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Diffusion tensor magnetic resonance imaging of the brain: Tractography analysis with application in healthy individuals and patients
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. (Neuroradiologi)
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In study 1, thirty-eight healthy controls were used for optimization of the method. Fifteen patients with progressive supranuclear palsy and an equal number of age-matched healthy controls underwent diffusion tensor MRI and were then investigated and compared groupwise.

It was shown that tractography analyses may preferably be performed regionally, such as along the tracts or in different segments of the tracts. Normalization of white matter tracts can be performed using anatomical landmarks.

In study 2, 104 males and 153 females in the age interval 13 to 84 years of age participated as healthy individuals in order to investigate age-related changes with diffusion tensor MRI.

It was shown that spatially differences in age-related changes exist between subdivided segments within white matter tracts. The aging processes within the CB and the IFO vary regionally.

In study 3, 38 human brains were used for investigation of the white matter tract inferior longitudinal fasciculus (ILF) and its subcomponents. Of these, white matter anatomical dissection was performed in 14 post-mortem normal human brains. The remaining 24 brains were investigated in vivo with diffusion tensor MRI in healthy individuals.

It was validated that fibers of the ILF in the occipito-temporal region have a clear, constant and detailed organisation. The anatomical connectivity pattern, and quantitative differences between the ILF subcomponents, confirmed a pivotal role of the ILF.

In study 4, 12 patients with iNPH were included in the study and examined with diffusion tensor at three time points. For comparison, 12 healthy controls, matched by gender and age were also included. Controls were examined with MRI only once.

It was shown that DTI measures differ significantly between patients with iNPH and healthy controls. DTI measures of the CC, the CST and the SLF, correlated to changes in clinical symptoms after shunt surgery.

Deeper knowledge about functions of the brain increases possibilities to take advantages from DTI analyses with tractography. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , p. 62
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1394
Keywords [en]
Magnetic Resonance Imaging, Diffusion Tensor Imaging, Tractography, white matter tracts
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
URN: urn:nbn:se:uu:diva-332596ISBN: 978-91-513-0147-1 (print)OAI: oai:DiVA.org:uu-332596DiVA, id: diva2:1153539
Public defence
2017-12-20, Gustavianum, Auditorium Minus, Akademigatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-11-29 Created: 2017-10-30 Last updated: 2018-03-07
List of papers
1. Spatial analysis of diffusion tensor tractography statistics along the inferior fronto-occipital fasciculus with application in progressive supranuclear palsy
Open this publication in new window or tab >>Spatial analysis of diffusion tensor tractography statistics along the inferior fronto-occipital fasciculus with application in progressive supranuclear palsy
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2013 (English)In: Magnetic Resonance Materials in Physics, Biology and Medicine, ISSN 0968-5243, E-ISSN 1352-8661, Vol. 26, no 6, p. 527-537Article in journal (Refereed) Published
Abstract [en]

The purpose of the study was to develop a method for analysis of diffusion parameters along white matter (WM) tracts, using spatial normalization based on anatomical landmarks, and to introduce the apparent area coefficient (AAC). The method's applicability was tested in the inferior fronto-occipital fasciculus (IFO) in patients with progressive supranuclear palsy (PSP) and healthy controls (HCs). A framework for analysis of diffusion parameters was developed. Spatial normalization of the tracts was performed using anatomical landmarks, to avoid deformations caused by cerebral atrophy. Initially, 38 HCs were used to optimize a threshold for the minimal size of regions that differ between groups. The fractional anisotropy, mean diffusivity, AAC, and the hemispheric asymmetry index (AI), were compared between 11 PSP patients and 15 HCs. The method was feasible for analysis of PSP patients and HCs. The AI showed that the observed hemispheric asymmetry of AAC was significantly larger in PSP patients compared with HCs in small regions of the IFO. The method was successfully employed for analysis of diffusion parameters along the IFO in a patient group. This method can be potentially useful in studies of WM diseases, with or without cerebral atrophy.

Keywords
DTI, Tractography, Inferior fronto-occipital fasciculus, PSP
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-213480 (URN)10.1007/s10334-013-0368-5 (DOI)000327438700003 ()
Available from: 2013-12-30 Created: 2013-12-23 Last updated: 2017-12-06Bibliographically approved
2. Diffusion tensor imaging and tractography of the white matter in normal aging: The rate-of-change differs between segments within tracts
Open this publication in new window or tab >>Diffusion tensor imaging and tractography of the white matter in normal aging: The rate-of-change differs between segments within tracts
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2018 (English)In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 45, p. 113-119, article id S0730-725X(17)30059-0Article in journal (Refereed) Published
Abstract [en]

Knowledge concerning the normal aging of cerebral white matter will improve our understanding of abnormal changes in neurodegenerative diseases. The microstructural basis of white matter maturation and aging can be investigated using diffusion tensor imaging (DTI). Generally, diffusion anisotropy increases during childhood and adolescence followed by a decline in middle age. However, this process is subject to spatial variations between tracts. The aim of this study was to investigate to what extent age-related variations also occur within tracts. DTI parameters were compared between segments of two white matter tracts, the cingulate bundle (CB) and the inferior fronto-occipital fasciculus (IFO), in 257 healthy individuals between 13 and 84years of age. Segments of the CB and the IFO were extracted and parameters for each segment were averaged across the hemispheres. The data was analysed as a function of age. Results show that age-related changes differ both between and within individual tracts. Different age trajectories were observed in all segments of the analysed tracts for all DTI parameters. In conclusion, aging does not affect white matter tracts uniformly but is regionally specific; both between and within white matter tracts.

Keywords
Tractography, Inferior fronto-occipital fasciculus, Cingulum, Aging, White matter degeneration, White matter tract
National Category
Medical and Health Sciences Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-319599 (URN)10.1016/j.mri.2017.03.007 (DOI)000417772500015 ()28359912 (PubMedID)
Available from: 2017-04-06 Created: 2017-04-06 Last updated: 2018-02-19Bibliographically approved
3. Segmentation of the inferior longitudinal fasciculus in the human brain: A white matter dissection and diffusion tensor tractography study.
Open this publication in new window or tab >>Segmentation of the inferior longitudinal fasciculus in the human brain: A white matter dissection and diffusion tensor tractography study.
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2017 (English)In: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, no 1675, p. 102-115, article id S0006-8993(17)30386-4Article in journal (Refereed) Published
Abstract [en]

The inferior longitudinal fascicle (ILF) is one of the major occipital-temporal association pathways. Several studies have mapped its hierarchical segmentation to specific functions. There is, however, no consensus regarding a detailed description of ILF fibre organisation. The aim of this study was to establish whether the ILF has a constant number of subcomponents. A secondary aim was to determine the quantitative diffusion proprieties of each subcomponent and assess their anatomical trajectories and connectivity patterns. A white matter dissection of 14 post-mortem normal human hemispheres was conducted to define the course of the ILF and its subcomponents. These anatomical results were then investigated in 24 right-handed, healthy volunteers using in vivo diffusion tensor imaging (DTI) and streamline tractography. Fractional anisotropy (FA), volume, fibre length and the symmetry coefficient of each fibre group were analysed. In order to show the connectivity pattern of the ILF, we also conducted an analysis of the cortical terminations of each segment. We confirmed that the main structure of the ILF is composed of three constant components reflecting the occipital terminations: the fusiform, the lingual and the dorsolateral-occipital. ILF volume was significantly lateralised to the right. The examined indices of ILF subcomponents did not show any significant difference in lateralisation. The connectivity pattern and the quantitative distribution of ILF subcomponents suggest a pivotal role for this bundle in integrating information from highly specialised modular visual areas with activity in anterior temporal territory, which has been previously shown to be important for memory and emotions.

Keywords
DTT, ILF, Occipital-temporal connectivity, Social cognition, Visual memory, White matter
National Category
Neurology
Identifiers
urn:nbn:se:uu:diva-329751 (URN)10.1016/j.brainres.2017.09.005 (DOI)000413608600011 ()28899757 (PubMedID)
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2018-02-02Bibliographically approved
4. Pre-operative DTI of corticospinal tract, corpus callosum and superior longitudinal fasciculus in patients with idiopathic normal pressure hydrocephalus correlates with changes in clinical findings after shunt surgery
Open this publication in new window or tab >>Pre-operative DTI of corticospinal tract, corpus callosum and superior longitudinal fasciculus in patients with idiopathic normal pressure hydrocephalus correlates with changes in clinical findings after shunt surgery
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(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-332594 (URN)
Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2017-10-30

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