Some concepts useful in analyzing CT scans of the brain

Some radiological diagnoses are demonstrated (e.g. hydrocephalus, intracerebral hematoma), some suspected (e.g., aqueduct stenosis, aneurysm rupture).

Particular areas are prone to particular sorts of pathology. Middle cerebral aneurysms occur in the Sylvian fissure, acoustic neuromas in the internal auditory canal.

Density can be measured in Hounsfield Units on the screen but is usually judged visually in relationship to the tissues around the area in question. Common hyperdensities include: blood, calcification or mineralization, foreign bodies, enhancing lesions such as tumours and subacute infarctions and contusions. Common hypodensities include: edema, non-enhancing tumours, infarctions, air, chronic hematoma.

Mass effect is very important to note. There may not always be a midline shift if the process is generalized but compression of CSF cisterns and sulci will be evident.

Vascular territories are quite typical so wedge shaped hypodensities can often be attributed to specific vessels.

White matter disorders are confined to the white matter and grey matter diseases are confined to the grey matter. Tumours, trauma, bleeds, infarctions, etc do not confine themselves to one or the other.

Artifact can sometimes explain the otherwise unexplainable. There can be movement artifact, metal object induced artifact, and the work of trolls or gremlins in the CT machine.