Forward projectors are needed for iterative image reconstruction algorithms for CT or PET image reconstruction. The major cost of iterative reconstruction algorithms is computing the forward and backward projections. Conventionally, this is done in the image domain as computing the lengths of intersections between each X-ray ray and each image voxel. These operations are the major computational...

The direct reconstruction approach employs an iterative procedure by selection of and angular averaging over projected trajectory data of volume elements. This avoids the blur effects of the classical Fourier method due to the sampling theorem. But longer computing time is required. The reconstructed tomographic images reveal at least the spatial resolution of the radiation detector. Any set of...

Using non-smooth regularization in X-ray computed tomography (CT) image reconstruction has become more popular these days due to the recent resurgence of the classic augmented Lagrangian (AL) methods in fields such as totalvariation (TV) denoising and compressed sensing (CS). For example, undersampling projection views is one way to reduce radiation dose in CT scans; however, this causes strong...

Tetrahedron beam computed tomography (TBCT) performs volumetric imaging using a stack of fan beams generated by a multiple pixel X-ray source. While the TBCT system was designed to overcome the scatter and detector issues faced by cone beam computed tomography (CBCT), it still suffers the same large cone angle artifacts as CBCT due to the use of approximate reconstruction algorithms. It has bee...

Tomography deals with the reconstruction of images from their projections. In this paper we focus on tomographic reconstruction of binary images (i.e., black-and-white) that do not have an intrinsic lattice structure from a small number of projections. We describe how the reconstruction problem from only two projections can be formulated as a network flow problem in a graph, which can be solved...

This work proposes a dedicated statistical algorithm to perform a direct reconstruction of material-decomposed images from data acquired with photon-counting detectors (PCDs) in computed tomography. It is based on local approximations (surrogates) of the negative logarithmic Poisson probability function. Exploiting the convexity of this function allows for parallel updates of all image pixels. ...

BACKGROUND To investigate the radiation dose and image quality for iterative reconstruction combined with the CARE kV technique in chest computed tomography (CT) scanning for physical examination. METHODS A total of 130 patients who underwent chest CT scanning were randomly chosen and the quality reference value was set as 80 mAs. The scanning scheme was set and the patients were randomly div...

In application of tomography imaging, limited-angle problem is a quite practical and important issue. In this paper, an iterative reprojection-reconstruction (IRR) algorithm using a modified Papoulis-Gerchberg (PG) iterative scheme is developed for reconstruction from limited-angle projections which contain noise. The proposed algorithm has two iterative update processes, one is the extrapolati...

AIM To assess quality and radiologists' preference of low-dose computed tomography (LDCT) reconstructed with filtered back projection (FBP) or Iterative Reconstruction. METHODS Thin-section LDCTs (1-mm thick contiguous images; 120 kVp; 30 mAs) of 38 consecutive unselected patients, evaluated for various clinical indications, were reconstructed by four different reconstruction algorithms: FBP ...