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Magnetic resonance imaging - Wikipedia
by: morpheus
Magnetic
resonance
imaging
(MRI)
is
a
medical
imaging
technique
used
in
radiology
to
form
pictures
of
the
anatomy
and
the
physiological
processes
of
the
body.
MRI
scanners
use
strong
magnetic
fields,
magnetic
field
gradients,
and
radio
waves
to
generate
images
of
the
organs
in
the
body.
MRI
does
not
involve
X-rays
or
the
use
of
ionizing
radiation,
which
distinguishes
it
from
CT
or
CAT
scans
and
PET
scans.
Magnetic
resonance
imaging
is
a
medical
application
of
nuclear
magnetic
resonance
(NMR).
NMR
can
also
be
used
for
imaging
in
other
NMR
applications
such
as
NMR
spectroscopy.
While the hazards of X-rays are now well controlled in most medical contexts, an MRI scan may still be seen as a better choice than a CT scan. MRI is widely used in hospitals and clinics for medical diagnosis, staging of disease and follow-up without exposing the body to radiation. An MRI may yield different information compared with CT. There may be risks and discomfort associated with MRI scans. Compared with CT scans, MRI scans typically take longer and are louder, and they usually need the subject to enter a narrow, confining tube. In addition, people with some medical implants or other non-removable metal inside the body may be unable to undergo an MRI examination safely.
MRI was originally called NMRI (nuclear magnetic resonance imaging), but "nuclear" was dropped to avoid negative associations.[1] Certain atomic nuclei are able to absorb and emit radio frequency energy when placed in an external magnetic field. In clinical and research MRI, hydrogen atoms are most often used to generate a detectable radio-frequency signal that is received by antennas in close proximity to the anatomy being examined. Hydrogen atoms are naturally abundant in people and other biological organisms, particularly in water and fat. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite the nuclear spin energy transition, and magnetic field gradients localize the signal in space. By varying the parameters of the pulse sequence, different contrasts may be generated between tissues based on the relaxation properties of the hydrogen atoms therein.
-from, https://en.wikipedia.org/wiki/Magnetic_resonance_imaging
While the hazards of X-rays are now well controlled in most medical contexts, an MRI scan may still be seen as a better choice than a CT scan. MRI is widely used in hospitals and clinics for medical diagnosis, staging of disease and follow-up without exposing the body to radiation. An MRI may yield different information compared with CT. There may be risks and discomfort associated with MRI scans. Compared with CT scans, MRI scans typically take longer and are louder, and they usually need the subject to enter a narrow, confining tube. In addition, people with some medical implants or other non-removable metal inside the body may be unable to undergo an MRI examination safely.
MRI was originally called NMRI (nuclear magnetic resonance imaging), but "nuclear" was dropped to avoid negative associations.[1] Certain atomic nuclei are able to absorb and emit radio frequency energy when placed in an external magnetic field. In clinical and research MRI, hydrogen atoms are most often used to generate a detectable radio-frequency signal that is received by antennas in close proximity to the anatomy being examined. Hydrogen atoms are naturally abundant in people and other biological organisms, particularly in water and fat. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite the nuclear spin energy transition, and magnetic field gradients localize the signal in space. By varying the parameters of the pulse sequence, different contrasts may be generated between tissues based on the relaxation properties of the hydrogen atoms therein.
-from, https://en.wikipedia.org/wiki/Magnetic_resonance_imaging
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