Anatomy of Brain by MRI In this presentation we will discuss the cross sectional anatomy of brain. Then we will discuss the Most common diseases to be evaluated by brain imaging. In my opinion this presentation is a road map for beginars.

1. MR IMAGING OF BRAIN
Muhammad Bin Zulfiqar
PGR II SIMS/SHL
New Radiology Department

2. Basics of MR
• MR sequences
• MR signal characteristic

3. MRI----conventional sequences
• SE sequence （ spin echo ）
– T1-weighted,T1-WI
TR: 200-800ms TE:15-30ms
– T2-weighted,T2-WI
TR:1500-2000ms TE:60-150ms
– Proton Density,N(H) ）
TR:1500-2500ms TE:15-30ms
• IR sequence （ inversion recovery sequence ）
TR （ short ） TE （ short ） TI （ short ）

4. MR signal characteristics
• SE sequences ：
– T1-WI: highest signal on fat tissue ,better for showing
anatomical structures
– T2-WI: highest signal in liquid, better for detecting
lesions
– N （ H ） Density(H): for characteristics of lesions
• GRE sequence ： flip angle ， fast scan
• IR sequence ： separation between of fat and
liquid

5. T2WI T1WI
MR signal characteristics

6. Fat supression Liquid supression
MR signal characteristics

7. THREE DIMENSIONAL
BRAIN ANATOMY

8. Fig. 1.1 Post Contrast Axial MR Image of the brain
1
2
3
4
5
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

9. Fig. 1.2 Post Contrast Axial MR Image of the brain
7
6
Post Contrast sagittal T1 Wtd
M.R.I.
Section at the level of medulla
Answers
6. Medulla
7. Sigmoid Sinus

10. Fig. 1.3 Post Contrast Axial MR Image of the brain
15
8
9
10
11
12
13
14
16
17
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

11. Fig. 1.4 Post Contrast Axial MR Image of the brain
18
19
20
21
22
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

12. Fig. 1.5 Post Contrast Axial MR Image of the brain
23
24
25
26
27
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

13. Fig. 1.6 Post Contrast Axial MR Image of the brain
28
29
30
31
32
38
33
34
36
35
37
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

14. Fig. 1.7 Post Contrast Axial MR Image of the brain
39
40
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

15. Fig. 1.8 Post Contrast Axial MR Image of the brain
42
43
44
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

16. Fig. 1.9 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

17. Normal anatomical structure of
head on MRI

18. T2WI

19. T1WI

20. Flair sequence

21. T2WI(coronal section ）

22. T1WI （ sagittal section ）
Corpus callosum; optic chiasm; pituitary gland; medulla oblongata

23. MRI diagnosis of brain vascular
diseases
• Intra cerebral Hemorrhage
• Cerebral Infarction
• Intracranial Aneurysm

24. Brain bleed (hemorrhage)
• Causes ： high blood pressure,
vascular malformation and tumor
• Stage ： acute, sub acute, chronic

25. MRI appearances of hemorrhage at
different stage
• Acute hemorrhage
MRI － iso-intensity on T1WI, slightly low or low
intensity on T2WI( ideally MR was poor than CT for
Acute hemorrhage ).
• Sub acute hemorrhage
MRI － iso- or high signal intensity on T1WI, iso- or
slightly high signal intensity on T2WI.
• Chronic hemorrhage
MRI － high signal intensity both on T1WI/T2WI.

26. acute/subacute hemorrhage
acute
subacute T2WI T1WI

27. Chronic intracranial hemorrhage

28. MRI diagnosis of cerebral infarction

29. MR appearances of cerebral
infarction
• High signal intensity at Acute , subacute and
chronic stage on T2WI because of increment of
fluid at infarction.
• Iso-intensity at acute stage , iso- or slightly low
intensity at subacute stage, low intensity at
chronic stage on T1WI.
• Flair and DWI sequences are more sensitive for
detecting acute infarction.

30. MR:44396
MR&CT appearances of acuteMR&CT appearances of acute
cerebral infarctioncerebral infarction
T2WI T1WI Flair

31. MR:44396
MR&CT appearances of acute cerebralMR&CT appearances of acute cerebral
infarctioninfarction
FlairT1WIT2WI

32. Acute infarction

33. Acute
infarction

34. Acute infarction
DWI

35. Subacute/chronic infarction—T2WI

36. T2WI--Coronal

37. Chronic infarction at brain stem and
cerebellum—T2WI

38. Chronic infarction at brain stem and
cerebellum—T1WI

39. MRI diagnosis of head
trauma

40. The types of head trauma
 Skull fracture
 traumatic cerebral swelling
 brain contusions
 Intracranial bleed of trauma
– Epidural hematoma
– Subdural hematoma
– Subarachnoid hemorrhage
– Intracerebral hematoma

41. MR diagnosis of cranial trauma
Epidural hematoma ：
‫٭‬ direct violence on skull
‫٭‬skull fracture and deformation
‫٭‬direct laceration or tearing of meningeal arteries
‫٭‬ local hematoma ,not across cranial suture
‫٭‬shape of duple convex mirror

42. MR appearances
‫٭‬ shape of hematoma is biconvex
‫٭‬ signal intensity of hematoma varies greatly depending
on times.
‫٭‬ at acute stage （ 0~2 days ）， iso-intensity on
T1WI ， low intensity on T2WI.
‫٭‬at subacute stage （ 3~14 days ）， becoming high
signal intensity from rim to center on T1WI, still low
signal intensity at 6~8 days and high signal intensity
after 8 day on T2WI.
‫٭‬ at chronic stage (14 days later) , high signal intensity on
both T1WI and T2WI for quite long times (may be
several months)

43. Subacute hematoma at
left frontal lobe

44. Subacute hematoma at
left frontal lobe

45. Subdural hematoma
‫٭‬Location: supratentorial convexity.
‫٭‬ Caused by stretching and tearing of bridging veins.
‫٭‬ Hematoma is located between dura mater and
arachnoid. Often quite large extent , across cranial
suture.
‫٭‬ MR appearances ： shape of hematoma semilunar ，
signal changes of hematoma similar to epidural
hematoma at different stages.

46. Subacute Subdural Hematoma
Axial T1-weighted magnetic resonance imaging
demonstrates bilateral subacute subdural hematomas with
increased signal intensity. Areas of intermediate intensity
represent more acute hemorrhage into the subacute
collections.
T2-weighted magnetic resonance imaging in a
patient with subdural hematoma shows blood
products of differing ages.

47. Subacute subdural hematoma at left
frontal-temporal area

48. Subacute subdural hematoma at left
frontal-temporal area

49. MR Features of brain contusion
‫٭‬ Often involve the temporal and frontal lobe.
• Temporal lobe lesions tend to lie just above the petrous
bone or posterior to the greater sphenoid wing.
• Frontal lobe lesions occur just above the cribriform plate,
orbit, planum sphnoidale, and lesser sphenoid wing.

50. MR appearances
‫٭‬ MR is more sensitive than CT to find small contusion
because of easy to find edema caused by contusion.
‫٭‬hemorrhagic foci appear petechia or multiple confluent
regions with high signal intensity.
‫٭‬ easy to find contusion at brain stem.

51. Contusion and epidural hemorrhage at
both temporal lobe and frontal lobe

52. Contusion and epidural hemorrhage at
both temporal lobe and frontal lobe

53. Multiple contusions at both sides of
frontal and temporal lobes

54. Multiple contusions at both sides of
frontal and temporal lobes

55. INTRACRANIAL TUMORS
‫٭‬ primary (80%) :originating from cranial bone,
cranial meninges, brain tissues,
vessels, cranial nerves, pituitary
gland, etc.
glioma(50%) , meningioma(14%) , pituitary
tumor (11%) , acoustic neuroma(7%)
‫٭‬secondary (20%) : metastasis , involved by tumor
from near structures.

56. The types of intracranial tumors
• Intraaxial brain tumors ：
1.glioma( astrocytoma and oligodendroglioma)
2.ependymoma
3.medulloblastoma
4.hemangioblastoma
5.papilloma choroideum
6.metastases

57. The types of intracranial tumors
• Extraaxial brain tumors
1.meningioma
2.craniopharyngioma
3.pituitary tumor
4.nerve sheath tumors-acoustic
schwannoma
5.epidermorid cyst, dermoid cyst and
hamartomas

58. Direct signs
1. tumor or occupying lesion.
2. abnormal density or signal.
3. enhancement in different
degree on enhanced scan.
CT and MRI Signs for diagnosis
of intracranial tumors
、、

59. Indirect signs
1. shift of near structures
2. edema in brain tissue near tumor
3. Intratumoral bleed
4. Intratumoral calcification
5. bone changes

60. Astrocytoma
lower grading of astrocytoma ， grading
I or II ．
• Often in adult （２０～４０
years ） -- more occult in
cerebral
hemisphere ， grading
II ， solid
• child– less seen ， more in
cerebellum ， grading I, cyst

61. Astrocytoma
MR ：
Isointensity on T1WI ， unclear border ,
high or slightly high signal intensity on T2WI
no or slight occupying effect , no or slight
enhancement.

62. Grade I Astrocytoma
T1WI T2WI

63. Grade II astrocytoma
T2W Gd+ Gd+
MR:39547

64. Astrocytoma
high grading （ grading III or IV)
• Fast growing
• Occur in any age

65. Imaging appearances of high
grading astrocytoma
• Obvious occupying effects ,infiltrating growing
with unclear margin , growing across lobe and
hemisphere.
• Necrosis, cyst , bleed.
• Obvious brain edema around tumor.
• Obvious uneven or ring-like enhancement.

66. Grade IV astrocytoma
MR:39985
T2W T1W Gd+

67. Grade IV
astrocytoma
MR:39985
T2W Gd+
T2W Gd+

68. MR ： 53847
Grading IV astrocytoma

69. Brain metastasis
• Old age
• Single or multiple
• Multiple appearances on CT or MR, but
often shown in nodule
• Heterogeneous density or signal, central
necrosis with lower density or signal on
T1WI.
• Ring-like or even enhancement
• Obviously finger-like peritumoral edema

70. Multiple
metastases

71. Metastasis from lung cancer
uncontrast
contrast

72. Metastasis from lung cancer
uncontrast contrast

73. Imaging of meningioma
• Round or hemishere mass occur mostly in convexity of
brain , especially sagittal sinus.
• Mass with clear margin which was encysted with cerebral
spinal fluid and/or vessels.
• Iso- or slightly high density on plain CT and low signal on
T1WI, iso- or slightly high signal on T2WI, which was
enhanced obviously and evenly.
• A broad thickened dural-based margin which was called
“tail sign” .
• Edema may be not or obvious.
• Local bone changes including destruction, thin or
thickness.

74. Right parietal meningioma
Plain T1WI
Contrast T1WI

75. T2WI AND
contrast T1WI

76. Meningioma
T2WI
T1WI
Gd-T1W

77. Acoustic schwannoma
• Benign tumor, occur mostly at middle age people,
approximately 7 ~8 of all primary intracranial neoplasms.﹪ ﹪
• Ovoid or tubular tumors may occur in the internal auditory canal
and cerebellopontine angle cistern .
• Tumor may be part of solid and cystic .
• On Plain CT, solid part of tumor was iso-density ,and cystic part
was low density.
• Iso-intensity or low signal intensity were seen in solid or cystic
part of tumor on T1WI, but high or very high signal intensity on
T2WI,.
• Obvious enhancement was seen on solid tumor.
• Enlargement of internal auditory canal.

78. Left acoustic
schwannoma

79. Left acoustic schwannoma
T2WI T1WI Contrast T1WI

80. Left acoustic
schwannoma