COMPARISON OF COMPUTED DENSITY AND MACROSCOPIC MORPHOMETRY IN PULMONARY-EMPHYSEMA

High-resolution computed tomography (HRCT) scans were obtained at 1 cm intervals in 63 subjects referred for surgical resection of a cancer or for transplantation to find out whether the relative area of lung o ccupied by attenuation values lower than a threshold would be a measur ement of macroscopic emphysema. Using a semiautomatic procedure, the r elative areas occupied by attenuation values lower than eight threshol ds ranging from -900 to -970 HU were calculated on the set of scans ob tained through the lobe or the lung to be resected. The extent of emph ysema was quantified by a computer-assisted method on horizontal paper -mounted lung sections obtained every 1 to 2 cm. The only level for wh ich no statistically significant difference was found between the HRCT and the morphometric data was -950 HU. To determine the number of sca ns sufficient for an accurate quantification, we recalculated the rela tive area occupied by attenuation values lower than -950 HU on progres sively fewer numbers of scans and investigated the departure from the results obtained with 1 cm intervals. Because of wide variations in th is departure from patient to patient, a standard cannot be recommended as the optimal distance between scans.