Estimations of lung structural properties from a single propagation-based dark-field x-ray image

Objective.To employ a single-projection dark-field imaging approach to obtain statistical information on alveolar size and number as key structural indicators of lung health.Approach.The algorithm employed here retrieves the projected thickness of the sample from a propagation-based phase contrast image using the transport-of-intensity equation. The first Born approximation is then used to isolate the dark-field signal associated with edge scattering, which increases the visibility of microstructure boundaries. Poly(methyl methacrylate) spheres of known sizes were imaged first as an idealised alveolar model. The dark-field signal was then recovered from propagation-based phase-contrast x-ray images of the lungs of small mammals using this method.Main results.The retrieved dark-field signal was found to be proportional to both the alveolar size (R2=0.85) and the number in projection (R2=0.69), and these measurements could be combined to provide an estimate of the total surface area of the alveolar interfaces (R2=0.78).Significance.This demonstrates the approach's ability to potentially indicate lung health using the dark-field signal retrieved from a single-phase-contrast x-ray image.