The document provides an introduction to cranial CT, including its usefulness for detecting acute intracranial lesions and blood collections in emergency situations. It discusses CT windows, artifacts, and a mnemonic for reading head CT scans to evaluate for blood, cisternas, brain symmetry and densities, ventricle size and shift, and bone fractures. The guidelines from the National Institute for Health and Clinical Excellence in the UK are also mentioned regarding use of CT versus MRI for different clinical scenarios.

1. INTRODUCTION TO CRANIAL CT
Hospital Eva Peron
DR.LAPAL MA, DORIAN

2. INTRODUCTION
CT is the most useful neuroimaging study in
emergency medicine it readily detects acute
blood collections and intracranial lesions
causing mass effect.
MRI is superior for imaging parenchymal
abnormalities and has replaced CT in most
nonemergency neurodiagnosis

3. GUIDELINES: (NICE)
• The national institute for health and clinical
excellence (NICE) is a special health authority
of the english nationa health service (NHS),
serving, both English NHS and the Welsh NHS.
It was set up as the National Institute for
Clinical Excellence in 1999

6. The Lancet, Volume 357, Issue 9266, Pages 1391 -
1396, 5 May 2001

7. BASIC PRINCIPALES OF CT
ATTENUATION COEFFICIENT
The ability to block x rays as they pasoo
through a substance (attenuation).For a given
body tissue, the amount of attenuation is
relatively constant an is known as that tissue’s
attenuation coefficient.
Sir Jeffery Hounsfield: mapping of attenuation
coefficient

8. THE CT HOUNSFIELD SCALE

9. WINDOWING
• It allows the CT scan reader to focus on
certain tissues within a set parameters. Most
CT imaging includes windows that are
optimized for brain, blood and bone.
• BRAIN : W 155 L 40
• STROKE : W 30 L 30
• SUBDURAL: W 150 L 5
• BONE: W 3000 L 570

10. WWINDOWING
BRAIN (W 155 L 40) STROKE (W 30 L 30)

11. WINDOWING
BONE (W3000 L 570) SUBDURAL (W150 L 5)

12. HEAD CT ARTIFACTS
Effects tha can potentially inhibit the ability to
accuerately interpret the images
Motion
Metal artifacts
Beam Hardening: when small amount of hypodense
brain tissue is immediately adjacent to dense bone
Partial volume: arises when the imaged area contains
different types of tissue. Ej: brain and bone, an
intermediate density will be represented that may have
the appearace of blood

13. HEAD CT ARTIFACTS

14. HEAD CT ARTIFACTS

15. HEAD CT ARTIFACTS
•Oriented obliquely.
•Reduces the number
of slices that are
degrade by artifacts.
•CT: the frontal lobes
are anterior, but
posteriorly, the
cerebelum is seen,
rather than the
occipital lobes

16. HOW TO READ A HEAD CT

17. HOW TO READ A HEAD CT

18. MNEMONIC: BLOOD CAN BE VERY BAD
• Blood: Acute (white), subacute (gray), chronic
(black)
• Cisternas
• Brain:
– symmetry
– Gray-white differentiation
– Shift
– Hyper/hypodensity

19. MNEMONIC: BLOOD CAN BE VERY BAD
(cont.)
• Ventricles:
– Dilatation
– Compression/shift
• Bone
– Fracture (asymmetry)
– Symmetry (suture)
– Air in mastoid cell