Current developments of white matter connectivity research in Schizophrenia; A study into voxel based versus track based DTI methodology
Summary
Research
in
schizophrenia
has
shown
that
structural
brain
abnormalities
exist
in
patients
with
this
disorder,
but
while
imaging
studies
mostly
pointed
in
the
direction
of
gray
matter
changes,
post‐mortem
studies
were
also
finding
abnormalities
in
neuronal
cytoarchitecture
and
glial
cells.
These
cells
are
highly
important
for
the
protection
and
formation
of
neuronal
axons,
and
defective
glial
cells
can
lead
to
white
matter
changes.
Newly
developed
MRI‐methods
such
as
diffusion
tensor
imaging
(DTI)
are
able
to
investigate
white
matter
changes
in
schizophrenia
in
vivo.
DTI
measures
describe
the
magnitude
and
orientation
of
water
diffusion
and
the
shape
of
the
diffusion
profile
and
are
often
described
with
a
scalar
value
named
the
fractional
anisotropy
(FA).
When
diffusion
weighted
images
are
analyzed
there
are
two
different
techniques
available
to
determine
and
compare
group
differences
in
region‐specific
FA
variations.
Voxel
Based
Morphometry
analysis
is
the
most
straightforward
method
to
look
at
group
differences
between
FA
values.
It
enables
you
to
do
whole
brain
analysis
to
indicate
what
regions
have
variations
in
FA
values
that
exceed
pure
statistical
chance.
This
means
that
it
is
a
broad
but
coarse
method.
Tract‐based
analysis
is
a
method
that
compares
FA
values
of
specific
white
matter
fiber
paths.
An
a
priori
region
of
interest
is
necessary
to
be
able
to
use
this
method.
This
method
increases
the
statistical
power
compared
to
VBM
methods,
which
will
allow
for
more
sensitive
detection
of
FA
group
differences.
In
this
thesis
both
methods
will
be
discussed,
as
well
as
the
current
developments
in
both
fields
in
schizophrenia
research.
Furthermore
research
methods
like
scan
protocol,
voxel
size,
patient
groups
and
VBM
blurring
will
be
compared
to
better
understand
contradicting
or
overlapping
research
results.