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Head CT Basics : Trauma. Micelle Haydel, MD LSU-New Orleans. First, a little test…. 1. 2. 3. 4. 5. 6. 7. 8. 9. Head CT Interpretation the basics. A Little History. In the early 1970s, Hounsfield developed a way of computerizing Xrays to select certain densities for viewing.
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Head CT Basics : Trauma Micelle Haydel, MD LSU-New Orleans
A Little History... • In the early 1970s, Hounsfield developed a way of computerizing Xrays to select certain densities for viewing. • Plain films: black, white or a few shades of grey • CT: thousands of shades of grey based on the density of the tissue (Hounsfield Units)
What We Need to Know • Air is very black (less than -300 HU) • Water/CSF is black (near 0 HU) • Bone is very dense/white (500-3000 HU) • Blood is white (60-80 HU) • Brain is gray 35-50 HU
Before we look at abnormal, A little normal geography: Supra 3rd 4th Quad • Use the Cisterns& Ventricles as landmarks
Sella turcica Suprasellar Suprasellar Cistern
3rd Ventricle Quadrigeminal Cistern
Lateral Ventricles Frontal Occipital
Review: Temp Horn Suprasellar 3rd Quad 4th
On each brain slice look for: • Symmetry, symmetry, symmetry • sulci • cisterns and ventricles • grey-white differentiation
Identify What Doesn’t Belong • Hyperdensities (whiter) • extra-axial hematomas (SDH, EDH) • ICB or contusion • SAH in sulci, cisterns or ventricles • Hypodensities (darker) • pneumocephaly (air is darker than CSF) • infarction
Identify What Doesn’t Belong • Localized or diffuse edema • effacement of sulci or cisterns • distortion of gray-white matter interface • enlarged ventricles, temporal horn • Fractures • soft tissue swelling • fluid (blood) in sinuses or mastoid air cells • in children, look for widened sutures • Always look at bone windows
Blood: Acute blood is white (60-80 HU) on CT, due to the density of hemoglobin. As hgb breaks down, the HU decrease (i.e. subacute and isodense hematomas)
Dura tightly adhered to skull, but loosely to brain. Dura mater Pia mater Arachnoid
Epidural Hematoma • Lens shaped (dura tightly adhered to skull • Can cross midline • Frequently assoc. with fracture
Subdural Hematoma Follows the contour of the brain & doesn’t cross the midline