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CBCT for dose calculation
Volumetric imaging, scatter from whole object contributes.
Fewer projections; less raw data.
Poor SNR cf. fan beam CT.
HU numbers less reliable – dependent on imaging
parameters, size of object, presence of inhomogeneities,
artefacts. Calibration curve may not apply.
6
Large uncertainties can result
from using CBCT HU for dose
calculation.
Motion artefact (gantry rotation
time).
Limited image length.
X-ray
source
Flat
panel
detector
Axis of
rotation