Correlation of pulmonary function indexes determined by low-dose MDCT with spirometric pulmonary function tests in patients with chronic obstructive pulmonary disease

Correlation of spirometry indices to chest radiology in the diagnosis of chronic airway disease among regional and rural Indigenous Australians

BACKGROUND

The majority of Indigenous Australians reside in non-urban locations, with reduced access to chest radiology such as computed tomography (CT). Spirometry and chest X-ray (CXR) may be used in the absence of CT; however, the correlation of spirometry indices to CT-defined chronic airway diseases (i.e. chronic obstructive pulmonary disease (COPD) and bronchiectasis) compared with CXR among Indigenous people is sparsely reported.

AIM

To evaluate spirometry indices against CXR and CT findings among adult Indigenous Australians.

METHODS

Indigenous patients who had undergone a spirometry test between 2012 and 2020 and had a CXR or chest CT scan assessed for the presence (+ )/absence (- ) of airway diseases were included in this study.

RESULTS

Of 643 patients (57% female, 31% remote/very remote), 364 (57%) had CT and CXR available. Patients who were 'CT- and CXR- ' for airway diseases (48%) recorded a mean FVC, FEV1 and FEV1 /FVC of 61%, 59% and 0.76 compared to 57%, 49% and 0.66 in the 'CT+ and CXR- ' group and 53%, 39% and 0.58 in the 'CT+ and CXR+ ' group. CXR showed sensitivity (44%) and specificity (88%), while spirometry showed 62% and 77% compared to CT. Spirometry demonstrated predominately restrictive impairment among 'CT- and CXR- ' and mixed/obstructive impairment among 'CT+ and CXR- ' and 'CT+ and CXR+ ' groups.

CONCLUSION

Indigenous Australians tend to demonstrate restrictive impairment in the absence of radiological evidence of airway disease. However, in the presence of airway disease, combinations of mixed and obstructive impairments were common. Obstructive impairment shows greater sensitivity for identifying COPD than that shown by CXR; however, CXR shows greater specificity. Hence, spirometry in conjunction with chest radiology should be utilised to aid in the assessment of airway diseases in this population.

Quantitative analysis of changes in lung density by dynamic chest radiography in association with CT values: a virtual imaging study and initial clinical corroboration

Dynamic chest radiography (DCR) identifies pulmonary impairments as decreased changes in radiographic lung density during respiration (Δpixel values), but not as scaled/standardized computed tomography (CT) values. Quantitative analysis correlated with CT values is beneficial for a better understanding of Δpixel values in DCR-based assessment of pulmonary function. The present study aimed to correlate Δpixel values from DCR with changes in CT values during respiration (ΔCT values) through a computer-based phantom study. A total of 20 four-dimensional computational phantoms during forced breathing were created to simulate both CT and projection images of the same virtual patients. The Δpixel and ΔCT values of the lung fields were correlated on a regression line, and the inclination was statistically evaluated to determine whether there were significant differences among physical types, sex, and breathing methods. The resulting conversion expression was also assessed in the DCR images of 37 patients. The resulting Δpixel values for 30/37 (81%) real patients, 6/7 (86%) normal controls, and 24/30 (80%) chronic obstructive pulmonary disorder patients were within the range of ΔCT values ± standard deviation (SD) reported in a previous study. In addition, no significant differences were detected for each condition of thoracic breathing, suggesting that the same regression line inclination values measured across the entire lung can be used for the conversion of Δpixel values, providing a quantitative analysis that can be correlated with ΔCT values. The developed conversion expression may be helpful for improving the understanding of respiratory changes using radiographic lung densities from DCR-based assessments of pulmonary function.

Quantitative CT Analysis of Small Airway Remodeling in Patients with Chronic Obstructive Pulmonary Disease by a New Image Post-Processing System

Purpose

To explore a practical marker for quantitatively analyzing the small airway remodeling in COPD by HRCT.

Patients and Methods

Twenty-four patients with COPD (GOLD I, n = 7; GOLD II, n = 8; GOLD III+IV, n = 9) and 14 healthy controls (7 normal pulmonary function; 7 small-airway disease (SAD)) were enrolled in the study as five groups, GOLD I, GOLD II, GOLD III+IV, normal and SAD. All subjects underwent HRCT and spirometry. With ISP 9.0, whole emphysema index (EI) and the airway parameters, including wall area (WA), lumen area (LA), airway area (AA) of the 3rd, 5th and 9th generations of bronchi, were measured successively. The ratio of LA/AA and WA/AA in the 3rd, 5th and 9th generations of bronchi were calculated and compared among groups.

Results

For the five groups, EI was increased only in GOLD III+IV group (P < 0.05), while the ratio of LA/AA (9-LA/AA) and WA/AA (9-WA/AA) in 9th generation of bronchi have significantly changed since SAD group (P < 0.05). There were significant correlation between FEV₁generations of bronchi (r3 = 0.429, r5 = 0.583, r9 = 0.592, respectively, P < 0.05); FEV₁% and WA/AA (r3 = –0.428, r5 = –0.532, r9 = –0.570, respectively, P < 0.05); as well as MMEF% and LA/AA (r3 = 0.421, r5 = 0.566, r9 = 0.610, respectively, P < 0.05); MMEF% and WA/AA (r3 = –0.421, r5 = –0.529, r9 = –0.593, respectively, P < 0.05).

Conclusion

Small airway remodeling has occurred in the early stage of COPD, while emphysema in the late stage of COPD. The 9-LA/AA and 9-WA/AA are accurate and practical markers for small airway remodeling of COPD.

CT phenotypes in mild-to-moderate chronic obstructive pulmonary disease: difference before and after the age of 60 years

AIM

To investigate the pulmonary phenotype of mild-to-moderate chronic obstructive pulmonary disease (COPD) using quantitative computed tomography CT analysis techniques.

MATERIALS AND METHODS

Sixty-three patients with stable-phase mild-to-moderate COPD and 78 healthy controls, categorised as those aged <60 (28 and 40 patients, respectively) and ≥60 years (35 and 38, respectively), underwent chest low-dose respiratory dual-phase CT and pulmonary function test. Automatic software was used to measure the proximal airway parameters, and the emphysema and air-trapping indices were recorded. The intergroup differences in each parameter were assessed by one-way analysis of variance.

RESULTS

At <60 years of age, the mean Pi10WA (Wall area of a hypothetical airway with an internal perimeter of 10 mm) was greater in the mild-to-moderate COPD group than in the healthy control group (17.04 ± 1.63 versus 16.03 ± 1.16 mm²; p=0.004). Mild or moderate air-trapping was observed in the mild-to-moderate COPD group aged <60 years. There was no significant difference in the proximal airway parameters and inspiratory VI_-950 (percent voxels less than -950 HU) between the two groups at age ≥60 years (all p>0.05); however, the expiratory VI_-856 (percent voxels less than -856 HU) and mean lung density expiratory/inspiratory ratio (MLD_E/I) were higher in the mild-to-moderate COPD group than those in the healthy control group (26.02 [30.23] versus 6.45 [11.16]; 0.88 ± 0.05 versus 0.84 ± 0.04; p<0.001 and p=0.024).

CONCLUSION

For patients with mild-to-moderate COPD, the CT phenotype was predominantly the "airway remodelling" type at <60 years of age, and the "air-trapping" type at ≥60 years of age. Thus, pulmonary CT phenotypes of mild-to-moderate COPD patients of different age groups are different.

Impact of Model-Based Iterative Reconstruction on the Correlation between Computed Tomography Quantification of a Low Lung Attenuation Area and Airway Measurements and Pulmonary Function Test Results in Normal Subjects

Objective

To compare correlations between pulmonary function test (PFT) results and different reconstruction algorithms and to suggest the optimal reconstruction protocol for computed tomography (CT) quantification of low lung attenuation areas and airways in healthy individuals.

Materials and Methods

A total of 259 subjects with normal PFT and chest CT results were included. CT scans were reconstructed using filtered back projection, hybrid-iterative reconstruction, and model-based IR (MIR). For quantitative analysis, the emphysema index (EI) and wall area percentage (WA%) were determined. Subgroup analysis according to smoking history was also performed.

Results

The EIs of all the reconstruction algorithms correlated significantly with the forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) (all p < 0.001). The EI of MIR showed the strongest correlation with FEV1/FVC (r = -0.437). WA% showed a significant correlation with FEV1 in all the reconstruction algorithms (all p < 0.05) correlated significantly with FEV1/FVC for MIR only (p < 0.001). The WA% of MIR showed the strongest correlations with FEV1 (r = -0.205) and FEV1/FVC (r = -0.250). In subgroup analysis, the EI of MIR had the strongest correlation with PFT in both ever-smoker and never-smoker subgroups, although there was no significant difference in the EI between the reconstruction algorithms. WA% of MIR showed a significantly thinner airway thickness than the other algorithms (49.7 ± 7.6 in ever-smokers and 49.5 ± 7.5 in never-smokers, all p < 0.001), and also showed the strongest correlation with PFT in both ever-smoker and never-smoker subgroups.

Conclusion

CT quantification of low lung attenuation areas and airways by means of MIR showed the strongest correlation with PFT results among the algorithms used, in normal subjects.

Risk factors for FEV1 decline in mild COPD and high-risk populations

Background

Early diagnosis of COPD is often not achieved due to limited recognition and limited access to the pulmonary function test. Our hypothesis was that lung function decline may be different between populations with mild COPD and those who are at high risk and do not receive treatment.

Patients and methods

Subjects with mild COPD and those from a high-risk COPD population were recruited from a community-based COPD epidemiological study after obtaining consent. Baseline clinical characteristics, symptom questionnaire, spirometry, low-dose computed tomography (LDCT) chest scan, and blood plasma biomarker data were collected initially and then 1 year later.

Results

A total of 617 participants were recruited, and 438 eventually completed the first-year follow-up visit; 72 participants (46 males) were in the mild COPD group, and 225 participants (165 males) were in the high-risk group. The mean forced expiratory volume in the first second of expiration (FEV₁) decline in the mild COPD group was 129 mL, which was significantly higher than the 30 mL decline in the high-risk population group (P=0.005). Group category (odds ratio [OR] =0.230) and COPD Assessment Test (CAT) score (OR =9.912) were independent risk factors for an FEV₁% predicted decline of >15% for all participants. In the mild COPD group, patients with a higher CAT (OR =5.310) and Emphysema Index (OR =5.681) were associated with a FEV₁% predicted decline of >15% at the first-year follow-up. No factor showed a significantly predictive effect on FEV₁ decline in the high-risk COPD group.

Conclusion

Group category was an independent influential factor associated with FEV₁ decline.