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
8. 5
3
Post Contrast sagittal T1 Weighted
M.R.I.
2
Section at the level of Foramen
Magnum
1
Answers
4
1. Cisterna Magna
2. Cervical Cord
3. Nasopharynx
Fig. 1.1 Post Contrast Axial MR Image of the brain
4. Mandible
5. Maxillary Sinus
9. Post Contrast sagittal T1 Wtd
M.R.I.
Section at the level of medulla
6
Answers
7
Fig. 1.2 Post Contrast Axial MR Image of the brain
6. Medulla
7. Sigmoid Sinus
10. 14
13
12
Post Contrast sagittal T1 Wtd
M.R.I.
11
17
10
16
15
Section at the level of Pons
Answers
9
13. Internal Carotid
Artery
14. Cavernous Sinus
10. IV Ventricle
Fig. 1.3 Post Contrast Axial MR Image of the brain
8. Cerebellar
Hemisphere
9. Vermis
8
15. Middle Cerebellar
Peduncle
11. Pons
12. Basilar Artery
16. Internal Auditory
Canal
17. Temporal Lobe
11. 20
22
19
18
21
Post Contrast sagittal T1 Wtd
M.R.I.
Section at the level of Mid Brain
Answers
18. Aqueduct of Sylvius
19. Midbrain
20. Orbits
Fig. 1.4 Post Contrast Axial MR Image of the brain
21. Posterior Cerebral Artery
22. Middle Cerebral Artery
12. 27
25
24
Post Contrast sagittal T1 Wtd
M.R.I.
Section at the level of the
III Ventricle
Answers
23
26
23. Occipital Lobe
24. III Ventricle
25. Frontal Lobe
Fig. 1.5 Post Contrast Axial MR Image of the brain
26. Temporal Lobe
27. Sylvian Fissure
13. 38
37
32
36
31
35
Post Contrast sagittal T1 Wtd
M.R.I.
30
Section at the level of Thalamus
29
Answers
34
28. Superior Sagittal Sinus
29. Occipital Lobe
33
28
33. Thalamus
34. Temporal Lobe
30. Choroid Plexus within the
35. Internal Capsule
occipital horn
Fig. 1.6 Post Contrast Axial MR Image of the brain
36. Putamen
31. Internal Cerebral Vein
37. Caudate Nucleus
32. Frontal Horn
38. Frontal Lobe
14. 41
40
Post Contrast sagittal T1 Wtd
M.R.I.
39
Section at the level of Corpus
Callosum
Answers
39. Splenium of corpus callosum
40. Choroid plexus within the
Fig. 1.7 Post Contrast Axial MR Image of the brain
body of lateral ventricle
41. Genu of corpus callosum
15. 44
43
Post Contrast sagittal T1 Wtd
M.R.I.
42
Section at the level of Body of
Corpus Callosum
Answers
42. Parietal Lobe
Fig. 1.8 Post Contrast Axial MR Image of the brain
43. Body of the Corpus Callosum
44. Frontal Lobe
16. 46
Post Contrast sagittal T1 Wtd
M.R.I.
Section above the Corpus Callosum
45
Answers
45. Parietal Lobe
46. Frontal Lobe
Fig. 1.9 Post Contrast Axial MR Image of the brain
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.
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.
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 FEATURES
٭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)
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 T2-weighted magnetic resonance imaging in a
increased signal intensity. Areas of intermediate intensity patient with subdural hematoma shows blood
products of differing ages.
represent more acute hemorrhage into the subacute
collections.
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.
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
from near structures.
tumor
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. CT and MRI Signs for diagnosis
of intracranial tumors
Direct signs
、
1. tumor or occupying lesion.
2. abnormal density or signal.
3. enhancement in different
degree on enhanced scan.
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.
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
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.
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.
