Introduction to CT




How does a CT scan work?

Why CT?

  • Conventional radiography (CR), AKA x-rays, is a 2D representation of a 3D structure​

  • Limitations​

    • Overlapping structures can obscure (e.g. skull obscures brain)​

    • CR images are a representation of density, although differentiation between similar densities is poor (e.g. soft tissue versus water)

What is CT?

  • Computed tomography (CT) uses rotating x-rays to create a cross sectional image slice​

  • Sequential slices are obtained as the patient moves through the gantry (circular opening of the CT)​

  • CT allows for rapid image acquisition in seconds, but requires higher radiation

Planes and Orientation, Hounsfield Units, Windowing

Phases and types