ct & mri of central nervous system
TRANSCRIPT
CT&MRI of Central nervous system
Dept. Radiology, the 2nd affiliated hospital, Sun Yat-Sen University
Huang Sui Qiao
CT Scanning
• Plain CT
• Contrast CT
CT scanner
CT characteristics of pictures
• CT value : depending on different organ and tissues to X ray.
call HU ( Hounsfield Unit ) .
Bone
Soft tissue
Water
Fat
Air
Magnetic Resonance Imaging
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 )
MR signal characteristics
• SE sequences :– T1-WI: highist signal on fat tissue ,better for showing
anatomical structures– T2-WI: highist signal in liquid, better for detecting lesio
ns– N ( H ) Density,N(H): for characteristics of lesions
• GRE sequence : flip angle , fast scan• IR sequence : separation between of fat and liq
uid
T2WI T1WI
MR signal charateristics
Fat supression Liquid supression
MR signal charateristics
Normal anatomical structure of head on CT
Brain stem; cerebellum;suprasellar cistern; lateral sulcus; quadrigeminal cistern; lateral ventricle; basilar ganglion
Normal anatomical structure of head on CT
Gray matter; white matter; cortex; frontal lobe; occipital lobe; parietal lobe; temporal lobe; internal capsule ; thalamus; falx
Normal anatomical structure of head on MRI
T2WI
T1WI
Flair sequence
T2WI(coronal section )
T1WI ( sagittal section )
Corpus callosum; optic chiasm; pituitary gland; medulla oblongata
Intracranial tumors
,primary (80%) :originating from cranial bone ٭
cranial meninges, brain tissues,
vessels, cranial nerves, pituitary
gland, etc.
glioma(50%) , mingioma(14%) , pituitary
tumor (11%) , acoustic neuroma(7%)
secondary (20%) : metastasis , involved by tumor٭
from near structures.
The types of intracranial tumors
• Intraaxial brain tumors : 1.glioma(astrocytoma and oligodendrogliom
a)
2.ependymoma
3.medulloblastoma
4.hemangioblastoma
5.papilloma choroideum
6.metastases
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
The rule for diagnosis of intracranial tumors
• There are or not a tumor
• The position of a tumor : intraaxial or
extraaxial
• The type of a tumor
一、 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
、、
二、 indirect signs
1. shift of near structures 2. edema in brain tissue near tumor 3. intratumoral bleed 4. intratumoral calcification 5. bone changes
astrocytoma
lower grading of astrocytoma , grading I or II .
• Often in adult (20~40years ) -- more occult in cerebral hemisphere , grading II , solid
• child– less see , more in cerebellum , grading I, cyst
astrocytoma
CT : low or slightly low density lesion , no or slight occupying effect , no or slight enhancement. MR : Isointensity on T1WI , unclear border , high or slightly high signal intensity on T2WI no or slight occupying effect , no or slight enhancement.
Grading I astrocytoma
Plain CT
Grading I astrocytoma
T1WI T2WI
Grading I astrocytoma
T2W Gd+ Gd+
MR:39547
astrocytomahigh grading ( grading III or IV)
• Fast growing
• Occur in any age
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.
Grading IV astrocytoma
MR:39985
T2W T1W Gd+
Grading IV astrocytoma
MR:39985
T2W Gd+
T2W Gd+
MR : 53847
Grading IV astrocytoma
Brain metastasis
• Old age• Single or multiple • Multiple appearances on CT or MR, but oft
en shown in nodule • Heterogeneous density or signal, central n
ecrosis with lower density or signal on T1WI.
• Ring-like or even enhancement• Obviously finger-like peritumoral edema
Multiple metastases
Metastasis from lung cancer
uncontrast contrast
Metastasis from lung cancer
uncontrast contrast
Lung cancer and brain metastases
MR:39491
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
meningioma
• Most common nanglial intracranial tumor.• Mostly affect 40-70 adults.• Extraaxial mass attaching dura matter,about 9
0% occult on suppratentorium of cerebellum, few of them can occult in ventricles
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 th
ickness.
Left parietal meningioma
Plain CT
Contrast CT
Round high density mass
Obviously and evenly enhanced
Right parietal meningioma
Plain T1WI
Contrast T1WI
T2WI AND contrast T1WI
meningioma
T2WI
T1WI
Gd-T1W
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 cysti
c part was low density.• Iso-intensity or low signal intensity were seen in solid or cy
stic 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.
Left acoustic schwannoma
Left acoustic schwannoma
T2WI T1WI Contrast T1WI
Left acoustic schwannoma
Right acoustic schwannoma
T1WI Contrast T1WI
Right acoustic schwannoma
Contrast T1WI
CT and MRI diagnosis of brain vascular diseases
• Bleed in high pressure patients
• Intracranial aneurysm
• Cerebral infarction
Brain bleed (hemorrhage)
• Causes : high blood pressure, vascular malformation and tumor
• Stage : acute, subacute, chronic
CT&MRI appearances of hemorrhage at different stage
• CT was more sensitive for acute hemorrhage CT - high density, CT value about 60 - 80Hu MRI - iso-intensity on T1WI, slightly low or low intensity on T2WI.• Subacute hemorrhage CT - iso- or slightly high density. MRI - iso- or high signal intensity on T1WI, iso- or slightly high signal intensity on T2WI.• chronic hemorrhage CT - iso- or low density MRI - high signal intensity both on T1WI/T2WI.
Acute hemorrhage ( high density on CT )
Acute hemorrhage ( high density on CT )
Subacute hemorrhage
Density lower than acute stage with unclear margin
acute/subacute hemorrhage
acute
subacute T2WI T1WI
Change from acute to subacute stage ( CT low density hemorrhage )
CT after bleed CT 2W latter MRI 2W latter
Chronic intracranial hemorrhage
Intracranial aneurysm
• causes : congenital ; acquired (often high blood pressure )
• type : according to morphology (saccular ,fusiform), size and location etc .
Aneurysm
●Incidence : 0.2~1%. ● Distribution of age: mid-old age(30~60years),seldon
in youth. ● morphology : saccular ( 95% ) ,fusiform . ●size : <0.5cm small; 0.5~1.5cm middle;1.5~2.5 larg
e ; >2.5 huge ●position : internal carotid A--41.3%; anterior commu
nicating A--24.4%; middle cerebral A—20.8%; anterior cerebral A—9%; vertebral-basilar A--4.5% 。
CT appearances
• Showing aneurysm directly, filing defect in large one ( thrombus )
• Subarachnoid hemorrhage in ruptured aneurysm.
MR appearance
1. aneurysm without thrombus: round or oval homogeneous very low signal lesion both on T1 and T2WI. 2. aneurysm with thrombus : heterogeneous both on T1 and T2WI , high signal in some area. 3. enhanced scan : may be heterogeneously enhanced
Aneurysm at left internal carotid A
Aneurysm at left internal carotid A
T1WI-contrast T1WI-contrast
Aneurysm at left internal carotid A
Aneurysm at left middle cerebral A
CT&MRI diagnosis of cerebral infarction
CT appearances of cerebral infarction
• Acute stage- onset within 4- 6h. normal/slightly low density and narrowing of sul
cus on infarction area because of edema; low density after 12- 24h, but no any abnormal finding within 24h.
• Subacute stage- within 1 week, typical CT appearance. Low density on infarction area with mass effect. After 2- 3 weeks , iso- or slightly low density
with unclear margin, enhancement at border area in contrast scan.
• Chronic stage - even low density with clear margin. Atrophy of local brain.
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 subacte stage, low intensity at chronic stage on T1WI.
• Flair and DWI sequences are more sensitive for detecting acute infarction.
MR:44396
Within 24h
After 3 days
After 2 weeks
Acute cerebral infarction
MR:44396
MR&CT appearances of acute MR&CT appearances of acute cerebral infarctioncerebral infarction
Within 24h after 3 days after 2 weeks
MR:44396
MR&CT appearances of acute cerebrMR&CT appearances of acute cerebral infarctional infarction
T2WI T1WI Flair
MR:44396
MR&CT appearances of acute cerebrMR&CT appearances of acute cerebral infarctional infarction
Flair T1WIT2WI
Acute infarction
MR : 66335 CT : 122740
M 39 , CT(-)
Acute infarction
MR : 66335 CT : 122740
M 39 , CT(-)
Acute infarction
MR : 66335 CT : 122740
Acute infarction DWI
MR : 66335 CT : 122740
Subacute/chronic infarction—T2WI
T2WI--Cor
Chronic infarction at brain stem and cerebellum—T2WI
Chronic infarction at brain stem and cerebellum—T1WI
CT&MRI diagnosis of head trauma
The types of head trauma
一、 Skull fracture 二、 traumatic cerebral swelling 三、 brain contusions 四、 Intracranial bleed of trauma ( 一 ) Epidural hematoma ( 二 ) Subdural hematoma ( 三 ) Subarachnoid hemorrhage ( 四 ) intracerebral hematoma
CT&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٭
CT appearances
local duple convex mirror with high density, CT v ٭ alue at 40~100Hu.
there are or not mass effect according the size o ٭f hematoma which compress gyri , ventricles. Midline is shifted to contralateral side.
the density of hematoma decrease during the tim٭e, become isodesity at about 2 weeks (subacute stage) and low density at about 1 month (chronic stage) .
acute epidural hematoma at leftfrontal lobe
acute epidural hematoma at rightfrontal lobe
Acute epidural hematoma at temporal-parietal lobe
MR appearances
shape of hematoma is seen like CT ٭signal intensity of hematoma varies greatly depend ٭
ing on times. at acute stage ٭ ( 0~2 days ), iso-intensity on T1
WI , low intensity on T2WI.at subacute stage٭ ( 3~14 days ), becoming hig
h 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 intensi ٭ty on both T1WI and T2WI for quite long times (may be several months)
Subacute hematoma at left frontal lobe
Subacute hematoma at left frontal lobe
Subacute hematoma at left frontal lobe
Subdural hematoma.location: supratentorial convexity٭caused by stretching and tearing of bridging vein ٭
s. hematoma is located between dura mater and ar ٭
achnoid. Often quite large extent , across cranial suture.
CT appearances ٭ : crescentic high density. Dividing into acute, subacte and chronic stages . Density changes of hematoma at different stages similar to epidural hematoma.
MR appearances ٭ : shape of hematoma seen as CT , signal changes of hematoma similar to epidural hematoma at different stages.
Acute subdural hematoma at right frontal-temporal area
Subacute subdural hematoma at left frontal-temporal area
Subacute subdural hematoma at left frontal-temporal area
Subacute subdural hematoma at left frontal-temporal area
Subacute subdural hematoma at left frontal-temporal area
Chronic subdural hematoma at left frontal lobe
CT&MR diagnosis of brain contusion
Often involve the temporal and frontal lobe. Temporal l ٭ obe 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.
CT appearances ٭ : high density of hemorrhagic foci (vary in size ) scattered throughout the larger nonhemorrhagic
zone or lower density area (edema). May be or may not be mass effect.
Contusion at frontal lobe
Contusion at both sides of frontal base
Contusion at temporal lobe
MR appearances
MR is more sensitive than CT to find small contu ٭ sion because of easy to find edema caused by contusion.
hemorrhagic foci appear petechia or multiple confl٭uent regions with high signal intensity.
.easy to find contusion at brain stem ٭
Contusion and epidural hemorrhage at both temporal lobe and frontal lobe
Contusion and epidural hemorrhage at both temporal lobe and frontal lobe
Multiple contusions at both sides of frontal and temporal lobes
Multiple contusions at both sides of frontal and temporal lobes