Computed Tomography (CT)
imaging uses x-rays to produce cross-sectional images (or slices) of
the brain. As x-rays pass through the body, they are absorbed or
attenuated differently. These varying attenuation values give
information on normal and abnormal structures in the brain and
spine, producing an image.
In helical CT imaging the
x-ray tube which produces the x-rays is housed within a big
ring-like structure opposite a detector. A fan beam of x-ray is
created as the rotating frame spins the x-ray tube and the detector
around the patient. The information from the detectors is then
transferred to a computer, which will reconstruct a cross-sectional
When is CT performed?
The helical CT scanner is the workhorse
of neuroimaging, and is the imaging method of choice for trauma and
intracranial haemorrhage. The speed and real-time review capability
of CT allows a quick overview in life threatening situations, with
added advantage of ease of repeat studies. CT also plays a critical role in
the early screening and diagnosis of many brain diseases, in spine
imaging and in orbital-facial disease.