Aminuddin, Niferiti
(2023)
Fractal analysis approach in the
characterisation of cerebrovascular
complexity in asymptomatic cerebral
small vessel disease.
PhD thesis, Universiti Sains Malaysia.
Abstract
Cerebral small vessel disease (CSVD) refers to a spectrum of clinical and
neuroimaging findings caused by pathological damage of small vessels of the cerebral
parenchyma. Cerebral white matter hyperintensity (WMH) is one of the commonest
neuroimaging findings of CSVD. Often, CSVD is diagnosed once the symptoms
developed. Detection of the underlying vascular structural changes might facilitate
early disease risk stratification and disease monitoring as vascular alteration precedes
cerebral parenchymal injury. Of interest, fractal analysis allows us to quantitatively
measure the complexity of the cerebral vascular structure in terms of fractal dimension
(Df). The cerebral vascular Df changes are indicative of inefficient tissues perfusion
which renders the cerebral parenchyma vulnerable to damage. The aim of this study is
to explore a novel vascular neuroimaging marker of asymptomatic CSVD by
characterising the complexity of the circle of Willis (CoW) and its tributaries as
measured by Df. An exploratory cross-sectional study was conducted involving 22
subjects of age between 25 - 75 years old with low to moderate QRISK2 score who
underwent magnetic resonance imaging/angiography (MRI/MRA) examination.
These subjects presented with or without WMH. The cerebral vascular complexity of
the MRA image was characterised using Df. The cerebral vascular Df was compared
between asymptomatic subjects with (WMH+; n = 8) and without cerebral WMH
(WMH-; n = 14). Furthermore, cerebral vascular Df was also compared between asymptomatic subjects with both CSVD risk factors and cerebral WMH (RF+ & WMH+; n = 6), subjects with CSVD risk factors only (RF+ & WMH-; n = 5), and
subjects without both CSVD risk factors and cerebral WMH (RF- & WMH-; n = 9).
Simple linear regression (SLR) was performed between QRISK2 score and cerebral
vascular Df. Mean cerebral vascular Df was significantly lower in the WMH+ group
than WMH- group. Moreover, the mean cerebral vascular Df of the RF+ & WMH- and
RF+ & WMH+ groups were significantly lower than RF- & WMH- group. The SLR
model had indicated that increased QRISK2 score significantly predicted reduction in
cerebral vascular Df. The cerebral vascular Df was reduced in the subjects with CSVD
risk factors and asymptomatic CSVD subjects with WMH. The SLR model had
indicated that QRISK2 score significantly predicted cerebral vascular Df. The results
indicate that cerebral vascular Df is a promising biomarker of asymptomatic CSVD
subjects with WMH. Larger-scaled studies are required to explore its potential in a
broader population setting.
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