This document provides an overview of CT and MRI interpretation for various neurological conditions. It includes labeled images showing normal anatomical structures and examples of: stroke demonstrated on perfusion and diffusion MRI; hemorrhage on CT and MRI; brain infection; tumors; traumatic brain injuries; dementia; multiple sclerosis lesions; and epileptic foci. The document serves as an educational guide for medical students and residents to learn cross-sectional brain anatomy and recognize key imaging findings for common neurological disorders.

1. CT and MRI
INTERPRETATION
SAMIR EL ANSARY
ICU PROFESSOR

2. 1
A midline Post-contrast Sagittal T1 Weighted MRI
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Identify anatomical
structures 1 - 24

3. 1
A midline Post-contrast Sagittal T1 Weighted MRI
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1. Scalp fat
2. Bone
3. Inferior sagittal sinus
4. Corpus callosum
5. Internal cerebral vein
6. Vein of Galen
7. Superior sagittal sinus
8. Parietal lobe
9. Occipital lobe
10. Straight sinus
11. Vermis
12. IV ventricle
13. Cerebellar tonsil
14. Cervical cord
15. Medulla
16. Pons
17. Midbrain
18. Mass intermedia of thalamus
19. Anterior III ventricle
20. Optic chiasm
21. Pituitary gland
22. Sphenoid sinus
23. Nasopharynx
24. Frontal lobe

4. Coronal Section of the Brain at the level of IV Ventricle
Post Contrast Coronal T1 Weighted MRI
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Identify anatomical structures
1 - 8

5. Coronal Section of the Brain at the level of IV Ventricle
Post Contrast Coronal T1 Weighted MRI
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1. Cerebellar tonsil
2. Cerebellar hemisphere
3. IV ventricle
4. Superior vermis
5. Tentorium
6. Posterior temporal lobe
7. Choroid plexus within lateral
ventricle
8. Posterior frontal lobe

6. Coronal Section of the Brain at the level of Pituitary gland
Post Contrast Coronal T1 Weighted MRI
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1 - 12

7. Coronal Section of the Brain at the level of Pituitary gland
Post Contrast Coronal T1 Weighted MRI
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1. Frontal lobe
2. Corpus callosum
3. Frontal horn
4. Caudate nucleus
5. III ventricle
6. Optic nerve
7. Pituitary stalk
8. Pituitary gland
9. Internal carotid artery
10. Cavernous sinus
11. Sphenoid sinus
12. Nasopharynx

8. Coronal Section of the Brain at the level of the orbits.
Post Contrast Coronal T1 Weighted MRI.
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Identify anatomical structures
1 - 5

9. 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

10. Post Contrast Axial MR Image of
the brain
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2
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Post Contrast sagittal T1
Weighted M.R.I.
Section at the level of Foramen
Magnum
Answers
1. Cisterna Magna
2. Cervical Cord
3. Nasopharynx
4. Mandible
5. Maxillary Sinus

11. Post Contrast Axial MR Image of the
brain
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6
Post Contrast sagittal T1
Wtd M.R.I.
Section at the level of
medulla
Answers
6. Medulla
7. Sigmoid Sinus

12. 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. Cerebellar
Hemisphere
9. Vermis
10. IV Ventricle
11. Pons
12. Basilar
Artery
13. Internal Carotid
Artery
14. Cavernous Sinus
15. Middle Cerebellar
Peduncle
16. Internal Auditory
Canal
17. Temporal Lobe

13. 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
Answers
18. Aqueduct of Sylvius
19. Midbrain
20. Orbits
21. Posterior Cerebral
Artery
22. Middle Cerebral
Artery

14. 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
Answers
23. Occipital Lobe
24. III Ventricle
25. Frontal Lobe
26. Temporal Lobe
27. Sylvian Fissure

15. 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 Sinus
29. Occipital Lobe
30. Choroid Plexus within
the occipital horn
31. Internal Cerebral Vein
32. Frontal Horn
33. Thalamus
34. Temporal
Lobe
35. Internal
Capsule
36. Putamen
37. Caudate
Nucleus
38. Frontal Lobe

16. Post Contrast Axial MR Image of the brain
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41
Post Contrast sagittal T1 Wtd
M.R.I.
Section at the level of Corpus
Callosum
Answers
39. Splenium of corpus callosum
40. Choroid plexus within the
body of lateral ventricle
41. Genu of corpus callosum

17. 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 Lobe
43. Body of the Corpus Callosum
44. Frontal Lobe

18. Post Contrast Axial MR Image of the brain
45
46
Post Contrast sagittal T1 Wtd
M.R.I.
Section above the Corpus
Callosum
Answers
45. Parietal Lobe
46. Frontal Lobe

19. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

20. 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

21. CT Signs in Early MCA Ischemia
Hyperdense MCA Insular Ribbon Lentiform Nucleus

22. 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

23. Pipes  Perfusion  Parenchyma
MRA Perfusion MR Diffusion MR
“Penumbra”
MRI in Stroke Intervention
“The 4 P’s”

24. MCA Infarct
MCA

25. PCA Infarct
PCA

26. ACA Infarct ACA

27. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

28. Cerebral Hemorrhage
• Trauma
• Ruptured aneurysm
• Hypertensive
• Hemorrhagic transformation of ischemic infarction
(esp. venous)
• Venous infarction
• Tumor
• Vascular malformations
• Angioinvasive infection
• Amyloid angiopathy

29. Acute intraparenchymal hematoma
Cerebral Hemorrhage

30. Hemorrhagic melanoma metastases
Cerebral Hemorrhage

31. Acute subarachnoid hemorrhage
(and intraventricular)
Cerebral Hemorrhage

32. Subdural vs. Epidural Hematoma

33. Acute subdural hematoma
Cerebral Hemorrhage

34. Acute epidural hematoma
Cerebral Hemorrhage

35. 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
*

36. Mixed acute/chronic subdural hematoma
Cerebral Hemorrhage
ACUTE
CHRONIC

37. Hematocrit level!
Cerebral Hemorrhage

38. 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*

39. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

40. Infection
• Meningitis
• Encephalitis
• Cerebritis and parenchymal abscess
• Empyema (subdural/epidural)

41. Leptomeningitis:
pia-arachnoid
Meningitis
Pachymeningitis: dura
Most common imaging findings in meningitis: NONE !!

42. Herpes
Encephalitis

43. Cerebritis w/ Bacterial Abscess
T1 + Gd T2 Diffusion

44. Cerebritis w/ Subdural Empyema
T1 + Gd T2 FLAIR Diffusion

45. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

46. Brain Tumor Imaging
Diagnosis
• 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

47. T1 + Gd T2
Intra- or Extra-axial?

48. Intra- or Extra-axial?

49. Tumor vs. Other Masses
Arachnoid Cyst
Abscess
Hematoma
“Tumefactive” MS
GBM

50. Tumor vs. Stroke
Cytotoxic Edema Vasogenic Edema
Cellular swelling
Gray-white margin lost
Leaky capillaries
Gray matter is spared

51. T1 T1 + Gd
T2 T2 FLAIR
Tumor?
Stroke?
Encephalitis?

52. 3D Imaging for XRT
or Surgical Guidance

53. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

54. Fractures: CT not MRI !

55. Traumatic Brain Swelling
Cerebellopontine
angle
PontineCerebellomedullary
(Cisterna Magna)
Know your basal cisterns!

56. Traumatic Brain Swelling
Know your basal cisterns!
Quadrigeminal
Interpeduncular
Suprasellar
Ambient

57. Effacement of basal cisterns
Traumatic brain swelling with
downward herniation
Traumatic Brain Swelling

58. Traumatic brain swelling

59. Extra-axial Hemorrhage
Subdural Epidural Subarachnoid

60. Intra-axial Hemorrhage
Hemorrhagic contusions

61. 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)

62. 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

63. Diffuse Axonal (Shear) Injury (DAI)
Intra-axial Hemorrhage

64. Diffuse Axonal (Shear) Injury (DAI)
T2: Reveals non-hemorrhagic lesions occult on CT

65. Diffuse Axonal (Shear) Injury (DAI)
T2: Increased sensitivity to hemorrhage

66. 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

67. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

68. Dementia
• Primary role of imaging is to
exclude treatable causes, e.g.:
–Hydrocephalus
–Subdural hematoma
–Neoplasm

69. Dementia
Irreversible dementias (imaging non-
specific):
• Alzheimer’s disease
• Multi-infarct dementia
• Dementias associated with
Parkinson’s disease and similar
disorders
• AIDS dementia complex

70. Alzheimer’s: Temporal-Parietal Lobe Atrophy (Late)

71. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

72. 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)

73. MS

74. Tumefactive MS

75. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

76. 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

77. Congenital anomalies: Polymicrogyria

78. Congenital anomalies: Schizencephaly

79. Mesial Temporal Sclerosis
Most common pathology found in
medically refractory epilepsy patients
Rare under age 10 or with new seizures
Pathogenesis unknown
- Post ictal / kindling?
Pathology:
Hippocampal atrophy / gliosis

80. Mesial
Temporal
Sclerosis
FLAIR
T1
T2
• Atrophy
• Loss gray-white
•↑T2 / FLAIR

81. Brain Imaging: “The Big 10”
• Infarction
• Hemorrhage
• Infection
• Tumor
• Trauma
• Dementia
• MS
• Epilepsy
• Cranial neuropathy
• Orbits / Ophtho dx

82. Cranial Nerve Imaging
FIESTA
CN-5
CN-8
CN-7

83. Vestibular Schwannoma

84. Intracochlear Schwannoma

85. 30 y/o F
with 6wk
h/o blurred
vision
Craniopharyngioma

86. CT vs. MRI
Wide doughnutOpening
10-20 minutesLength
Adjust windowTechnique
AialPlane
BrightBone
Long, narrow
30-60 min
T1, T2, Pd
3-D
Dark
Magnetic fldX-ray beamObtained
MRICT

87. 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

88. Disadvantages to CT
• Resolution
• Beam-hardening artifact
• Limited views of the posterior fossa and
poor visualization of white-matter
disease

90. 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

91. Advantages to MRI
• No radiation exposure
• Gadolinium contrast is relatively nontoxic
• Capacity for quantitative imaging, 3-D
reconstruction, angiography, spectroscopy

92. Disadvantages of MRI
• Cost
• Some patients ineligible because
of pacemakers, other metal
• Claustrophobia
• Long exam
• Access

93. What Is Bright
on CT?
• Blood
• Contrast
• Bone
• Calcium
• Metal
What Is Dark
on CT?
•Air
•CSF/H20

94. Artifacts
• Beam
hardening
• Bone
• Foreign body
• Motion

98. 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

104. 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

105. 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

109. Normal
Hippo-
Campus

110. Atrophic
Hippo-
campus
in AD
62 year old
woman with
rapid
progression of
memory loss

111. 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

112. Introduction to Scan Interpretation
(Cont.)
• Signal intensity
– High signal,
hyperdense
– Low signal, hypodense
– Isointense, isodense
– Mixed signal
• Location

113. Vascular Dementia
Three types of vascular dementia
Multiple large
Vessel infarctions
Bilateral strategic
thalamic infarcts
Binswanger’s
Disease

114. Normal Pressure Hydrocephalus: NPH
• Cognitive Impairment
• Gait Disturbance
• Bladder Control
• May Have:
Behavior Problems
Parkinsonism

115. 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

116. NPH: pre-op NPH: post-op-130
mm H2O

117. 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

119. DTI reconstruction of the corpus callosum

120. 3D reconstruction
with functional
overlay
fMRI:Visual
stimulation

121. 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.

122. GOOD LUCK
SAMIR EL ANSARY
ICU PROFESSOR
AIN SHAMS
CAIRO