<s>
The	O
detective	B-General_Concept
quantum	I-General_Concept
efficiency	I-General_Concept
(	O
often	O
abbreviated	O
as	O
DQE	B-General_Concept
)	O
is	O
a	O
measure	O
of	O
the	O
combined	O
effects	O
of	O
the	O
signal	O
(	O
related	O
to	O
image	O
contrast	O
)	O
and	O
noise	O
performance	O
of	O
an	O
imaging	O
system	O
,	O
generally	O
expressed	O
as	O
a	O
function	O
of	O
spatial	O
frequency	O
.	O
</s>
<s>
This	O
value	O
is	O
used	O
primarily	O
to	O
describe	O
imaging	O
detectors	O
in	O
optical	B-Algorithm
imaging	I-Algorithm
and	O
medical	O
radiography	O
.	O
</s>
<s>
In	O
medical	O
radiography	O
,	O
the	O
DQE	B-General_Concept
describes	O
how	O
effectively	O
an	O
x-ray	O
imaging	O
system	O
can	O
produce	O
an	O
image	O
with	O
a	O
high	O
signal-to-noise	O
ratio	O
(	O
SNR	O
)	O
relative	O
to	O
an	O
ideal	O
detector	O
.	O
</s>
<s>
It	O
is	O
sometimes	O
viewed	O
to	O
be	O
a	O
surrogate	O
measure	O
of	O
the	O
radiation	O
dose	O
efficiency	O
of	O
a	O
detector	O
since	O
the	O
required	O
radiation	O
exposure	O
to	O
a	O
patient	O
(	O
and	O
therefore	O
the	O
biological	O
risk	O
from	O
that	O
radiation	O
exposure	O
)	O
decreases	O
as	O
the	O
DQE	B-General_Concept
is	O
increased	O
for	O
the	O
same	O
image	O
SNR	O
and	O
exposure	O
conditions	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
is	O
also	O
an	O
important	O
consideration	O
for	O
CCDs	O
,	O
especially	O
those	O
used	O
for	O
low-level	O
imaging	O
in	O
light	O
and	O
electron	O
microscopy	O
,	O
because	O
it	O
affects	O
the	O
SNR	O
of	O
the	O
images	O
.	O
</s>
<s>
However	O
,	O
other	O
physical	O
processes	O
may	O
also	O
degrade	O
image	O
quality	O
,	O
and	O
in	O
1946	O
,	O
Albert	O
Rose	O
proposed	O
the	O
concept	O
of	O
a	O
useful	O
quantum	O
efficiency	O
or	O
equivalent	O
quantum	O
efficiency	O
to	O
describe	O
the	O
performance	O
of	O
those	O
systems	O
,	O
which	O
we	O
now	O
call	O
the	O
detective	B-General_Concept
quantum	I-General_Concept
efficiency	I-General_Concept
.	O
</s>
<s>
Early	O
reviews	O
of	O
the	O
importance	O
and	O
application	O
of	O
the	O
DQE	B-General_Concept
were	O
given	O
by	O
Zweig	O
and	O
Jones	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
was	O
introduced	O
to	O
the	O
medical-imaging	O
community	O
by	O
Shaw	O
for	O
the	O
description	O
of	O
x-ray	O
film-screen	O
systems	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
is	O
the	O
ratio	O
of	O
what	O
an	O
image	O
is	O
worth	O
to	O
what	O
it	O
cost	O
in	O
terms	O
of	O
numbers	O
of	O
Poisson-distributed	O
quanta	O
:	O
</s>
<s>
In	O
this	O
sense	O
the	O
DQE	B-General_Concept
describes	O
how	O
effectively	O
an	O
imaging	O
system	O
captures	O
the	O
information	O
content	O
available	O
in	O
an	O
x-ray	O
image	O
relative	O
to	O
an	O
ideal	O
detector	O
.	O
</s>
<s>
This	O
is	O
critically	O
important	O
in	O
x-ray	O
medical	O
imaging	O
as	O
it	O
tells	O
us	O
that	O
radiation	O
exposures	O
to	O
patients	O
can	O
only	O
be	O
kept	O
as	O
low	O
as	O
possible	O
if	O
the	O
DQE	B-General_Concept
is	O
made	O
as	O
close	O
to	O
unity	O
as	O
possible	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
the	O
DQE	B-General_Concept
is	O
widely	O
accepted	O
in	O
regulatory	O
,	O
commercial	O
,	O
scientific	O
and	O
medical	O
communities	O
as	O
a	O
fundamental	O
measure	O
of	O
detector	O
performance	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
is	O
generally	O
expressed	O
in	O
terms	O
of	O
Fourier-based	O
spatial	O
frequencies	O
as	O
:	O
</s>
<s>
As	O
this	O
is	O
a	O
Fourier-based	O
method	O
of	O
analysis	O
,	O
it	O
is	O
valid	O
only	O
for	O
linear	O
and	O
shift-invariant	O
imaging	O
systems	O
(	O
analogous	O
to	O
linear	O
and	O
time-invariant	O
system	O
theory	O
but	O
replacing	O
time	O
invariance	O
with	O
spatial-shift	O
invariance	O
)	O
involving	O
wide-sense	O
stationary	O
or	O
wide-sense	O
cyclostationary	O
noise	O
processes	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
can	O
often	O
be	O
modelled	O
theoretically	O
for	O
particular	O
imaging	O
systems	O
using	O
cascaded	O
linear-systems	O
theory	O
.	O
</s>
<s>
The	O
DQE	B-General_Concept
is	O
often	O
expressed	O
in	O
alternate	O
forms	O
that	O
are	O
equivalent	O
if	O
care	O
is	O
used	O
to	O
interpret	O
terms	O
correctly	O
.	O
</s>
<s>
resulting	O
in	O
the	O
popularized	O
interpretation	O
of	O
the	O
DQE	B-General_Concept
being	O
equal	O
to	O
the	O
ratio	O
of	O
the	O
squared	O
output	O
SNR	O
to	O
the	O
squared	O
input	O
SNR	O
:	O
</s>
<s>
A	O
report	O
by	O
the	O
International	O
Electrotechnical	O
Commission	O
(	O
IEC	O
62220-1	O
)	O
was	O
developed	O
in	O
an	O
effort	O
to	O
standardize	O
methods	O
and	O
algorithms	O
required	O
to	O
measure	O
the	O
DQE	B-General_Concept
of	O
digital	O
x-ray	O
imaging	O
systems	O
.	O
</s>
<s>
It	O
's	O
the	O
combination	O
of	O
very	O
low	O
noise	O
and	O
superior	O
contrast	O
performance	O
that	O
allows	O
some	O
digital	O
x-ray	O
systems	O
to	O
offer	O
such	O
significant	O
improvements	O
in	O
the	O
detectability	O
of	O
low-contrast	O
objects	O
-	O
a	O
quality	O
that	O
is	O
best	O
quantified	O
by	O
a	O
single	O
parameter	O
,	O
the	O
DQE	B-General_Concept
.	O
</s>
<s>
As	O
one	O
medical	O
physics	O
expert	O
recently	O
reported	O
,	O
The	O
DQE	B-General_Concept
has	O
become	O
the	O
de	O
facto	O
benchmark	O
in	O
the	O
comparison	O
of	O
existing	O
and	O
emerging	O
x-ray	O
detector	O
technologies	O
.	O
</s>
<s>
DQE	B-General_Concept
especially	O
affects	O
one	O
's	O
ability	O
to	O
view	O
small	O
,	O
low-contrast	O
objects	O
.	O
</s>
<s>
Even	O
if	O
a	O
digital	O
system	O
has	O
very	O
high	O
LSR	O
,	O
it	O
ca	O
n't	O
take	O
advantage	O
of	O
the	O
resolution	O
if	O
it	O
has	O
low	O
DQE	B-General_Concept
,	O
which	O
prevents	O
the	O
detection	O
of	O
very	O
small	O
objects	O
.	O
</s>
<s>
A	O
study	O
comparing	O
film/screen	O
and	O
digital	O
imaging	O
demonstrates	O
that	O
a	O
digital	O
system	O
with	O
high	O
DQE	B-General_Concept
can	O
improve	O
one	O
's	O
ability	O
to	O
detect	O
small	O
,	O
low-contrast	O
objects	O
–	O
even	O
though	O
the	O
digital	O
system	O
may	O
have	O
substantially	O
lower	O
Limiting	O
Spatial	O
Resolution	O
(	O
LSR	O
)	O
than	O
film	O
.	O
</s>
<s>
Reducing	O
radiation	O
dose	O
is	O
another	O
potential	O
advantage	O
of	O
digital	O
x-ray	O
technology	O
;	O
and	O
high	O
DQE	B-General_Concept
should	O
make	O
significant	O
contributions	O
to	O
this	O
equation	O
.	O
</s>
<s>
Compared	O
with	O
film/screen	O
imaging	O
,	O
a	O
digital	O
detector	O
with	O
high	O
DQE	B-General_Concept
has	O
the	O
potential	O
to	O
deliver	O
significant	O
object-detectability	O
improvements	O
at	O
an	O
equivalent	O
dose	O
,	O
or	O
to	O
permit	O
object	O
detectability	O
comparable	O
to	O
film	O
's	O
at	O
reduced	O
dose	O
.	O
</s>
<s>
Equally	O
important	O
,	O
high	O
DQE	B-General_Concept
provides	O
the	O
requisite	O
foundation	O
for	O
advanced	O
digital	O
applications	O
-	O
dual-energy	O
imaging	O
,	O
tomosynthesis	O
,	O
and	O
low-dose	O
fluoro	O
,	O
for	O
instance	O
.	O
</s>
<s>
Combined	O
with	O
advanced	O
image-processing	O
algorithms	O
and	O
fast	O
acquisition	O
and	O
readout	O
capability	O
,	O
high	O
DQE	B-General_Concept
is	O
key	O
to	O
making	O
such	O
applications	O
as	O
these	O
clinically	O
practical	O
in	O
the	O
years	O
to	O
come	O
.	O
</s>
