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Abstract

A method and apparatus for calibrating detectors in a computed tomography (CT) system to compensate for differential errors in the detectors are disclosed. Multiple sets of scan data are acquired for a phantom at multiple thicknesses of the phantom. The phantom can be made from multiple slabs of material positioned on the scanner table in a horizontal orientation or in a vertical orientation. Horizontal slabs are removed or added to the stack of slabs to vary the thickness of the phantom. With vertically oriented slabs, each slab is of a different height such that scans of different slabs produce X-ray data for rays having different path lengths and, therefore, attenuations. For each detector, errors in the scan data at the multiple phantom thicknesses are identified and fit to a parametric equation with respect to the log attenuation associated with each thickness. In one embodiment, the parametric equation is a quadratic polynomial. The polynomial is used during subsequent scanning of actual objects to adjust attenuation measurements.

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First Claim