Young Kyung Lee, Presenter: Nothing to Disclose

Joon Beom Seo MD, PhD, Abstract Co-Author: Speaker, Siemens AG

Namkug Kim PhD, Abstract Co-Author: Nothing to Disclose

Song Soo Kim MD, PhD, Abstract Co-Author: Nothing to Disclose

Yeon-Mok Oh MD, PhD, Abstract Co-Author: Nothing to Disclose

Sang Do Lee MD, Abstract Co-Author: Nothing to Disclose

To develop and validate correction method to minimize the variability of emphysema severity assessment between CT protocols and CT machines.

 162 patients with chronic obstructive pulmonary disease (COPD) had been recruited from pulmonary clinics in four hospitals, from June 2005 to December 2009. The institutional review board approved the analyses of the clinical and imaging data. All subjects had CT scans and pulmonary function tests on the same day. Volumetric CT scans were performed in all 162 patients with COPD at full inspiration from four MDCT scanners from different vendors. Images were reconstructed with standard kernels. Siemens 16 (n=64), Philips 16 (n=48), Philips 40 (n=30), and Toshiba 64 (n=20) scanners were used. Emphysema index (EIbase), which is the percentage of the area of relatively low attenuation below – 950HU of the lung, was measuredwith in-house software. For the correction of CT values, regions of interest were drawn at the air inside the trachea (inner air), outer patient air (outer air) and proximal descending aorta. Volume density correction was applied based on the assumption that density of aorta is 50 HU and that of air is -1000 HU. Using in-house software, CT pixels of the whole images were rescaled automatically. From the rescaled CT data, emphysema indexes (EIvd-inner, and EIvd-outer) were measured again. EIbase, EIvd-inner, and EIvd-outer were correlated with the pulmonary function values, including FEV1, FEV1/FVC, and DLco adjusted by age, sex and CT scanner and those correlation values were compared.

 Age, sex, and CT scanner adjusted partial correlation analysis showed that the correlation coefficients between CT quantification indexes and FEV1 (EIbase, EIvd-inner, EIvd-outer: -0.41, -0.55, -0.45, respectively), FEV1/FVC (EIbase, EIvd-inner, EIvd-outer: -0.60, -0.63, -0.60, respectively), and DLco (EIbase, EIvd-inner, EIvd-outer: -0.60, -0.60, -0.63, respectively) improved after density correction.

 Volume density correction of CT data based on air and aorta density can lessen intervendor density measurement variation and improve correlation between CT emphysema quantification and pulmonary function test.

 Volumetric density correction shows possibility to decrease the intervendor density measurement variation in CT quantification of emphysema.

Lee, Y, Seo, J, Kim, N, Kim, S, Oh, Y, Lee, S, Correction Method to Minimize the Differences between CT Protocols and CT Machines in Evaluating Emphysema Severity.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008531.html