Low-dose, large-angled cone-beam helical CT data reconstruction using algebraic reconstruction techniques

We report on results on the use of two variants of the algebraic reconstruction techniques (ART) for reconstructing from helical cone-beam computerized tomography (CT) data: a standard one that considers a single ray in an iterative step and a block version which treats simultaneously several cone-beam projections when calculating an iterative step. Both algorithms were implemented using the modified Kaiser-Bessel window functions, also known as blobs, placed on the body-centered cubic (bcc) grid. The algorithms were used to reconstruct phantoms from data collected for the PI-geometry for four different maximum cone-beam angles (2.39, 7.13, 9.46 and 18.43°). Both scattering and quantum noise (for three different noise levels) were introduced to create noisy projections that simulate low-dose examinations. The results presented here (for both noiseless and noisy data sets) point to the facts that, as opposed to a filtered back-projection algorithm, the quality of the reconstructions produced by the ART methods does not suffer from the increase in the cone-beam angle and it is more robust in the presence of noise.