Automated continuous quantitative measurement of proximal airways on dynamic ventilation CT: initial experience using an ex vivo porcine lung phantom

Quantitative analyzes of the variability in airways via four-dimensional dynamic ventilation CT in patients with chronic obstructive pulmonary disease: correlation with spirometry data and severity of airflow limitation

Background

In chronic obstructive pulmonary disease (COPD) patients, the diagnosis and assessment of disease severity are mainly based on spirometry, which may lead to misjudgments due to poor patient compliance. Thoracic four-dimensional dynamic ventilation computed tomography (4D-CT) provides more airway data approximating true physiological function than conventional CT. We aimed to determine dynamic changes in airways to elucidate the pathological mechanism underlying COPD and predict the severity of airflow limitation in patients.

Methods

Forty-two COPD patients underwent 4D-CT and spirometry. The minimum lumen diameter changed with the breathing cycle in 4th-generation airways and was continuously measured in the apical (RB1), lateral (RB4) and posterior basal segments (RB10) of the right lung. The minimum lumen diameter in the peak inspiration and peak expiration as well as the peak expiratory/peak inspiratory ratio (E/I ratio), and dynamic coefficient of variance (CV) were calculated.

Results

Correlations of FEV1% with the CV of minimum lumen diameter in RB1 (ρ=-0.473, P=0.002) and in RB10 (ρ=-0.480, P=0.005) were observed, suggesting that the dynamic variability in 4th-generation airways was associated with airflow limitation in COPD patients. The CV of the minimum lumen diameter in RB1 significantly differed between the GOLD I + II and GOLD III + IV groups {8.59 [interquartile range (IQR), 6.63-14.86] vs. 14.64 (10.65-25.88), respectively; P=0.016}, suggesting that the dynamic CV in RB1 increased significantly in the GOLD III + IV group, which had worse pulmonary ventilation function. Based on the receiver operating characteristic (ROC) curve analysis, CV-RB1 predicted FEV1% <50% with an optimal cut-off of 9.43% [sensitivity 85.7%, specificity 57.1%, area under the curve (AUC) 0.717].

Conclusions

4D-CT might be an available method to help diagnose and evaluate the severity of COPD.

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.

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

Purpose

The 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 methods

Preoperative 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.

Results

The ΔMLD_1.05 (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 ΔAi_1.05 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.

Conclusion

In 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.

Computed tomography trachea volumetry in patients with scleroderma: Association with clinical and functional findings

BACKGROUND

In scleroderma, excessive collagen production can alter tracheal geometry, and computed tomography (CT) volumetry of this structure may aid in detecting possible abnormalities. The objectives of this study were to quantify the morphological abnormalities in the tracheas of ​​patients with scleroderma and to correlate these findings with data on clinical and pulmonary function.

METHODS

This was a cross-sectional study in which 28 adults with scleroderma and 27 controls matched by age, gender and body mass index underwent chest CT with posterior segmentation and skeletonization of the images. In addition, all participants underwent pulmonary function tests and clinical evaluation, including the modified Rodnan skin score (mRSS).

RESULTS

Most patients (71.4%) had interstitial lung disease on CT. Compared to controls, patients with scleroderma showed higher values ​​in the parameters measured by CT trachea volumetry, including area, eccentricity, major diameter, minor diameter, and tortuosity. The tracheal area and equivalent diameter were negatively correlated with the ratio between forced expiratory flow and forced inspiratory flow at 50% of forced vital capacity (FEF50%/FIF50%) (r = -0.44, p = 0.03 and r = -0.46, p = 0.02, respectively). The tracheal tortuosity was negatively correlated with peak expiratory flow (r = -0.51, p = 0.008). The mRSS showed a positive correlation with eccentricity (r = 0.62, p < 0.001) and tracheal tortuosity (r = 0.51, p = 0.007), while the presence of anti-topoisomerase I antibody (ATA) showed a positive correlation with tracheal tortuosity (r = 0.45, p = 0.03).

CONCLUSIONS

In a sample composed predominantly of scleroderma patients with associated interstitial lung disease, there were abnormalities in tracheal geometry, including greater eccentricity, diameter and tortuosity. In these patients, abnormalities in the geometry of the trachea were associated with functional markers of obstruction. In addition, tracheal tortuosity was correlated with cutaneous involvement and the presence of ATA.

Hyperinflated lungs compress the heart during expiration in COPD patients: a new finding on dynamic-ventilation computed tomography

Purpose

The aims of this study were to evaluate dynamic changes in heart size during the respiratory cycle using four-dimensional computed tomography (CT) and to understand the relationship of these changes to airflow limitation in smokers.

Materials and methods

A total of 31 smokers, including 13 with COPD, underwent four-dimensional dynamic-ventilation CT during regular breathing. CT data were continuously reconstructed every 0.5 s, including maximum cross-sectional area (CSA) of the heart and mean lung density (MLD). Concordance between the cardiac CSA and MLD time curves was expressed by cross-correlation coefficients. The CT-based cardiothoracic ratio at inspiration and expiration was also calculated. Comparisons of the CT indices between COPD patients and non-COPD smokers were made using the Mann–Whitney test. Spearman rank correlation analysis was used to evaluate associations between CT indices and the forced expiratory volume in 1 s (FEV_1.0) relative to the forced vital capacity (FVC).

Results

Cardiac CSA at both inspiration and expiration was significantly smaller in COPD patients than in non-COPD smokers (P<0.05). The cross-correlation coefficient between cardiac CSA and MLD during expiration significantly correlated with FEV_1.0/FVC (ρ=0.63, P<0.001), suggesting that heart size decreases during expiration in COPD patients. The change in the cardiothoracic ratio between inspiration and expiration frames was significantly smaller in COPD patients than in non-COPD smokers (P<0.01).

Conclusion

Patients with COPD have smaller heart size on dynamic-ventilation CT than non-COPD smokers and have abnormal cardiac compression during expiration.

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.

Parietal pleural invasion/adhesion of subpleural lung cancer: Quantitative 4-dimensional CT analysis using dynamic-ventilatory scanning

PURPOSE

Using 4-dimensional dynamic-ventilatory scanning by a 320-row computed tomography (CT) scanner, we performed a quantitative assessment of parietal pleural invasion and adhesion by peripheral (subpleural) lung cancers.

METHODS

Sixteen patients with subpleural lung cancer underwent dynamic-ventilation CT during free breathing. Neither parietal pleural invasion nor adhesion was subsequently confirmed by surgery in 10 patients, whereas the other 6 patients were judged to have parietal pleural invasion or adhesion. Using research software, we tracked the movements of the cancer and of an adjacent structure such as the rib or aorta, and converted the data to 3-dimensional loci. The following quantitative indices were compared by the Mann-Whitney test: cross-correlation coefficient between time curves for the distances moved from the inspiratory frame by the cancer and the adjacent structure, the ratio of the total movement distances (cancer/adjacent structure), and the cosine similarities between the inspiratory and expiratory vectors (from the cancer to the adjacent structure) and between vectors of the cancer and of the adjacent structure (from inspiratory to expiratory frames).

RESULTS

Generally, the movements of the loci of the lung cancer and the adjacent structure were similar in patients with parietal pleural invasion/adhesion, while they were independent in patients without. There were significant differences in all the parameters between the two patient groups (cross-correlation coefficient and the movement distance ratio, P<0.01; cosine similarities, P<0.05).

CONCLUSION

These observations suggest that quantitative indices by dynamic-ventilation CT can be utilized as a novel imaging approach for the preoperative assessment of parietal pleural invasion/adhesion.

Continuous quantitative measurement of the proximal airway dimensions and lung density on four-dimensional dynamic-ventilation CT in smokers

Purpose

Four-dimensional dynamic-ventilation computed tomography (CT) imaging demonstrates continuous movement of the airways and lungs, which cannot be depicted with conventional CT. We aimed to investigate continuous changes in lung density and airway dimensions and to assess the correlation with spirometric values in smokers.

Materials and methods

This retrospective study was approved by the Institutional Review Board, and informed consent was waived. Twenty-one smokers including six patients with COPD underwent four-dimensional dynamic-ventilation CT during free breathing (160 mm in length). The mean lung density (MLD) of the scanned lung and luminal areas (Ai) of fixed points in the trachea and the right proximal bronchi (main bronchus, upper bronchus, bronchus intermedius, and lower bronchus) were continuously measured. Concordance between the time curve of the MLD and that of the airway Ai values was expressed by cross-correlation coefficients. The associations between these quantitative measurements and the forced expiratory volume in 1 second/forced vital capacity (FEV₁/FVC) values were assessed by Spearman’s rank correlation analysis.

Results

On the time curve for the MLD, the Δ-MLD1.05 values between the peak inspiratory frame to the later third frame (1.05 seconds later) were strongly correlated with the FEV₁/FVC (ρ=0.76, P<0.0001). The cross-correlation coefficients between the airway Ai and MLD values were significantly correlated with the FEV₁/FVC (ρ=−0.56 to −0.66, P<0.01), except for the right upper bronchus. This suggested that the synchrony between the airway and lung movement was lost in patients with severe airflow limitation.

Conclusion

Respiratory changes in the MLD and synchrony between the airway Ai and the MLD measured with dynamic-ventilation CT were correlated with patient’s spirometric values.