<s>
It	O
is	O
a	O
problem	O
which	O
can	O
be	O
explored	O
from	O
several	O
points	O
of	O
view	O
—	O
as	O
a	O
deconvolution	B-Algorithm
problem	O
,	O
a	O
modeling	O
problem	O
,	O
an	O
estimation	O
problem	O
,	O
or	O
an	O
interpolation	B-Algorithm
problem	O
.	O
</s>
<s>
The	O
problem	O
of	O
reconstruction	O
form	O
projections	O
has	O
arisen	O
independently	O
in	O
a	O
large	O
number	O
of	O
scientific	O
fields	O
,	O
since	O
it	O
is	O
widely	O
applied	O
in	O
areas	O
such	O
as	O
medical	B-Application
imaging	I-Application
,	O
geophysical	O
tomography	O
,	O
industrial	O
radiography	O
and	O
so	O
on	O
.	O
</s>
<s>
Given	O
the	O
projection-slice	B-Algorithm
theorem	I-Algorithm
,	O
,	O
the	O
slice	O
of	O
the	O
Fourier	O
transform	O
of	O
at	O
angle	O
theta	O
,	O
is	O
equivalent	O
to	O
,	O
the	O
Fourier	O
Transform	O
of	O
the	O
projection	O
.	O
</s>
<s>
In	O
MRI	O
,	O
energy	O
from	O
an	O
oscillating	O
magnetic	O
field	O
is	O
temporarily	O
applied	O
to	O
the	O
patient	O
at	O
the	O
appropriate	O
resonance	B-Application
frequency	O
.	O
</s>
<s>
The	O
protons	B-Application
(	O
hydrogen	O
atoms	O
)	O
emit	O
a	O
radio	O
frequency	O
signal	O
which	O
is	O
measured	O
by	O
a	O
receiving	O
coil	O
.	O
</s>
