Continuous quantitative measurement of the main bronchial dimensions and lung density in the lateral position by four-dimensional dynamic-ventilation CT in smokers and COPD patients

Abstract

PurposeThe purpose of this study was to measure changes in lung density and airway dimension in smokers in the lateral position using four-dimensional dynamic-ventilation computed tomography (CT) during free breathing and to evaluate their correlations with spirometric values.Materials and methodsPreoperative pleural adhesion assessments included dynamic-ventilation CT of 42 smokers (including 22 patients with COPD) in the lateral position, with the unoperated lung beneath (dependent lung). The scanned lungs’ mean lung density (MLD) and the bilateral main bronchi’s luminal areas (Ai) were measured automatically (13–18 continuous image frames, 0.35 seconds/frame). Calculations included cross-correlation coefficients (CCCs) between the MLD and Ai time curves, and correlations between the quantitative measurements and spirometric values were evaluated by using Spearman’s rank coefficient.ResultsThe ΔMLD1.05 (from the peak inspiration frame to the third expiratory frame, 1.05 seconds later) in the nondependent lung negatively correlated with FEV1/FVC (r=−0.417, P<0.01), suggesting that large expiratory movement of the nondependent lung would compensate limited expiratory movement of the dependent lung due to COPD. The ΔAi1.05 negatively correlated with the FEV1/FVC predicted in both the lungs (r=−0.465 and −0.311, P<0.05), suggesting that early expiratory collapses of the main bronchi indicate severe airflow limitation. The CCC correlated with FEV1/FVC in the dependent lung (r=−0.474, P<0.01), suggesting that reduced synchrony between the proximal airway and lung occurs in patients with severe airflow limitation.ConclusionIn COPD patients, in the lateral position, the following abnormal dynamic-ventilation CT findings are associated with airflow limitation: enhanced complementary ventilation in the nondependent lung, early expiratory airway collapses, and reduced synchrony between airway and lung movements in the dependent lung.

Usability of the lateral decubitus position on four-dimensional ultra-low-dose computed tomography for the detection of localized pleural adhesion in the pulmonary apical region

“…A several-year smoking habit reduced respiratory movement of the chest wall and the maximal expiratory pressure of respiratory muscle even in a younger generation (25), which could be associated with the susceptibility of predominantly perfused lung regions to collapse during the early expiratory phase. As shown in our previous study (21), the correlation between the main bronchial dimensions and peripheral lung field density was impaired along with airflow limitation in COPD. In COPD, the collapse of peripheral lung regions adjacent to the lateral region may become more prominent compared with the other aspects and lead to regional delay in both inflation and deflation, resulting in smaller increases in PCD ACA in the dependent lateral decubitus position compared with the supine position.…”

Association of Respiratory Functional Indices and Smoking with Pleural Movement and Mean Lung Density Assessed Using Four-Dimensional Dynamic-Ventilation Computed Tomography in Smokers and Patients with COPD

“…Moreover, data analysis of DVCT obtained in the lateral position demonstrated that MLD at peak inspiration in the dependent lung field was higher by 40 HU than in the non-dependent lung field. 25 Considering the preserved association between central airway dimension and MLD in the dependent lung field in the NCS group, relatively large pleural movements in the dependent aspect may be a complementary phenomenon to preserve ventilation within the normal range, even in parenchymal regions with collapse, to some extent.

Figure 6 Example images on the median sagittal plane for the left lower lung field for three intermittent time frames in a non-COPD smoker.

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Right main pulmonary artery distensibility on dynamic ventilation CT and its association with respiratory function

“…Some study subjects have been previously included in one of our previous studies [ 15 , 16 , 20 , 21 , 24 ] in the following way. In the selection process for the study population in the present study, 32 patients were identified among 72 patients who were enrolled between July 2015 and May 2016 in our previous study for different purposes: assessment of the detectability of localized benign pleural adhesion [ 15 , 16 , 24 ], continuous measurement of the main bronchial dimensions and lung density in the lateral position for smokers [ 20 ], and evaluation of the association of respiratory functional indices and smoking with pleural movement [ 21 ].…”

“…Each patient underwent preoperative routine protocol CT, followed approximately 10 min later by DVCT with the following protocol; in most of the patients, 28 of 37, contrast-enhanced CT was performed, and the remaining 9 patients underwent non-contrast CT. First, a scanning range of 16 cm in the z -axis direction was set as the field of view to include all target lesions in the lungs, and the patient was asked to breathe according to a predefined breathing cycle [ 15 , 16 , 20 , 21 ]. Dynamic image data were acquired using DVCT for 7.04 ± 1.33 s including at least 1 breath on a 320-row CT (Canon Medical Systems, Otawara, Tochigi, Japan) in wide-volume scan mode.…”