Informatics in Radiology: Dual-Energy Electronic Cleansing for Fecal-Tagging CT Colonography

Abstract

Electronic cleansing (EC) is an emerging technique for the removal of tagged fecal materials at fecal-tagging computed tomographic (CT) colonography. However, existing EC methods may generate various types of artifacts that severely impair the quality of the cleansed CT colonographic images. Dual-energy fecal-tagging CT colonography is regarded as a nextgeneration imaging modality. EC that makes use of dual-energy fecal-tagging CT colonographic images promises to be effective in reducing cleansing artifacts by means of applying the material decomposition capability of dual-energy CT. The dual-energy index (DEI), which is calculated from the relative change in the attenuation values of a material at two different photon energies, is a reliable and effective indicator for differentiating tagged fecal materials from various types of tissues on fecal-tagging CT colonographic images. A DEI-based dual-energy EC scheme uses the DEI to help differentiate the colonic lumen-including the luminal air, tagged fecal materials, and air-tagging mixture-from the colonic soft-tissue structures, and then segments the entire colonic lumen for cleansing of the tagged fecal materials. As a result, dual-energy EC can help identify partialvolume effects in the air-tagging mixture and inhomogeneous tagging in residual fecal materials, the major causes of EC artifacts. This technique has the potential to significantly improve the quality of EC and promises to provide images of a cleansed colon that are free of the artifacts commonly observed with conventional single-energy EC methods.

Electronic cleansing of tagged residue in CT colonography: what radiologists need to know

“…However, the potential usefulness of this software application is still limited by a number of artefacts that can affect the colonic evaluation and interpretation, as well as the size measurement of colonic lesions that are submerged under tagged faecal residue. Future strategies to further reduce EC-related pitfalls and artefacts may include EC schemes that are based on the material decomposition capability of dual-energy CT [25,26].…”

Spectral Photon-counting CT: Initial Experience with Dual–Contrast Agent K-Edge Colonography

“…However, colonic preparation is suboptimal in up to 66% of patients (22). In addition, several artifacts typically occur in single-energy CT colonography, such as beam-hardening pseudo-enhancement caused by incomplete cleansing of folds and polyps adjacent to contrast materialtagged fecal materials, partial volume effects, and inhomogeneous tagging with incomplete cleansing (23). Improvements can be obtained with dual-energy CT, but this technology does not overcome all challenges of laxative-free colonography.…”

Electronic Cleansing in Fecal-Tagging Dual-Energy CT Colonography Based on Material Decomposition and Virtual Colon Tagging

“…The resulting material decomposition ability in DE-CT works especially well for materials such as iodine [28], [29], which is a commonly used orally administered contrast agent in fecal-tagging CTC [30]. Applying fecal-tagging dual-energy CTC (DE-CTC) images in EC provides a promising solution to removal of the residual fecal materials in CTC images while largely reducing the major EC artifacts in existing EC methods, such as spectral EC [31] and dual-energy index (DEI) EC [32]. The former is based on a material-specific spectral response to identify and segment tagged fecal materials, and the latter is based on the DEI values of materials to identify the air and tagging mixture.…”

“…Different from our previous DEI-EC method [32], which used DEI to differentiate soft tissue from other materials, this paper presents a localized three-material decomposition model that decomposes each voxel into a mixture of three base materials: air, soft tissue, and tagged fecal materials, and calculates the partial derivatives of the base materials. A Poisson-based derivative smoothing algorithm smoothes the derivatives and implicitly smoothes the associated scalar field, i.e., the material mixture field of each base material.…”