<s>
The	O
partial	B-Algorithm
volume	I-Algorithm
effect	I-Algorithm
can	O
be	O
defined	O
as	O
the	O
loss	O
of	O
apparent	O
activity	O
in	O
small	O
objects	O
or	O
regions	O
because	O
of	O
the	O
limited	O
resolution	O
of	O
the	O
imaging	O
system	O
.	O
</s>
<s>
It	O
occurs	O
in	O
medical	B-Application
imaging	I-Application
and	O
more	O
generally	O
in	O
biological	O
imaging	O
such	O
as	O
positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
and	O
single-photon	O
emission	O
computed	O
tomography	O
(	O
SPECT	O
)	O
.	O
</s>
<s>
Partial	B-Algorithm
volume	I-Algorithm
loss	O
alone	O
occurs	O
only	O
when	O
the	O
surrounding	O
activity	O
of	O
the	O
object	O
or	O
region	O
is	O
zero	O
,	O
</s>
<s>
And	O
the	O
loss	O
of	O
activity	O
in	O
the	O
object	O
generally	O
involves	O
an	O
increase	O
in	O
activity	O
in	O
adjacent	O
regions	O
,	O
which	O
are	O
considered	O
outside	O
the	O
object	O
(	O
i.e.	O
,	O
spillover	B-Algorithm
)	O
.	O
</s>
<s>
For	O
a	O
small	O
object	O
(	O
e.g.	O
,	O
a	O
voxel	B-Algorithm
)	O
or	O
an	O
object	O
of	O
size	O
comparable	O
to	O
the	O
spatial	O
resolution	O
of	O
the	O
imaging	O
system	O
,	O
the	O
observed	O
activity	O
is	O
the	O
sum	O
of	O
activity	O
due	O
to	O
partial	B-Algorithm
volume	I-Algorithm
loss	O
plus	O
spillover	B-Algorithm
from	O
adjacent	O
regions	O
.	O
</s>
<s>
The	O
method	O
to	O
correct	O
for	O
the	O
partial	B-Algorithm
volume	I-Algorithm
effect	I-Algorithm
is	O
referred	O
to	O
as	O
partial	B-Algorithm
volume	I-Algorithm
correction	O
(	O
see	O
)	O
.	O
</s>
