| 摘要 |
<p>A method and means is presented to estimate the contour of a body to compensate for attenuation in the production of a reconstructed image in fan beam computed tomographic systems having a detector system for taking a plurality of projections of a scanned body at a plurality of angles. The method and means defines a set of variable parameters representing an arbitrary ellipse and projects the arbitrary ellipse into fan beam projection space to determine the expected edges of the arbitrary ellipse at each angle in terms of the variable parameters. A series of fan beam projections is taken having sufficient information for reconstructing a cross-sectional image of the scanned body, and the fan beam coordinates of the apparent body edges in each of the projections are determined. The expected edges of the projected ellipse are fitted to the determined apparent body edge coordinates for each projection by iteratively optimizing all of the variable parameters of the arbitrary ellipse to determine a final set of parameters which defines an elliptical contour which best fits the scanned body. A cross sectional image of the body using the plurality of projections is then reconstructed and compensated by assigning attenuation values to the portion of the reconstructed image encompassed by the elliptical contour.</p> |
