PURPOSE: The radiographic pulmonary densities values we take today as normals have been obtained through low accuracy methods. A new method for determining these values, based on the comparison of the lung volumes quantified through computed tomography and body plethysmography, might establish them with better accuracy.We attempt to determine the normal pulmonary density interval on tomography, and to weigh the correlation between the volumes acquired by tomography and by plethysmography.
METHODS: Criteriously selected respiratory disease-free individuals (by medical interview and radiologic and functional testing) were submitted to thoracic tomography and to body plethysmography for inspiratory and expiratory volumes measurement. The plethysmographic volumes were admitted to be the real ones. By using a specific software, the tomographic images were initially processed for isolation of the lung images from the rest of the thoracic content, through density differences of adjacent tissues, as to obtain three-dimensional lung images with quantifiable volumes. With this done, and based on the inspiratory and expiratory volumes obtained through body plethysmography (taken as real), the cut values of lung tissue density were changed until we could achieve a three-dimensional tomographic image whose volumes matched the plethysmographic data (with a ± 3% error interval). By doing this, we obtained inspiration and expiration lung volumes much similar to the real ones, allowing a highly-trustable data analysis (e.g., the pulmonary densities of these individuals).
RESULTS: Thirty-five individuals were studied. The mean radiographic pulmonary density was –837,17 ± 21,69 Hounsfield Units (HU) in the female gender, and –841,22 ± 29,52 HU in the male gender. Joining both groups, the mean density was –838,33 ± 23,80 HU.
CONCLUSION: The mean pulmonary density was –838,33 ± 23,80 HU for the study population.There was agreement between the lung volumes measured by computed tomography and body plethysmography.
CLINICAL IMPLICATIONS: The normal values of lung densities in healthy subjects are now more precisely known.Computed tomography is a reliable method for the evaluation of pulmonary densities inf healthy subjects. Further studies in specific populations are necessary (e.g., COPD-affected individuals).
DISCLOSURE: Hassan Yassine Neto, None.