Shape estimation in computer tomography from minimal data

An algorithm is discussed that estimates the smallest convex polygon that circumscribes an opacity in a medical image. This is called the minimum polygon image (MPI). The algorithm requires only O(n) operations to produce the MPI. Thus it offers the following advantages over conventional image reconstruction: (1) it is computationally fast; (2) it submits the patient to much lower X-ray doses; and (3) it is much less likely to ionize a radiation-sensitive substance during inspection. An analysis confirms the high performance of the algorithm but it shows that it depends strongly on an appropriate choice of system parameters. These parameters, the number of views N _θ and the detector spacing Δs are shown to be linked, and the choice of Δs strongly constraints the choice of N_θ. It is shown how an optimum N_θ can be determined for a fixed, practical value of Δs. A series of simulation experiments that verify the theory is reported