Do you have a systematic approach to interpret non contrast head CTs? Let’s learn to read one like a radiologist. Start on the outside and evaluate the scalp and face. Work your way all the way around the head. Keep an eye out for trauma, infection, or tumor. Next, trace around the skull and look for any evidence of fracture.
Also look at your air spaces like the sinuses and mastoid air cells. Make sure that they’re black, which means they’re full of air. Make sure the air hasn’t been replaced by fluid or blood. Next, it’s time to go inside the head. Remember that there are three main structures. Gray matter, white matter, and CSF.
Each of these structures will appear a different shade of gray based on its density on CT. Gray matter is the densest structure because it’s made of cell bodies and will thus be the lightest shade of gray. The white matter tracks are a mix of fat and axons. And is the intermediate density, and thus the intermediate shade of gray.
CSF is essentially water, and the least dense substance, and is thus the darkest shade of gray. Notice how the normal brain parenchyma has this very distinct three shades of gray architecture. Most brain pathology will cause either hemorrhage or edema, which will distort this normal architecture, as we can see here, in the case of stroke, tumor, So let’s review.
One, look at the scalp for trauma. Two, look at the bones for fractures. And three, check the brain parenchyma. And don’t forget about your three shades of grey. Now you can read a head CT like a radiologist.