ORCID Profile
0000-0003-1692-5115
Current Organisation
CSIRO Australian e-Health Research Centre
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 25-05-2016
DOI: 10.1002/MRM.26281
Abstract: Magnetic susceptibility is a physical property of matter that varies depending on chemical composition and abundance of different molecular species. Interest is growing in mapping of magnetic susceptibility in the human brain using magnetic resonance imaging techniques, but the influences affecting the mapped values are not fully understood. We performed quantitative susceptibility mapping on 7 Tesla (T) multiple echo time gradient recalled echo data and evaluated the trend in 10 regions of the human brain. Temporal plots of susceptibility were performed in the caudate, pallidum, putamen, thalamus, insula, red nucleus, substantia nigra, internal capsule, corpus callosum, and fornix. We implemented an existing three compartment signal model and used optimization to fit the experimental result to assess the influences that could be responsible for our findings. The temporal trend in susceptibility is different for different brain regions, and subsegmentation of specific regions suggests that differences are likely to be attributable to variations in tissue structure and composition. Using a signal model, we verified that a nonlinear temporal behavior in experimentally computed susceptibility within imaging voxels may be the result of the heterogeneous composition of tissue properties. Decomposition of voxel constituents into meaningful parameters may lead to informative measures that reflect changes in tissue microstructure. Magn Reson Med 77:1946–1958, 2017. © 2016 International Society for Magnetic Resonance in Medicine
Publisher: University of Queensland Library
Date: 2019
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.MRI.2019.05.011
Abstract: Ultra-high field magnetic resonance imaging data obtained using a multi-echo gradient echo sequence has been shown to contain information on tissue microstructure. Quantitative assessment of water fraction, relaxation time and frequency shift using multi-compartment signal modelling may help improve our understanding of diseases and disorders affecting the human brain. In this study, we explored tissue microstructure information by analysing voxel compartment water fraction and frequency shifts derived from 7 T multi-echo gradient recalled echo MRI data. We aimed to test whether the parameters of a three compartment model could distinguish the normal cortex from the cortex affected by focal cortical dysplasia. We compartmentalised normal and dysplastic cortical regions in patients diagnosed with focal cortical dysplasia. We found the frequency shift parameter of the shortest T
Publisher: SciELO Agencia Nacional de Investigacion y Desarrollo (ANID)
Date: 2013
Publisher: Elsevier BV
Date: 2020
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.EPLEPSYRES.2022.107039
Abstract: Epilepsy surgery is the best therapeutic option for patients with drug-resistant focal epilepsy. During presurgical investigation, interictal spikes can provide important information on eligibility, lateralisation and localisation of the surgical target. However, their relationship to epileptogenic tissue is variable. Interictal spikes with concurrent high-frequency oscillations (HFOs) have been postulated to reflect epileptogenic tissue more reliably. Here, we studied the voltage distribution of scalp-recorded spikes with and without concurrent HFO and identified their respective haemodynamic correlates using simultaneous electroencephalography and functional Magnetic Resonance Imaging (EEG-fMRI). The scalp topography of spikes with and without concurrent HFOs were assessed in 31 consecutive patients with focal drug-resistant epilepsy who showed interictal spikes during presurgical evaluation. Simultaneous EEG-fMRI was then used in 17 patients with spikes and concurrent HFOs. Haemodynamic changes were obtained from the spatial correlation between the patient-specific voltage map of each spike population and the intra-scanner EEG. The haemodynamic response of spikes with and without HFOs were compared in terms of their spatial similarity, strength, the distance between activation peaks and concordance with interictal localisation. Twenty-five patients showed spikes with and without concurrent HFOs. Among patients with both types of spikes, most spikes were not associated with HFOs (p < 0.0001, Mann-Whitney test). Twenty of the 25 patients showed an average of 8 ± 6 (standard deviation) electrodes with significant voltage differences (p = 0.025, permutation test corrected for multiple comparisons) on scalp electrodes within and distant to the spike field. Comparing the haemodynamic response between both spike populations, we found no significant differences in the peak strength (p = 0.71, Mann-Whitney test), spatial distribution (p = 0.113, One-s le Wilcoxon test) and distance between activation peaks (p = 0.5, One-s le Wilcoxon test), with all peaks being co-localised in the same lobe. Our data showed that spikes with and without HFOs have different scalp voltage distributions. However, when assessing the haemodynamic changes of each spike type, we found that both elicit similar haemodynamic changes and share high spatial similarity suggesting that the epileptic networks of spikes with and without HFOs have the same underlying neural substrate.
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.NEUROIMAGE.2013.09.030
Abstract: We describe the visualization of the barrel cortex of the primary somatosensory area (S1) of ex vivo adult mouse brain with short-tracks track density imaging (stTDI). stTDI produced much higher definition of barrel structures than conventional fractional anisotropy (FA), directionally-encoded color FA maps, spin-echo T1- and T2-weighted imaging and gradient echo T1/T2*-weighted imaging. 3D high angular resolution diffusion imaging (HARDI) data were acquired at 48 micron isotropic resolution for a (3mm)(3) block of cortex containing the barrel field and reconstructed using stTDI at 10 micron isotropic resolution. HARDI data were also acquired at 100 micron isotropic resolution to image the whole brain and reconstructed using stTDI at 20 micron isotropic resolution. The 10 micron resolution stTDI maps showed exceptionally clear delineation of barrel structures. In idual barrels could also be distinguished in the 20 micron stTDI maps but the septa separating the in idual barrels appeared thicker compared to the 10 micron maps, indicating that the ability of stTDI to produce high quality structural delineation is dependent upon acquisition resolution. Close homology was observed between the barrel structure delineated using stTDI and reconstructed histological data from the same s les. stTDI also detects barrel deletions in the posterior medial barrel sub-field in mice with infraorbital nerve cuts. The results demonstrate that stTDI is a novel imaging technique that enables three-dimensional characterization of complex structures such as the barrels in S1 and provides an important complementary non-invasive imaging tool for studying synaptic connectivity, development and plasticity of the sensory system.
No related grants have been discovered for Javier Urriola.