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Comparative Study
. 2015 Oct 2;10(10):e0139102.
doi: 10.1371/journal.pone.0139102. eCollection 2015.

Quantification of Pathologic Air Trapping in Lung Transplant Patients Using CT Density Mapping: Comparison with Other CT Air Trapping Measures

Olga Solyanik  1 , Patrick Hollmann  2 , Sabine Dettmer  1 , Till Kaireit  1 , Cornelia Schaefer-Prokop  3 , Frank Wacker  1 , Jens Vogel-Claussen  1 , Hoen-oh Shin  1
Affiliations
Comparative Study

Quantification of Pathologic Air Trapping in Lung Transplant Patients Using CT Density Mapping: Comparison with Other CT Air Trapping Measures

Olga Solyanik et al. PLoS One. .

Abstract

To determine whether density mapping (DM) is more accurate for detection and quantification of pathologic air trapping (pAT) in patients after lung transplantation compared to other CT air trapping measures. One-hundred forty-seven lung and heart-lung transplant recipients underwent CT-examinations at functional residual capacity (FRC) and total lung capacity (TLC) and PFT six months after lung transplantation. Quantification of air trapping was performed with the threshold-based method in expiration (EXP), density mapping (DM) and the expiratory to inspiratory ratio of the mean lung density (E/I-ratio MLD). A non-rigid registration of inspiration-expiration CT-data with a following voxel-to-voxel mapping was carried out for DM. Systematic variation of attenuation ranges was performed for EXP and DM and correlated with the ratio of residual volume to total lung capacity (RV/TLC) by Spearman rank correlation test. AT was considered pathologic if RV/TLC was above the 95th percentile of the predicted upper limit of normal values. Receiver operating characteristic (ROC) analysis was performed. The optimal attenuation range for the EXP method was from -790 HU to -950 HU (EXP(-790 to -950HU)) (r = 0.524, p<0.001) to detect air trapping. Within the segmented lung parenchyma, AT was best defined as voxel difference less than 80 HU between expiration and registered inspiration using the DM method. DM correlated best with RV/TLC (r = 0.663, p<0.001). DM and E/I-ratio MLD showed a larger AUC (0.78; 95% CI 0.69-0.86; 0.76, 95% CI 0.67-0.85) than EXP(-790 HU to -950 HU) (0.71, 95% CI 0.63-0.78). DM and E/I-ratio MLD showed better correlation with RV/TLC and are more suited quantitative CT-methods to detect pAT in lung transplant patients than the EXP(-790HU to -950HU).

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Bland-Altman plots of RV/TLC against the three evaluated CT measures for quantification of AT%.
In comparison to RV / TLC, EXP-790 to -950 HU (A) showed the smallest mean difference (bias) of -3.08% but the highest range in the 95% limits of agreement (-34.7% to 28.5%). E/I-ratio MLD and DM (B, C) showed smaller ranges of the 95% limits of agreement (-58.9% to -28.5% and -9.8% to 34.8%, respectively) suggesting a higher agreement with RV / TLC. Bias was highest with E/I-ratio MLD (-43.7%) while DM showed a moderate bias of 12.5%.
Fig 2
Fig 2. ROC curves of three quantitative CT measures to detect pAT in patients after lung transplantation.
Measurements were corrected for bias. Density mapping showed the largest AUC under the ROC curve of 0.78.
See this image and copyright information in PMC

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Grants and funding

Funding was provided by German Federal Ministry of Education and Research (reference number: 01EO0802). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.