[Study of a CT scanning method that improves gravity effects to enable differentiation of inflammatory diseases in chest CT].

In chest CT images, the dorsal lower lung field often shows an infiltration-like shadow in patients who cannot stop breathing or take a deep breath. The cause of this phenomenon might be due to the effects of gravity. Since we had observed decreased effects of gravity by conducting additional CT scanning for patients in an oblique position (55 degrees ) or a nearly lateral position, we conducted a clinical study to investigate this matter. Forty-three patients (23 patients in the normal group and 20 patients in the inflammatory disease group) who underwent additional CT scanning were included in this study. CT values for the region in which infiltration-like shadow was observed in both positions (dorsal position and oblique position) were measured. The ratio of fluctuation in the CT value of the dorsal lower lung field at a positional change from the dorsal to the oblique position was calculated as a coefficient of fluctuation C (%). As a result, the coefficient of fluctuation C (%) was 32.6+/-13.6 in the normal group and 6.7+/-6.8 in the inflammatory disease group. The effects of gravity were improved by additional CT scanning in an oblique position (55 degrees ) or a nearly lateral position, and this enabled differentiation of the effects of gravity vs. inflammatory diseases.