COMPUTED TOMOGRAPHIC MEASUREMENT OF LUNG DENSITY - CHANGES IN LUNG WATER WITH HEMODIALYSIS

In 10 hemodialysis patients, with an ultrafiltration volume ranging fr om 1 to 4.5 Liters per session, the lung density was measured by compu ted tomography (CT) and the Lung volumes by total body plethysmography . From tile CT numbers (difference in X-ray attenuation between lung a nd water, measured in Hounsfield units, HU), and by using a special co mputer program, quantitative estimates of the densities of normally in flated (pixels between -1,000 and -500 HU), poorly inflated (pixels be tween -500 and -100 HU) and noninflated lung tissue (pixels between -1 00 and +100 KU) were obtained. The sizes of the normally and poorly in flated areas were also measured. The results showed that, after dialys is, the normally inflated area was decreased in density and increased in size, and conversely, the size of the poorly inflated area was dimi nished but without change in density. This finding implied introductio n of more gas into the lung. The above observation was reflected by th e results of pulmonary function measurements, in that the total Lung c apacity and functional residual capacity were significantly increased after dialysis, in conclusion, changes in lung fluid (both intra- and extravascular) with hemodialysis call be measured quantitatively by ti le changes in lung density as estimated by the CT densitometry techniq ue.