K Uesugi

Imaging lung aeration and lung liquid clearance at birth

Aeration of the lung and the transition to air‐breathing at birth is fundamental to mammalian life and initiates major changes in cardiopulmonary physiology. However, the dynamics of this process and the factors involved are largely unknown, because it has not been possible to observe or measure lung aeration on a breath‐by‐breath basis. We have used the high contrast and spatial resolution of phase contrast X‐ray imaging to study lung aeration at birth in spontaneously breathing neonatal rabbits. As the liquid‐filled fetal lungs provide little absorption or phase contrast, they are not visible and only become visible as they aerate, allowing a detailed examination of this process. Pups were imaged live from birth to determine the timing and spatial pattern of lung aeration, and relative levels of lung aeration were measured from the images using a power spectral analysis. We report the first detailed observations and measurements of lung aeration, demonstrating its dependence on inspiratory activity and body position; dependent regions aerated at much slower rates. The air/liquid interface moved toward the distal airways only during inspiration, with little proximal movement during expiration, indicating that trans‐pulmonary pressures play an important role in airway liquid clearance at birth. Using these imaging techniques, the dynamics of lung aeration and the critical role it plays in regulating the physiological changes at birth can be fully explored.—Hooper S. B., Kitchen, M. J., Wallace, M. J., Yagi, N., Uesugi, K., Morgan M. J., Hall, C., Siu, K. K. W., Williams, I. M., Siew, M., Irvine, S. C., Pavlov, K., Lewis R. A. Imaging lung aeration and lung liquid clearance at birth. FASEB J. 21, 3329–3337 (2007)

Dynamic measures of regional lung air volume using phase contrast x-ray imaging

Phase contrast x-ray imaging can provide detailed images of lung morphology with sufficient spatial resolution to observe the terminal airways (alveoli). We demonstrate that quantitative functional and anatomical imaging of lung ventilation can be achieved in vivo using two-dimensional phase contrast x-ray images with high contrast and spatial resolution (<100 microm) in near real time. Changes in lung air volume as small as 25 microL were calculated from the images of term and preterm rabbit pup lungs (n = 28) using a single-image phase retrieval algorithm. Comparisons with plethysmography and computed tomography showed that the technique provided an accurate and robust method of measuring total lung air volumes. Furthermore, regional ventilation was measured by partitioning the phase contrast images, which revealed differences in aeration for different ventilation strategies.

High-resolution visualization of airspace structures in intact mice via synchrotron phase-contrast X-ray imaging (PCXI)

Anatomical visualization of airspace‐containing organs in intact small animals has been limited by the resolution and contrast available from current imaging methods such as X‐ray, micro‐computed tomography and magnetic resonance imaging. Determining structural relationships and detailed anatomy has therefore relied on suitable fixation, sectioning and histological processing. More complex and informative analyses such as orthogonal views of an organ and three‐dimensional structure visualizations have required different animals and image sets, laboriously processed to gather this complementary structural information. Precise three‐dimensional anatomical views have always been difficult to achieve in small animals. Here we report the ability of phase‐contrast synchrotron X‐ray imaging to provide detailed two‐ and three‐dimensional visualization of airspace organ structures in intact animals. Using sub‐micrometre square pixel charge‐coupled device array detectors, the structure and anatomy of hard and soft tissues, and of airspaces, is readily available using phase‐contrast synchrotron X‐ray imaging. Moreover, software‐controlled volume‐reconstructions of tomographic images not only provide unsurpassed image clarity and detail, but also selectable anatomical views that cannot be obtained with established histological techniques. The morphology and structure of nasal and lung airways and the middle ear are illustrated in intact mice, using two‐ and three‐dimensional representations. The utility of phase‐contrast synchrotron X‐ray imaging for non‐invasively localizing objects implanted within airspaces, and the detection of gas bubbles transiting live airways, are other novel features of this visualization methodology. The coupling of phase‐contrast synchrotron X‐ray imaging technology with software‐based reconstruction techniques holds promise for novel and high‐resolution non‐invasive examination of airspace anatomy in small animal models.

Phase contrast X-ray imaging for the non-invasive detection of airway surfaces and lumen characteristics in mouse models of airway disease.

We seek to establish non-invasive imaging able to detect and measure aspects of the biology and physiology of surface fluids present on airways, in order to develop novel outcome measures able to validate the success of proposed genetic or pharmaceutical therapies for cystic fibrosis (CF) airway disease. Reduction of the thin airway surface liquid (ASL) is thought to be a central pathophysiological process in CF, causing reduced mucociliary clearance that supports ongoing infection and destruction of lung and airways. Current outcome measures in animal models, or humans, are insensitive to the small changes in ASL depth that ought to accompany successful airway therapies. Using phase contrast X-ray imaging (PCXI), we have directly examined the airway surfaces in the nasal airways and tracheas of anaesthetised mice, currently to a resolution of approximately 2 microm. We have also achieved high resolution three-dimensional (3D) imaging of the small airways in mice using phase-contrast enhanced computed tomography (PC-CT) to elucidate the structure-function relationships produced by airway disease. As the resolution of these techniques improves they may permit non-invasive monitoring of changes in ASL depth with therapeutic intervention, and the use of 3D airway and imaging in monitoring of lung health and disease. Phase contrast imaging of airway surfaces has promise for diagnostic and monitoring options in animal models of CF, and the potential for future human airway imaging methodologies is also apparent.

In-situ observation of peritectic solidification in Sn-Cd and Fe-C alloys

Time-resolved absorption imaging using synchrotron radiation X-rays allows us to observe solidification of metallic alloys of interest. This paper presents peritectic solidification in Sn-Cd alloy and Fe-C alloys. In unidirectional solidification of Sn-Cd alloy, the formation of a banded structure, in which two phases were alternatively piled up in the growth direction, was clearly observed. Sequence of nucleation or fluctuation of triple junction (primary phase / secondary phase / liquid) resulted in the banded structure. Ease of nucleation for both phases contributed to the banded structure formation. In carbon steel (Fe-0.45mass%C), the transformation from δ phase to γ phase was observed. At lower cooling rates, γ phase was produced in semisolid state of δ phase and liquid, indicating the peritectic reaction occurred during solidification. In contrast, δ phase transformed into γ phase when solidification nearly completed at temperatures 100K below the liquidus temperature. Namely, the transformation seemed to be massive. The observation showed that two different transformation modes operated in Fe-C alloy.

Influence of Mg on Solidification of Hypereutectic Cast Iron: X-ray Radiography Study

Radiography using a synchrotron radiation X-ray source was performed to examine solidification and melting behaviors in hypereutectic cast iron specimens containing 0.002 and 0.05massxa0pctMg. The solidification sequence in the alloy containing 0.002massxa0pctMg was (1) nucleation and growth of graphite particles of which transformed to a flake-like shape, (2) growth of γ-Fe dendrites, (3) nucleation of graphite particles ahead of the interface just prior to the eutectic solidification, and (4) the eutectic solidification. In contrast, (1) and (2) occurred nearly at the same time in the specimen containing 0.05 massxa0pct Mg. The addition of 0.05massxa0pctMg significantly reduced the temperature range in which the graphite particles grew as the primary phase. Image-based analysis of melting behavior showed that even 0.05 massxa0pct addition was sufficient to modify the phase equilibrium of the liquid, γ-Fe, and graphite phases. Thus, the observed influence of Mg on the solidification sequence was attributed to the modification of the phase equilibrium. The influence was consistently explained by considering the shift of the eutectic composition to the carbon side in the pseudo-ternary system. It was also suggested that supersaturation of carbon in the melt increased as the temperature decreased even though the primary graphite particles existed. The supersaturation may cause the nucleation of the graphite particles just before the eutectic solidification.

Microcalcifications of Breast Tissue: Appearance on Synchrotron Radiation Imaging with 6-μm Resolution

OBJECTIVEnThe purpose of this study was to use synchrotron radiation imaging with 6-microm resolution to evaluate amorphous and pleomorphic breast tissue microcalcifications.nnnCONCLUSIONnSynchrotron radiation imaging depicted microcalcifications as small as 24 microm. Imaging with this technique revealed that most amorphous and pleomorphic calcifications on conventional mammograms are clusters of fine specks and that in addition to the shape or density of a speck, the distribution density of clustered specks is a factor determining the apparent shape.

Sensitive detection of voids in solid materials by refraction-enhanced synchrotron radiation imaging

Voids in opaque materials (minute air bubbles) were imaged with synchrotron radiation in a refraction enhancement mode. The voids are imaged by an enhanced x-ray intensity inside the bubble, surrounded by a border region with decreased x-ray intensity, thus allowing sensitive detection of air bubbles in plastic materials. As those “impurities” could not be depicted with conventional radiography, and optical inspection is not useful if the matrix is opaque, this in-situ imaging technique offers the potential to obtain information of air inclusions, voids, and cracking that appear inadvertently in opaque plastics and possibly in metals as well.

Synchrotron radiation microtomography of lung specimens

We have applied a synchrotron radiation computed tomography (SRCT) system to the lung specimens and evaluated its resolving power compared with the histopathologic appearances, precisely. An SRCT system has been constructed in the bending magnet beamline at the SPring-8. The system consists of a double-crystal monochromator, a rotating sample stage, a fluorescent screen, and a charge-coupled device (CCD) array detector (1024 X 1024 pixels with 12 X 12 micrometers 2 pixel size). The energy of the x-ray beam was tuned to 9 - 12 keV. The lungs obtained at autopsy were inflated and fixed by Heitzmans method. A cylindrical specimen (diameter, approximately 8 mm; height, 15 - 25 mm) was rotated in the plane parallel to the beam. The detected signal was transferred to a workstation; then, SRCT images (matrix size, 800 X 800 pixels) were reconstructed by a filtered back- projection. Finally, 6 - 12 micrometer-thick microscopic sections were obtained and stained with hematoxylin and eosin for histopathologic examination. SRCT images well depicted the terminal bronchiole, respiratory bronchiole, alveolar duct, alveolar sac, and alveolar septum. Different pathologic processes (alveolar hemorrhage, alveolitis) demonstrated on SRCT images were well correlated with the histopathologic appearances.

Synchrotron radiography of direct-shear in semi-solid alloys

Understanding phenomena occurring at the scale of the crystals during the deformation of semi-solid alloys is important for the development of physically-based rheological models. A range of deformation mechanisms have been proposed including agglomeration and disagglomeration, viscoplastic deformation of the solid skeleton, and granular phenomena such as jamming and dilatancy. This paper overviews in-situ experiments that directly image crystal-scale deformation mechanisms in equiaxed Al alloys at solid fractions shortly after the crystals have impinged to form a loose crystal network. Direct evidence is presented for granular deformation mechanisms including shear-induced dilation in both equiaxed-dendritic and globular microstructures. Modelling approaches suitable for capturing this behaviour are then discussed.