Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Keishi Sugino, Masahiro Kobayashi, Yasuhiko Nakamura, Kyoko Gocho, Fumiaki Ishida, Kazutoshi Isobe, Nobuyuki Shiraga, Sakae Homma, Christophe Leroyer.
Little has been reported on the feasibility of xenon-enhanced dual-energy computed tomography (Xe-DECT) in the visual and quantitative analysis of combined pulmonary fibrosis and emphysema (CPFE).
We compared CPFE with idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), as well as correlation with parameters of pulmonary function tests (PFTs).
Studied in 3 groups were 25 patients with CPFE, 25 with IPF without emphysema (IPF alone), 30 with COPD. Xe-DECT of the patients’ entire thorax was taken from apex to base after a patient’s single deep inspiration of 35% stable nonradioactive xenon. The differences in several parameters of PFTs and percentage of areas enhanced by xenon between 3 groups were compared and analyzed retrospectively.
The percentage of areas enhanced by xenon in both lungs were calculated as CPFE/IPF alone/COPD = 72.2 ± 15.1% / 82.2 ± 14.7% /45.2 ± 23.2%, respectively. In the entire patients, the percentage of areas enhanced by xenon showed significantly a positive correlation with FEV1/FVC (R = 0.558, P < 0.0001) and %FEV1, (R = 0.528, P < 0.0001) and a negative correlation with %RV (R = -0.594, P < 0.0001) and RV/TLC (R = -0.579, P < 0.0001). The percentage of areas enhanced by xenon in patients with CPFE showed significantly a negative correlation with RV/TLC (R = -0.529, P = 0.007). Xenon enhancement of CPFE indicated 3 different patterns such as upper predominant, diffuse, and multifocal defect. The percentage of areas enhanced by xenon in upper predominant defect pattern was significantly higher than that in diffuse defect and multifocal defect pattern among these 3 different patterns in CPFE. The percentage of areas enhanced by xenon demonstrated strong correlations with obstructive ventilation impairment. Therefore, we conclude that Xe-DECT may be useful for distinguishing emphysema lesion from fibrotic lesion in CPFE.
Xenon-enhanced dual-energy computed tomography (Xe-DECT) has recently been found to be feasible to assess visualizing lung ventilation [1–3]. This imaging technique has also been proven to be safe without serious side effects in both children and adults. In asthmatics or bronchiolitis obliterans setting, the ventilation defects seen on Xe-DECT showed significant correlations with the airflow obstruction on pulmonary function tests (PFTs) [4, 5]. Therefore, we believe that it will enable us to understand more precisely the distribution and localization of chronic obstructive pulmonary disease (COPD) including emphysematous lesions or combined pulmonary fibrosis and emphysema (CPFE).
This study was approved by our institutional review board (Toho university school of medicine ethical committee, approval number; 23–28) and written informed consent for the study protocols was obtained from all patients. Our clinical trial was registered with http://www.umin.ac.jp/english/ (UMIN000012523). The protocol for this trial and supporting TREND Statement Checklist are available as supporting information; see S1 Protocol and S1 Checklist. The primary outcome was the percentage of areas enhanced by xenon, and secondary outcomes were the relationship between the percentage of areas enhanced by xenon and PFTs parameters.
The percentage of areas enhanced by xenon showed strong correlations with obstructive ventilatory impairment. Xe enhancement of CPFE showed 3 distinct patterns in terms of Xe-DECT 3D images. This is the first study describing 3 distinct patterns of xenon enhancement and usefulness of Xe-DECT for distinguishing emphysema lesion from fibrotic lesion in CPFE.