IMRT Course 2016

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.

Flat panel detector

Axis of rotation

Large uncertainties can result from using CBCT HU for dose calculation. Motion artefact (gantry rotation time). Limited image length.

X-ray source

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