Transcript the MRI

Brain Imaging Techniques
http://www.cis.rit.edu/htbooks/mri/
Computed Tomography Scan
(CT Scan)
CT scans use a series of Xray beams passed through
the head. The images are
then developed on sensitive
film. This method creates
cross-sectional images of
the brain and shows the
structure of the brain, but
not its function.
•Image courtesy of the Yousef Mohammad, M.D., MSc; Assistant Professor of Neurology
Division of Cerebrovascular Diseases, The Ohio State University Medical Center
http://faculty.washington.edu/chudler/ima
ge.html
PET Scans
Courtesy of Dr. Susan Courtney
of the National Institute of
Mental Health of the NIH.
A person getting a PET scan lies down
on a table. The brain is surrounded by
detectors. The PET imager will be able
to show, in three dimensions, where in
the brain specific mental activities are
taking place or where a tumor might be
growing. The PET scanner picks these
up because when a portion of the brain
is active or when a tumor is growing,
the flow of blood to that region is
increased.
The detectors pick up radiation emitted
from tagged (radioactive) compounds
that are injected into the person's vein
right before the scanner is turned on.
The compounds travel in the
bloodstream and arrive in the brain
within a minute or so.
Magnetic Resonance Imaging
(MRI)
http://www.howstuffworks.com/mri.htm
How an MRI works
• Using strong magnets, radiofrequency waves are
directed at protons, the nuclei of hydrogen atoms, in a
strong magnetic field. The protons are first "excited"
and then "relaxed," emitting radio signals that can be
computer-processed to form an image.
• In the body, protons are most abundant in the hydrogen
atoms of water—the "H" of H2O —so that an MR image
shows differences in the water content and distribution in
various body tissues. Even different types of tissue
within the same organ, such as the gray and white
matter of the brain, can easily be distinguished.
The “sections” of an MRI in action
http://en.wikipedia.org/wiki/Magnetic_resonance_imaging
•
http://www.functionalmri.org/
An “fMRI” of a patient involved in
using the sense of sight
A fMRI scan showing regions of
activation in orange, including the
primary visual cortex
Functional MRI
detects changes
in blood flow to
particular areas of
the brain. It
provides both an
anatomical and a
functional view of
the brain.
http://faculty.washington.edu/chudler/image.html
How fMRI technology works
fMRI uses MRI technology to identify
regions of the brain where blood vessels
are expanding, chemical changes are
taking place or extra oxygen is being
delivered—all signs that this part of the
brain is currently processing information
and giving commands to the body.
http://www.functionalmri.org/
Here are some examples of using a
combination of PET and MRI techniques:
Thalamus
Cortex
These 2 images show the averaged data from 14 subjects who
received a painful injection of the chemical capsaicin into the
upper arm. The colored part of the images show increased
blood flow (the PET) to the thalamus and primary
somatosensory cortex after the injection. The gray areas of the
images (the MRI) show the brain anatomy. So using this method
can identify the areas of the brain that are active during specific
conditions. This technique could be used to study just about
any other cognitive function.
http://faculty.washington.edu/chudler/image.html
(These two PET/MRI images were provided by Dr. Robert C. Coghill at Wake Forest University School of Medicine. )