Multi-Source Cone Beam Computed Tomography for Image-Guided Radiation Therapy

Image-guided radiation therapy (IGRT) relies on cone-beam computed tomography (CBCT) to localize radiation treatment targets, but conventional single-source CBCT suffers from poor soft tissue contrast, spatial non-uniformity, and inaccurate Hounsfield unit (HU) values caused by X-ray scatter from its wide cone angle beam. This work investigates multi-source CBCT as an alternative imaging modality for IGRT that mitigates these limitations by replacing the single wide-angle source with an array of narrower-angle sources, reducing scatter at each source while maintaining comparable volumetric coverage. Standard CBCT and multi-source CBCT images were acquired of the Kyoto Lungman chest phantom and the American College of Radiology (ACR) 464 phantom using a benchtop CBCT system. Multi-source CBCT yielded a 30% reduction in HU root mean square error (RMSE) for the chest phantom and a 14% reduction for the ACR phantom relative to standard CBCT, along with a 19% improvement in spatial HU uniformity and a partial reduction of the cupping artifact. Absolute contrast also improved for both phantoms; however, contrast-to-noise ratio decreased by 9% to 11%, attributed to elevated noise inconsistent with previous results. These results demonstrate the feasibility of multi-source CBCT for IGRT and motivate future work on further reduction of the per-source cone angle, radiation dose characterization, and eventual replacement of the current CNT source with a dedicated multi-source array.