The aim of this study was to evaluate an influence of post-processing scatter correction in portable abdominal radiography using a low ratio anti-scatter grid (grid). Methods: To assess tube voltage on portable abdominal radiography, a burger phantom was used to measure for inverse of image quality figure (IQFinv ). For evaluation of the influence on using or not the grid, IQFinv were measured. Abdominal phantom radiographies were assessed subjectively, in random order, by six radiologic technologists. The radiographies were performed without scatter correction [IG (-) ] and with scatter correction at equivalent for grid ratio 6 [IG (6) ] and 8 [IG (8) ]. Results: There was no significant decrease in IQFinv with 75 and 80 kV in comparison of 70 kV. Even processing scatter correction, IQFinv with using the grid was significantly higher than that without using the grid. The ability to detect nasogastric tube and stomach gas were significantly better in the scatter correction. Deviation index for IG (6) and IG (8) were significantly lower than that of IG (-). Discussion: Portable abdominal radiographies will be improved image quality by utilizing scatter correction, although, it is necessary to consider the scatter correction processing as this may significant decrease deviation index in the practical situation. Conclusion: The post-processing scatter correction should be useful for detection nasogastric tube and stomach gas in portable abdominal radiography.
SummaryPurpose: Diagnosis for right-to-left shunt was determined by the assessment of shunt-rate, which was obtained by using 99 m Tc-macroaggregated albumin. However, it is difficult to diagnose right-to-left shunt, using the normal level of shunt-rate measured by using conventional methods. To solve this problem, we investigated ourselves the normal level of shunt-rate. Method: We researched 20 patients with pulmonary embolism, and they didn't have right-to-left shunt. We investigated three points for the normal level of shunt-rate. First, we examined the region of interest (ROI) area of the lungs to modify the upper level of gray scale. Second, we confirmed the difference between the whole visual field and body contour of the ROI area. Third, we examined the necessity whether we correct the background of whole body and the lungs. Result: We resulted three points. First, stable right-to-left shunt rate is got to set that the upper level of gray scale is 35%. Second, there is no significant difference between the whole visual field and body contour of the ROI area. Third, correcting background isn't needed to get right-to-left shunt rate. The normal level of the shunt-rate was 12.6±2.8% in the condition. Conclusion: We are able to decide the optimal condition for the normal level of shunt-rate. It is important to evaluate the normal level of the shunt-rate fixed on each factor in each hospital.
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.
Purpose: The purpose of this study was to evaluate the detectability of the observers and motion detection software for blurred portable chest radiographies. Methods: The chest phantom radiographies of various blur sizes were obtained by moving the phantom using 4° slope. The phantom was moved in two directions, vertical (the upper and lower parts of the chest phantom were parallel to rails) and horizontal (the left and right parts of the chest phantom were parallel to rails). Six observers performed receiver operating characteristic (ROC) studies on blurred images. We used the results to compare detectability for vertical and horizontal blur by ROC analysis, and calculated sensitivity and specificity. In addition, the motion detection software was enabled during image acquisition, and the detectability was compared with that of the observers. Results: The average of the area under the ROC curve for the detection of blur in the vertical and horizontal directions for the observers were 0.918 and 0.943, respectively, and no significant difference was found depending on the direction. The motion detection software performed better than the observers in most of the sensitivity and specificity scores. Conclusion: The motion detection software could be a useful support tool for motion detection in portable chest radiography.
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