<s>
T2*	B-Algorithm
-weighted	I-Algorithm
imaging	I-Algorithm
is	O
an	O
MRI	B-Algorithm
sequence	I-Algorithm
to	O
quantify	O
observable	O
or	O
effective	B-Algorithm
T2	I-Algorithm
(	O
T2*	B-Algorithm
or	O
"	O
T2-star	B-Algorithm
"	O
)	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	I-Algorithm
imaging	I-Algorithm
is	O
built	O
from	O
the	O
basic	O
physics	B-Algorithm
of	I-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
where	O
there	O
is	O
spin	B-Algorithm
–	I-Algorithm
spin	I-Algorithm
relaxation	I-Algorithm
,	O
that	O
is	O
,	O
the	O
transverse	O
component	O
of	O
the	O
magnetization	O
vector	O
exponentially	O
decays	O
towards	O
its	O
equilibrium	O
value	O
.	O
</s>
<s>
It	O
is	O
characterized	O
by	O
the	O
spin	B-Algorithm
–	I-Algorithm
spin	I-Algorithm
relaxation	I-Algorithm
time	O
,	O
known	O
as	O
2	O
.	O
</s>
<s>
The	O
corresponding	O
transverse	O
relaxation	O
time	O
constant	O
is	O
thus	O
T2*	B-Algorithm
,	O
which	O
is	O
usually	O
much	O
smaller	O
than	O
T2	O
.	O
</s>
<s>
Unlike	O
T2	O
,	O
T2*	B-Algorithm
is	O
influenced	O
by	O
magnetic	O
field	O
gradient	O
irregularities	O
.	O
</s>
<s>
The	O
T2*	B-Algorithm
relaxation	O
time	O
is	O
always	O
shorter	O
than	O
the	O
T2	B-Algorithm
relaxation	I-Algorithm
time	O
and	O
is	O
typically	O
milliseconds	O
for	O
water	O
samples	O
in	O
imaging	O
magnets	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	I-Algorithm
imaging	I-Algorithm
can	O
be	O
created	O
as	O
a	O
postexcitation	O
refocused	O
gradient	O
echo	O
(	O
GRE	O
)	O
sequence	O
with	O
small	O
flip	O
angle	O
.	O
</s>
<s>
The	O
sequence	O
of	O
gradient	O
echo	O
T2*	B-Algorithm
-weighted	I-Algorithm
imaging	I-Algorithm
(	O
GRE	O
T2*WI	O
)	O
requires	O
a	O
high	O
uniformity	O
of	O
the	O
magnetic	O
field	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	O
sequences	O
are	O
used	O
to	O
detect	O
deoxygenated	O
hemoglobin	O
,	O
methemoglobin	O
,	O
or	O
hemosiderin	O
in	O
lesions	O
and	O
tissues	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	O
GRE	O
sequences	O
can	O
detect	O
microhemorrhages	O
as	O
seen	O
in	O
most	O
vestibular	O
schwannomas	O
,	O
thereby	O
differentiating	O
them	O
from	O
meningiomas	O
.	O
</s>
<s>
The	O
T2*	B-Algorithm
-weighted	O
GRE	O
sequence	O
can	O
detect	O
a	O
"	O
middle	O
cerebral	O
artery	O
susceptibility	O
sign	O
"	O
,	O
which	O
is	O
a	O
dark	O
linear	O
filling	O
defect	O
that	O
is	O
wider	O
than	O
the	O
corresponding	O
artery	O
on	O
the	O
contralateral	O
side	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	O
sequences	O
are	O
very	O
useful	O
for	O
evaluation	O
of	O
articular	O
cartilages	O
and	O
ligaments	O
because	O
a	O
relatively	O
long	O
T2*	B-Algorithm
makes	O
the	O
articular	O
cartilage	O
becomes	O
more	O
hyperintense	O
,	O
while	O
bone	O
becomes	O
hypointense	O
.	O
</s>
<s>
T2*	B-Algorithm
-weighted	O
sequences	O
can	O
be	O
used	O
with	O
MRI	B-Algorithm
contrast	I-Algorithm
,	O
mainly	O
ferucarbotran	O
or	O
superparamagnetic	O
iron	O
oxide	O
(	O
SPIO	O
)	O
,	O
to	O
depict	O
liver	O
lesions	O
.	O
</s>
