Dose minimization in computed tomography overscanning

Abstract

The relationship of noise and dose in overscanning in computed tomography is reviewed to show that maximal variance reduction is obtained when the overscanning weights are proportional to the x-ray flux. It is also shown that maximal motion artifact suppression requires that the weights vary smoothly from zero at the beginning and ending of the scan to one in the central portion of the scan. Optimal noise and dose considerations suggest that the x-ray flux should be varied during the course of a scan in order to be proportional to the desired weighting. Computer simulations of a head phantom with a moving pin are used to show that such x-ray flux variations do achieve maximal artifact suppression with no additional dose to the patient over a standard (non-overscanned) scan.