We investigate the manifestation of speckle in propagation-based x-ray phase-contrast imaging of mouse lungs in situ by use of a benchtop imager. The key contributions of the work are the demonstration that lung speckle can be observed by use of a benchtop imaging system employing a polychromatic tube-source and a systematic experimental investigation of how the texture of the speckle pattern depends on the parameters of the imaging system. Our analyses consists of image texture characterization based on the statistical properties of pixel intensity values.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: To generate a plasma light source with a small spot size by reducing the expansion of the plasma plume, we studied the plume expansion dynamics of a plasma generated from a dot target that consisted of a photoresist with a hole coated on a pure Al plate. A time-resolved ultraviolet (UV) image of the plasma plume and a UV spectrometer were used to study the expansion of the plasma plume produced from a dot target and from an Al plate target. The measurements of the plume size from the emission of Al II ions showed that due to the strong collision between the core Al plasma and the plasma generate from the outer part of the dot, the expansion speed in the lateral direction was reduced to 70 % that of the plasma generated from the pure Al plate. However, for the case of the emission from neutral Al atoms, the plume sizes of the two targets were almost the same because of the weak collision between the Al atoms and the surrounding plasmas. Thus, these collisional effects in the plasma produced from a dot target can reduce the size of the core plasma ion and can be used to generate a small-spot-size laser plasma light source.
Journal- Korean Physical Society 12/2013; 64(1). DOI:10.3938/jkps.64.30 · 0.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Herein a propagation-based phase contrast x-ray imaging technique for measuring particle size and number is presented. This is achieved with an algorithm that utilizes the Fourier space signature of the speckle pattern associated with the images of particles. We validate this algorithm using soda-lime glass particles, demonstrating its effectiveness on random and non-randomly packed particles. This technique is then applied to characterise lung alveoli, which are difficult to measure dynamically in vivo with current imaging modalities due to inadequate temporal resolution and/or depth of penetration and field-of-view. We obtain an important result in that our algorithm is able to measure changes in alveolar size on the micron scale during ventilation and shows the presence of alveolar recruitment/de-recruitment in newborn rabbit kittens. This technique will be useful for ventilation management and lung diagnostic procedures.
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