Cone-beam computed tomography (CBCT) is an imaging technique with which radiotherapy patients can be accurately localized prior to treatment. A recent development has been to acquire CBCT during rotational radiotherapy, allowing for images of patient anatomy during treatment rather than before or after. However, this technique is adversely affected by x-ray scatter from the treatment beam onto the imager, making the CBCTs difficult to clinically interpret. The purpose of this study was to investigate a scatter correction method to improve the quality of CBCTs taken during treatment. The correction involved acquiring a set of scatter-only images during treatment and using these to correct subsequent in-treatment CBCTs. The correction was applied to a phantom and patient data sets, and image quality was observed to increase compared to the uncorrected images. In conclusion, the scatter correction technique offers an effective method for improving the clinical quality of CBCTs acquired during rotational radiotherapy.

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