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CT BRAIN - BASICS. Dr Mohamed el Safwany , MD. Intended learning outcome. The student should learn at the end of this lecture CT brain basics. CT Principle. RING OF XRAY DETECTORS. Frankfurt plan e. HOUNSFIELD UNITS. Numeric information in each pixel of ct image

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Ct brain basics

CT BRAIN - BASICS

Dr Mohamed el Safwany, MD.


Intended learning outcome
Intended learning outcome

The student should learn at the end of this lecture CT brain basics.


CT Principle

RING OF XRAY DETECTORS



Hounsfield units
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


Ct mri
CT /MRI

  • CT PICTURE

  • WHITE MATTER IS DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT

  • CSF IS BLACK

  • MR PICTURE


Step wise approach
Step wise approach

  • Ventricles/ cisterns

  • Cortex

  • Deep gray matter

  • Focal lesions

  • Bone

  • Extracranial soft tissue

  • Para nasal sinuses


LV

FRONTAL HORN

3V

OCCIPITAL HORN

FORAMEN OF MONRO

trigone

TEMBORAL HORN

4 V

AQUEDUCT OF SYLVIUS



ABOVE THE LEVEL OF FORAMEN MAGNUM

VA

MEDULLA

4 V

TONSIL

INT OCC PROT


LEVEL OF FOURTH VENTRICLE

Optic nerve

CPCISTERN

TEM HORN

PONS

4V

MCP


LEVEL ABOVE FOURTH VENTRICLE

OLF SULCUS

SYLV FISSURE

SUPRA SELLAR CISTERN

AMB CIST

MB

4V

vermis





Cerebral arterial territory
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


ACA

MCA

PCA


  • 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




Cerebral ischemia1
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


Goal of imaging
Goal of imaging

  • Excludehemorrhage

  • 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)


Infarct vs pneumbra
Infarct vspneumbra

  • 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.



Ct hyperacute infarct
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






Ct acute infarct
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


Ct chronic infarct
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


Infarct tumour
INFARCT / TUMOUR

  • CLINICAL HISTROY

  • DISTRIBUTION

  • SHAPES

  • GRAY / WHITE INVOLVEMENT

  • ADVANCED IMAGING


Venous infarct
VENOUS INFARCT

  • HISTROY

  • BEYOND VASCULAR DISTRIBUTION

  • HAEMORRHAGIC INFARCT

  • THORMBUS IN VENOUS SINUSES

  • SYMMETRICAL LOW ATTENUATION IN DEEP GRAY MATTER - DEEP CEREBRAL VEIN THORMBUS


Edema infarct
EDEMA/ INFARCT

  • INFARCT TYPICAL VASCULAR DISTRIBUTION

    GRAY MATTER INVOLVEMENT

  • EDEMA

    NOT CONFINED TO VASCULAR DISTRIBUTION

    MOSTLY INVOLVES WHITE MATTER







H gic infarct
H’gic infarct


Text book
Text Book

David Sutton’s Radiology

Clark’s Radiographic positioning and techniques


Assignment
Assignment

Two students will be selected for assignment.


Question
Question

Describe CT of acute brain infarction?