Transcript Clinical Application: Brain Function Measures

Clinical Application:
Brain Function Measures
Perry C. Hanavan, Au.D.
Question
Which shows imaging plus blood flow
assesses correlates function with structure?
A. EEG
B. PET
C. MRI
D. Ct Scan
E. MEG
Brain Structure Vs. Function
• Imaging technologies assess
structure
– MRI
– Ct Scan
• Electrophysiologic technologies
assess function
– EEG
– EP
• auditory, visual, tactile, vestibular
• Imaging plus blood flow
assesses correlates function
with structure
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SPECT
IB-PET & lorbetapir -F18 PET
PET
fMRI
• Imaging (MRI) plus EEG
– Magnetoencephalography (MEG)
Computerized Tomography
Ct Scan
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x-ray technology
sensitive to tissue densities
relatively quick procedure
detects calcification,
hemorrhages, tumors,
cerebrovascular disease,
head trauma, cerebral
atrophy
• potential health risk due to xray
Magnetic Resonance Imaging
• MRI technology able to assess differences
in water and hydrogen atom distribution in
various tissues combined with radio
frequency signals
• no radiation
• easily detects fine differences between
soft tissues such as grey and white matter,
cerebrospinal fluid, vascular structures
• detects plaque occurring with MS
• clearly identifies cranial nerves and
subcortical structures
• diagnosis various brain diseases and
disorders
• imaging times longer than CT, thus more
costly
• Metal devices prevent MRI such as CI,
clips, pacemakers
Diffusion-tensor MRI (DTMRI)
• Used to visualize white matter tracts
connecting different parts of neural
networks in the brain
• Used in pre-surgical planning for removal
of a brain tumor to ensure tracts are
spared during surgery.
• Used to the study of 14 neurological
conditions such ADHD and other
developmental disorders, thought to arise
from problems in white matter connections
Diffusion-weighted (DWMRI)
• Shows whether brain tissue damage due
to insufficient blood flow to the tissue
• Can visualize tissue within minutes after
damage by an “ischemic” injury (such as a
stroke-producing blood clot)
• Thus, allows early identification of damage
Perfusion-weighted MRI
• Show areas of brain blood flow has been
altered based on time course of regional
signal changes induced by exogenously
administered MRI contrast agent
Diffusion-Perfusion-weighted MRI
Used together to estimate “ischemic
penumbra,” tissue damaged from reduced
blood flow but not yet dead.
This tissue is target of intensive therapy for
patients who have had ischemic stroke
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Brain or pituitary gland tumor
Pituitary disease
Brainstem or cerebellum abnormalities
Multiple sclerosis
Magnetic Resonance Spectroscopy
• MRS provides biochemical
information about tissues of
body (without the need for a
biopsy)
• MRI gives structure
informationof the body
• Whereas MRI shows
tumour (cancer) location,
MRS, in theory, tells
aggressiveness of
(malignant) tumour
EEG
• Electroencephalography
measures and records
the electrical activity of
the brain from multiple
scalp electrodes.
– Special sensors
(electrodes) are attached
to the scalp and
connected to a computer
to record and store the
electrical activity of the
brain.
Quantitative Electroencephalography
(qEEG)
• The digital EEG data is
statistically analyzed,
sometimes comparing values
with “normative” database
reference values and is
converted into color maps or
“Brain maps”.
• Measure of various aspects
of cognitive function
• qEEG (quantitative)
– qEEG
– qEEG
– qEEG
Evoked Potentials
• Measure event related
activity
– visual
– auditory
– tactile
• Auditory Evoked
Potentials
– ABR, middle, slow, late
– Mismatch negativity
(MMG)
• odd ball paradigm
Auditory Evoked Potentials
Auditory evoked potential analyzed on logarithmic time-base to reveal the component
potentials with approximately equal weighting and categorized in arbitrary but commonly used
time windows of short- (SLR), middle- (MLR), and long- (LLR) latency responses. (Figure
modified and redrawn from Michelini et al., 1982.)
ABR
fMRI
• hemodynamic response
– increase in blood flow to region is
related to amount of neural activity in
region of the brain
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indirect measure of brain function
assess cognitive function
safe noninvasive technology
assess brain function over time
assess effects of brain damage
assess recovery from damage
– Intro to fMRI
fMRI
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Shows brain in action
Elucidate processes involved in higher cognitive
functioning
Highly sensitive - can detect small changes
Method of choice for identifying areas of brain
activated with specific cognitive or motor task.
Indirect measure as dynamic changes in blood
flow is much longer than neurons to fire
electrochemical messages.
Used to study the reorganization of function
following injury to a single brain area.
Positron Emission Tomography
• Uses radioactive tracer combining
with human chemical element
(oxygen, nitrogen, etc.) to measure
hemodynamic response
• Disintegration of radioactive tracer
emits positrons (positively charge
particles) which collide with
electrons producing gamma rays
that are detected and measured by
computers
• PET scans displayed in 3D with
various colors representative of
hemodynamic response
Positron emission tomography (PET)
Radiation or nuclear medicine
imaging
Produces 3-dimensional color
images of functional processes
Detects pairs of gamma rays
emitted indirectly by a tracer
(positron-emitting radionuclide)
placed in body on biologically
active molecule.
Images are reconstructed by
computer analysis.
PIB-PET & lorbetapir -F18 PET
PIB-PET (Pittsburgh Compound B”) and
“florbetapir -F18 PET”
Tracers developed that bind solely to beta
amyloid proteins
These proteins accumulate in the brains of
people with
o presymptomatic mild cognitive impairment
(MCI),
o overt MCI, and Alzheimer’s disease,
o Not in the brains of cognitively healthy adults
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Single Photon Emission Computed
Tomography
• SPECT scan is a type of
nuclear imaging test that
shows how blood flows to
tissues and organs through
arteries and veins in the brain
• Integrates two technologies:
computed tomography (CT) and a
radioactive material (tracer).
• gamma photon–emitting
radionuclides are administered
and then detected by one or
more gamma cameras
Uses in Communication Disorders
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ADD
ADHD
Alzheimer’s
Arteriovenous Malformation
Auditory processing
Developmental Delays
Epilepsy Epilepsy
Hearing assessment
MS MS
Parkinson’s
Stroke
Stuttering
Vestibular
TBI