & dementia (Amsterdam, Netherlands)
2024; 16 (4): e70040
Abstract
Olfactory dysfunction can be an early sign of Alzheimer's disease (AD). We used tau positron emission tomography-magnetic resonance (PET-MR) to analyze a key region of the olfactory circuit, the piriform cortex, in comparison to the adjacent medial temporal lobe.Using co-registered magnetic resonance imaging (MRI) and 18F-PI-2620 tau PET-MR scans in 94 older adults, we computed tau uptake in the piriform-periamygdaloid cortex, amygdala, entorhinal-perirhinal cortices, and hippocampus.We found an ordinal cross-sectional increase in piriform cortex tau uptake with increasing disease severity (amyloid-negative controls, amyloid-positive controls, mild cognitive impairment [MCI] and AD), comparable to entorhinal-perirhinal cortex. Amyloid-positive controls showed significantly greater tau uptake than amyloid-negative controls. Negative correlations were present between memory performance and piriform uptake. Piriform uptake was not elevated in cognitively unimpaired Parkinson's disease.Cross-sectionally, there is an early increase in tau uptake in the piriform cortex in AD but not in Parkinson's disease.Positron emission tomography-magnetic resonance (PET-MR) analysis of the piriform cortex sheds light on its role as a potential early region affected by neurodegenerative disorders underlying olfactory dysfunction.Uptake of tau tracer was elevated in the piriform cortex in Alzheimer's disease (AD) and mild cognitive impairment (MCI) but not in Parkinson's disease (PD).Memory performance was worse with greater piriform uptake.
View details for DOI 10.1002/dad2.70040
View details for PubMedID 39583648
View details for PubMedCentralID PMC11585164
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Uncovering microstructural architecture from histology.
bioRxiv : the preprint server for biology
2024
Abstract
Microstructural tissue organization underlies the complex connectivity of the brain and controls properties of connective, muscle, and epithelial tissue. However, discerning microstructural architecture with high resolution for large fields of view remains prohibitive. We address this challenge with computational scattered light imaging (ComSLI), which exploits the anisotropic light scattering of aligned structures. Using a rotating lightsource and a high-resolution camera, ComSLI determines fiber architecture with micrometer resolution from histological sections across preparation and staining protocols. We show complex fiber architecture in brain and non-brain sections, including histological paraffin-embedded sections with various stains, and demonstrate its applicability on animal and human tissue, including disease cases with altered microstructure. ComSLI opens new avenues for investigating fiber architecture in new and archived sections across organisms, tissues, and diseases.One Sentence Summary: We uncover microstructural architecture of new or archived human and animal histological sections in health and disease.
View details for DOI 10.1101/2024.03.26.586745
View details for PubMedID 38585744
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Longitudinal alterations of cerebral blood flow in high-contact sports.
Annals of neurology
2023
Abstract
Repetitive head trauma is common in high-contact sports. Cerebral blood flow (CBF) can measure changes in brain perfusion that could indicate injury. Longitudinal studies with a control group are necessary to account for interindividual and developmental effects. We investigated whether exposure to head impacts causes longitudinal CBF changes.We prospectively studied 63 American football (high-contact cohort) and 34 volleyball (low-contact controls) male collegiate athletes, tracking CBF using 3D-pseudo-continuous arterial-spin-labeling (ASL) MRI for up to four years. Regional relative CBF (rCBF, normalized to cerebellar CBF) was computed after co-registering to T1-weighted images. A linear-mixed-effects model assessed the relationship of rCBF to sport, time, and their interaction. Within football players, we modeled rCBF against position-based head impact risk and baseline SCAT (Standardized Concussion Assessment Tool) score. Additionally, we evaluated early (1-5 days) and delayed (3-6 months) post-concussion rCBF changes (in-study concussion).Supratentorial gray matter rCBF declined in football compared to volleyball (sport-time interaction p=0.012), with a strong effect in the parietal lobe (p=0.002). Football players with higher position-based impact-risk had lower occipital rCBF over time (interaction p=0.005), while players with lower baseline SCAT score (worse performance) had relatively decreased rCBF in the cingulate-insula over time (interaction effect: p=0.007). Both cohorts showed a left-right rCBF asymmetry that decreased over time. Football players with an in-study concussion exhibited an early increase in occipital lobe rCBF (p=0.0166).These results suggest head impacts may result in an early increase in rCBF, but cumulatively a long-term decrease in rCBF. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/ana.26718
View details for PubMedID 37306544
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Imaging crossing fibers in mouse, pig, monkey, and human brain using small-angle X-ray scattering.
Acta biomaterialia
2023
Abstract
Myelinated axons (nerve fibers) efficiently transmit signals throughout the brain via action potentials. Multiple methods that are sensitive to axon orientations, from microscopy to magnetic resonance imaging, aim to reconstruct the brain's structural connectome. As billions of nerve fibers traverse the brain with various possible geometries at each point, resolving fiber crossings is necessary to generate accurate structural connectivity maps. However, doing so with specificity is a challenging task because signals originating from oriented fibers can be influenced by brain (micro)structures unrelated to myelinated axons. X-ray scattering can specifically probe myelinated axons due to the periodicity of the myelin sheath, which yields distinct peaks in the scattering pattern. Here, we show that small-angle X-ray scattering (SAXS) can be used to detect myelinated, axon-specific fiber crossings. We first demonstrate the capability using strips of human corpus callosum to create artificial double- and triple-crossing fiber geometries, and we then apply the method in mouse, pig, vervet monkey, and human brains. We compare results to polarized light imaging (3D-PLI), tracer experiments, and to outputs from diffusion MRI that sometimes fails to detect crossings. Given its specificity, capability of 3-dimensional sampling and high resolution, SAXS could serve as a ground truth for validating fiber orientations derived using diffusion MRI as well as microscopy-based methods. STATEMENT OF SIGNIFICANCE: : To study how the nerve fibers in our brain are interconnected, scientists need to visualize their trajectories, which often cross one another. Here, we show the unique capacity of small-angle X-ray scattering (SAXS) to study these fiber crossings without use of labelling, taking advantage of SAXS's specificity to myelin - the insulating sheath that is wrapped around nerve fibers. We use SAXS to detect double and triple crossing fibers and unveil intricate crossings in mouse, pig, vervet monkey, and human brains. This non-destructive method can uncover complex fiber trajectories and validate other less specific imaging methods (e.g., MRI or microscopy), towards accurate mapping of neuronal connectivity in the animal and human brain.
View details for DOI 10.1016/j.actbio.2023.04.029
View details for PubMedID 37098400
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The Adverse Effects of Climate Change on Congenital Birth Defects.
International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics
2022
View details for DOI 10.1002/ijgo.14542
View details for PubMedID 36321221
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High-resolution hippocampal diffusion tensor imaging of mesial temporal sclerosis in refractory epilepsy.
Epilepsia
2022
Abstract
OBJECTIVE: We explore the possibility of using diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to discern microstructural abnormalities in the hippocampus indicative of mesial temporal sclerosis (MTS) at the subfield level.METHODS: We analyzed data from 57 patients with refractory epilepsy who previously underwent 3.0-T magnetic resonance imaging (MRI) including DTI as a standard part of presurgical workup. We collected information about each subject's seizure semiology, conventional electroencephalography (EEG), high-density EEG, positron emission tomography reports, surgical outcome, and available histopathological findings to assign a final diagnostic category. We also reviewed the radiology MRI report to determine the radiographic category. DTI- and NODDI-based metrics were obtained in the hippocampal subfields.RESULTS: By examining diffusion characteristics among subfields in the final diagnostic categories, we found lower orientation dispersion indices and elevated axial diffusivity in the dentate gyrus in MTS compared to no MTS. By similarly examining among subfields in the different radiographic categories, we found all diffusion metrics were abnormal in the dentate gyrus and CA1. We finally examined whether diffusion imaging would better inform a radiographic diagnosis with respect to the final diagnosis, and found that dentate diffusivity suggested subtle changes that may help confirm a positive radiologic diagnosis.SIGNIFICANCE: The results suggest that diffusion metric analysis at the subfield level, especially in dentate gyrus and CA1, maybe useful for clinical confirmation of MTS.
View details for DOI 10.1111/epi.17330
View details for PubMedID 35751514