Radiomics-based differentiation of lung disease models generated by polluted air based on X-ray computed tomography data

Abstract

Background: Lung diseases (resulting from air pollution) require a widely accessible method for risk estimation and early diagnosis to ensure proper and responsive treatment. Radiomics-based fractal dimension analysis of X-ray computed tomography attenuation patterns in chest voxels of mice exposed to different air polluting agents was performed to model early stages of disease and establish differential diagnosis.

Methods: To model different types of air pollution, BALBc/ByJ mouse groups were exposed to cigarette smoke combined with ozone, sulphur dioxide gas and a control group was established. Two weeks after exposure, the frequency distributions of image voxel attenuation data were evaluated. Specific cut-off ranges were defined to group voxels by attenuation. Cut-off ranges were binarized and their spatial pattern was associated with calculated fractal dimension, then abstracted by the fractal dimension -- cut-off range mathematical function. Nonparametric Kruskal-Wallis (KW) and Mann-Whitney post hoc (MWph) tests were used.

Results: Each cut-off range versus fractal dimension function plot was found to contain two distinctive Gaussian curves. The ratios of the Gaussian curve parameters are considerably significant and are statistically distinguishable within the three exposure groups.

Conclusions: A new radiomics evaluation method was established based on analysis of the fractal dimension of chest X-ray computed tomography data segments. The specific attenuation patterns calculated utilizing our method may diagnose and monitor certain lung diseases, such as chronic obstructive pulmonary disease (COPD), asthma, tuberculosis or lung carcinomas.

Fig. 1

The reconstruction of the lungs of an untreated mouse shown with the sole intent of representing the attenuation profile of the chest. Sagittal (left b), coronal (center b), transaxial (right b) planes and minimum intensity projection (a). Certain attenuation ranges were abstracted from these slices in sagittal, coronal and transaxial planes. c −700 – -400 relative HU (lung parenchyma), (d): −100 – +200 relative HU (pleura, endothoracic fascia, epipleural fat and interlobar fissures), (e): +200 – +500 relative HU (respiratory- and heart muscles, diaphragm), (f): +500 – +800 relative HU (blood inside the vessels, aorta and heart, lymphatic fluid and interlobar fissures), and (g): +1400 – +3800 relative HU (bones)

Fig. 2

Width and position parameters (mean, SD) of attenuation histograms. CON, SAO, SDO groups

Fig. 3

Representation of the five steps of data analysis. a: The entire attenuation range of the reconstructed chest area of animals was divided into 100 distinct cut-off ranges (Step 1). b: Binary images are generated (Step 2 and 3) and each such derived binary pattern was next associated with a calculated fractal dimension via box-counting algorithms (Step 4). c: The fractal dimension – cut-off range function plot (Step 5)

Fig. 4

The fractal dimension – cut-off range function fitted by Gaussian curves “a” and “b”

Fig. 5

Calculated height, width and position parameters of the fractal dimension - cut-off range functions. a: Height, width and position parameters of Gaussian curve „A” (CON, SDO, SAO groups). b: Height, width and position parameters of Gaussian curve „B” (CON, SDO, SAO groups). c: The ratios of the relevant parameters of Gaussian curves „A” and „B” (CON, SDO, SAO groups). * p < 0.05, Kruskal-Wallis (KW) test with Mann–Whitney post hoc (MWph) test