Impact of CT calibration curves on radiotherapy planning using diagnostic CT scans and a planning CT supporting DirectDensity reconstruction.

Using a DirectDensity calibration curve in emergency workflows with image data acquired without DirectDensity leads to clinically acceptable treatment plans. Dose deviations can be reduced by carefully evaluating the entire treatment chain. A self-generated hybrid CT density curve shows the best results, although deviations remain larger (< 1.5%) than when planning directly on a calibrated planning CT. The combined phantom- and patient-based analysis demonstrates that calibration curve selection can influence dose distributions under clinically realistic conditions, supporting the superior performance of the hybrid curve and highlighting clinical relevance beyond technical feasibility.