<s>
Radiofrequency	B-Algorithm
coils	I-Algorithm
(	O
RF	O
coils	O
)	O
are	O
the	O
receivers	O
,	O
and	O
sometimes	O
also	O
the	O
transmitters	O
,	O
of	O
radiofrequency	O
(	O
RF	O
)	O
signals	O
in	O
equipment	O
used	O
in	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	B-Algorithm
)	O
.	O
</s>
<s>
The	O
MR	O
signal	O
in	O
MRI	B-Algorithm
is	O
produced	O
by	O
the	O
process	O
of	O
resonance	O
,	O
which	O
is	O
the	O
result	O
of	O
radiofrequency	O
pulses	O
.	O
</s>
<s>
Atomic	O
nuclei	O
of	O
interest	O
in	O
MRI	B-Algorithm
studies	O
have	O
their	O
own	O
resonant	O
frequencies	O
,	O
in	O
the	O
radiofrequency	O
portion	O
of	O
the	O
electromagnetic	O
spectrum	O
.	O
</s>
<s>
Although	O
the	O
electromagnetic	O
fields	O
produced	O
by	O
the	O
transmitting	O
coil	O
are	O
in	O
the	O
RF	O
range	O
of	O
tens	O
of	O
megahertz	O
(	O
often	O
in	O
the	O
shortwave	O
radio	O
portion	O
of	O
the	O
electromagnetic	O
spectrum	O
)	O
at	O
powers	O
usually	O
exceeding	O
the	O
highest	O
powers	O
used	O
by	O
amateur	O
radio	O
,	O
there	O
is	O
very	O
little	O
RF	O
interference	O
produced	O
by	O
the	O
MRI	B-Algorithm
machine	O
.	O
</s>
<s>
The	O
reason	O
for	O
this	O
is	O
that	O
the	O
MRI	B-Algorithm
is	O
a	O
very	O
poor	O
radio	O
transmitter	O
,	O
and	O
is	O
without	O
an	O
antenna	O
.	O
</s>
<s>
The	O
RF	O
frequency	O
electromagnetic	O
field	O
produced	O
in	O
the	O
"	O
transmitting	O
coil	O
"	O
is	O
a	O
magnetic	O
near-field	B-Algorithm
with	O
very	O
little	O
associated	O
changing	O
electric	O
field	O
component	O
(	O
such	O
as	O
all	O
conventional	O
radio	O
wave	O
transmissions	O
have	O
)	O
.	O
</s>
<s>
Thus	O
,	O
the	O
high-powered	O
electromagnetic	O
field	O
produced	O
in	O
the	O
MRI	B-Algorithm
transmitter	O
coil	O
does	O
not	O
produce	O
much	O
electromagnetic	O
radiation	O
at	O
its	O
RF	O
frequency	O
,	O
and	O
the	O
RF	O
power	O
is	O
confined	O
to	O
the	O
coil	O
space	O
and	O
not	O
radiated	O
as	O
"	O
radio	O
waves.	O
"	O
</s>
<s>
Thus	O
,	O
the	O
transmitting	O
coil	O
is	O
a	O
good	O
EM	O
near-field	B-Algorithm
generator	O
at	O
radio	O
frequency	O
,	O
but	O
a	O
poor	O
EM	O
radiation	O
transmitter	O
at	O
radio	O
frequency	O
.	O
</s>
<s>
MRI	B-Algorithm
scanners	O
are	O
generally	O
situated	O
in	O
metal	O
mesh	O
lined	O
rooms	O
which	O
act	O
as	O
Faraday	O
cages	O
.	O
)	O
</s>
<s>
RF	O
coils	O
for	O
MRI	B-Algorithm
can	O
be	O
grouped	O
into	O
two	O
different	O
classes	O
:	O
volume	O
coils	O
and	O
surface	O
coils	O
.	O
</s>
<s>
Most	O
clinical	O
MRI	B-Algorithm
scanners	O
include	O
a	O
built	O
in	O
volume	O
coil	O
to	O
perform	O
whole-body	O
imaging	O
,	O
and	O
smaller	O
volume	O
coils	O
have	O
been	O
constructed	O
for	O
the	O
head	O
and	O
other	O
extremities	O
.	O
</s>
<s>
The	O
condition	O
to	O
attain	O
a	O
high	O
RF	O
magnetic	O
field	O
homogeneity	O
is	O
to	O
approximate	O
spatial	O
cosine	O
current	O
distribution	O
in	O
radiofrequency	B-Algorithm
coil	I-Algorithm
.	O
</s>
