Optimized scanning conditions of high resolution CT in the follow-up of pulmonary emphysema

Purpose: To address the optimal scanning condition of high resolution computerized tomography from the perspective of minimizing exposed dose. Method: The influence of the electric current, the slice number, and the slice thickness on precise percent ratio of the low attenuation area to whole lung field (LAA%) of chronic obstructive pulmonary disease patients was examined. The standard conditions were 250 mA, 3 slices, 2 mm slice thickness, and a varied parameter. Results: In cases showing an LAA% less than 30, LAA% obtained by less than or equal to 150 mA were significantly larger than those by 250 mA. The mean LAA% with 3 and 10 slices were well correlated and the correlation with lung function was similar. The correlation of LAA% with lung function was approximately the same between the 2 and 5 mm slice thicknesses. Conclusion: The electrical current must be greater than or equal to 200 mA, and 3 Slices and 2 mm slice thickness are appropriate.