Evaluation of a Preprocessing Algorithm for Truncated CT Projections

Abstract

A preprocessing algorithm for completing truncated computed tomography (CT) projections (so that reconstruction methods suitable for complete projections can be applied) was investigated. The problem of patients too obese to fit into the fan beam of a rotate-only (3rd generation) scanner and dose reduction were considered. Four sets of patient data collected by a rotate-only scanner were used. The reconstructions from the complete and truncated projections were compared. The preprocessing algorithm led to qualitatively good images, since local variations were nearly identical in the reconstructions from the complete and from the truncated data. Quantitatively, the images were less encouraging; the exact values of CT numbers differed in the 2 reconstructions by a significant (although slowly varying) amount across the 2 reconstructed images.