Correction for spectral artifacts in cross‐sectional reconstruction from x rays

Abstract

A monoenergetic response correction is described which, along with adequate filtration, may be used to remove the spectral shift artifact encountered in three-dimensional reconstruction from x rays. Reconstructions were carried out by means of a convolution algorithm for simulated data using this method. These are compared with reconstructions obtained using fixed-length water-bath scans as a remedy for the special artifact. These studies suggest that the spectral artifact can be successfully eliminated from computerized cross-sectional scans without resorting to the use of the water bath while, at the same time, improving quantum statistics and/or permitting operation at a lower tube current.

An iterative maximum-likelihood polychromatic algorithm for CT

“…The number of unknowns in (14) is now . This equation is implemented more efficiently by bringing and outside the summation over (projection) (15) resulting in two projections instead of . Substituting (15) in ( Intermediate results are given in the Appendix.…”

“…This equation is implemented more efficiently by bringing and outside the summation over (projection) (15) resulting in two projections instead of . Substituting (15) in ( Intermediate results are given in the Appendix. At the points of inflection, and are defined as (17) Finally, the result is convolved with a Gaussian smoothing kernel with standard deviation to suppress Gibbs overshoots at sharp edges (cf.…”

“…A first approach is to limit the amount of beam hardening by physically pre-filtering the X-ray beams [4], [15].…”

“…The method of water correction or linearization correction assumes that all substances in the scanning plane have the same energy dependence and corrects the measurements prior to reconstruction [4], [15]- [17]. The so-called postreconstruction methods [18]- [27] make a first reconstruction, from which a rough material distribution is estimated.…”

Complete scheme for beam hardening correction in small animal computed tomography

“…Usually, a filter [2] is included in most of commercial scans between the source and the sample to pre harden the beam, but it is not sufficient to eliminate the beam hardening artifacts. The linearization method [2][3][4] cupping artifact in homogeneous volumes but is insufficient for eliminating the dark streaks present between dense objects like bones.…”