Srikar Reddy BS, Abstract Co-Author: Nothing to Disclose

Graham Barr MD, PhD, Abstract Co-Author: Nothing to Disclose

Kevin Staley Berbaum PhD, Abstract Co-Author: Nothing to Disclose

Geoffrey McLennan MD, PhD, Abstract Co-Author: Nothing to Disclose

Edwin J. R. Van Beek MD, PhD, Abstract Co-Author: Nothing to Disclose

Eric A. Hoffman PhD, Presenter: Nothing to Disclose

MDCT is used to screen subjects at risk for lung cancer and coronary atherosclerosis. We have previously shown that quantitative analysis of full lung scans provides extent and distribution of emphysema and is closely correlated with PFT-based COPD categories. An important question is whether a CT performed to screen for coronary calcium (CCS-CT) can also be used to assess presence and distribution of emphysema.

We analyzed 386 full lung CTs of heavy smokers imaged via the American College of Radiology Imaging Network-sponsored National Lung Screening Trial. To match CCS-CT studies, we limited our analysis to slices from the pulmonary artery bifurcation to the heart apex. We compared % emphysema from just the cardiac region with that computed from the whole lung. Next, the cardiac region was divided into three sections along the length of the lung (1/8-3/4-1/8) and cumulative histograms of lung densities were computed for each. The apical-basal difference in % emphysema between the top and bottom 1/8 of the cardiac region was compared to the apical-basal difference in % emphysema for the whole lung.

Defining emphysema at -910 HU cut-off, % emphysema from partial lung data sets was correlated with the % emphysema from full lung data sets. Emphysema Presence: The following linear regression equation was generated: full lung % = 0.94 (partial lung %) + 1.33. 98% of the variation in emphysema from analyzing the full lung was accounted for by variation in emphysema from analyzing the cardiac region only (R2= 0.98). Emphysema Distribution (apical-basal difference): The regression equation was: full lung apical-basal difference = 1.02 (partial lung apical-basal difference) + 1.33. This time 68% of the variation in apical-basal difference from full lung data was accounted for by variation in apical-basal difference from CCS-CT data (R2= 0.68).

While full lung imaging is preferred, the reduced coverage associated with coronary calcium screening provides almost identical information on emphysema presence and reasonable information on distribution without the need for additional radiation exposure. Funded in part by:, HL-064368, HL-077612 and a Doris Duke Fellowship

G.M.,E.A.H.: Partner, VIDA Diagnostics

Reddy, S, Barr, G, Berbaum, K, McLennan, G, Van Beek, E, Hoffman, E, Quantitative Evaluation of Emphysema: Is Coronary Calcium Screening CT a Surrogate for a Full Lung Study?.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4407991.html