A.P. Happonen and S. Alenius (Finland)
medical imaging, sinogram, locus, stackgram
A new general concept for filtering a sinogram from any tomographic modality is presented. In tomography, in formation of an unknown object are collected to the sino gram consisting of projection profiles. The sinogram is reconstructed to an image by some approximation of the inverse Radon transform. The reconstruction is often an ill-posed problem and a less noisy sinogram would al leviate it. A direct two–dimensional filtering of a noisy sinogram easily distorts sinusoids of the sinogram and ef ficient filtering causes generally noticeable blurring. The new method is based on an idea to find and filter all the sinusoidal loci of the sinogram. This can be done by transforming the sinogram to a three–dimensional “stackgram” domain. The stackgram domain consists of a stack of projection images, each containing the pro jection of one projection profile. The sinusoidal loci of the sinogram are parallel to the vertical axis of the stack gram. These 1–D signals are filtered in order to reduce the noise. The stackgram domain offers a more robust domain to filter the sinogram than the two–dimensional sinogram domain filtering.
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