COMPARISON OF COMPUTED DENSITY AND MICROSCOPIC MORPHOMETRY IN PULMONARY-EMPHYSEMA

The purpose of this prospective study was to verify whether the percen tage area of lung occupied by lowest attenuation values on high-resolu tion computed tomography (HRCT) scans reflects microscopic emphysema a nd to compare this quantification with the Information yielded by the most widely used pulmonary function tests (PFT). Preoperative HRCT sca ns were obtained with 1-cm intervals in 38 subjects. With a semiautoma tic evaluation procedure, the percentage areas occupied by attenuation values inferior to thresholds ranging from -900 Hounsfield units (HU) to -970 HU were calculated for the lobe or lung to be resected. Emphy sema was microscopically quantified by using a computer-based method, measuring the perimeters and interwall distances of alveoli and alveol ar ducts. The strongest correlation was found for -950 HU. As a second step, we evaluated possible correlations between PFT and microscopic measurements. Finally, considering the microscopic measurements as a s tandard, we tried to investigate their relationships with each of the PFT and with the relative area occupied by attenuation values lower th an -950 HU for both lungs. This revealed that the diffusing capacity f or carbon monoxide associated with HRCT quantification is sufficient t o predict microscopic measurements. We concluded that the percentage a rea of lung occupied by attenuation values lower than -950 HU is a val id index of pulmonary emphysema.