We investigated artifacts due to late-arriving contrast medium (CM) during C-arm cone-beam computed tomography. We scanned a phantom filled with water or with 100,

The coherent-scattering distribution is useful for characterization of materials in the medical field, and obtaining this information from a given position in the object is a useful new diagnostic approach. We propose a simpler geometric approach, which requires only a single-direction X-ray beam with no collimator in front of the detector. This method iteratively estimates coherent-scattering profiles from given positions along the beam path, based on the projections positioned at different object-to-detector distances. We confirmed the proposed calculation algorithm by numerical simulation and performed a simple experiment including attenuation correction. The accuracy of matching with the original profiles was dependent on the number of iterations, the distance between the first and second detectors, the distance between two objects, and the shape of the scattering profile. Whereas multiple scattering was the main problem in the experiment, the calculated scattering profiles matched well with the original profile. This technique indicates the feasibility of developing a coherent-scatter imaging system.

SummaryObjectives: The aim of this study was to evaluate the effectiveness of scatter correction in the portable chest radiography. Methods: Digital radiographies were performed without anti-scatter grid (grid) , with the scatter correction and with the grid ratio of 3 : 1 in this study. The scatter fraction and the detectability of low contrast signals were measured using the four acrylic phantoms of different thicknesses. The chest phantom radiographs were assessed subjectively, in random order, by six radiologic technologists. Results: The scatter fraction was higher in the no-grid technique, and was lower for the grid technique. The detectability of low contrast signals did not significantly differ between the scatter correction and the grid technique (p>0.05). The area under the receiver operating characteristic curve for the grid technique was higher than that for the scatter correction technique (0.888 vs. 0.855), although no significant difference was found between the grid and the scatter correction technique (p> 0.05). The ability to detect the nasogastric tube was significantly better in the grid technique (p<0.001). Discussion: In the scatter correction technique, the ability of scatter removal increased as the scatter fraction increased. The scatter correction technique was unnecessary to extremely accurate alignment. In addition, patient dose can be reduced by the scatter correction technique. Conclusions: It seemed to be effective for the scatter correction in the portable chest radiography.

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