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Normal CT BRAIN

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By Dr Piyush Ojha , DM Resident, GMC Kota
under guidance of Prof. Dr Vijay Sardana (HOD,Neurology)

Published in: Health & Medicine
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Normal CT BRAIN

  1. 1. RADIOLOGICAL ANATOMY OF NORMAL CT BRAIN DR. PIYUSH OJHA DM RESIDENT DEPARTMENT OF NEUROLOGY GOVT MEDICAL COLLEGE, KOTA
  2. 2. LOBES OF BRAIN
  3. 3. MEDIAL SURFACE OF THE BRAIN
  4. 4. CT History SIR GODFREY N. HOUNSFIELD • 1979 Nobel Laureate in Medicine
  5. 5. COMPUTED TOMOGRAPHY (CT) • Also known as Computer Assisted Tomography (CAT) • The term Tomography refers to a process for generating 2D image slices of an examined organ of three dimensions (3D). • Based on differential absorption of X- ray by various tissues.
  6. 6. Structure of CT scan collimator
  7. 7. TECHNIQUE • Patient is placed on the CT table in a supine position and the tube rotates around the patient in the gantry. • To prevent unnecessary irradiation of the orbits, Head CTs are performed at an angle parallel to the base of the skull.
  8. 8. • Slice thickness may vary, but in general, it is between 5 and 10 mm for a routine Head CT. • Intravenous contrast is not routinely used, but may be useful for evaluation of tumors, cerebral infections.
  9. 9. • The degree of x-ray absorption by various tissues is expressed and displayed as shades of gray in the CT image. • Darker shades correspond to lesser attenuation. • The shades of gray correspond to a number on an arbitrary linear scale, expressed as Hounsefield Units (HU). (-1000 to +3000) • WINDOWING- changing the settings to preferentially display tissues of interest in image. Eg. Bone window in cases of craniofacial trauma.
  10. 10. Pure water has an HU value of ‘0’. DESCRIPTION Approx. HU DENSITY Calcium > 1000 Hyperdense Acute blood 60-80 Hyperdense Grey matter 38 (32-42) Hyperdense (light grey) White matter 30 (22-32) Hyperdense (dark grey) CSF 0-10 ISODENSE Fat -50 to - 80 Hypodense Air - 1000 Hypodense
  11. 11. Low density High density CSF Bone Fluid (Edema) Calcification Air Blood Fat Contrast Metallic Foreign Bodies
  12. 12. CT ARTIFACTS Artifacts are distortions or errors in the image that are unrelated to the object scanned . Most common artifacts in CT are • Motion artifacts • Streak artifacts • Beam hardening artifacts • Partial volume averaging artifacts • Ring artifacts
  13. 13. MOTION ARTIFACT
  14. 14. STREAK ARTIFACTS Cause: Presence and movements of objects of very high density(contrast media, metallic implants,surgical clips) Appearance: Streaks REMEDY:- •Remove the offending object if possible.
  15. 15. RING ARTIFACT DUE TO DEFECT IN DETECTOR SYSTEM OF THE MACHINE
  16. 16. CT Scan • Advantages – – Easy availabilty – Fast – Better for bone and acute blood,lesions of skull base and calvarium – Calcification – Less limited by patient factors • Disadvantages- – high radiation – poor visualisation of posterior fossa lesions
  17. 17. Normal CT
  18. 18. Systemic Approach to Head CT & MRI Interpretation • Symmetry – Compare left and right side of the cranium • Midline – Look for midline shift • Cross-sectional anatomy – Review anatomical landmark for each section. – Brain tissue : gray matter, white matter , intracerebral lesions – CSF space : ventricle (dilated or not) – Skull and soft tissue : scalp swelling, fractures, sinuses, orbit • Subdural windows : Look for blood collection adjacent to the skull • Bone windows : Skull, orbit and sinuses, intracranial air
  19. 19. Normal CT of Brain • Ventricles are normal sized, the grey versus white distinction is clear. • Midline is straight. • Sulci are symmetrical on bothsides. • Skull is intact with no scalp edema.
  20. 20. 1 day 1 year 2 years
  21. 21. AXIAL SECTIONS OF CT HEAD POSTERIOR FOSSA CUTS • Above the Foramen Magnum Level • level of the Fourth Ventricle • Above the Fourth Ventricular Level • Tentorial Cuts Supratentorial Sections : • third ventricular level • lateral ventricular level • above the level of Lateral Ventricle
  22. 22. A B C D E F G ABOVE THE LEVEL OF FORAMEN MAGNUM
  23. 23. A B C D E F G AT THE LEVEL OF FOURTH VENTRICLE
  24. 24. A B C D E F ABOVE THE LEVEL OF FOURTH VENTRICLE
  25. 25. A B C D E F G H I AT THE THIRD VENTRICULAR LEVEL
  26. 26. A B C D E F G AT THE LATERAL VENTRICULAR LEVEL
  27. 27. B A C D E F G ABOVE THE VENTRICULAR LEVEL
  28. 28. A B C D ABOVE THE VENTRICULAR LEVEL
  29. 29. Physiologic Calcification

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