Introduction to Scan Interpretation

Report
Clinical Brain Imaging
Stephen Salloway, M.D., M.S.
Department of Clinical Neurosciences and
Psychiatry
Brown Medical School
Nobel Prize for Medicine 2003
Paul C. Lauterbur
Sir Peter Mansfield
Objectives
• Learn about the use of CT, MRI and
SPECT scanning in clinical practice
• Recognize key anatomical landmarks and
begin to recognize and describe the
appearance of common disorders
Please look at the scans on your patients.
Neanderthal
Homo Sapiens
CT vs. MRI
CT
MRI
Obtained
X-ray beam
Magnetic fld
Bone
Bright
Dark
Cost
$330
$900
Plane
Axial
3-D
Technique
Adjust window
T1, T2, Pd
Length
10-20 minutes
30-60 min
Opening
Wide doughnut
Long,
narrow
Advantages to CT
•
•
•
•
•
Costs less than MRI
Better access
Shows up acute bleed
A good quick screen
Good visualization of bony structures
and calcified lesions
Disadvantages to CT
• Resolution
• Beam-hardening artifact
• Limited views of the posterior fossa and
poor visualization of white-matter
disease
Advantages to MRI
• Good resolution—excellent view of brain
structure
• 3 dimensions
• Good gray-white differentiation
• Adjust settings based on characteristics of
the lesion
• Good view of the posterior fossa
Advantages to MRI
• No radiation exposure
• Gadolinium contrast is relatively nontoxic
• Capacity for quantitative imaging, 3-D
reconstruction, angiography, spectroscopy
Disadvantages of MRI
• Cost
• Some patients ineligible because of
pacemakers, other metal
• Claustrophobia
• Long exam
• Access
FLAIR Image
MRI Is the Test of Choice for
Evaluating
• Most lesions causing epilepsy—temporal lobe glioma,
mesial temporal sclerosis
• White-matter disease—subcortical dementia, HIV, MS
• Lesions in the posterior fossa
• TBI—axonal injury
• Extent of anoxic injury, herpes encephalitis
• Frontal atrophy, NPH
• Other—brain anomalies, SLE, vasculitis, sagittal sinus
thrombosis, pituitary lesions, AVM
What Is Bright
on CT?
•
•
•
•
•
Blood
Contrast
Bone
Calcium
Metal
What Is Dark
on CT?
•Air
•CSF/H20
Artifacts
• Beam
hardening
• Bone
• Foreign body
• Motion
Uses for SPECT and PET
• Acute stroke
• Identify a seizure focus-increased
flow during sz and decreased
interictal flow
• Dementia-frontal pattern in FTLD,
temporo-parietal pattern in AD
• Ligand imaging in PD, others
Landmarks
• Axial views
–
–
–
–
–
–
–
Fourth ventricle
Petrous bone and sphenoid ridge
Aqueduct
Third ventricle
Lateral ventricles
Frontal horns
Calcifications in the choroid plexus, pineal,
basal ganglia and falx
– Caudate, putamen and globus pallidus
Landmarks (Cont.)
– Internal capsule—anterior and posterior
limbs
– Thalami
– Sylvian fissures
• Sagittal views
– Severity of cortical atrophy
– Corpus callosum and cingulate gyrus
• Pituitary
– Coronal views
– Hippocampus and amygdala
• 65 year old man
with right carotid
occlusion, left
hemiparesis,
apathy, and
depression. What
is wrong with his
scan?
72 year old woman
with gradually
progressive memory
loss and word
finding difficulty. Can
you find the Sylvian
fissures? What is
wrong with this
scan?
Normal
Hippocampus
Atrophic
Hippocampus
in AD
62 year old
woman with
rapid
progression of
memory loss
Mesial Temporal Sclerosis
31 year old woman
from Africa with
frequent complex
partial seizures and
mild developmental
delay. Can you find
the hippocampi?
What is wrong with
her scan?
Introduction to Scan Interpretation
• Is the scan
– Contrast or noncontrast?
– Good quality?
• Describe the abnormality
– Size—small, punctuate, medium, large
– Shape—round, well circumscribed, ovoid,
irregular, patchy
Introduction to Scan Interpretation
(Cont.)
• Signal intensity
–
–
–
–
High signal, hyperdense
Low signal, hypodense
Isointense, isodense
Mixed signal
• Location
Which scan is a normal variant? What is the
abnormality on the other scan?
3 year old boy with mild developmental delay.
What does this scan show?
65 year old with
dizziness, mild
hearing loss, and
mild tinnitus on
the left. Can you
detect the subtle
abnormality on
this scan?
66 year old admitted to
the hospital with the
abrupt onset of
expressive aphasia
and mild right hand
weakness. Describe
the abnormality on
the CT on hospital
day 2.
55 year old with new
onset of seizure
discovered to have
a small bleed from a
communicating
artery aneurysm.
Describe the
abnormality on the
CT 2 days post-op
aneurysm surgery.
45 year old with left subclavian occlusion
developed Wernicke’s aphasia following a
revascularization procedure. Describe the
abnormality on the MRI 7 days after the surgery.
50 year old with new
onset seizure. What
does the contrast
enhanced CT show?
A 32 year old woman
with anticardiolipin
antibody syndrome on
coumadin for stroke
prophylaxis was
admitted to the
hospital for confusion.
What does her
admission CT scan
show?
30 year old IV drug
abuser admitted to
the hospital with
headache, confusion,
and fever. What does
the contrast CT scan
show? How many
different types of
abnormal signal do
you see?
30 year old woman with right sided numbness
for 2 weeks. MRI on left is non-contrast, MRI on
right is enhanced with gadolinium. Describe the
abnormalities. What is the most likely diagnosis?
72 year old man with
short-term memory loss
and trouble recalling
people’s names. He is
driving without difficulty
and works out at the
gym 3 times per week.
What does the MRI
show?
Vascular Dementia
Three types of vascular dementia
Multiple large
Vessel infarctions
Bilateral strategic
thalamic infarcts
Binswanger’s
Disease
Normal Pressure Hydrocephalus:
NPH
• Cognitive Impairment
• Gait Disturbance
• Bladder Control
• May Have:
Behavior Problems
Parkinsonism
MRI findings
• Ventricular enlargement disproportionate to the
amount of atrophy
• Bowing of the corpus callosum
• Smooth rimming of high signal around the ventricles
due to transependymal flow of CSF
NPH: pre-op
NPH: post-op-130
mm H2O
Types of fMRI
• BOLD-fMRI which measures regional differences in
oxygenated blood
• Diffusion-weighted fMRI which measures random
movement of water molecules. Diffusion tensor
imaging (DTI) measures diffusion of water in
different directions and is a good test for studying
white matter tracts.
• MRI spectroscopy which can measure certain
cerebral metabolites non-invasively
DTI reconstruction of the corpus callosum
3D reconstruction
with functional
overlay
fMRI:Visual
stimulation
MR Spectroscopy
MR spectroscopy of N
acetyl aspartate
(NAA) showing
decline of NAA over
time in patients with
Alzheimer’s disease
(lower line)
compared to agematched controls.
Questions
The best initial test for the following is:
1) Routine screen for dementia
2) Rule out multiple sclerosis
3) Acute subdural hematoma
4) Closed head injury with personality change
5) Fever and delirium in an HIV + patient
a. CT without contrast b. MRI without contrast
c. CT with and without d. MRI with and without
Questions
6. Which of the following is not bright on CT?
a. Bone
d. Contrast
b. Acute blood
e. Metal
c. CSF
7. MRI is the best test for evaluating all of the
following except
a.
b.
c.
d.
e.
Lesions in the posterior fossa
Calcified lesions at the base of the skull
Small lesions in the temporal lobe
Multiple sclerosis plaques
Herpes encephalitis
Answers
1. A
5. D
2. B
6. C
3. A
7. B
4. B

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