SUMMARY

Excessive imaging dose from repeated scans and poor image quality mainly due to scatter contamination are the two bottlenecks of cone-beam CT (CBCT) imaging. This study investigates a method that combines measurement-based scatter correction and CS-based iterative reconstruction algorithm to generate scatter-free images from low-dose data. The blocked areas are distributed the detector where primary signals are considered redundant in a full scan. Scatter distribution is estimated by interpolating/extrapolating measured scatter samples inside blocked areas. CS-based iterative reconstruction is finally carried out on the under-sampled data to obtain scatter-free and low-dose CBCT images. Dual-energy CT (DECT) is another important application of CBCT. DECT shows promises in differentiating materials that are indistinguishable in single-energy CT and facilities rapid and accurate diagnosis. A general problem of dual-energy CT is that the decomposition is sensitive to noise in the two sets of projection data, resulting in severely degraded qualities of decomposed images. The first study is focused on the image-domain decomposition method. In this study, a combined iterative dual-energy method is proposed, such that the decomposition step is carried out iteratively. The noise on the two initial CT images from separate scans becomes well correlated, which avoids noise accumulation during the decomposition process. To fully explore the benefits of DECT on beam-hardening correction, the second study on DECT is to expand the framework of an iterative image-domain decomposition to include non-linear decomposition models for noise suppression in DECT with projection-domain decomposition.