Abstract: A method and apparatus are provided for updating an image pixel in both ray-driven and pixel-driven tomographic systems. The method includes the steps of determining (300) a distance and a ray angle of the pixel from an X-ray source of the ray-driven tomographic system and retrieving (302) a plurality of projection data elements based upon the ray angle. The method further includes the steps of retrieving (304) a corresponding set of interpolation values from a lookup table based upon the determined distance and ray angle and multiplying (306) the interpolation value by a respective projection data element. The method also includes the step of summing (308) the multiplied projection data elements and interpolation values.

Abstract: A method of real time compensating for patient movement associated with expansion and contraction in computed tomography utilizes the determination of the centroids of successive images, rescaling of each projection data, the alignment of the centroids, and display of the aligned images.

Abstract: Parallel accumulation of the density functions of image picture elements is done for a number of elements located at the same radial distance from the axis of rotation for the fan-beam scanner. This allows the computation of weighting factor to be done in common for these elements, as well as the computation of interpolation coefficients for ray sums not registering exactly with x-ray detectors.

Abstract: A crossbar switch is constructed in monolithic integrated circuit form together with respective memory cells controlling each of the component crosspoint switches in the crossbar switch. The memory cells permit control signals for the crosspoint switches to be supplied serially to the monolithic integrated circuit and thus permit those control signals to be supplied in coded form as orthogonal cross addressing for the memory cells. This reduces the number of bits which must be provided in parallel to the integrated circuit for controlling the crosspoint switches. In preferred embodiments of the crossbar switch, provision is made for operation as a corner-turn array for rotating bit matrices and for faster operation as a barrel shifter.

Abstract: An approach to A/D converter architecture is based on a "pipelined and submerged" architecture which includes a pipeline of elemental stages (10.sub.i). Each stage of the pipeline comprises a low-resolution flash A/D subconverter (12), a D/A converter (14), and a unity-gain buffer (16). To minimize converter nonlinearity due to component mismatches, a self calibration technique based on an "interpolation" scheme is used. This technique employs an on-chip delta-sigma A/D converter (32) to provide the reference for calibration and a 100-bit memory (50) to store nonlinearity information. Long term drift is corrected by a calibrator (34) in parallel with data conversion.