Projection and Reconstruction-Based Noise Filtering Methods in Cone Beam CT

A reduction of the radiation dose in computed tomography typically leads to more noise in the acquired projections. Here filtering methods can help to reduce the noise level and preserve the diagnostic value of the low-dose images. In this work, six variants of Gaussian and bilateral filters are applied in both projection and reconstruction domain. Our comparison of noise reduction and image resolution shows that 2D and 3D bilateral filtering in the projection domain can reduce the noise level, but must be applied carefully to avoid streaking artifacts. By smoothing homogeneous regions while preserving sharp edges, the 3D bilateral filter applied in the reconstruction domain yielded the best results in terms of noise reduction and image sharpness.