Quantative analysis of brain white matter using diffusion tensor imaging
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Date
2014-12
Authors
Mohd Taib, Nur Hartini
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
This research is concerned with the application of diffusion tensor imaging (DTI) in
the study of leukoaraiosis and normal white matter. Four main objectives outlined in
the study have been achieved. A head phantom was used and a total of 15 normal
subjects and 51 leukoaraiosis subjects participated in the study. A total of 5128 slices
were analysed in this work. Brain imaging was performed using 1.5 Tesla MRI
system.
Feasibility of acquiring DTI data and constructing fiber tracts for
leukoaraiosis study was investigated. Results obtained showed capability of DTI to
distinguish leukoaraiosis from normal white matter. Fiber tractography exhibited a
good structural differentiation of nerve fibers in the white matter region. Acquiring
DTI data and constructing fiber tractography for assessment of leukoaraiosis was
found to be feasible.
Optimum combination of voxel size resolution and b-value for the whole
brain imaging has also been determined. Six protocols which consist of the
combination of various voxel size and b-value were evaluated. Measurement of
signal-to-noise ratio (SNR) and DTI parameter indices was carried out for both
phantom and in-vivo studies. It was found that protocols with voxel 2.5 × 2.5 × 2.5
mm3 give the desired SNR of at least 20. The optimal combination of parameters are
the voxel size of 2.5 × 2.5 × 2.5 mm3 with b-value of 700 s/mm2.
Assessment of leukoaraosis (LA) at different region in the brain using mean
diffusivity (MD) and fractional anisotropy (FA) values were carried out. The MD
and FA values were compared with that of measured at normal appearing brain tissue
(NABT) from leukoaraiosis subjects and normal brain tissue (CONTROL) from
healthy subjects. It was found that LA demonstrated a significantly higher MD and
lower FA as compared to NABT in frontal and occipital white matter areas. No
differences were noted in MD and FA with regard to all white and grey matter
regions between NABT and CONTROL categories. From fibre tractography it was
also found that there is major reduction in the number of neural fibres in
leukoaraiosis subject as compared to normal subject.
Characterization of leukoaraiosis was performed using lesion-to-normal
appearing white matter ratio (LNR). This method is proposed for the first time.
Another new approach is measurement of lesion volume at each specific lesion spot.
Correlation between LNR and lesion volume indicated that LNR is not associated
with the lesion volume. Therefore, it is suggested that the degree of tissue destruction
is not associated with size of the lesion.
Description
Keywords
Diffusion tensor imaging (DTI)