FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2912990936> ?p ?o ?g. }

• W2912990936 abstract "Exchange of oxygen and nutrients between blood and tissue occurs at the capillary level of the blood system. The blood volume flow rate in the capillaries is often referred to as perfusion, and knowledge about perfusion provides important information about the function and viability of the tissue, for example, in patients with ischaemic stroke, cancer, and neurodegenerative diseases.Dynamic susceptibility contrast magnetic resonance imaging (DSC–MRI) is the basic data collection approach used to obtain perfusion information from the studies reported in this doctoral thesis. The approach shows the advantage of providing estimates of not only brain perfusion, or cerebral blood flow (CBF), but also cerebral blood volume (CBV) and mean transit time (MTT). All of these parameters are required for a comprehensive description of microcirculation. When using standard implementations of DSC–MRI image acquisition and post-processing routines, the CBF and CBV values are often overestimated. In DSC–MRI, a contrast agent (CA) bolus is injected intravenously in an arm vein and is subsequently tracked by rapid imaging when passing through the brain. To calculate CBF, CBV, and MTT, CA concentration information from both tissue and blood is required. The main problem of DSC–MRI is estimating reliable CA concentration levels in tissue and artery simultaneously. Relatedly, if transverse relaxivity-based information is used, then the response to the CA, in terms of the change in relaxation rate, ΔR2∗, differs between blood and tissue. Additionally, there is a non-linear dependence on CA concentration in whole blood. Another issue related to estimations of blood concentration is the practical difficulty of finding a voxel containing only blood, implying that the concentration time curve representing blood will be affected by the surrounding tissue, possibly influencing both the shape of the curve and the absolute levels of estimated concentrations. One approach is to obtain CBV estimates with alternative methods, where contrast agent concentration is quantified using the longitudinal relaxation time, T1, or by using a special MRI pulse sequence designed to study the blood contribution to the MRI signal. The information from these additional CBV estimates is used to calibrate the conventional DSC–MRI data. This approach provided perfusion results with the expected absolute levels but showed moderate repeatability and low correlation with arterial spin labelling (ASL), used as a reference perfusion imaging method. Another study included in the context of this doctoral thesis dealt with the issue of partial-volume effects in the voxel selected to represent blood. By rescaling the area under the curve (AUC) of the concentration-versus-time curve measured in an artery (assumed to show the desired shape), with the AUC of a large vein, measured under circumstances more favourable for blood-data registration, CBF and CBV values were calibrated. This method aims primarily to correct for partial volume effects in the blood voxel (i.e. it does not directly address relaxivity issues). An observation of interest in this context was that absolute perfusion levels similar to what was expected from literature data were obtained. Furthermore, the repeatability was more promising using this approach, compared to the ones described above. The phase of the MRI signal is related to the magnetic field strength, which, in turn, is related to the magnetic susceptibility. As the CA alters the magnetic susceptibility, it should, in principle, be possible to obtain information about CA concentration using MRI phase information. This approach was used in three of the studies described in this thesis, for calculation of perfusionrelated parameters in relative and absolute terms. These studies indicated that information about (or related to) magnetic susceptibility is a promising method for estimating CA concentration, whereas a number of methodological issues still need to be resolved or further investigated. It was also shown that the shape of an arterial ΔR2* curve, based on DSC–MRI data, displayed a shape similar to the corresponding curve obtained by using magnetic susceptibility information for assessment of concentration. Thus, the shape of a typical arterial blood concentration curve used in a standard DSC–MRI experiment can probably be regarded reasonably reliable. However, the AUC is likely to be underestimated because of partial-volume effects. (Less)" @default.
• W2912990936 created "2019-02-21" @default.
• W2912990936 creator A5020330698 @default.
• W2912990936 date "2019-02-01" @default.
• W2912990936 modified "2023-09-23" @default.
• W2912990936 title "MRI Perfusion Measurements using Magnetic Susceptibility Effects: : Calibration Approaches and Contrast Agent Quantification" @default.
• W2912990936 hasPublicationYear "2019" @default.
• W2912990936 type Work @default.
• W2912990936 sameAs 2912990936 @default.
• W2912990936 citedByCount "0" @default.
• W2912990936 crossrefType "dissertation" @default.
• W2912990936 hasAuthorship W2912990936A5020330698 @default.
• W2912990936 hasConcept C126838900 @default.
• W2912990936 hasConcept C12722491 @default.
• W2912990936 hasConcept C135691158 @default.
• W2912990936 hasConcept C136229726 @default.
• W2912990936 hasConcept C143409427 @default.
• W2912990936 hasConcept C146957229 @default.
• W2912990936 hasConcept C157767197 @default.
• W2912990936 hasConcept C158846371 @default.
• W2912990936 hasConcept C164705383 @default.
• W2912990936 hasConcept C2989005 @default.
• W2912990936 hasConcept C37557685 @default.
• W2912990936 hasConcept C71924100 @default.
• W2912990936 hasConceptScore W2912990936C126838900 @default.
• W2912990936 hasConceptScore W2912990936C12722491 @default.
• W2912990936 hasConceptScore W2912990936C135691158 @default.
• W2912990936 hasConceptScore W2912990936C136229726 @default.
• W2912990936 hasConceptScore W2912990936C143409427 @default.
• W2912990936 hasConceptScore W2912990936C146957229 @default.
• W2912990936 hasConceptScore W2912990936C157767197 @default.
• W2912990936 hasConceptScore W2912990936C158846371 @default.
• W2912990936 hasConceptScore W2912990936C164705383 @default.
• W2912990936 hasConceptScore W2912990936C2989005 @default.
• W2912990936 hasConceptScore W2912990936C37557685 @default.
• W2912990936 hasConceptScore W2912990936C71924100 @default.
• W2912990936 hasLocation W29129909361 @default.
• W2912990936 hasOpenAccess W2912990936 @default.
• W2912990936 hasPrimaryLocation W29129909361 @default.
• W2912990936 hasRelatedWork W1939083185 @default.
• W2912990936 hasRelatedWork W1964241670 @default.
• W2912990936 hasRelatedWork W1983016275 @default.
• W2912990936 hasRelatedWork W1998684439 @default.
• W2912990936 hasRelatedWork W2002896046 @default.
• W2912990936 hasRelatedWork W2037506613 @default.
• W2912990936 hasRelatedWork W2040481122 @default.
• W2912990936 hasRelatedWork W2046201687 @default.
• W2912990936 hasRelatedWork W2052410524 @default.
• W2912990936 hasRelatedWork W2071086554 @default.
• W2912990936 hasRelatedWork W2076987741 @default.
• W2912990936 hasRelatedWork W2087254727 @default.
• W2912990936 hasRelatedWork W2094429026 @default.
• W2912990936 hasRelatedWork W2300975783 @default.
• W2912990936 hasRelatedWork W2467223444 @default.
• W2912990936 hasRelatedWork W2576934488 @default.
• W2912990936 hasRelatedWork W2625527054 @default.
• W2912990936 hasRelatedWork W2743760829 @default.
• W2912990936 hasRelatedWork W53140849 @default.
• W2912990936 hasRelatedWork W1484798139 @default.
• W2912990936 isParatext "false" @default.
• W2912990936 isRetracted "false" @default.
• W2912990936 magId "2912990936" @default.
• W2912990936 workType "dissertation" @default.