Head CT Basics Trauma Micelle Haydel MD LSUNew

Head CT Basics : Trauma Micelle Haydel, MD LSU-New Orleans

First, a little test…

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Head CT Interpretation the basics

A Little History. . . • In the early 1970 s, 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: • Use the Cisterns& Ventricles as landmarks Supra 4 th 3 rd Quad

4 th Ventricle

Suprasellar Cistern

Sella turcica Suprasellar Cistern

3 rd Ventricle Quadrigeminal Cistern

Temporal Horn of Lateral Ventricle

3 rd Ventricle & Quadrigeminal Cistern

Lateral Ventricles Frontal Occipital

Lateral Ventricles

Review: Temp Horn Suprasellar 4 th 3 rd Quad

Normal Head

ABNORMAL CTs

On each brain slice look for: § 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)