Imaging of the CNS

Contents• Diagnostic tools• Anatomical localization: Brain• Diseases:

- Infection- Tumor- Trauma- Stroke- Cord compression

Tools

• Plain film• CT• MR• Angiography

Plain radiography

5 densities

• Air• Fat• Soft tissue

(water,muscles,etc)• Bone, calcification• Metallic

Advantage & I/C

Adventage

- Convenience

- Safe

- Fast

- Availability

Indication- Fracture skull- Increase ICP- Intrasellar mass- Osteolytic/

osteoblastic lesion- Calcifying pathology

View and positioning

PA

• Petrous pyramid อยู่��ภายู่ในกระบอกตา

• Frontal bone and parietal bone• Frontal sinus • Nasal cavity• Mandible• Roof of orbits

Lateral skull

• Cranial vault• Suture : coronal and

lambdoid • Occipital bone • Sellar turcica• Floor of cranial fossa• Clivus • Nasopharyngeal soft tissue• Sphenoid air sinus• lateral of calvarium• lateral of mandible• Cervical spine 1st-2nd

LateralOuter table

Inner table

Diploic space

External occipital protuberance

Suture

Sphenoid air sinus

Sellar turcica

Caldwell view

• Orbital wall• Frontal and ethmoid

sinuses• Mandible

Ethmoid sinusMaxillary sinus

Orbital wallCaldwell view

Towne’s view

• Occipital bone• Lamdoid suture• Foramen magnum• Petrous ridge และ

mastoid sinuses• Zygomotic arch• Mandible ส่�วน head,

neck และ rami

Waters’ view

• Facial bone• Orbital roof• Maxillary, frontal

and ethmoid sinus

Waters’ view

Maxillary sinus

Orbital wallFrontal sinus

Water’ s view

Caldwell view

Paranasal sinuses

Paranasal sinusitisParanasal sinusitis

Air-fluid level at both maxillary and both frontal sinuses

Linear fracture skull right parietal bone

Nasal bone

Outer table destruction : histiocytosis X

Fx nasal bone

Normal sella turcica

Posterior clinoidAnterior clinoid

Dorsum sellae

Floor of sella

ICP

“loss of dorsum sella sign”

Pituitary tumor

“Double floor sign”

Large intrasella mass

2

3

1

“ballooning sella”

CECT

CT : Pituitary tumour

CT scan

CT /Spiral CT/ MDCT

CT scan

Advantage- Axial imaging- Reconstruction, reformatted to coronal,

sagittal planes- Providing contrast- noncontrast study- Differentiation tissues by densities(HU)- Additional software: CTA, CTV, 3D, CTP

etc.

Indication

• Trauma case• 1st line imaging of Stroke• Infection• Tumor• Intracranial calcification• C/I: pregnancy, contrast enhancement

injection: limited in patient with azotemia

Attenuation number of CT (HU)Hounsfield Units

• CSF = 0-20 HU.• Gray matter = 40 HU.• White matter = 23-46 H• Clot blood & hematoma = 70-100 HU.• Calcification and bone = +100-200 HU.• Fat = -100-200 HU.• Air = >- 600 HU.• Density ของ lesion ใดๆจะด�เที�ยู่บก�บ gray matter

Normal CT brain

Basal ganglia

Gray matter

White matter

Thalamus

cerebellum

Normal CT brain : Ventricular system

4th ventricle

Temporal horn

Frontal horn

Occipital horn

Lateral ventricle

Physiologic calcification• Pineal gland

– Age > 10 year– Size < 10 mm.

• Basal ganglia– Middle aged – Young aged :

hypoxia or abnormal serum Calcium

• Choroid plexus• Dura

– Falx cerebri– Calcification of

diaphragmatic sellae

Enhancement by contrast media

• Abnormal blood brain barrier (BBB)

• Identify vascular and dural structures

• Differential pathology by pattern of enhancement

DSA

ANGIOGRAM – MCA BIFURCATION ANEURYSM

MCA aneurysm

25-YEAR-OLD NORMOTENSIVE MAN WITH UNEXPLAINED ICH

LT ICA ANGIOGRAM – AVM

Indication

• Gold standard for vascular imaging ( ex. Aneurysm, AVM)

• Arterial / venous• Risk=1%• C/I : azotemia, pregnancy

MRI machine

MRI

• Magnet Field : 0.5-3Tesla• Pulse sequences : Spin Echo ( SE)• Parameters : T1 : T2 : TR : TE

Advantage MRI

1. Multiplanar imaging

( axial/coronal/sagittal/any planar)

2. No radiation

3. No bony artifact

4. Safer contrast agent (Gadolinium)

5. Best for analysis: posterior fossa and leptomeningeal lesions

MRI- three planars

Axial Coronal Sagittal

Contraindications

• Implantable Cardiac defibrillator• Pace Maker• wt. > 136 Kg • Severe Claustrophobia• Pregnancy (+/- )• Cochlear Implant• Aneurysm Clips• Ferromagnetic eye prosthesis /

F.B.

SIGNAL INTENSITY(SI)

• BRAIN : GM

: WM

• Muscles • Nerve :dorsal root

:ventral• CSF• Fat• Pituitary: anterior

posterior

T1W T2W

intermediate high

high low

intermediate

intermediate intermediate

intermediate intermediate

low high

high low

Intermediate intermediate

high high

Tissue

T1WI

T2WI

MRI of brain tumor

T1W T2W T1W-GD