Exxim Computing Corporation. Feldkamp artifact reduction


	CFA mode Curved reformat image illustrating Feldkamp artifact in form of horizontal streaks on a half beam scan reconstruction Curved reformat image illustrating the same scan reconstruction after correction of Feldkamp artifact. Feldkamp algorithm is an approximation and as such can produce artifacts known as Feldkamp artifacts. The artifact comes from the nature of the algorithm itself and independent on its implementation. It is more critical in half beam and 3x view modes, because in full beam it is largely compensated by presence of the projections from the opposite sides. Feldkamp artifact correction algorithm (CFA) is an iterative method that significantly reduces this artifact (compare illustration on the left). This method is approximately 2-3 times slower than standard Feldkamp. Cobra supports using graphics card acceleration for speeding up re-projecting phase of iterations.

Describing a reconstruction task

Within the COBRA reconstruction package, all input, output and intermediate data are kept on the hard disk. The user defines and controls the reconstruction task through a parameter file, a text file with extension .xxm. This file contains tags and assigned values, and describes the scanner hardware setup, input and output data characteristics and representation, and the chosen reconstruction method. Some of the reconstruction options are only accessible through SDK API’s. These are related to synchronization and control of in-line reconstruction (recon concurrent with acquisition), and the setup of COBRA’s working folders.

Tags defining CFA parameters

OPTTAG_CFA

Feldkamp algorithm is an approximate algorithm and as such can produce artifacts known as Feldkamp artifacts. The artifact comes from the nature of the algorithm itself and is independent of its implementation. It is more critical in half beam mode, because of lack of projections from the opposite sides. Feldkamp artifact correction algorithm is an iterative method that significantly reduces this artifact This method is 1.5-2 times slower than standard Feldkamp algorithm in halfbeam mode. It is activated by OPTTAG_CFA tag.
Value type: integer (0-1)
Default value: 0

PARTAG_FP_GPU

Defines: Performing re-projecting step on GPU. Relevant for Feldkamp artifact correction algorithm.
Value type: integer (0-1)
Default value: 0

CFA mode

Curved reformat image illustrating Feldkamp artifact in form of horizontal streaks on a half beam scan reconstruction

Curved reformat image illustrating the same scan reconstruction after correction of Feldkamp artifact.

OPTTAG_CFA

PARTAG_FP_GPU

Curved reformat image illustrating Feldkamp
artifact in form of horizontal streaks on a half beam scan reconstruction