Rationale and Technology of Cone-beam Computed Tomography-based Image-guided Radiotherapy

Cone-beam Computed Tomography-based Image-guided Radiotherapy Variation of the target position is a major challenge in the clinical practice of external beam radiotherapy (EBRT). Variability of the tumour position from day to day is caused by breathing, changes of the filling of hollow organs and peristaltic or more complex changes of the anatomy of patients. If not corrected or compensated for, this variation of the target position may cause imprecise delivery of the irradiation dose with increased doses to the normal tissue and decreased doses to the tumour. Consequences are increased rates of toxicity and decreased tumour control probability. Traditionally, these uncertainties have been compensated for using safety margins around the tumour, which ensure dose coverage of the target volume despite these uncertainties.