how to read a head ct
DESCRIPTION
How to Read a Head CT. Dr Mohamed El Safwany . MD. Intended learning outcome. The student should learn at the end of this lecture interpretation of CT Brain. Head CT. - PowerPoint PPT PresentationTRANSCRIPT
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How to Read a Head CT
Dr Mohamed El Safwany. MD. 1
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Intended learning outcome• The student should learn at the end of this lecture interpretation of CT
Brain.
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Head CT• Has assumed a critical role in the daily practice of
Emergency Medicine for evaluating intracranial emergencies. (e.g. Trauma, Stroke, SAH, ICH).
• Most practitioners have limited experience with interpretation.
• In many situations, the Emergency Physician must initially interpret and acton the CT without specialist assistance.
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Head CT
“Blood Can Be Very Bad”4
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Blood Can Be Very Bad
•Blood•Cisterns •Brain •Ventricles•Bone 5
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Blood Can Be Very Bad
•Blood•Cisterns •Brain •Ventricles•Bone 6
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Blood Can Be Very Bad
•Blood•Cisterns •Brain •Ventricles•Bone 7
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Blood Can Be Very Bad
•Blood•Cisterns •Brain •Ventricles•Bone 8
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Blood Can Be Very Bad
•Blood•Cisterns •Brain •Ventricles•Bone 9
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CT Scan Basics• A CT image is a computer-generated picture
based on multiple x-ray exposures taken around the periphery of the subject.
• X-rays are passed through the subject, and a scanning device measures the transmitted radiation.
• The denser the object, the more the beam is attenuated, and hence fewer x-rays make it to the sensor.
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CT Scan Basics• The denser the object, the whiter it is on CT
• Bone is most dense = + 1000 Hounsfield U. • Air is the least dense = - 1000H Hounsfield U.
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CT Scan Basics: Windowing
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Focuses the spectrum of gray-scale used on a particular image.
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2 Sheet Head CT
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Posterior Fossa
•Brainstem•Cerebellum•Skull Base
–Clinoids–Petrosal bone–Sphenoid bone–Sella turcica–Sinuses
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CT ScanCT Scan
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CT ScanCT Scan
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22ndnd Key Level Sagittal View Key Level Sagittal View2nd Key Level
Circummesencephalic Cistern
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Cisterns at Cerebral Peduncles Cisterns at Cerebral Peduncles LevelLevel
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CT ScanCT Scan
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CT ScanCT Scan
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33rdrd Key Level Sagittal View Key Level Sagittal View
Circummesencephalic Cistern
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Cisterns at High Mid-Brain LevelCisterns at High Mid-Brain Level
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CT ScanCT Scan
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CSF Production
• Produced in choroid plexus in the lateral ventricles Foramen of Monroe IIIrd Ventricle Acqueduct of Sylvius IVth Ventricle Lushka/Magendie
• 0.5-1 cc/min• Adult CSF volume is approx. 150 cc’s.• Adult CSF production is approx. 500-700 cc’s
per day. 24
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Andrew D. Perron, MD, FACEP25
1 day 1 day 1 year 1 year 2 years 2 years
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B is for Blood• 1st decision: Is blood present?• 2nd decision: If so, where is it?• 3rd decision: If so, what effect is it having?
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BB is for Blood is for Blood
• Blood becomes hypodense at approximately 2 weeks.
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•Blood becomes isodense at approximately 1 week.
• Acute blood is bright white on CT (once it clots).
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BB is for Blood is for Blood
• Blood becomes hypodense at approximately 2 weeks. 28
• Blood becomes isodense at approximately 1 week.
• Acute blood is bright white on CT (once it clots).
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BB is for Blood is for Blood
• Blood becomes hypodense at approximately 2 weeks. 29
• Blood becomes isodense at approximately 1 week.
• Acute blood is bright white on CT (once it clots).
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CT ScansCT Scans
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Subdural Hematoma
• Typically falx or sickle-shaped.• Crosses sutures, but does not
cross midline.• Acute subdural is a marker for
severe head injury. (Mortality approaches 80%)
• Chronic subdural usually slow venous bleed and well tolerated.
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Subarachnoid Hemorrhage
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Subarachnoid Hemorrhage• Blood in the cisterns/cortical gyral surface
• Aneurysms responsible for 75-80% of SAH• AVM’s responsible for 4-5%• Vasculitis accounts for small proportion (<1%)• No cause is found in 10-15%• 20% will have associated acute hydrocephalus
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CT ScanCT Scan
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CT ScanCT Scan
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Intraventricular/Intraparenchymal Hemorrhage
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CT ScanCT Scan
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C is for CISTERNS
• 4 key cisterns• Circummesencephalic• Suprasellar• Quadrigeminal• Sylvian
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((BBlood lood CCan an BBe e VVery ery BBad)ad)
Circummesencephalic
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Cisterns• 2 Key questions to answer regarding cisterns:
• Is there blood?• Are the cisterns open?
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Andrew D. Perron, MD, FACEP41
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B is for BRAIN
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((BBlood lood CCan an BBe e VVery ery BBad)ad)
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TumorTumor
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AtrophyAtrophy
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AbscessAbscess
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Hemorrhagic ContusionHemorrhagic Contusion
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Mass EffectMass Effect
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Intracranial AirIntracranial Air
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Intracranial AirIntracranial Air
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Andrew D. Perron, MD, FACEP55
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Blood Can Be Very Bad
If no blood is seen, all cisterns are present and open, the brain is symmetric with normal gray-white differentiation, the ventricles are symmetric without dilation, and there is no fracture, then there is no emergent diagnosis from the CT scan.
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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• Define differences between subdural and epidural hematoma?
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• Thank You