Region-of-Interest CT Reconstruction using One-Endpoint Hilbert Inversion in Optimized Directions
Résumé
In computed tomography, scanning the entire object is sometimes impossible, causing truncated projection data. Reconstruction is however still possible: using differentiated backprojection, the Hilbert transform of the object can be calculated and inverted along line segments in the field-of-view. When two endpoints of the line segment are outside the object extent, a stable analytic reconstruction formula exists. When only one endpoint is outside the object extent, every pixel can be reconstructed, but no inversion formula is known yet. Uniqueness of the inverse Hilbert transform is nevertheless guaranteed along such segments, and a numerical inverse can be used. Most pixels of the field-of-view accept more than one "one-endpoint line segment" and one can choose the direction; we propose here to select the optimal direction based on an empirical criterion. Image quality improvement is assessed against a reconstruction that uses a single direction for every pixel.
Domaines
Imagerie médicale
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