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[Preprint]. 2024 Apr 13:2024.04.10.24305577.
doi: 10.1101/2024.04.10.24305577.

Exploratory Study on COPD Phenotypes and their Progression: Integrating SPECT and qCT Imaging Analysis

Frank Li  1   2 , Xuan Zhang  3   2 , Alejandro P Comellas  4 , Eric A Hoffman  5   1 , Michael M Graham  5 , Ching-Long Lin  3   1   2   5
Affiliations

Exploratory Study on COPD Phenotypes and their Progression: Integrating SPECT and qCT Imaging Analysis

Frank Li et al. medRxiv. .

Abstract

Background: The objective of this study is to understand chronic obstructive pulmonary disease (COPD) phenotypes and their progressions by quantifying heterogeneities of lung ventilation from the single photon emission computed tomography (SPECT) images and establishing associations with the quantitative computed tomography (qCT) imaging-based clusters and variables.

Methods: Eight COPD patients completed a longitudinal study of three visits with intervals of about a year. CT scans of these subjects at residual volume, functional residual capacity, and total lung capacity were taken for all visits. The functional and structural qCT-based variables were derived, and the subjects were classified into the qCT-based clusters. In addition, the SPECT variables were derived to quantify the heterogeneity of lung ventilation. The correlations between the key qCT-based variables and SPECT-based variables were examined.

Results: The SPECT-based coefficient of variation (CVTotal), a measure of ventilation heterogeneity, showed strong correlations (|r| ≥ 0.7) with the qCT-based functional small airway disease percentage (fSAD%Total) and emphysematous tissue percentage (Emph%Total) in the total lung on cross-sectional data. As for the two-year changes, the SPECT-based maximum tracer concentration (TCmax), a measure of hot spots, exhibited strong negative correlations with fSAD%Total, Emph%Total, average airway diameter in the left upper lobe, and airflow distribution in the middle and lower lobes.

Conclusion: Small airway disease is highly associated with the heterogeneity of ventilation in COPD lungs. TCmax is a more sensitive functional biomarker for COPD progression than CVTotal. Besides fSAD%Total and Emph%Total, segmental airways narrowing and imbalanced ventilation between upper and lower lobes may contribute to the development of hot spots over time.

Keywords: COPD; CT; SPECT; Small Airway Disease; Ventilation.

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Conflict of interest statement

Competing Interests There is no conflict of interest for all authors.

Figures

Figure 1.
Figure 1.
The multiscale structural and functional qCT variables.
Figure 2.
Figure 2.
(a) A scatter plot showing the strong correlation (r=0.73) between TC% and ΔVairF of the lobes. (b) A scatter plot showing the strong correlations between CVTotal and PFT results (FEV1% predicted: r=-0.74, FEV1/FVC%: r=-0.80). The data points were from both three visits.
Figure 3.
Figure 3.
Normalized SPECT images transformed to TLC domain at the three visits. Subject 1 and 2 did not have ventilation scans at V0.
Figure 4.
Figure 4.
(a) Former smokers in this study placed on the two-dimensional space formed by the first and the second principal components derived from previous study (14). (b) Current smokers in this study placed on the two-dimensional space formed by the first and the second principal components derived from previous study (13). C1, C2, C3, and C4 in the figure legend denote all of the subjects analyzed in previous studies (13,14). Those enclosed by a circle denote the change of cluster membership.
Figure 5.
Figure 5.
The correlations between the SPECT variables and the qCT variables for cross-sectional and longitudinal data. Magnitudes of correlations greater than 0.7 were bounded by blue boxes.
Figure 6.
Figure 6.
The fSAD-voxel maps for each subject (left column) along with their SPECT images (right column). These images were plotted in coronal planes of the CT images
Figure 7.
Figure 7.
A constricted segmental airway in LUL (red arrow) of Subject 3 at V2, which may contribute to the TC hot spot found in LUL. In addition, a constricted segmental airway in LUL (red arrow) of Subject 5 at V0 resolved at V2, which may increase the homogeneity of ventilation.
See this image and copyright information in PMC

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