CT head (an approach)

CT head review will likely be performed differently by the majority of radiologists. So, this is just a proposition of one way to read a CT head. 

What it does do is make use of windowing to maximise pickup rate. With PACS, windowing appropriately is simple, and there is no excuse for not windowing. Reviewing bone-windows and subdural windows should be mandatory.

The starting point will likely depend on preference or the way in which the images are presented to you, e.g. whether the patient was scanned from the top, down or bottom, up. Starting at the top can be helpful in that it gives you the first few images to decide which side has mass effect. If there is not any, you already know it will be something potentially smaller, and you can take more time reviewing the "busy" slides at the bottom.

Reporting regime

Brain matter

• windows: 80:40

Start at the vertex. Look at the brain matter and gyral pattern. Are there any masses, abnormal attenuation or mass effect? Assess the basal cisterns and foramen magnum for patency.

Grey-white differentiation

• windows: 40:40

From the foramen magnum scrolling up, look at the grey-white differentiation. The cortical grey matter should be readily differentiated from the white matter. The deep grey matter should be distinct from the white matter also.

Blood/subdural

• windows: 175:50

Now concentrate specifically on reviewing for blood. Look for tiny subdural haemorrhage around the tentorium and circumferentially as thin crescents. Also, look in the dependent areas for any small volume subarachnoid haemorrhage.

Soft tissues

• windows: 260:80

This study does not just look at the brain. As you scroll back up again, look in the soft tissues and especially in the anterior face including the globe, sinuses, palate and pharynx. 

Bony review

• windows: 3000:500

Now review the bones. This should always be performed, even when a bony algorithm hasn't been provided or where slice thickness is suboptimal. However, if a fracture is not seen on a thick slice, standard algorithm CT, the negative predictive value is low.

Remember to look at the petrous air cells, maxillary antra and the auditory canals. Localised opacification may point to the location of a fracture and highlight the need to ask for the bony reformats to be provided.

Other reformats

Increasingly, coronal and sagittal reformats are either provided or available via volume reconstruction software. If they are provided, look at them. If you have isotropy, and the ability to use such software, remember to consider using a different reformat to view an area of pathology.

Review areas

Review areas are different for everybody, but some common review areas for a CT head include:

• tentorium
• globe
• retropharyngeal space