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 อยู่ภายในกระบอกตา 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
Lateral Outer table Suture Diploic space Sellar turcica Inner table External occipital protuberance Sphenoid air sinus
Caldwell view Orbital wall Frontal and ethmoid sinuses Mandible
Ethmoid sinus Maxillary sinus Caldwell view Orbital wall
Towne’s view Occipital bone Lamdoid suture Foramen magnum Petrous ridge และ mastoid sinuses Zygomotic arch Mandible ส่วน head, neck และ rami
Waters’ view Facial bone Orbital roof Maxillary, frontal and ethmoid sinus
Waters’ view Frontal sinus Orbital wall Maxillary sinus
Paranasal sinuses Water’ s view Caldwell view
Air-fluid level at both maxillary and both frontal sinuses Paranasal sinusitis Air-fluid level at both maxillary and both frontal sinuses
Linear fracture skull right parietal bone
Outer table destruction : histiocytosis X Nasal bone Fx nasal bone Outer table destruction : histiocytosis X
Normal sella turcica Anterior clinoid Posterior clinoid Dorsum sellae Floor of sella
“loss of dorsum sella sign” ICP “loss of dorsum sella sign”
Pituitary tumor “Double floor sign”
Large intrasella mass 1 3 2 “ballooning sella”
CT : Pituitary tumour CECT
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 ใดๆจะดูเทียบกับ gray matter
Normal CT brain Gray matter White matter Basal ganglia cerebellum Thalamus
Normal CT brain : Ventricular system Temporal horn Frontal horn Lateral ventricle 4th ventricle Occipital horn
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 Multiplanar imaging ( axial/coronal/sagittal/any planar) No radiation No bony artifact Safer contrast agent (Gadolinium) 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) Tissue T1W T2W intermediate high high low intermediate intermediate low high Intermediate intermediate high high BRAIN : GM : WM Muscles Nerve :dorsal root :ventral CSF Fat Pituitary: anterior posterior
T1WI
T2WI
MRI of brain tumor T2W T1W-GD T1W