Dose reduction achieved by dynamically collimating the redundant rays in fan-beam and cone-beam CT

In X-ray computed tomography (CT), short-scan acquisition that acquires data only over a range of π plus the fan angle, rather than a full range of 2π, is commonly used in circular fan-beam and cone-beam geometry. Such scan aims to reduce acquisition time and radiation dose during data acquisition. However, during a partial circle scan some data are measured once, while other measurements are observed twice. Traditionally, the redundant data are weighted by a smooth function (e.g. the Parker weights) before filtering. In this paper, we present an algorithmic setup that employs dynamic collimation to shield the redundant rays and propose two algorithms to correct the resulting truncation. This approach is able to potentially decrease the dose of 10% for a C-arm CT with fan angle of 10° and of 23% for a diagnostic CT with fan angle of 50°. Evaluation shows that the reconstruction results are of comparable accuracy to the one from standard short-scan FDK, with less dose to the patient.