Measurement of absolute regional lung air volumes from near-field x-ray speckles

Abstract

Propagation-based phase contrast x-ray (PBX) imaging yields high contrast images of the lung where airways that overlap in projection coherently scatter the x-rays, giving rise to a speckled intensity due to interference effects. Our previous works have shown that total and regional changes in lung air volumes can be accurately measured from two-dimensional (2D) absorption or phase contrast images when the subject is immersed in a water-filled container. In this paper we demonstrate how the phase contrast speckle patterns can be used to directly measure absolute regional lung air volumes from 2D PBX images without the need for a water-filled container. We justify this technique analytically and via simulation using the transport-of-intensity equation and calibrate the technique using our existing methods for measuring lung air volume. Finally, we show the full capabilities of this technique for measuring regional differences in lung aeration.

Real-time measurement of alveolar size and population using phase contrast x-ray imaging

“…This derivation follows closely to that developed in Leong et al [21], but in that derivation alveoli were assumed to be randomly distributed. In Figs.…”

“…The imaginary number is denoted by i. The power spectrum of its PB-PCX image ( ( , ) object-to-detector propagation distance (ODD) L, along the optic axis z can be expressed as [21]:…”

“…These assumptions have been shown to be valid when imaging the thorax of a newborn rabbit kitten using 24 keV x-rays [21]. Equation (1) is restricted to the near-field regime, which is where the Fresnel number, N F , defined by,…”

“…Leong et al [21] showed that the area under the first peak in the spectrum, which is bounded by adjacent minima k ⊥ R = 0 and k ⊥ R = 4.493, is given by,…”

Recovering low spatial frequencies in wavefront sensing based on intensity measurements

“…One very popular approach toward wavefront reconstruction from intensity measurements at different planes of focus is the transport of intensity equation (TIE) [5,8] which, due to its simple mathematical formulation and straightforward computational implementation, has attracted much attention in research communities as diverse as cold atom clouds [9], digital optical holography [10], and medical X-ray imaging [11].…”