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Dr Mohamed el Safwany, MD.
CT BRAIN - BASICS Dr Mohamed el Safwany, MD.
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Intended learning outcome
The student should learn at the end of this lecture CT brain basics.
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CT Principle RING OF XRAY DETECTORS
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Frankfurt plane
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HOUNSFIELD UNITS Numeric information in each pixel of ct image
Related to composition & nature of tissue Represent the density of tissue Also called as CT NUMBER
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air fat ---70 Pure water Csf +8 White matter +30 Gray matter +45 blood +70 Bone/cacification +1000
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CT /MRI CT PICTURE MR PICTURE
WHITE MATTER IS DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT CSF IS BLACK MR PICTURE GREY MATTER T1WI DARK T2WI BRIGHT WHITE MATTR CSF GREY TO DARK WHITE
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Step wise approach Ventricles/ cisterns Cortex Deep gray matter
Focal lesions Bone Extracranial soft tissue Para nasal sinuses
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LV 3V FORAMEN OF MONRO 4 V FRONTAL HORN trigone OCCIPITAL HORN
TEMBORAL HORN 4 V AQUEDUCT OF SYLVIUS
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COMMON SECTIONS AXIAL SECTIONS CORONAL SECTIONS SAGITTAL SECTIONS
POSTERIOR FOSSA CUTS -ABOVE THE FORAMEN MAGNUM LEVEL -LEVEL OF THE FOURTH VENTRICLE -ABOVE THE FOURTH VENTRICULAR LEVEL - TENTORIAL SUPRATENTORIAL CUTS -THIRD VENTRICULAR LEVEL -LOW VENTRICULAR LEVEL -ABOVE THE VENTRICULAR LEVEL -FRONTAL HORN LEVEL -THIRD VENTRICULAR LEVEL -MID VENTRICULAR LEVEL -OCCIPITAL HORN LEVEL -MID SAGITTAL LEVEL -PARASAGITTAL LEVEL THROUGH THE LATERAL VENTRICULAR BODY -LATERAL ORBITAL LEVEL
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ABOVE THE LEVEL OF FORAMEN MAGNUM
VA MEDULLA 4 V TONSIL INT OCC PROT
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LEVEL OF FOURTH VENTRICLE
Optic nerve CPCISTERN TEM HORN PONS 4V MCP
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4V LEVEL ABOVE FOURTH VENTRICLE vermis SUPRA SELLAR CISTERN OLF SULCUS
SYLV FISSURE SUPRA SELLAR CISTERN AMB CIST MB 4V vermis
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THIRD VENTRICULAR LEVEL
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LOW VENTRICULAR
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Above ventricle level
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Cerebral Arterial Territory
MCA-most of lateral hemisphere, Basal ganglia, insula, ACA-Inferomedial basal ganglia,ventromedial frontal lobes, anterior 2/3rd medial cerebral hemispheres, 1 cm supero medial brain convexity PCA-Thalami, midbrain, posterior 1/3of medial hemisphere, occipital lobe, postero medial temporal lobe
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ACA MCA PCA
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AICA- inferolateral part of pons, middle cerebellar peduncle, floccular region, anterior petrosal surface of cerebellar hemisphere PICA-posteroinferior surface of cerebellar hemisphere , ipsilateral part of inferior vermis, Superior cerebellar artery-superior aspect of cerebellar hemisphere (tentorial surface), ipsilateral superior vermis, largest part of deep white matter including dentate nucleus, pons
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Water shed infarct
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CEREBRAL ISCHEMIA
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Cerebral ischemia Significantly diminished blood supply to all parts(global ischemia) or selected areas(regional or focal ischemia) of the brain Focal ischemia- cerebral infarction Global ischemia-hypoxic ischemic encephalopathy(HIE),hypotensive cerebral infarction
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Goal of imaging Exclude hemorrhage
Identify the presence of an underlying structural lesion such as tumour , vascular malformation ,subdual hematoma that can mimic stroke Identify stenosis or occlusion of major extra- and intracranial arteries Differentiate between irreversibly affected brain tissue and reversibly impaired tissue (dead tissue versus tissue at risk)
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Infarct vs pneumbra In the central core of the infarct, the severity of hypoperfusion results in irreversible cellular damage . Around this core, there is a region of decreased flow in which either: The critical flow threshold for cell death has not reached Or the duration of ischemia has been insufficient to cause irreversible damage.
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Hyper acute infarct(<12 hours)
Subacute infarct( days) Chronic infarct(>2 weeks) Old infarct(>2 months)
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CT-Hyperacute infarct
Hyperdense MCA sign-acute intraluminal thrombus Attenuation of lentiform nulei Dot sign-occluded MCA branch in sylvian fissure Insular ribbon sign –grey white interface loss along the lateral insula
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Dense mca sign
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‘ loss of insular ribbon’
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M C A DOT SIGN
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ATTENUATION OF LENTICULAR NUCLEUS
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CT- Acute infarct Low density basal ganglia Sulcal effacement
Wedge shaphed parenchymal hypo density area that involves both grey and white matter Increasing mass effect Hemorrhagic transformation may occur -15 to 45% ( basal ganglia and cortex common site) in 24 to 48 hours
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CT-chronic infarct Plain ct
Focal, well-delineated low-attenuation areas in affected vascular distribution sulci become prominent; ipsilateral ventricle enlarges Dystrophic Ca++ may occur in infarcted brain but is very rare CECT: No enhancement
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INFARCT / TUMOUR CLINICAL HISTROY DISTRIBUTION SHAPES
GRAY / WHITE INVOLVEMENT ADVANCED IMAGING
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VENOUS INFARCT HISTROY BEYOND VASCULAR DISTRIBUTION
HAEMORRHAGIC INFARCT THORMBUS IN VENOUS SINUSES SYMMETRICAL LOW ATTENUATION IN DEEP GRAY MATTER - DEEP CEREBRAL VEIN THORMBUS
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EDEMA/ INFARCT INFARCT TYPICAL VASCULAR DISTRIBUTION
GRAY MATTER INVOLVEMENT EDEMA NOT CONFINED TO VASCULAR DISTRIBUTION MOSTLY INVOLVES WHITE MATTER
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PCA INFARCT
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MCA INFARCT
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ACA INFARCT
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WATERSHED INFARCT
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Old infarct
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H’gic infarct
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Text Book David Sutton’s Radiology
Clark’s Radiographic positioning and techniques
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Assignment Two students will be selected for assignment.
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Question Describe CT of acute brain infarction?
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Thank u
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