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CT and MRIINTERPRETATION
SAMIR EL ANSARY
ICU PROFESSOR
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A midline Post-contrast Sagittal T1 Weighted MRI
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Identify anatomical structures 1 - 24
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A midline Post-contrast Sagittal T1 Weighted MRI
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1. Scalp fat2. Bone3. Inferior sagittal sinus4. Corpus callosum5. Internal cerebral vein6. Vein of Galen7. Superior sagittal sinus8. Parietal lobe9. Occipital lobe10. Straight sinus11. Vermis12. IV ventricle13. Cerebellar tonsil14. Cervical cord15. Medulla16. Pons17. Midbrain18. Mass intermedia of thalamus19. Anterior III ventricle 20. Optic chiasm21. Pituitary gland22. Sphenoid sinus23. Nasopharynx24. Frontal lobe
Coronal Section of the Brain at the level of IV VentriclePost Contrast Coronal T1 Weighted MRI
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Identify anatomical structures 1 - 8
Coronal Section of the Brain at the level of IV VentriclePost Contrast Coronal T1 Weighted MRI
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1 1. Cerebellar tonsil2. Cerebellar hemisphere3. IV ventricle4. Superior vermis5. Tentorium6. Posterior temporal lobe7. Choroid plexus within lateral ventricle8. Posterior frontal lobe
Coronal Section of the Brain at the level of Pituitary glandPost Contrast Coronal T1 Weighted MRI
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12 Identify anatomical structures 1 - 12
Coronal Section of the Brain at the level of Pituitary glandPost Contrast Coronal T1 Weighted MRI
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1. Frontal lobe2. Corpus callosum3. Frontal horn4. Caudate nucleus5. III ventricle6. Optic nerve7. Pituitary stalk8. Pituitary gland9. Internal carotid artery10. Cavernous sinus11. Sphenoid sinus12. Nasopharynx
Coronal Section of the Brain at the level of the orbits.Post Contrast Coronal T1 Weighted MRI.
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5Identify anatomical structures 1 - 5
Coronal Section of the Brain at the level of the orbits.Post Contrast Coronal T1 Weighted MRI.
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1. Frontal lobe
2. Orbital Fat
3. Globe
4. Nasal Cavity
5. Maxillary Sinus
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Weighted M.R.I.
Section at the level of Foramen Magnum
Answers
1. Cisterna Magna2. Cervical Cord3. Nasopharynx4. Mandible5. Maxillary Sinus
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I.
Section at the level of medulla
Answers
6. Medulla7. Sigmoid Sinus
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of Pons
Answers
8. CerebellarHemisphere9. Vermis10. IV Ventricle11. Pons12. Basilar Artery
13. Internal Carotid Artery14. Cavernous Sinus15. Middle CerebellarPeduncle16. Internal Auditory Canal17. Temporal Lobe
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I.
Section at the level of Mid Brain
Answers18. Aqueduct of Sylvius19. Midbrain20. Orbits21. Posterior Cerebral Artery22. Middle Cerebral Artery
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of the
III Ventricle
Answers23. Occipital Lobe24. III Ventricle25. Frontal Lobe26. Temporal Lobe27. Sylvian Fissure
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of Thalamus
Answers
28. Superior Sagittal Sinus29. Occipital Lobe30. Choroid Plexus within the occipital horn31. Internal Cerebral Vein32. Frontal Horn
33. Thalamus34. Temporal Lobe35. Internal Capsule36. Putamen37. Caudate Nucleus38. Frontal Lobe
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I.
Section at the level of Corpus Callosum
Answers
39. Splenium of corpus callosum40. Choroid plexus within the body of lateral ventricle41. Genu of corpus callosum
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 Wtd M.R.I.
Section at the level of Body of Corpus Callosum
Answers
42. Parietal Lobe43. Body of the Corpus Callosum44. Frontal Lobe
Post Contrast Axial MR Image of the brain
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Post Contrast sagittal T1 WtdM.R.I.
Section above the Corpus Callosum
Answers
45. Parietal Lobe46. Frontal Lobe
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Acute Ischemic Stroke Imaging
Confirm diagnosis
Triage for therapy (risk / prognosis)
– Rule out hemorrhage
– Assess damage: location, pattern, extent
– Is there salvageable brain (“penumbra”)?
Follow outcome
– Vessel patency, ultimate infarct size, hemorrhagic transformation
CT Signs in Early MCA Ischemia
Hyperdense MCA Insular Ribbon Lentiform Nucleus
Pathophysiology of Ischemic Injury:Duration and Degree of CBF
Normal neuronal function
Reversible injury
(penumbra)
Infarction
25
20
15
10
5
0
CBF
ml /
100g /
min
Time (hrs)1 2
Pipes Perfusion Parenchyma
MRA Perfusion MR Diffusion MR
“Penumbra”
MRI in Stroke Intervention“The 4 P’s”
MCA Infarct
MCA
PCA Infarct
PCA
ACA Infarct ACA
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Cerebral Hemorrhage
• Trauma• Ruptured aneurysm • Hypertensive• Hemorrhagic transformation of ischemic infarction
(esp. venous)• Venous infarction• Tumor • Vascular malformations• Angioinvasive infection• Amyloid angiopathy
Acute intraparenchymal hematoma
Cerebral Hemorrhage
Hemorrhagic melanoma metastases
Cerebral Hemorrhage
Acute subarachnoid hemorrhage
(and intraventricular)
Cerebral Hemorrhage
Subdural vs. Epidural Hematoma
Acute subdural hematoma
Cerebral Hemorrhage
Acute epidural hematoma
Cerebral Hemorrhage
Subdural: Follows inner layer of dura
“Rounds the bend” to follow falx or tentorium
Not affected by sutures of skull
Tendency for crescentic shapes
More mass effect than expected for their size
Typical source of SDH: cortical vein
Epidural: Follows outer layer of dura (periosteum)
Crosses falx or tentorium
Limited by sutures of skull (typically)
Tendency for lentiform shapes
Typical source of EDH:
skull fracture with arterial or sinus laceration
Subdural vs. Epidural Hematoma
*
Mixed acute/chronic subdural hematoma
Cerebral Hemorrhage
ACUTE
CHRONIC
Hematocrit level!
Cerebral Hemorrhage
MRI of Hemorrhage
MR appearance of hematomas depends on image type.
Magnetic properties change over time (Hgb breakdown products), allowing approximate dating
T1 T2 T2*
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Infection
• Meningitis
• Encephalitis
• Cerebritis and parenchymal abscess
• Empyema (subdural/epidural)
Leptomeningitis: pia-arachnoid
Meningitis
Pachymeningitis: dura
Most common imaging findings in meningitis: NONE !!
Herpes Encephalitis
Cerebritis w/ Bacterial Abscess
T1 + Gd T2 Diffusion
Cerebritis w/ Subdural Empyema
T1 + Gd T2 FLAIR Diffusion
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Brain Tumor ImagingDiagnosis
• Location: Intra- / Extra-axial, Supra- / Infra-tentorial, Grey / white matter, etc.
• Single or multiple?• Tumor or tumor-like alternatives?• Histology: Type and grade?
Treatment Planning• Surgery, radiation, chemo tx• Functional MRI for eloquent brain mapping• 3D scans to guide surgery, radiation
Follow-up • Stable vs. recurrence / progression• Complications
T1 + Gd T2
Intra- or Extra-axial?
Intra- or Extra-axial?
Tumor vs. Other MassesArachnoid Cyst
Abscess
Hematoma
“Tumefactive” MS
GBM
Tumor vs. Stroke
Cytotoxic Edema Vasogenic EdemaCellular swelling
Gray-white margin lostLeaky capillaries
Gray matter is spared
T1 T1 + Gd
T2T2 FLAIR
Tumor?Stroke?
Encephalitis?
3D Imaging for XRTor Surgical Guidance
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Fractures: CT not MRI !
Traumatic Brain Swelling
Cerebellopontine angle
PontineCerebellomedullary (Cisterna Magna)
Know your basal cisterns!
Traumatic Brain Swelling
Know your basal cisterns!
QuadrigeminalInterpeduncular
SuprasellarAmbient
Effacement of basal cisterns
Traumatic brain swelling with downward herniation
Traumatic Brain Swelling
Traumatic brain swelling
Extra-axial Hemorrhage
Subdural Epidural Subarachnoid
Intra-axial Hemorrhage
Hemorrhagic contusions
Intra-axial Hemorrhage
Hemorrhagic contusions
Mechanism
Direct contact with skull
Shear-strain deformation
Lesion locations
Commonly located along inferior, lateral, and anterior
frontal and temporal lobes
Often above bony prominences (petrous pyramid,
sphenoid wing, orbital roof)
Intra-axial Hemorrhage
Hemorrhagic contusions
Appearance of cortical contusions
Overlying cortex, by definition, always involved (vs. DAI)
“Salt and pepper” appearance due to intermixed hemorrhage
and edema
Non-hemorrhagic contusions often not initially seen on CT scans
Lesions often more visible days after injury as edema and
hemorrhage increase
Acute lesions much more conspicuous on T2 or T2-FLAIR MRI
Diffuse Axonal (Shear) Injury (DAI)
Intra-axial Hemorrhage
Diffuse Axonal (Shear) Injury (DAI)
T2: Reveals non-hemorrhagic lesions occult on CT
Diffuse Axonal (Shear) Injury (DAI)
T2: Increased sensitivity to hemorrhage
Diffuse Axonal (Shear) Injury (DAI)
• Tissues w/ differing elastic properties shear against each other, tearing axons
• Caused by rapid deceleration/rotation of head • Locations:
• Cerebral hemispheres near gray-white junction• Basal ganglia• Corpus callosum, especially splenium• Dorsal brainstem
• High morbitity & mortality – common cause of post-traumatic vegetative state
• Initial CT often normal despite poor GCS• Lesions often non-hemorrhagic and seen only on MRI
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Dementia
• Primary role of imaging is to exclude treatable causes, e.g.:
–Hydrocephalus
–Subdural hematoma
–Neoplasm
Dementia
Irreversible dementias (imaging non-specific):• Alzheimer’s disease• Multi-infarct dementia • Dementias associated with
Parkinson’s disease and similar disorders
• AIDS dementia complex
Alzheimer’s: Temporal-Parietal Lobe Atrophy (Late)
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Multiple Sclerosis (MS) Imaging
• MRI is the imaging study of choice
• Help establish “dissemination of lesions in time and space”
• Estimate disease burden
• Identify acute (inflammatory) vs. chronic lesions (enhancement = active inflammation)
MS
Tumefactive MS
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Seizure Imaging
• MRI is the imaging study of choice
• Identify and localize offending lesion
• New onset vs. chronic epilepsy
• Younger vs. older patients
• Search may be guided by EEG / clinical sx
• Preoperative planning
e.g. language lateralization before temporal
lobectomy
Congenital anomalies: Polymicrogyria
Congenital anomalies: Schizencephaly
Mesial Temporal Sclerosis
Most common pathology found in medically refractory epilepsy patientsRare under age 10 or with new seizuresPathogenesis unknown
- Post ictal / kindling?
Pathology: Hippocampal atrophy / gliosis
MesialTemporal Sclerosis
FLAIR
T1
T2
• Atrophy• Loss gray-white•↑T2 / FLAIR
Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx
Cranial Nerve Imaging
FIESTA
CN-5CN-8
CN-7
Vestibular Schwannoma
Intracochlear Schwannoma
30 y/o F with 6wk
h/o blurred vision
Craniopharyngioma
CT vs. MRI
Wide doughnutOpening
10-20 minutesLength
Adjust windowTechnique
AialPlane
Bright Bone
Long, narrow
30-60 min
T1, T2, Pd
3-D
Dark
Magnetic fldX-ray beamObtained
MRICT
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
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
NormalHippo-
Campus
Atrophic
Hippo-campus
in AD62 year old
woman with
rapid
progression of
memory loss
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
Vascular DementiaThree types of vascular dementia
Multiple large
Vessel infarctions
Bilateral strategic
thalamic infarctsBinswanger’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:Visualstimulation
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 age-
matched controls.
GOOD LUCK
SAMIR EL ANSARYICU PROFESSOR
AIN SHAMSCAIRO