Angular weighted hybrid cone-beam CT reconstruction for circular trajectories

Hybrid reconstruction techniques have been introduced for the volume recons truction of axially truncated cone-beam computed tomography projection data acquired along a circular source-detector trajectory. The introduction of weighted half-scan techniques into this framework is described in this pape r. Due to the cone-beam geometry it is not possible to perform the weightin g on the projections as is typically done in conventional single-line compu ted tomography. Hence, in this paper we present an efficient way to incorpo rate angular weighting functions, depending on the object point position, i nto the framework of hybrid cone-beam reconstruction. Four different angula r weighting functions are introduced and discussed with respect to their co ne-beam artefact behaviour and their influence on the signal-to-noise ratio . As a result, the most effective angular weighting function for hybrid cir cular cone-beam reconstruction is determined by means of a simulation study based on mathematical phantoms and clinical data sets. This distance-weigh ted angular weighting scheme yields the best results in terms of high image quality, low computational complexity and signal-to-noise variations in th e reconstruction volume.