CHAPTER 2 - NORMAL BRAIN IMAGES
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How SPECT Is Interpreted
SPECT studies can be displayed in a variety of different ways. Traditionally, the brain is
examined in three different planes: horizontally (cut from top to bottom), coronally (cut
from front to back), and sagittally (cut from side to side) - see below for examples of
each of these planes. What do physicians see when they look at a SPECT study? We examine
it for symmetry and activity levels indicated by shades of color (in different color
scales selected depending on the physician's preference, including gray scales) and
compare it to what we know a normal brain looks like. A normal SPECT brain image reveals
homogeneous and uniform tracer accumulation throughout the cerebral cortex, with the
cerebellum being the area with the most intense activity. Chiron studied the normal
progression of cerebral perfusion in children and found that by the age of 2 or 3 there is
the same relative perfusion patterns as those seen in adults.
The images that accompany this atlas will be mostly two kinds of three dimensional (3D)
images of the brain.
One kind is a 3D surface brain image, looking at the blood flow of the brain's cortical
surface. These images are helpful for picking up cortical surface areas of good activity
as well as underactive areas. They are helpful to look at strokes, brain trauma, the
effects from drug abuse, etc. A normal 3D surface scan shows good, full, symmetrical
activity across the brain's cortical surface.
The other kind is a 3D active brain image comparing average brain activity to the hottest
15% of activity. These images are helpful for picking up areas of overactivity, as seen in
active seizures, obsessive compulsive disorder, anxiety problems, certain forms of
depression, etc. A normal 3D active scan shows increased activity (seen by the light
color) in the back of the brain (the cerebellum and visual or occipital cortex) and
average activity everywhere else (shown by the background grid).
Physicians are usually alerted that something is wrong in one of three ways: (a) they see
too much activity in a certain area; (b) they see too little activity in a certain area;
or (c) they see asymmetrical areas of activity, which ought to be symmetrical.
VIEWING BRAIN SPECT STUDIES
HORIZONTAL VIEW (transaxial)
The brain is viewed in horizontal slices, cut from top to bottom.
It is as if you are looking down from a bird's eye view.
CORONAL VIEW (front on view)
The brain is viewed in vertical slices, cut from front to back.
It is as if you are looking face on or front on to the brain.
SAGITTAL VIEW (side to side)
The brain is viewed in vertical slices, cut from side to side.
It is as if you are looking at the brain from the side.
Normal 3D Brain SPECT Studies
Brain Images Table of Contents
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