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Types of Brain Imaging Techniques

Types of Brain Imaging Techniques
Brain imaging techniques allow doctors and researchers to view activity or problems within the human brain,
without invasive neurosurgery. There are a number of accepted, safe imaging techniques in use today in research
facilities and hospitals throughout the world.
The electroencephalogram (EEG) is one of the earliest brain scanning technologies, with
research on humans dating back to the 1920s and 30s. The EEG scan relies on the fact that
nerve impulses within the brain take the form of (or generate) tiny electric currents, which
indirectly cause changes in electric current at the scalp. Electrodes placed on the scalp can
detect these changes and create a readout that can be interpreted to discern brain activity.
They don't indicate much about what's going on inside the brain. However, since we know what a "normal"
brain's EEG readout looks like, a scan can help determine if a mental problem such as dementia or a coma is due
to a physiological problem within the brain or some other issue. EEGs are also used in sleep studies, since they
can show how a sleeping subject's brain patterns are being disrupted. They're crucial in diagnosing epilepsy,
since different forms of epilepsy show very different EEG readings during seizures.
X-rays use invisible electromagnetic energy beams to make images of the skull. Standard X-rays are done for
many reasons, including diagnosing tumors, infection, foreign bodies, or bone injuries. The more solid a structure
is, the whiter it appears on the film. While X-rays of the skull are not used as often as in the past, due to the use of
newer technologies such as computed tomography (CT scans) and magnetic resonance imaging (MRI), they are
still helpful for looking at the bones of the skull for fractures and detecting other conditions of the skull and brain.
Magnetic resonance imaging (MRI) is a test that uses powerful magnets, radio waves, and a
computer to make detailed pictures inside your body. Unlike X-rays and CT scans, an MRI
doesn't use radiation. MRIs are used for brain
structure imaging. When in some cases a CT scan
cannot detect the existing problem, an MRI is helpful
for discovering unnoticed anatomical anomalies
caused by a disease process or traumatic event. It is a utility used for
grand research in determining structural differences and a behavior
Functional magnetic resonance imaging, or fMRI, is a technique for
measuring brain activity. It works by detecting the changes in blood oxygenation and flow that occur in response
to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand
blood flow increases to the active area. fMRI can be used to produce activation maps showing which parts of the
brain are involved in a particular mental process.
COMPARISONS: MRI and fMRI differ from each other in a way that an MRI views the anatomical
structure while an fMRI views the metabolic function.
CT, or CAT scans, are special X-ray tests that produce cross-sectional images of
the body using X-rays and a computer. CT scans are also referred to as
computerized axial tomography. CT scan can help doctors to visualize small
nodules or tumors, which they cannot see with a plain film X-ray. CT scan images
allow the doctor to look at the inside of the body just as one would look at the inside
of a loaf of bread by slicing it. This type of special X-ray, in a sense, takes "pictures"
of slices of the body so doctors can look right at the area of interest. CT scans are
frequently used to evaluate the brain, neck, spine, chest, abdomen, pelvis, and
CT is a commonly performed procedure. Scanners are found not only in hospital X-ray departments, but also in
outpatient offices.
COMPARISONS: CT and MRI are similar to each other, but provide a much different view of the body
than an X-ray does. CT and MRI produce cross-sectional images that appear to open the body up,
allowing the doctor to look at it from the inside. MRI uses a magnetic field and radio waves to produce
images, while CT uses X-rays to produce images. Plain X-rays are an inexpensive, quick test and are
accurate at diagnosing things such as pneumonia, arthritis, and fractures. CT and MRI better to evaluate
soft tissues such as the brain, liver, and abdominal organs, as well as to visualize subtle abnormalities
that may not be apparent on regular X-ray tests.
Positron Emission Tomography (PET) uses trace amounts of short-lived radioactive material to
map functional processes in the brain. When the material undergoes radioactive decay a
positron is emitted, which can be picked up by the detector. Areas of high radioactivity are
associated with brain activity, because that is where the blood flows to.
Electroencephalography (EEG) is the measurement of the electrical activity of the brain by recording from
electrodes placed on the scalp. The resulting traces are known as an electroencephalogram (EEG) and represent
an electrical signal from a large number of neurons.
EEGs are frequently used in experimentation because the process is non-invasive to the research subject. The
EEG is capable of detecting changes in electrical activity in the brain on a millisecond-level. It is one of the few
techniques available that has such high temporal resolution.
Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic
fields produced by electrical activity in the brain via extremely sensitive devices known as
SQUIDs (which need liquid helium and are very expensive). These measurements are
commonly used in both research and clinical settings. There are many uses for the MEG,
including assisting surgeons in localizing a pathology, assisting researchers in determining
the function of various parts of the brain, neurofeedback, and others.
Near infrared spectroscopy is an optical technique for measuring blood oxygenation in the brain. It works by
shining light in the near infrared part of the spectrum (700-900nm) through the skull and detecting how much the
remerging light is attenuated. How much the light is attenuated depends on blood oxygenation and thus NIRS can
provide an indirect measure of brain activity.
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