3D lung motion assessments on inspiratory/expiratory thin-section CT: Capability for pulmonary functional loss of smoking-related COPD in comparison with lung destruction and air trapping

Application of 3D computed tomography in emphysematous parenchyma patients scheduled for bronchoscopic lung volume reduction

Bronchoscopic lung volume reduction (BLVR) is a feasible, safe, effective and minimally invasive technique to significantly improve the quality of life of advanced severe chronic obstructive pulmonary disease (COPD). In this study, three-dimensional computed tomography (3D-CT) automatic analysis software combined with pulmonary function test (PFT) was used to retrospectively evaluate the postoperative efficacy of BLVR patients. The purpose is to evaluate the improvement of lung function of local lung tissue after operation, maximize the benefits of patients, and facilitate BLVR in the treatment of patients with advanced COPD. All the reported cases of advanced COPD patients treated with BLVR with one-way valve were collected and analysed from 2017 to 2020. Three-dimensional-CT image analysis software system was used to analyse the distribution of low-density areas <950 Hounsfield units in both lungs pre- and post- BLVR. Meanwhile, all patients performed standard PFT pre- and post-operation for retrospective analysis. We reported six patients that underwent unilateral BLVR with 1 to 3 valves according to the range of emphysema. All patients showed a median increase in forced expiratory volume in 1 second (FEV1) of 34%, compared with baseline values. Hyperinflation was reduced by 16.6% (range, 4.9%-47.2%). The volumetric measurements showed a significant reduction in the treated lobe volume among these patients. Meanwhile, the targeted lobe volume changes were inversely correlated with change in FEV1/FEV1% in patients with heterogeneous emphysematous. We confirm that 3D-CT analysis can quantify the changes of lung volume, ventilation and perfusion, to accurately evaluate the distribution and improvement of emphysema and rely less on the observer.

Area-Detector Computed Tomography for Pulmonary Functional Imaging

An area-detector CT (ADCT) has a 320-detector row and can obtain isotropic volume data without helical scanning within an area of nearly 160 mm. The actual-perfusion CT data within this area can, thus, be obtained by means of continuous dynamic scanning for the qualitative or quantitative evaluation of regional perfusion within nodules, lymph nodes, or tumors. Moreover, this system can obtain CT data with not only helical but also step-and-shoot or wide-volume scanning for body CT imaging. ADCT also has the potential to use dual-energy CT and subtraction CT to enable contrast-enhanced visualization by means of not only iodine but also xenon or krypton for functional evaluations. Therefore, systems using ADCT may be able to function as a pulmonary functional imaging tool. This review is intended to help the reader understand, with study results published during the last a few decades, the basic or clinical evidence about (1) newly applied reconstruction methods for radiation dose reduction for functional ADCT, (2) morphology-based pulmonary functional imaging, (3) pulmonary perfusion evaluation, (4) ventilation assessment, and (5) biomechanical evaluation.

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

Purpose

To correlate the ratio of the non-dependent to dependent aspects of the maximal pleural movement vector (MPMV_ND/D) and gravity-oriented collapse ratio (GCR_ND/D), and the mean lung field density (MLD) obtained using four-dimensional (4D) dynamic-ventilation computed tomography (DVCT) with airflow limitation parameters and the Brinkman index.

Materials and Methods

Forty-seven patients, including 22 patients with COPD, 13 non-COPD smokers, and 12 non-smokers, with no/slight pleural adhesion confirmed using a thoracoscope, underwent 4D-DVCT with 16 cm coverage. Coordinates for the lung field center, as well as ventral and dorsal pleural points, set on the central trans-axial levels in the median and para-median sagittal planes at end-inspiration, were automatically measured (13-17 frame images, 0.35 seconds/frame). MPMV_ND/D and GCR_ND/D were calculated based on MPMV and GCR values for all the included points and the lung field center. MLD was automatically measured in each of the time frames, and the maximal change ratio of MLD (MLD_CR) was calculated. These measured values were compared among COPD patients, non-COPD smokers, and non-smokers, and were correlated with the Brinkman index, FEV₁/FVC, FEV₁ predicted, RV/TLC, and FEF_25-75% using Spearman's rank coefficients.

Results

MPMV_ND/D was highest in non-smokers (0.819±0.464), followed by non-COPD smokers (0.405±0.131) and patients with COPD (-0.219±0.900). GCR_ND/D in non-smokers (1.003±1.384) was higher than that in patients with COPD (-0.164±1.199). MLD_CR in non-COPD smokers (0.105±0.028) was higher than that in patients with COPD (0.078±0.027). MPMV_ND/D showed positive correlations with FEV₁ predicted (r=0.397, p=0.006), FEV₁/FVC (r=0.501, p<0.001), and FEF_25-75% (r=0.368, p=0.012). GCR_ND/D also demonstrated positive correlations with FEV₁ (r=0.397, p=0.006), FEV₁/FVC (r=0.445, p=0.002), and FEF_25-75% (r=0.371, p=0.011). MPMV_ND/D showed a negative correlation with the Brinkman index (r=-0.398, p=0.006).

Conclusion

We demonstrated that reduced MPMV_ND/D and GCR_ND/D were associated with respiratory functional indices, in addition to a negative association of MPMV_ND/D with the Brinkman index, which should be recognized when assessing local pleural adhesion on DVCT, especially for ventral pleural aspects.

Analysis of predicted factors for bronchoalveolar lavage recovery failure: An observational study

Background

The bronchoalveolar lavage (BAL) recovery rate should generally be more than 30% for effective diagnosis. However, there have been no reports investigating a target bronchus for BAL, and the cause of BAL recovery failure is uncertain. Therefore, this study detected predictive factors for BAL recovery failure through investigations on a target bronchus for BAL by using a 3D image analysis system. Therefore, this study detected predictive factors for BAL recovery failure.

Materials and methods

We retrospectively collected data from 338 adult patients who underwent BAL procedures at Fukujuji Hospital from June 2018-March 2022. Factors correlated with the BAL recovery rate were detected. Furthermore, the patients were divided into the failure group (recovery rate <30%; 36 patients) and the success group (recovery rate ≥30%; 302 patients), and data were compared between the two groups by analysing the target bronchus by using a 3D image analysis system.

Results

The patients in the failure group were older (median 74.5 years old [IQR 68.0–79.0] vs. median 70.0 years old [IQR 59.0–76.0], p = 0.016), more likely to be male (n = 27 [75.0%] vs. n = 172 [57.0%], p = 0.048), more likely to have COPD (n = 7 [19.4%] vs. n = 14 [4.6%], p = 0.003), and more likely to perform a target site of BAL other than the middle/lingual lobe (n = 11 [30.5%] vs. n = 35 [11.6%], p = 0.004) than those in the success group. The area of the bronchial wall was positively related to the recovery rate (r = 0.141, p = 0.009), and the area of the bronchial wall in the failure group was lower than that in the success group (median 10.5 mm2 [interquartile range (IQR) 8.1–14.6] vs. median 14.5 mm2 [11.4–19.0], p<0.001).

Conclusion

The study shows that a thin bronchial wall, COPD, and a target site of BAL other than the middle/lingual lobe were identified as the predicted factors for BAL recovery failure. The weakness of the bronchial wall might cause bronchial collapse during the BAL procedure.

The thickness of erector spinae muscles can be easily measured by computed tomography for the assessment of physical activity: An observational study

The loss of muscle mass and changes in muscle composition are important factors for assessing skeletal muscle dysfunction. The cross-sectional area (CSA) of muscle is usually used to assess skeletal muscle function. However, the CSA of skeletal muscle can be difficult for clinicians to measure because a specific 3D image analysis system for computed tomography (CT) scans is needed. Therefore, we conducted a study to develop a new method of easily assessing physical activity, in which the thickness of the erector spinae muscles (ESMT) was measured by CT, and to compare ESMT to the CSA of the erector spinae muscles (ESMCSA) in patients with nontuberculous mycobacteria (NTM) pulmonary infections who underwent surgery after some preoperative examinations, such as laboratory tests, chest CT scans, spirometry, and 6-minute walk tests (6MWT). We retrospectively studied adult patients with NTM pulmonary infections who underwent a lobectomy at Fukujuji Hospital from April 2010 to March 2016. We assessed the correlations between ESMT and different variables, including ESMCSA. Sixty-one patients with NTM pulmonary infections were included. The median ESMT and ESMCSA were 1371 mm2 (IQR 1178-1784 mm2) and 28.5 mm (IQR 25.4-31.7 mm), respectively, and a very strong linear correlation was observed between ESMT and ESMCSA (R = 0.858, P < .001). ESMT and ESMCSA were positively associated with body weight (ESMT: R = 0.540, P < .001, ESMCSA: R = 0.714, P < .001), body mass index (ESMT: R = 0.421, P < .001, ESMCSA: R = 0.560, P < .001), the 6MWT value (ESMT: R = 0.413, P = .040, ESMCSA: R = 0.503, P = .010), vital capacity (ESMT: R = 0.527, P < .001, ESMCSA: R = 0.577, P < .001), and the forced expiratory volume in 1 second (ESMT: R = 0.460, P < .001, ESMCSA: R = 0.532, P < .001). We demonstrated that compared to ESMCSA, ESMT is easily measured by CT and can be a useful parameter for clinically evaluating physical activity. Furthermore, ESMT and ESMCSA were related to physical activity, as measured by the 6MWT and spirometry.

Vector-field dynamic x-ray (VF-DXR) using optical flow method in patients with chronic obstructive pulmonary disease

BACKGROUND

We assessed the difference in lung motion during inspiration/expiration between chronic obstructive pulmonary disease (COPD) patients and healthy volunteers using vector-field dynamic x-ray (VF-DXR) with optical flow method (OFM).

METHODS

We enrolled 36 COPD patients and 47 healthy volunteers, classified according to pulmonary function into: normal, COPD mild, and COPD severe. Contrast gradient was obtained from sequential dynamic x-ray (DXR) and converted to motion vector using OFM. VF-DXR images were created by projection of the vertical component of lung motion vectors onto DXR images. The maximum magnitude of lung motion vectors in tidal inspiration/expiration, forced inspiration/expiration were selected and defined as lung motion velocity (LMV). Correlations between LMV with demographics and pulmonary function and differences in LMV between COPD patients and healthy volunteers were investigated.

RESULTS

Negative correlations were confirmed between LMV and % forced expiratory volume in one second (%FEV1) in the tidal inspiration in the right lung (Spearman's rank correlation coefficient, rs = -0.47, p < 0.001) and the left lung (rs = -0.32, p = 0.033). A positive correlation between LMV and %FEV1 in the tidal expiration was observed only in the right lung (rs = 0.25, p = 0.024). LMVs among normal, COPD mild and COPD severe groups were different in the tidal respiration. COPD mild group showed a significantly larger magnitude of LMV compared with the normal group.

CONCLUSIONS

In the tidal inspiration, the lung parenchyma moved faster in COPD patients compared with healthy volunteers. VF-DXR was feasible for the assessment of lung parenchyma using LMV.

Inspiratory Lung Expansion in Patients with Interstitial Lung Disease: CT Histogram Analyses

This study aimed to evaluate inspiratory lung expansion in patients with interstitial lung disease (ILD) using histogram analyses based on advanced image registration between inspiratory and expiratory CT scans. We included 16 female ILD patients and eight age- and sex-matched normal controls who underwent full-inspiratory and expiratory CT scans. The CT scans were sequentially aligned based on the surface, landmarks, and attenuation of the lung parenchyma. Histogram analyses were performed on the degree of lung expansion (DLE) of each pixel between the aligned images in x-, y-, z-axes, and 3-dimensionally (3D). The overall mean registration error was 1.9 mm between the CT scans. The DLE_3D in ILD patients was smaller than in the controls (mean, 17.6 mm vs. 26.9 mm; p = 0.023), and less heterogeneous in terms of standard deviation, entropy, and uniformity (p < 0.05). These results were mainly due to similar results in the DLE_Z of the lower lungs. A forced vital capacity tended to be weakly correlated with mean (r² = 0.210; p = 0.074), and histogram parameters (r² = 0.194-0.251; p = 0.048-0.100) of the DLE_3D in the lower lung in ILD patients. Our findings indicate that reduced and less heterogeneous inspiratory lung expansion in ILD patients can be identified by using advanced accurate image registration.

Changes of Emphysema Parameters over the Respiratory Cycle During Free Breathing: Preliminary Results Using Respiratory Gated 4D-CT

The purpose of this research was to evaluate respiratory gated CT of the lung in patients with COPD for analysis of parenchymal characteristics who were potential candidates for volume reduction surgery. Eleven patients with clinically known emphysematous disease underwent a respiratory gated, free-breathing 64-multislice-CT (Aquilion 64, Toshiba). Retrospective image reconstruction was performed similar to cardiac CT at every 10% of the respiratory loop, resulting in 10 complete volumetric datasets at 10 equidistant time points. All images were transferred onto a PC for calculation of the total lung volume, emphysema volume, emphysema index, and mean lung density. Complete datasets could be successfully reconstructed in all patients. The mean lung volume increased from 6.9 L to 7.5 L over the respiratory cycle. Emphysema volume increased from 1.6 L to 2.0 L and emphysema index from 22.6% to 26.5% from expiration to inspiration. In conclusion, respiratory gated chest 4D-CT allows for combined morphologic and functional image analysis, which can provide new insight into functional impairment and individual treatment planning.

Quantitative evaluation of interstitial pneumonia using 3D-curved high-resolution CT imaging parallel to the chest wall: A pilot study

Objectives

To quantify the imaging findings of patients with interstitial pneumonia (IP) and emphysema using three-dimensional curved high-resolution computed tomography (3D-cHRCT) at a constant depth from the chest wall, and compare the results to visual assessment of IP and each patient’s diffusing capacity of the lungs for carbon monoxide (DLco).

Methods

We retrospectively reviewed the axial CT findings and pulmonary function test results of 95 patients with lung cancer (72 men and 23 women, aged 45–84 years) with or without IP, as follows: non-IP (n = 47), mild IP (n = 31), and moderate IP (n = 17). The 3D-cHRCT images of the lung at a 1-cm depth from the chest wall were reconstructed automatically using original software; total area (TA), high-attenuation area (HAA) >-500 HU, and low-attenuation area (LAA) <-950 HU were calculated on a workstation. The %HAA and %LAA were calculated as follows: %HAA=HAATA×100, and %LAA=LAATA×100.

Results

The %HAA and %LAA respective values were 3.2±0.9 and 27.7±8.2, 3.9±1.2 and 27.6±5.9, and 6.9±2.2 and 25.4±8.7 in non-IP, mild IP, and moderate IP patients, respectively. There were significant differences in %HAA between the 3 groups of patients (P<0.001), but no differences in %LAA (P = 0.558). Multiple linear regression analysis revealed that %HAA and %LAA were negatively correlated with predicted DLco (standard partial regression coefficient [b*] = -0.453, P<0.001; b* = -0.447, P<0.001, respectively).

Conclusions

The %HAA and %LAA values computed using 3D-cHRCT were significantly correlated with DLco and may be important quantitative parameters for both IP and emphysema.

Asynchrony in respiratory movements between the pulmonary lobes in patients with COPD: continuous measurement of lung density by 4-dimensional dynamic-ventilation CT

Purpose

Four-dimensional dynamic-ventilation CT imaging demonstrates continuous movement of the lung. The aim of this study was to assess the correlation between interlobar synchrony in lung density and spirometric values in COPD patients and smokers, by measuring the continuous changes in lung density during respiration on the dynamic-ventilation CT.

Materials and methods

Thirty-two smokers, including ten with COPD, underwent dynamic-ventilation CT during free breathing. CT data were continuously reconstructed every 0.5 sec. Mean lung density (MLD) of the five lobes (right upper [RU], right middle [RM], right lower [RL], left upper [LU], and left lower [LL]) was continuously measured by commercially available software using a fixed volume of volume of interest which was placed and tracked on a single designated point in each lobe. Concordance between the MLD time curves of six pairs of lung lobes (RU-RL, RU-RM, RM-RL, LU-LL, RU-LU, and RL-LL lobes) was expressed by cross-correlation coefficients. The relationship between these cross-correlation coefficients and the forced expiratory volume in one second/forced vital capacity (FEV_1.0/FVC) values was assessed by Spearman rank correlation analysis.

Results

In all six pairs of the pulmonary lobes, the cross-correlation coefficients of the two MLD curves were significantly positively correlated with FEV_1.0/FVC (ρ =0.60–0.73, P<0.001). The mean value of the six coefficients strongly correlated with FEV_1.0/FVC (ρ =0.80, P<0.0001).

Conclusion

The synchrony of respiratory movements between the pulmonary lobes is limited or lost in patients with more severe airflow limitation.

Sagittal-lung CT measurements in the evaluation of asthma-COPD overlap syndrome: a distinctive phenotype from COPD alone

OBJECTIVES

This study aimed at investigating the capability of sagittal-lung computed tomography (CT) measurements in differentiating chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap syndrome (ACOS).

METHODS

Clinical and high-resolution CT of 229 patients including 123 pure COPD patients and 106 ACOS patients were included. Sagittal-lung CT measurements in terms of bilateral lung height (LH), anterior-posterior lung diameter (APLD), diaphragm height (DH), and anterior sterno-diaphragmatic angle (ASDA), as well as inter-pulmonary septum length (IPSL) on axial images were measured both before and after bronchodilator (BD) administration. Comparisons of clinical characteristics and CT measurements between patient groups were performed.

RESULTS

All pre-BD quantitative sagittal features measuring diaphragm flattening and hyperinflation were not significantly different between patients with COPD and patients with ACOS (P values all >0.05). Following BD administration, the ACOS patients exhibited lower left LH, bilateral APLD, and bilateral ASDA, but higher right DH, compared to pure COPD patients (P values all <0.05). Right LH, left DH and IPSL were not significantly different between patient groups. Besides, variations of all sagittal-lung CT measurements were significantly larger in patients with ACOS than in patients with pure COPD (P values all <0.001) and showed high performance in differentiating these two kinds of patient, with diagnostic sensitivities ranging from 76.4 to 97.2%, specificities ranging from 86.2 to 100.0%, and accuracies ranging from 80.9 to 90.7%.

CONCLUSIONS

Sagittal-lung CT measurements allow for differentiating patients with ACOS from those with pure COPD. The ACOS patients had larger post-BD variations of sagittal-lung CT measurements than patients with pure COPD.