Search results for "Magneettikuvaus"
showing 10 items of 53 documents
Shift-Invariant Canonical Polyadic Decomposition of Complex-Valued Multi-Subject fMRI Data with a Phase Sparsity Constraint
2020
Canonical polyadic decomposition (CPD) of multi-subject complex-valued fMRI data can be used to provide spatially and temporally shared components among groups with both magnitude and phase information. However, the CPD model is not well formulated due to the large subject variability in the spatial and temporal modalities, as well as the high noise level in complex-valued fMRI data. Considering that the shift-invariant CPD can model temporal variability across subjects, we propose to further impose a phase sparsity constraint on the shared spatial maps to denoise the complex-valued components and to model the inter-subject spatial variability as well. More precisely, subject-specific time …
Knowledge discovery using diffusion maps
2013
Aberrant brain functional networks in type 2 diabetes mellitus: A graph theoretical and support-vector machine approach
2022
ObjectiveType 2 diabetes mellitus (T2DM) is a high risk of cognitive decline and dementia, but the underlying mechanisms are not yet clearly understood. This study aimed to explore the functional connectivity (FC) and topological properties among whole brain networks and correlations with impaired cognition and distinguish T2DM from healthy controls (HC) to identify potential biomarkers for cognition abnormalities.MethodsA total of 80 T2DM and 55 well-matched HC were recruited in this study. Subjects’ clinical data, neuropsychological tests and resting-state functional magnetic resonance imaging data were acquired. Whole-brain network FC were mapped, the topological characteristics were ana…
Magneettikuvaus, ultraääni ja ihopoimumittaus ihonalaisen rasvakudoksen mittareina
2007
Kehon koostumuksen mittausmenetelmät jaetaan kenttä- ja laboratoriomenetelmiin.Laboratoriomenetelmiä ovat vedenalaispunnitus, kaksienergisen röntgensäteen absorptiometria(DXA), magneettikuvaus ja ultraääni, ja kenttämenetelmiä ovat esimerkiksiihopoimumittaus, biosähköinen impedanssi, antropometria ja infrapunasäde. Laboratoriomenetelmätovat yleensä tarkempia, kalliimpia ja vaativat erikoisolosuhteet toisinkuin kenttämenetelmät. Tutkimuksen tarkoituksena oli vertailla magneettikuvaa, ultraääntäja ihopoimumittausta ihonalaisen rasvakerroksen mittarina uloimman reisilihaksenkohdalta (m. vastus lateralis) 19-35-vuotiailla kuntosaliharjoittelemattomilla miehillä.Koehenkilöiltä mitattiin paino ja…
Identification of proprioceptive thalamocortical tracts in children: comparison of fMRI, MEG, and manual seeding of probabilistic tractography
2022
Publisher Copyright: © The Author(s) 2022. Published by Oxford University Press. Studying white matter connections with tractography is a promising approach to understand the development of different brain processes, such as proprioception. An emerging method is to use functional brain imaging to select the cortical seed points for tractography, which is considered to improve the functional relevance and validity of the studied connections. However, it is unknown whether different functional seeding methods affect the spatial and microstructural properties of the given white matter connection. Here, we compared functional magnetic resonance imaging, magnetoencephalography, and manual seedin…
Anxiety reduction with music and tempo synchronization on magnetic resonance imaging patients
2017
Anxiety and claustrophobic reactions in MRI examinations cause unintentional movements, and such motion artifacts lead to interpretation problems. Furthermore, requested anesthesia makes the process costly. A total of 60 outpatients were examined in the Diagnostic Centre of Pécs, Hungary, to test whether synchronizing recorded music to the gradient pulsation of the MRI device can improve the sedative effect of the music. The patients were assigned to three groups: a nonmusic (control), an original tempo (random) and a synchronized music (synchronous) group. Results showed a significantly decreased state anxiety level after the MRI examination in the random and synchronous groups as compared…
Consistency of Independent Component Analysis for FMRI
2021
Background Independent component analysis (ICA) has been widely used for blind source separation in the field of medical imaging. However, despite of previous substantial efforts, the stability of ICA components remains a critical issue which has not been adequately addressed, despite numerous previous efforts. Most critical is the inconsistency of some of the extracted components when ICA is run with different model orders (MOs). New Method In this study, a novel method of determining the consistency of component analysis (CoCA) is proposed to evaluate the consistency of extracted components with different model orders. In the method, “consistent components” (CCs) are defined as those whic…
Tensor clustering on outer-product of coefficient and component matrices of independent component analysis for reliable functional magnetic resonance…
2019
Background. Stability of spatial components is frequently used as a post-hoc selection criteria for choosing the dimensionality of an independent component analysis (ICA) of functional magnetic resonance imaging (fMRI) data. Although the stability of the ICA temporal courses differs from that of spatial components, temporal stability has not been considered during dimensionality decisions. New method. The current study aims to (1) develop an algorithm to incorporate temporal course stability into dimensionality selection and (2) test the impact of temporal course on the stability of the ICA decomposition of fMRI data via tensor clustering. Resting state fMRI data were analyzed with two popu…
The relationship between electrophysiological and hemodynamic measures of neural activity varies across picture naming tasks: A multimodal magnetoenc…
2022
Funding Information: This work was financially supported by the Academy of Finland (Finnish Center of Excellence in Computational Inference Research COIN and grants #292334, #294238 to SK; #255349, #315553 to RS; #257576 to JK; #286405 funding for TM), the Sigrid Jusélius Foundation (grant to RS), the Finnish Cultural Foundation (grant to ML), the Swedish Cultural Foundation in Finland (grant to ML), the Maud Kuistila Memorial Foundation (grant to ML), and Aalto Brain Center. Publisher Copyright: Copyright © 2022 Mononen, Kujala, Liljeström, Leppäaho, Kaski and Salmelin. Different neuroimaging methods can yield different views of task-dependent neural engagement. Studies examining the relat…
Mechanical loading influences the lumbar intervertebral disc : A cross‐sectional study in 308 athletes and 71 controls
2021
There is evidence in animal populations that loading and exercise can positively impact the intervertebral disc (IVD). However, there is a paucity of information in humans. We examined the lumbar IVDs in 308 young athletes across six sporting groups (baseball, swimming, basketball, kendo, soccer and running; mean age 19yrs) and 71 non‐athletic controls. IVD status was quantified via the ratio of IVD to vertebral body height (IVD hypertrophy) and ratio of signal intensity in the nucleus to that in the annulus signal (IVD nucleus hydration) on sagittal T2‐weighted MRI. P‐values were adjusted via the false discovery rate method to mitigate false positives. In examining the whole collective, co…