Local-filtration Based Scatter Correction for Conebeam CT Using Planning CT as a Prior

High-performance image guided radiation therapy (IGRT) increasingly requires high-quality cone-beam CT (CBCT) images. However, due to severe scatter contamination, the clinical application of CBCT is presently limited to patient setup although various means have been developed to improve the quality of CBCT images. In the paper, we propose a local-filtration based scatter correction method using planning CT (pCT) as prior information but which does not require a high registration accuracy of pCT and CBCT. We evaluate the proposed method via two patient studies, and compare the results with existing correction method. Compared with images from Varian Medical systems and a previous method which is similar to our method but uses a different type of filter. The maximum error of CT number is reduced from over 50 HU to below 11 HU in selected regions of interest (ROIs). Meanwhile, the SNR is decreased from over 60 HU to less than 32 HU. The proposed method has improved the CBCT images with more simple process and less computation time.