  Online dose calculations before radiation treatment have applications in dose
delivery verification, plan adaptation, and treatment planning. We propose a
novel CBCT imaging pipeline to enhance accuracy. Our approach aims to improve
HU accuracy in CBCT images for more precise dose calculations. A quantitative
CBCT pipeline was implemented, combining data correction strategies and scatter
rejection, achieving high CT number accuracy. We evaluated the pipeline's
effect using pelvis anatomy phantoms and found that dosimetric errors in
quantitative CBCT-based dose calculations were minimal. In contrast, clinical
CBCT and high-performance ASG CBCT-based plans showed significant errors. The
proposed quantitative CBCT pipeline offers comparable dose calculation accuracy
to the gold-standard planning CT, eliminating the need for density overrides
and enabling precise dose delivery monitoring or online plan adaptations in
radiation therapy.
