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The Different Tests
CT Scan or CAT Scan (Computerized Axial Tomography Scan)
The CT Scan, or CAT Scan has been in use since 1973.
It takes x-rays of the brain and then combines them to form a 3 dimensional
picture on the computer. In doing this, it can examine thin sections of
the brain at different depths and therefore show much greater detail than a
regular x-ray.
The CT Scan is useful for testing for a variety of damage.
It shows if there is bleeding in the skull, tumors, hemorrhages, fluid
collection, and can also determine the amount of swelling. In depressed
fractures, the CT Scan has the advantage of showing the amount of depression
more clearly than the regular skull x-ray.
Some advantage of the CT Scan over other tests include
such factors as it is painless, it can be performed much faster than many other
tests, and it can be repeated with little risk to the patient (that is, repeated
changes can be monitored). One major disadvantage, however, is that the
CT Scan sometimes shows normal in patients who have seizures.
PET Scan (Positron Emission
Tomography)
A PET scan differs from a CT scan in that while a CT
scan is limited to distinguishing anatomical features, a PET scan measures metabolic
processes, thus allowing an appraisal of how the brain is functioning.
It tracks natural compounds, such as glucose, as the
brain metabolizes them. By showing the areas of different metabolic activity,
it then makes it easier to make diagnoses, such as determining the areas responsible
for epileptic seizures.
EEG (Electroencephalograph)
The EEG is a recording of the electrical activity of
the brain. Its computerized printout looks similar to that of an EKG which
monitors the heart. Brain activity is represented by a graph which shows peaks
and valleys which lessen with decreasing levels of consciousness.
An EEG is given by attaching small electrodes (flat
pieces of plastic with wires attached to them) to the scalp. The wires
running from the electrodes are connected to a computer which then interprets
the signals it is receiving and produces a print-out of the electrical activity.
EEGs are often given to patients who have seizures. They are very
useful in locating the areas of the brain where there is abnormal electrical
activity.
MRI (Magnetic Resonance Imaging)
The MRI is similar to the CT Scan; however, it uses
magnetic fields instead of x-rays to produce a three-dimensional picture of
brain tissue. The MRI is useful for minor brain injuries in that it shows
very small changes in the brain which may not be detected by a CT Scan or an
x-ray.
X-Rays
The patient is placed underneath the X-ray machine and
a special photographic plate which is sensitive to X-rays is placed under the
patient. The X-ray photograph is then taken. X-rays pass through
the flesh and are absorbed by the bone. An image of the bone is therefore
left on the photographic plate and is extremely useful for diagnosing the extent
of an injury. X-rays are used to identify the presence and the extent
of fractures in the skull.
References:
Carson, R.C., Butcher, J.N., & Mineka, S. (1996). Abnormal Psychology and
Modern Life, tenth edition. New York: HarperCollins.
Freeman, E.A. (1987). The Catastrophe of Coma: A Way Back. Queensland, Austrailia:
David Bateman Ltd.
Ivan, L.P. & Bruce, D.A. (1982). Coma: Physiopathology, Diagnosis and Management.
Springfield: Charles C. Thomas.
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