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Conventional CT:
‘Fan beam’ highly collimated
Multiple gantry rotations. Most now multi-slice
resulting in broadening of fan beam
approaching a cone beam
Planning CT scanners and in-room CT
scanners traditionally fan beam geometry.
Cone Beam CT:
Single gantry rotation with 2D rows/planar
detectors
‘cone beam’ poorly collimated with
scattered photons results in reduced image
quality
Now also available with 4D mode
RT x-ray systems that are integrated with
the linear accelerator tend to use cone
beam geometry