Scatter correction for cone-beam computed tomographyusing moving blocker strips
2011
One well-recognized challenge of cone-beam computed tomography (CBCT) is the presence of scatter contamination
within the projection images. Scatter degrades the CBCT image quality by decreasing the contrast, introducing shading
artifacts and leading to inaccuracies in the reconstructed CT number. We propose a blocker-based approach to
simultaneously estimate scatter signal and reconstruct the complete volume within the field of view (FOV) from a single
CBCT scan. A physical strip attenuator (i.e., "blocker"), consists of lead strips, is inserted between the x-ray source and
the patient. The blocker moves back and forth along z-axis during the gantry rotation. The two-dimensional (2D) scatter
fluence is estimated by interpolating the signal from the blocked regions. A modified Feldkamp-Davis-Kress (FDK)
algorithm and an iterative reconstruction based on the constraint optimization are used to reconstruct CBCT images from
un-blocked projection data after the scatter signal is subtracted. An experimental study is performed to evaluate the
performance of the proposed scatter correction scheme. The scatter-induced shading/cupping artifacts are substantially
reduced in CBCT using the proposed strategy. In the experimental study using a CatPhan©600 phantom, CT number
errors in the selected regions of interest are reduced from 256 to less than 20. The proposed method allows us to
simultaneously estimate the scatter signal in projection data, reduce the imaging dose and obtain complete volumetric
information within the FOV.
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