Reference Values for Lung Density and Structure Measured by Quantitative CT

Noninvasive in vivo assessment of lung density and structure by quantitative computed tomography (QCT) has a long tradition in the scientific literature. Early efforts were limited, however, as reproducibility was insufficient due to a lack of respiratory control during scanning and appropriate evaluation software was missing (e.g. Goddard et al. 1982; Gilman et al. 1983; Van Dyk and Hill 1983; Mueller et al. 1988; Rienmoller et al. 1988). We have worked on the respective methodology to improve both accuracy and precision and to provide specific evaluation capabilities. Decisive steps were the design of spirometric control and gating for the CT scan process (Kalender et al. 1990a, b; Rienmoller et al, 1990), dedicated evaluation algorithms (Kalender et al. 1991; Rienmoller et al. 1991) and quality control measures as described below. All these steps were incorporated into the PULMO CT option on the SOMATOM PLUS which meanwhile is in broad clinical use. Reference data on lung density and histograms in a healthy population for comparison purposes are still missing, however. It is the purpose of this paper to present first results of a multicenter study established to gather such data. These results still have to be considered preliminary. An extended publication is intended when all participating centers will have acquired the planned numbers of examinations.