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Unit 21: Medical Physics Applications U21A1: Radiation use in medical diagnosis and treatment
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Unit 21: Medical Physics Applications U21A1: Radiation use in medical diagnosis and treatment
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Unit 21: Medical Physics ApplicationsU21A1: Radiation use in medical diagnosis and treatment.
Resub completely re-written
Non-ionisation radiation
Magnetic resonance of imaging (MRI)
MRI is scanning technique for creating detailed
images of the human body. The scan uses strong
magnetic field, radio frequency waves to create
image that cant seen by CT scans, X- ray or
ultrasound.
Human body is mostly water; the water has a
hydrogen proton which acts as magnet and can be
easily affected by a strong magnetic field. The
different tissue in our body contains different
amount.
MRI scanner interacts with protons in the body. Randomly orientated protons become aligned with
the powerful magnetic field in the bore of the scanner. A rapidly repeating sequence of
radiofrequency pulses, produced by the scanner then causes excitation and resonance of protons. As
each radiofrequency pulse is removed, the protons relax to realign with the magnetic field, and as
they do so they give off radiofrequency signal which is detected by the scanner and transformed into
an image.
To conclude MRI:
To produce image the MRI scan applies strong magnetic field and the proton in our body gets
aligned with the magnetic field.
Then the scanner produce a radio frequency to create varying magnetic field, the proton
absorbs the energy and spins around.
, Unit 21: Medical Physics Applications
U21A1: Radiation use in medical diagnosis and treatment.
When the MRI scan turn off the proton that spin returns to their original spin as they spin
they release the energy they absorb in the form of radio signals and this signals get picked up
by the receiver on the scanner and convert it into image.
Proton in different tissue returns to their normal state at different rate which the scanner uses to
distinguish one tissue from another. For example l-H is found in water and organic molecule while 31-
Phosphurs is found in metabolite, cell membrane, ADP and ATP.
Doctors and technician use the scanner to produce detailed picture of soft tissue and make their
diagnosis from it.
Treatment and diagnosis
MRI scanner can be used to diagnosis and examine our body structure and different disorder such as
stroke, tumours, and aneurysms. Spinal cord, internal injuries, multiple sclerosis. It is effective in part
of our body of soft tissue especially water and fat as they are rich in hydrogen atom. MRI can be used
to help diagnose or monitor treatment for a variety of conditions within the chest, abdomen and
pelvis. If you’re pregnant, body MRI may be used to safely monitor development of baby, It can also
detect problems related to the blood circulation by using an injection to highlight the blood flow.
MRI scan produce a detail 3D image of the body internal organ this image can be used to see any
abnormalities with in the body from cell to organs as different tissue has different amount of proton
which acts as a magnet in our body.
Infrared thermography (IRT)
IRT is method used to detect heat energy emitted from an object. Any object with a temperature
above the absolute zero kelvin will emit radiant energy according to the Stefan Boltzmann law. So all
object emits a radiant energy (infrared ray) according to their temperature and this heat energy can
be used to measure warmth of an object. In medicine the heat energy emitted from our body is
converted into temperature reading and shows the temperature distribution in our body which we
can use to diagnosis medical problems.
Medical IRT has a sensitivity of 0.05 oc this can help us to detect temperature drop or rise caused by
bruising, viruses, inflammations and bacterial infection. But the IRF can only detect the change seen
on outer skin only.
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