The use of a brain SPECT scan is based on the principal of blood flow.
Areas of increased blood flow take up more Radioactive tracer than areas
of less blood flow. Blood flow in the brain is directly related to brain
activity. Areas or regions of interest in the brain are related in their
demand for blood flow which can be imaged with this specific nuclear
The basis of the brain image comes from the temporary uptake of
radioactive particles; from the blood into the brain tissue. The
radioactive particles are � tagged" to a drug that flows into the brain.
These particles come from the radioactive decay of the element
Technetium; TC99. The SPECT Gamma camera system collects these particles
and passes them to a complex system which reconstructs a working image
of the brain. This snapshot view of the imagination is referred to as a
functional image. SPECT is an abbreviation of this process described
Advances in the field of nuclear medicine over the past 30 years have
improved the image quality with these cameras through the modifications
of both the camera design and the radiopharmaceuticals developed. The
triple headed camera designed by Picker-Marconi is the one that Dr. Kohn
uses. Images are acquired in less than thirty minutes with excellent visualization of the
cortex and subcortical regions of interest.
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BASELINE & ACTIVATION
The clinical diagnosis of ADHD is not determined by reliance on brain
SPECT imaging. This test is helpful at times, in viewing the
response of the brain at rest and during a continuous performance test;
baseline and activation.
At times patients with ADHD demonstrate less blood flow to the frontal
cortex areas when performing the activation test, The normal
response is the opposite; greater activation - blood flow in the frontal
cortical are during this test.
after Performance Test
after Performance Test
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The procedure takes nearly one hour. The first 30 minutes requires
the patient to relax before and after the intravenous injection of
"Ceretec". The later 30 minutes requires the patient to rest
comfortably on the image table.
An activation study involves injection of Ceretec
two to four minutes after a computerized working memory test has begun.
When the task is completed the patient then moves to the image table for
the same procedure as described above.
The state of brain activity during
the two minutes following each injection is captured on the scan.
This is referred to as a "functional image". The actual scan is
acquired 30 minutes after the injection.
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HOW DR. KOHN USES SPECT TECHNOLOGY
S P E C T is used as a tool
in the clinical evaluation process to help view areas of brain activity
and relate them to presenting symptoms. Symptoms and signs are clustered
based in part, on the brain networks activated.
Symptoms include those observations made by the person or parent, etc
while signs refer to those findings noted on clinical examination.
Common symptoms include sadness, anger, rage, worry,
obsessions-compulsions, fear- panic, fatigue, loss of motivation or
will, distractibility, inattention. Common signs include weight loss,
agitation, mood lability, illogical, tangential, circumstantial
" network" refers to a system
in which specific properties are common to its components and the
interaction of the parts in the system
is essential for the overall property of the system to be
maintained. There are natural and man made networks. The most well known
man made system is the INTERNET. In nature we think of examples such as
spider webs or water ways in which, although parts are separate, there
is an overall interaction that form the basis of the operation of the
The human brain has developed a system of interconnections that
coordinate the many functions that make us who we are; our personality,
our aptitude, our interests, our emotional state, etc. The tug and
pull between muscles that move bones occurs differently in the brain.
The working of one brain part occurs in coordination with many other
parts. Like a traffic officer that directs cars to move in and out of an
intersection; brain systems allow one part to function or " come on
line" while influencing another part to decrease its function or " come
Using SPECT imaging in the field of neurology and psychiatry allows
visualization of the components of the many systems that run our
emotional state, our motivation level, our concentration and memory
ability and more. Brain parts form a network of interacting pieces that
maintain the examples I mentioned.
There are very specific parameters set up for measuring brain activity
in these networks based on mathematical computations. Each image is
acquired through a sequence of steps that accepts and discards the "
radioactive counts" of the TC99m radiotracer in accordance with the
accuracy limitations of the SPECT GAMMA CAMERA that measure these counts. The
result of the computations is a display that is seen on a scale of
color. We use the geographical color scale at the University of Illinois
in Chicago because it allows accurate separation of degrees of brain
activity. Activity is recorded as relatively more than or less than or
Based on the model of networks, brain activation states and my
experience comes a very important statement.
There is NO one
simple "Signature Pattern" of a specific diagnosis!
There are patterns that are common to each diagnosis and patterns that
often overlap. Often this is seen clinically as the phenomenon of Co
morbidity. This means that more than one condition can be present at one
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WHAT DOES DR. KOHN DO?