ORCID Profile
0000-0002-0029-6660
Current Organisation
Monash University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Medical Physics | Radiology and Organ Imaging | Respiratory Diseases | Optical Physics | Classical and Physical Optics | Medical physics | Paediatrics and Reproductive Medicine | Simulation And Modelling | Classical physics | Nanotechnology | Biomedical Engineering | Biomaterials | Radiology And Organ Imaging | Artificial Intelligence and Image Processing | Biotechnology Not Elsewhere Classified | Paediatrics | Medical Physics | Classical and physical optics | Animal Physiology - Systems | Clinical Sciences | Cardiorespiratory Medicine and Haematology |
ANZSRC Socio-Economic Objective (SEO)
Respiratory System and Diseases (incl. Asthma) | Industrial Instruments | Medical Instruments | Biological sciences | Diagnostic methods | Expanding Knowledge in the Medical and Health Sciences | Diagnostic Methods | Expanding Knowledge in the Physical Sciences | Respiratory system and diseases (incl. asthma) | Expanding Knowledge in the Biological Sciences | Prevention—biologicals (e.g. vaccines) | Diagnostics
Related Links
Publications
Functional Lung Imaging during HFV in Preterm Rabbits
Publisher: Public Library of Science (PLoS)
Date: 30-10-2012
Material decomposition from a single x-ray projection via single-grid phase contrast imaging
Publisher: Optica Publishing Group
Date: 15-07-2020
DOI: 10.1364/OL.389770
Abstract: This study describes a new approach for material decomposition in x-ray imaging, utilizing phase contrast both to increase sensitivity to weakly attenuating s les and to act as a complementary measurement to attenuation, therefore allowing two overlaid materials to be separated. The measurements are captured using the single-exposure, single-grid x-ray phase contrast imaging technique, with a novel correction that aims to remove propagation-based phase effects seen at sharp edges in the attenuation image. The use of a single-exposure technique means that images can be collected in a high-speed sequence. Results are shown for both a known two-material s le and for a biological specimen.
Cardiorespiratory Monitoring during Neonatal Resuscitation for Direct Feedback and Audit
Publisher: Frontiers Media SA
Date: 18-04-2016
Pre-clinical phase-contrast imaging of the whole brain in situ: from traumatic to diffuse white matter injury
Publisher: SPIE
Date: 10-11-2022
DOI: 10.1117/12.2633340
Establishing functional residual capacity in the non-breathing infant
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.SINY.2013.08.011
Abstract: The transition to newborn life critically depends upon lung aeration and the onset of air-breathing, which triggers major cardiovascular changes required for postnatal life, including increases in pulmonary blood flow. Recent imaging studies indicate that lung aeration and functional residual capacity (FRC) recruitment results from inspiratory efforts, which create transpulmonary pressure gradients. During inspiration, these pressure gradients drive airway liquid movement through the conducting and into the distal airways where it crosses the pulmonary epithelium and enters the surrounding tissue. Although this process can occur rapidly (within 3-5 breaths), liquid clearance from lung tissue is much slower, resulting in oedema and increased interstitial tissue pressures, facilitating liquid re-entry into the airways at FRC. Whereas this liquid may be cleared during the next inspiration, liquid re-entry at FRC can be opposed by Na(+) reabsorption, oncotic pressures and expiratory braking manoeuvres. Recognition that transpulmonary pressure gradients mainly drive airway liquid clearance at birth has provided a clearer understanding of how this process may be facilitated in very preterm infants. In particular, it underpins the rationale for providing respiratory support that initially focuses on moving liquid through tubes (airways) rather than air. As the viscosity of liquid is much greater than air, the resistance to moving liquid is ≈ 100 times greater than air, necessitating the use of higher pressures or longer inflation times. Although it is unclear how this strategy could be safely applied clinically, it is clear that end-expiratory pressures are required to create and maintain FRC in preterm infants.
Expired CO2 Levels Indicate Degree of Lung Aeration at Birth
Publisher: Public Library of Science (PLoS)
Date: 12-08-2013
Dark-field tomography of an attenuating object using intrinsic x-ray speckle tracking
Publisher: SPIE-Intl Soc Optical Eng
Date: 07-02-2022
Investigation of the imaging quality of synchrotron-based phase-contrast mammographic tomography
Publisher: IOP Publishing
Date: 20-08-2014
Effect of prenatal diaphragmatic hernia on pulmonary arterial morphology
Publisher: Wiley
Date: 23-01-2023
DOI: 10.1002/AR.25159
Abstract: Congenital diaphragmatic hernia (CDH) is a major cause of severe lung hypoplasia and pulmonary hypertension in the newborn. While the pulmonary hypertension is thought to result from abnormal vascular development and arterial vasoreactivity, the anatomical changes in vascular development are unclear. We have examined the 3D structure of the pulmonary arterial tree in rabbits with a surgically induced diaphragmatic hernia (DH). Fetal rabbits ( n = 6) had a left‐sided DH created at gestational day 23 (GD23), delivered at GD30, and briefly ventilated sham‐operated litter mates ( n = 5) acted as controls. At postmortem the pulmonary arteries were filled with a radio‐opaque resin before the lungs were scanned using computed tomography (CT). The 3D reconstructed images were analyzed based on vascular branching hierarchy using the software Avizo 2020.2. DH significantly reduced median number of arteries (2,579 (8440) versus 576 (442), p = .017), artery numbers per arterial generation, mean total arterial volume (43.5 ± 8.4 vs. 19.9 ± 3.1 μl, p = .020) and mean total arterial cross‐sectional area (82.5 ± 2.3 vs. 28.2 ± 6.2 mm 2 , p =.036). Mean arterial radius was increased in DH kittens between the eighth and sixth branching generation and mean arterial length between the sixth and 28th branching generation. A DH in kittens resulted in threefold reduction in pulmonary arterial cross‐sectional area, primarily due to reduced arterial branching. Thus, the reduction in arterial cross‐sectional area could be a major contributor to pulmonary hypertension infants with CDH.
Spectral propagation-based x-ray phase-contrast computed tomography
Publisher: SPIE-Intl Soc Optical Eng
Date: 15-03-2022
CT dose reduction factors in the thousands using X-ray phase contrast
Publisher: Springer Science and Business Media LLC
Date: 21-11-2017
DOI: 10.1038/S41598-017-16264-X
Abstract: Phase-contrast X-ray imaging can improve the visibility of weakly absorbing objects (e.g. soft tissues) by an order of magnitude or more compared to conventional radiographs. Combining phase retrieval with computed tomography (CT) can increase the signal-to-noise ratio (SNR) by up to two orders of magnitude over conventional CT at the same radiation dose, without loss of image quality. Our experiments reveal that as the radiation dose decreases, the relative improvement in SNR increases. We show that this enhancement can be traded for a reduction in dose greater than the square of the gain in SNR. Upon reducing the dose 300 fold, the phase-retrieved SNR was still up to 9.6 ± 0.2 times larger than the absorption contrast data with spatial resolution in the tens of microns. We show that this theoretically reveals the potential for dose reduction factors in the tens of thousands without loss in image quality, which would have a profound impact on medical and industrial imaging applications.
X-ray specks: low dose in vivo imaging of lung structure and function
Publisher: IOP Publishing
Date: 08-09-2015
DOI: 10.1088/0031-9155/60/18/7259
Abstract: Respiratory health is directly linked to the structural and mechanical properties of the airways of the lungs. For studying respiratory development and pathology, the ability to quantitatively measure airway dimensions and changes in their size during respiration is highly desirable. Real-time imaging of the terminal airways with sufficient contrast and resolution during respiration is currently not possible. Herein we reveal a simple method for measuring lung airway dimensions in small animals during respiration from a single propagation-based phase contrast x-ray image, thereby requiring minimal radiation. This modality renders the lungs visible as a speckled intensity pattern. In the near-field regime, the size of the speckles is directly correlated with that of the dominant length scale of the airways. We demonstrate that Fourier space quantification of the speckle texture can be used to statistically measure regional airway dimensions at the alveolar scale, with measurement precision finer than the spatial resolution of the imaging system. Using this technique we discovered striking differences in developmental maturity in the lungs of rabbit kittens at birth.
Quantifying lung aeration in neonatal lambs at birth using lung ultrasound
Publisher: Frontiers Media SA
Date: 28-09-2022
Abstract: Lung ultrasound (LUS) is a safe and non-invasive tool that can potentially assess regional lung aeration in newborn infants and reduce the need for X-ray imaging. LUS produces images with characteristic artifacts caused by the presence of air in the lung, but it is unknown if LUS can accurately detect changes in lung air volumes after birth. This study compared LUS images with lung volume measurements from high-resolution computed tomography (CT) scans to determine if LUS can accurately provide relative measures of lung aeration. Deceased near-term newborn lambs (139 days gestation, term ∼148 days) were intubated and the chest imaged using LUS (bilaterally) and phase contrast x-ray CT scans at increasing static airway pressures (0–50 cmH 2 O). CT scans were analyzed to calculate regional air volumes and correlated with measures from LUS images. These measures included (i) LUS grade (ii) brightness (mean and coefficient of variation) and (iii) area under the Fourier power spectra within defined frequency ranges. All LUS image analysis techniques correlated strongly with air volumes measured by CT ( p & 0.01). When imaging statistics were combined in a multivariate linear regression model, LUS predicted the proportion of air in the underlying lung with moderate accuracy (95% prediction interval ± 22.15%, r 2 = 0.71). LUS can provide relative measures of lung aeration after birth in neonatal lambs. Future studies are needed to determine if LUS can also provide a simple means to assess air volumes and in idualize aeration strategies for critically ill newborns in real time.
Analysis of speckle patterns in phase-contrast images of lung tissue
Publisher: Elsevier BV
Date: 08-2005
Single-exposure dual-energy-subtraction X-ray imaging using a synchrotron source
Publisher: International Union of Crystallography (IUCr)
Date: 05-09-2012
Phase retrieval using coherent imaging systems with linear transfer functions
Publisher: Elsevier BV
Date: 04-2004
Dynamic measures of regional lung air volume using phase contrast x-ray imaging
Publisher: IOP Publishing
Date: 09-10-2008
DOI: 10.1088/0031-9155/53/21/012
Abstract: 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.
Full Field X-Ray Scatter Tomography
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2022
The past, present, and future of x-ray technology for in vivo imaging of function and form
Publisher: AIP Publishing
Date: 15-05-2009
DOI: 10.1063/1.3115643
Abstract: Scientists and clinicians have a keen interest in studying not just the structure of physiological systems, but their motion also, or more generally their form and function. This paper focuses on the technologies that underpin in vivo measurements of form and function of the human body for both research and medical treatment. A concise literature review of x-ray imaging, ultrasonography, magnetic resonance imaging, radionuclide imaging, laser Doppler velocimetry, and particle image velocimetry is presented. Additionally, a more detailed review of in vivo x-ray imaging is presented. Finally, two techniques, which the authors believe are representative of the present and future of in vivo x-ray imaging techniques, are presented.
Surfactant increases the uniformity of lung aeration at birth in ventilated preterm rabbits
Publisher: Springer Science and Business Media LLC
Date: 07-2011
GPU accelerated regional lung air volume measurements from phase contrast X-ray images
Publisher: Springer Science and Business Media LLC
Date: 31-12-2016
Imaging lung aeration and lung liquid clearance at birth
Publisher: Wiley
Date: 29-05-2007
Abstract: 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.
Establishing functional residual capacity at birth: The effect of sustained inflation and positive end-expiratory pressure in a preterm rabbit model
Publisher: Springer Science and Business Media LLC
Date: 05-2009
Decoding the structure of granular and porous materials from speckled phase contrast X-ray images
Publisher: The Optical Society
Date: 05-08-2013
DOI: 10.1364/OE.21.019153
Laryngeal closure impedes non-invasive ventilation at birth
Publisher: BMJ
Date: 20-10-2018
DOI: 10.1136/ARCHDISCHILD-2017-312681
Abstract: Non-invasive ventilation is sometimes unable to provide the respiratory needs of very premature infants in the delivery room. While airway obstruction is thought to be the main problem, the site of obstruction is unknown. We investigated whether closure of the larynx and epiglottis is a major site of airway obstruction. We used phase contrast X-ray imaging to visualise laryngeal function in spontaneously breathing premature rabbits immediately after birth and at approximately 1 hour after birth. Non-invasive respiratory support was applied via a facemask and images were analysed to determine the percentage of the time the glottis and the epiglottis were open. Immediately after birth, the larynx is predominantly closed, only opening briefly during a breath, making non-invasive intermittent positive pressure ventilation (iPPV) ineffective, whereas after lung aeration, the larynx is predominantly open allowing non-invasive iPPV to ventilate the lung. The larynx and epiglottis were predominantly closed (open 25.5%±1.1% and 17.1%±1.6% of the time, respectively) in pups with unaerated lungs and unstable breathing patterns immediately after birth. In contrast, the larynx and the epiglottis were mostly open (90.5%±1.9% and 72.3%±2.3% of the time, respectively) in pups with aerated lungs and stable breathing patterns irrespective of time after birth. Laryngeal closure impedes non-invasive iPPV at birth and may reduce the effectiveness of non-invasive respiratory support in premature infants immediately after birth.
Respiratory transition in the newborn: a three-phase process
Publisher: BMJ
Date: 05-11-2015
DOI: 10.1136/ARCHDISCHILD-2013-305704
Abstract: We propose that the respiratory transition at birth passes through three distinct, but overlapping phases, which reflect different physiological states of the lung. Accordingly, respiratory support given to infants should be optimised to suit the underlying physiological state of the lung as it passes through each phase. During the first phase, the airways are liquid-filled and so no pulmonary gas exchange can occur. Respiratory support should, therefore, be focused on clearing the gas exchange regions of liquid. In the absence of gas exchange, little or no CO2will accumulate within the airways and, therefore, interrupting inflation pressures to allow the lung to deflate and exhale CO2is unnecessary. This is the primary rationale for administering a sustained inflation at birth. During the second phase, the gas exchange regions are mostly cleared of liquid, allowing pulmonary gas exchange to commence. However, the liquid cleared from the airways resides within the tissue during this phase, which increases perialveolar interstitial tissue pressures and the risk of liquid re-entry back into the airways. As a result, respiratory support should be optimised to minimise alveolar re-flooding during expiration, which can be achieved by applying an end-expiratory pressure. The third and final phase occurs when the liquid is eventually cleared from lung tissue. Although gas exchange may be restricted by lung immaturity, injury and inflammation during this phase, considerations of how fetal lung liquid can adversely affect lung function are no longer relevant.
In situ phase contrast X-ray brain CT
Publisher: Springer Science and Business Media LLC
Date: 30-07-2018
DOI: 10.1038/S41598-018-29841-5
Abstract: Phase contrast X-ray imaging (PCXI) is an emerging imaging modality that has the potential to greatly improve radiography for medical imaging and materials analysis. PCXI makes it possible to visualise soft-tissue structures that are otherwise unresolved with conventional CT by rendering phase gradients in the X-ray wavefield visible. This can improve the contrast resolution of soft tissues structures, like the lungs and brain, by orders of magnitude. Phase retrieval suppresses noise, revealing weakly-attenuating soft tissue structures, however it does not remove the artefacts from the highly attenuating bone of the skull and from imperfections in the imaging system that can obscure those structures. The primary causes of these artefacts are investigated and a simple method to visualise the features they obstruct is proposed, which can easily be implemented for preclinical animal studies. We show that phase contrast X-ray CT (PCXI-CT) can resolve the soft tissues of the brain in situ without a need for contrast agents at a dose ~400 times lower than would be required by standard absorption contrast CT. We generalise a well-known phase retrieval algorithm for multiple-material s les specifically for CT, validate its use for brain CT, and demonstrate its high stability in the presence of noise.
Analyser-based phase contrast image reconstruction using geometrical optics
Publisher: IOP Publishing
Date: 15-06-2007
DOI: 10.1088/0031-9155/52/14/010
Abstract: Analyser-based phase contrast imaging can provide radiographs of exceptional contrast at high resolution (<100 microm), whilst quantitative phase and attenuation information can be extracted using just two images when the approximations of geometrical optics are satisfied. Analytical phase retrieval can be performed by fitting the analyser rocking curve with a symmetric Pearson type VII function. The Pearson VII function provided at least a 10% better fit to experimentally measured rocking curves than linear or Gaussian functions. A test phantom, a hollow nylon cylinder, was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility. Our phase retrieval method yielded a more accurate object reconstruction than methods based on a linear fit to the rocking curve. Where reconstructions failed to map expected values, calculations of the Takagi number permitted distinction between the violation of the geometrical optics conditions and the failure of curve fitting procedures. The need for synchronized object/detector translation stages was removed by using a large, ergent beam and imaging the object in segments. Our image acquisition and reconstruction procedure enables quantitative phase retrieval for systems with a ergent source and accounts for imperfections in the analyser.
Single-shot X-ray measurement of alveolar size distributions
Publisher: SPIE
Date: 13-03-2014
DOI: 10.1117/12.2043415
Phase-Contrast Clinical Breast CT: Optimization of Imaging Setups and Reconstruction Workflows
Publisher: Springer International Publishing
Date: 2016
Effect of sustained inflation length on establishing functional residual capacity at birth in ventilated premature rabbits
Publisher: Springer Science and Business Media LLC
Date: 09-2009
Simultaneous acquisition of dual analyser-based phase contrast X-ray images for small animal imaging
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.EJRAD.2008.04.028
Abstract: Analyser-based phase contrast X-ray imaging can provide high-contrast images of biological tissues with exquisite sensitivity to the boundaries between tissues. The phase and absorption information can be extracted by processing multiple images acquired at different analyser orientations. Recording both the transmitted and diffracted beams from a thin Laue analyser crystal can make phase retrieval possible for dynamic systems by allowing full field imaging. This technique was used to image the thorax of a mechanically ventilated newborn rabbit pup using a 25 keV beam from the SPring-8 synchrotron radiation facility. The diffracted image was produced from the (111) planes of a 50 mm x 40 mm, 100 microm thick Si analyser crystal in the Laue geometry. The beam and analyser were large enough to image the entire chest, making it possible to observe changes in anatomy with high contrast and spatial resolution.
Contrast enhanced refraction imaging
Publisher: SPIE
Date: 05-01-2004
DOI: 10.1117/12.515135
Vagal denervation inhibits the increase in pulmonary blood flow during partial lung aeration at birth
Publisher: Wiley
Date: 14-02-2017
DOI: 10.1113/JP273682
Altered lung motion is a sensitive indicator of regional lung disease
Publisher: Springer Science and Business Media LLC
Date: 22-12-2012
DOI: 10.1007/S10439-011-0493-0
Abstract: Since lung diseases adversely affect airflow during breathing, they must also alter normal lung motion, which can be exploited to detect these diseases. However, standard imaging techniques such as CT and MRI imaging during breath-holds provide little or no information on lung motion and cannot detect diseases that cause subtle changes in lung structure. Phase-contrast X-ray imaging provides images of high contrast and spatial resolution with temporal resolutions that allow multiple images to be acquired throughout the respiratory cycle. Using X-ray phase-contrast imaging, coupled with velocimetry, we have measured lung tissue movement and determined velocity fields that define speed and direction of regional lung motion throughout a breath in normal Balb/c nude male mice and mice exposed to bleomycin. Regional maps of lung tissue motion reveal both the heterogeneity of normal lung motion, as well as abnormal motion induced by bleomycin treatment. Analysed histologically, bleomycin treatment caused pathological changes in lung structure that were heterogenous, occupying less than 12% of the lung at 6 days after treatment. Moreover, plethysmography failed to detect significant changes in compliance at either 36 h or 6 days after treatment. Detailed analysis of the vector fields demonstrated major differences (p < 0.001) in regional lung motion between control and bleomycin-treated mice at both 36 h and 6 days after treatment. The results of this study demonstrate that X-ray phase-contrast imaging, coupled with velocimetry, can detect early stage, subtle and non-uniform lung disease.
X-ray phase, absorption and scatter retrieval using two or more phase contrast images
Publisher: The Optical Society
Date: 03-09-2010
DOI: 10.1364/OE.18.019994
Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress
Publisher: Cambridge University Press (CUP)
Date: 21-09-2020
DOI: 10.1017/S2040174420000884
Abstract: Advanced imaging techniques are enhancing research capacity focussed on the developmental origins of adult health and disease (DOHaD) hypothesis, and consequently increasing awareness of future health risks across various subareas of DOHaD research themes. Understanding how these advanced imaging techniques in animal models and human population studies can be both additively and synergistically used alongside traditional techniques in DOHaD-focussed laboratories is therefore of great interest. Global experts in advanced imaging techniques congregated at the advanced imaging workshop at the 2019 DOHaD World Congress in Melbourne, Australia. This review summarizes the presentations of new imaging modalities and novel applications to DOHaD research and discussions had by DOHaD researchers that are currently utilizing advanced imaging techniques including MRI, hyperpolarized MRI, ultrasound, and synchrotron-based techniques to aid their DOHaD research focus.
Increasing Respiratory Effort With 100% Oxygen During Resuscitation of Preterm Rabbits at Birth
Publisher: Frontiers Media SA
Date: 22-10-2019
Emphysema quantified: mapping regional airway dimensions using 2D phase contrast X-ray imaging
Publisher: Optica Publishing Group
Date: 09-07-2020
DOI: 10.1364/BOE.390587
Abstract: We have developed an analyser-based phase contrast X-ray imaging technique to measure the mean length scale of pores or particles that cannot be resolved directly by the system. By combining attenuation, phase and ultra-small angle X-ray scattering information, the technique was capable of measuring differences in airway dimension between lungs of healthy mice and those with mild and severe emphysema. Our measurements of airway dimensions from 2D images showed a 1:1 relationship to the actual airway dimensions measured using micro-CT. Using 80 images, the sensitivity and specificity were measured to be 0.80 and 0.89, respectively, with the area under the ROC curve close to ideal at 0.96. Reducing the number of images to 11 slightly decreased the sensitivity to 0.75 and the ROC curve area to 0.90, whilst the specificity remained high at 0.89.
Precise phase retrieval for propagation-based images using discrete mathematics
Publisher: Springer Science and Business Media LLC
Date: 02-11-2022
DOI: 10.1038/S41598-022-19940-9
Abstract: The ill-posed problem of phase retrieval in optics, using one or more intensity measurements, has a multitude of applications using electromagnetic or matter waves. Many phase retrieval algorithms are computed on pixel arrays using discrete Fourier transforms due to their high computational efficiency. However, the mathematics underpinning these algorithms is typically formulated using continuous mathematics, which can result in a loss of spatial resolution in the reconstructed images. Herein we investigate how phase retrieval algorithms for propagation-based phase-contrast X-ray imaging can be rederived using discrete mathematics and result in more precise retrieval for single- and multi-material objects and for spectral image decomposition. We validate this theory through experimental measurements of spatial resolution using computed tomography (CT) reconstructions of plastic phantoms and biological tissues, using detectors with a range of imaging system point spread functions (PSFs). We demonstrate that if the PSF substantially suppresses high spatial frequencies, the potential improvement from utilising the discrete derivation is limited. However, with detectors characterised by a single pixel PSF (e.g. direct, photon-counting X-ray detectors), a significant improvement in spatial resolution can be obtained, demonstrated here at up to 17%.
Dynamic imaging of the lungs using X-ray phase contrast
Publisher: IOP Publishing
Date: 12-10-2005
DOI: 10.1088/0031-9155/50/21/006
Abstract: High quality real-time imaging of lungs in vivo presents considerable challenges. We demonstrate here that phase contrast x-ray imaging is capable of dynamically imaging the lungs. It retains many of the advantages of simple x-ray imaging, whilst also being able to map weakly absorbing soft tissues based on refractive index differences. Preliminary results reported herein show that this novel imaging technique can identify and locate airway liquid and allows lung aeration in newborn rabbit pups to be dynamically visualized.
Changes in positive end-expiratory pressure alter the distribution of ventilation within the lung immediately after birth in newborn rabbits
Publisher: Public Library of Science (PLoS)
Date: 04-2014
Spectral x-ray imaging: Conditions under which propagation-based phase-contrast is beneficial
Publisher: IOP Publishing
Date: 07-10-2020
Establishing lung gas volumes at birth: Interaction between positive end-expiratory pressures and tidal volumes in preterm rabbits
Publisher: Springer Science and Business Media LLC
Date: 11-03-2013
DOI: 10.1038/PR.2013.48
Abstract: We investigated the effects of positive end-expiratory pressure (PEEP) and tidal volume (VT) on lung aeration, pulmonary mechanics, and the distribution of ventilation immediately after birth using a preterm rabbit model. Sixty preterm rabbits (27 d) received volume-targeted positive pressure ventilation from birth, with one of the 12 combinations of PEEP (0, 5, 8, or 10 cm H2O) and VT (4, 8, or 12 ml/kg). Outcomes included functional residual capacity (FRC), peak inflating pressure (PIP), dynamic compliance (Cd), and distribution of ventilation. Increasing PEEP from 0 to 10 cm H2O increased FRC by 4 ml/kg, increased Cd by 0.2 ml/kg/cm H2O, and reduced PIP by 5 cm H2O. Increasing VT from 4 to 12 ml/kg increased FRC by 2 ml/kg, increased Cd by 0.3 ml/kg/cm H2O, and increased PIP by 4 cmH2O. No effect of VT on FRC occurred at 0 or 5 PEEP, and no effect of PEEP occurred at VT = 4 ml/kg. At 0 PEEP, increasing VT increased the proportion of gas entering the smaller apical regions, whereas at 10 PEEP, increasing VT increased the proportion of gas entering basal regions, from 47% to 63%. Both PEEP and VT have independent, additive effects on FRC, lung mechanics, and the distribution of ventilation during the immediate newborn period.
Theory of X-ray Phase-Contrast Imaging
Publisher: CRC Press
Date: 14-12-2017
Increase in pulmonary blood flow at birth: Role of oxygen and lung aeration
Publisher: Wiley
Date: 10-09-2016
DOI: 10.1113/JP270926
Increased end-expiratory pressures improve lung function in near-term newborn rabbits with elevated airway liquid volume at birth
Publisher: American Physiological Society
Date: 09-2021
DOI: 10.1152/JAPPLPHYSIOL.00918.2020
Abstract: Term babies born by cesarean section have elevated airway liquid volumes, which predisposes them to respiratory distress. Treatments targeting molecular mechanisms to clear lung liquid are ineffective for term newborn respiratory distress. We showed that respiratory support with an end-expiratory pressure supports lung function in near-term rabbits with elevated airway liquid volumes at birth. This study provides further physiological understanding of lung function in newborns with elevated airway liquid volumes at risk of respiratory distress.
Improving lung aeration in ventilated newborn preterm rabbits with a partially aerated lung
Publisher: American Physiological Society
Date: 10-2020
DOI: 10.1152/JAPPLPHYSIOL.00426.2020
Abstract: Preterm newborns commonly receive intermittent positive pressure ventilation (iPPV) at birth, but the optimal approach that facilitates uniform lung aeration is unknown, particularly in a partially aerated lung. Using phase contrast X-ray imaging, we showed that combining a long inflation time (1.0 s) with surfactant improved lung mechanics and aeration in the immediate newborn period. The current clinical practice of using short inflation times during iPPV might be suboptimal, and a different approach is needed.
Elevated airway liquid volumes at birth: a potential cause of transient tachypnea of the newborn
Publisher: American Physiological Society
Date: 11-2017
DOI: 10.1152/JAPPLPHYSIOL.00464.2017
Abstract: Excessive liquid in airways and/or distal lung tissue may underpin the respiratory morbidity associated with transient tachypnea of the newborn (TTN). However, its effects on lung aeration and respiratory function following birth are unknown. We investigated the effect of elevated airway liquid volumes on newborn respiratory function. Near-term rabbit kittens (30 days gestation term ~32 days) were delivered, had their lung liquid-drained, and either had no liquid replaced (control n = 7) or 30 ml/kg of liquid re-added to the airways [liquid added (LA) n = 7]. Kittens were mechanically ventilated in a plethysmograph. Measures of chest and lung parameters, uniformity of lung aeration, and airway size were analyzed using phase contrast X-ray imaging. The maximum peak inflation pressure required to recruit a tidal volume of 8 ml/kg was significantly greater in LA compared with control kittens (35.0 ± 0.7 vs. 26.8 ± 0.4 cmH 2 O, P 0.001). LA kittens required greater time to achieve lung aeration (106 ± 14 vs. 60 ± 6 inflations, P = 0.03) and had expanded chest walls, as evidenced by an increased total chest area (32 ± 9%, P 0.0001), lung height (17 ± 6%, P = 0.02), and curvature of the diaphragm (19 ± 8%, P = 0.04). LA kittens had lower functional residual capacity during stepwise changes in positive end-expiratory pressures (5, 3, 0, and 5 cmH 2 0). Elevated lung liquid volumes had marked adverse effects on lung structure and function in the immediate neonatal period and reduced the ability of the lung to aerate efficiently. We speculate that elevated airway liquid volumes may underlie the initial morbidity in near-term babies with TTN after birth. NEW & NOTEWORTHY Transient tachypnea of the newborn reduces respiratory function in newborns and is thought to result due to elevated airway liquid volumes following birth. However, the effect of elevated airway liquid volumes on neonatal respiratory function is unknown. Using phase contrast X-ray imaging, we show that elevated airway liquid volumes have adverse effects on lung structure and function in the immediate newborn period, which may underlie the pathology of TTN in near-term babies after birth.
Dynamic studies of lung fluid clearance with phase contrast imaging
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2436444
Inspiration regulates the rate and temporal pattern of lung liquid clearance and lung aeration at birth
Publisher: American Physiological Society
Date: 06-2009
DOI: 10.1152/JAPPLPHYSIOL.91526.2008
Abstract: At birth, the initiation of pulmonary gas exchange is dependent on air entry into the lungs, and recent evidence indicates that pressures generated by inspiration may be involved. We have used simultaneous plethysmography and phase-contrast X-ray imaging to investigate the contribution of inspiration and expiratory braking maneuvers (EBMs) to lung aeration and the formation of a functional residual capacity (FRC) after birth. Near-term rabbit pups ( n = 26) were delivered by cesarean section, placed in a water plethysmograph, and imaged during the initiation of spontaneous breathing. Breath-by-breath changes in lung gas volumes were measured using plethysmography and visualized using phase-contrast X-ray imaging. Pups rapidly (1–5 breaths) generate a FRC (16.2 ± 1.2 ml/kg) by inhaling a greater volume than they expire (by 2.9 ± 0.4 ml·kg −1 ·breath −1 over the first 5 breaths). As a result, 94.8 ± 1.4% of lung aeration occurred during inspiration over multiple breaths. The incidence of EBMs was rare early during lung aeration, with most ( %) occurring after % of max FRC was achieved. Although EBMs were associated with an overall increase in FRC, 34.8 ± 5.3% of EBMs were associated with a decrease in FRC. We conclude that lung aeration is predominantly achieved by inspiratory efforts and that EBMs help to maintain FRC following its formation.
Accuracy of currently available neonatal respiratory function monitors for neonatal resuscitation
Publisher: Springer Science and Business Media LLC
Date: 08-06-2016
Pulmonary Transition at Birth
Publisher: Elsevier
Date: 2014
Aberrations in shift-invariant linear optical imaging systems using partially coherent fields
Publisher: Elsevier BV
Date: 11-2015
Determining particle size distributions from a single projection image
Publisher: The Optical Society
Date: 28-06-2012
DOI: 10.1364/OE.20.015962
Requirements for dynamical differential phase contrast x-ray imaging with a laboratory source
Publisher: IOP Publishing
Date: 28-11-2016
DOI: 10.1088/1361-6560/61/24/8720
Abstract: X-ray phase contrast enables weakly-attenuating structures to be imaged, with bright synchrotron sources adding the ability to capture time sequences and analyse s le dynamics. Here, we describe the translation of dynamical differential phase contrast imaging from the synchrotron to a compact x-ray source, in order to achieve this kind of time sequence imaging in the laboratory. We formulate broadly-applicable set-up guidelines for the single-grid, single-exposure imaging technique using a ergent source, exploring the experimental factors that restrict set-up size, imaging sensitivity and s le size. Experimental images are presented using the single-grid phase contrast technique with a steel attenuation grid and a liquid-metal-jet x-ray source, enabling exposure times as short as 0.5 s for dynamic imaging. Differential phase contrast images were retrieved from phantoms, incorporating noise filtering to improve the low-count images encountered when imaging dynamics using short exposures.
Lung hypoplasia in newborn rabbits with a diaphragmatic hernia affects pulmonary ventilation but not perfusion
Publisher: Springer Science and Business Media LLC
Date: 31-05-2017
DOI: 10.1038/PR.2017.91
Positive end-expiratory pressure enhances development of a functional residual capacity in preterm rabbits ventilated from birth
Publisher: American Physiological Society
Date: 05-2009
DOI: 10.1152/JAPPLPHYSIOL.91591.2008
Abstract: The factors regulating lung aeration and the initiation of pulmonary gas exchange at birth are largely unknown, particularly in infants born very preterm. As hydrostatic pressure gradients may play a role, we have examined the effect of a positive end-expiratory pressure (PEEP) on the spatial and temporal pattern of lung aeration in preterm rabbit pups mechanically ventilated from birth using simultaneous phase-contrast X-ray imaging and plethysmography. Preterm rabbit pups were delivered by caesarean section at 28 days of gestational age, anesthetized, intubated, and placed within a water-filled plethysmograph (head out). Pups were imaged as they were mechanically ventilated from birth with a PEEP of either 0 cmH 2 O or 5 cmH 2 O. The peak inflation pressure was held constant at 35 cmH 2 O. Without PEEP, gas only entered into the distal airways during inflation. The distal airways collapsed during expiration, and, as a result, the functional residual capacity (FRC) did not increase above the lung's anatomic dead space volume (2.5 ± 0.8 ml/kg). In contrast, ventilation with 5-cmH 2 O PEEP gradually increased aeration of the distal airways, which did not collapse at end expiration. The FRC achieved in pups ventilated with PEEP (19.9 ± 3.2 ml/kg) was significantly greater than in pups ventilated without PEEP (−2.3 ± 3.5 ml/kg). PEEP greatly facilitates aeration of the distal airways and the accumulation of FRC and prevents distal airway collapse at end expiration in very preterm rabbit pups mechanically ventilated from birth.
Extraction of depth moments by exploiting the partial coherence of radiation
Publisher: IOP Publishing
Date: 19-05-2016
Ring artifact suppression in X-ray computed tomography using a simple, pixel-wise response correction
Publisher: The Optical Society
Date: 02-05-2019
DOI: 10.1364/OE.27.014231
Imaging lung aeration and lung liquid clearance at birth using phase contrast x-ray imaging
Publisher: Wiley
Date: 2009
DOI: 10.1111/J.1440-1681.2008.05109.X
Abstract: The transition to extra-uterine life at birth is critically dependent on airway liquid clearance to allow the entry of air and the onset of gaseous ventilation. We have used phase contrast X-ray imaging to identify factors that regulate lung aeration at birth in spontaneously breathing term and mechanically ventilated preterm rabbit pups. Phase contrast X-ray imaging exploits the difference in refractive index between air and water to enhance image contrast, enabling the smallest air-filled structures of the lung (alveoli < 100 microm) to be resolved. Using this technique, the lungs become visible as they aerate, allowing the air-liquid interface to be observed as it moves distally during lung aeration. Spontaneously breathing term rabbit pups rapidly aerate their lungs, with most fully recruiting their functional residual capacity (FRC) within the first few breaths. The increase in FRC occurs mainly during in idual breaths, demonstrating that airway liquid clearance and lung aeration is closely associated with inspiration. We suggest that transpulmonary pressures generated by inspiration provide a hydrostatic pressure gradient for the movement of water out of the airways and into the surrounding lung tissue after birth. In mechanically ventilated preterm pups, lung aeration is closely associated with lung inflation and a positive end-expiratory pressure is required to generate and maintain FRC after birth. In summary, phase contrast X-ray imaging can image the air-filled lung with high temporal and spatial resolution and is ideal for identifying factors that regulate lung aeration at birth in both spontaneously breathing term and mechanically ventilated preterm neonates.
Phase contrast X-ray imaging of mice and rabbit lungs: A comparative study
Publisher: British Institute of Radiology
Date: 11-2005
DOI: 10.1259/BJR/13024611
Abstract: The significant degree of X-ray phase contrast created by air-tissue interfaces, coupled with the poor radiographic contrast of conventional chest radiographs, makes the inflated lung an ideal candidate for investigating the potential diagnostic improvement afforded by phase contrast X-ray imaging. In small animals these methods highlight the lung airways and lobe boundaries and reveal the lung tissue as a speckled intensity pattern not seen in other soft tissues. We have compared analyser-based and propagation-based phase contrast imaging modalities, together with conventional radiographic imaging, to ascertain which technique shows the greatest image enhancement for various lung sizes. The conventional radiographic image of a mouse was obtained on a Siemens Nova 3000 mammography system, whilst phase contrast images of mice and rabbit chests were acquired at the medical imaging beamline (20B2) at the SPring-8 synchrotron radiation research facility in Japan. For mice aged 1 day, 1 week and 1 month old it was determined that analyser-based imaging showed the greatest overall image contrast, however, for an adult rabbit both techniques yielded excellent contrast. The success of these methods in creating high quality images for rabbit lungs raises the possibility of improving human lung imaging using phase contrast techniques.
Real-time measurement of alveolar size and population using phase contrast x-ray imaging
Publisher: The Optical Society
Date: 24-10-2014
DOI: 10.1364/BOE.5.004024
Duality between phase vortices and Argand-plane caustics
Publisher: Elsevier BV
Date: 10-2012
Material Decomposition Using Spectral Propagation-Based Phase-Contrast X-Ray Imaging
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2020
The physiology of neonatal resuscitation
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2018
Phase contrast image segmentation using a Laue analyser crystal
Publisher: IOP Publishing
Date: 06-01-2011
DOI: 10.1088/0031-9155/56/3/001
Abstract: Dual-energy x-ray imaging is a powerful tool enabling two-component s les to be separated into their constituent objects from two-dimensional images. Phase contrast x-ray imaging can render the boundaries between media of differing refractive indices visible, despite them having similar attenuation properties this is important for imaging biological soft tissues. We have used a Laue analyser crystal and a monochromatic x-ray source to combine the benefits of both techniques. The Laue analyser creates two distinct phase contrast images that can be simultaneously acquired on a high-resolution detector. These images can be combined to separate the effects of x-ray phase, absorption and scattering and, using the known complex refractive indices of the s le, to quantitatively segment its component materials. We have successfully validated this phase contrast image segmentation (PCIS) using a two-component phantom, containing an iodinated contrast agent, and have also separated the lungs and ribcage in images of a mouse thorax. Simultaneous image acquisition has enabled us to perform functional segmentation of the mouse thorax throughout the respiratory cycle during mechanical ventilation.
Higher CPAP levels improve functional residual capacity at birth in preterm rabbits
Publisher: Springer Science and Business Media LLC
Date: 22-07-2022
DOI: 10.1038/S41390-021-01647-8
Abstract: Preterm infants are commonly supported with 4-8 cm H Preterm rabbits delivered at 29/32 days (~26-28 weeks human) gestation received 0, 5, 8, 12, 15 cm H FRC was lower in the 0 (6.8 (1.0-11.2) mL/kg) and 5 (10.1 (1.1-16.8) mL/kg) compared to the 15 (18.8 (10.9-22.4) mL/kg) cm H In all, 15 cm H Although preterm infants are commonly supported with 4-8 cm H
On the origin of speckle in x-ray phase contrast images of lung tissue
Publisher: IOP Publishing
Date: 04-09-2004
DOI: 10.1088/0031-9155/49/18/010
Abstract: Phase contrast x-ray imaging of small animal lungs reveals a speckled intensity pattern not seen in other tissues, making the lungs highly visible in comparison to other organs. Although bearing a superficial resemblance to alveoli, the cause of this speckle has not been established. With a view to determining the mechanism for the formation of speckle, this paper details the results of propagation-based phase contrast experiments performed on mice lungs, together with packed glass microspheres used to emulate lung tissue. These experimental studies are compared to numerical simulations, based on wave propagation techniques. We find that speckle arises from focusing effects, with multiple alveoli acting as aberrated compound refractive lenses. Both experiments and modelling suggest that this speckle-formation phenomenon may lead to better screening methods for human lungs than conventional radiography.
Photon-counting, energy-resolving and super-resolution phase contrast X-ray imaging using an integrating detector.
Publisher: Optica Publishing Group
Date: 25-02-2020
DOI: 10.1364/OE.384928
Abstract: This work demonstrates the use of a scientific-CMOS (sCMOS) energy-integrating detector as a photon-counting detector, thereby eliminating dark current and read-out noise issues, that simultaneously provides both energy resolution and sub-pixel spatial resolution for X-ray imaging. These capabilities are obtained by analyzing visible light photon clouds that result when X-ray photons produce fluorescence from a scintillator in front of the visible light sensor. Using low-fluence monochromatic X-ray projections to avoid overlapping photon clouds, the centroid of in idual X-ray photon interactions was identified. This enabled a tripling of the spatial resolution of the detector to 6.71 ± 0.04 µm. By calculating the total charge deposited by this interaction, an energy resolution of 61.2 ± 0.1% at 17 keV was obtained. When combined with propagation-based phase contrast imaging and phase retrieval, a signal-to-noise ratio of up to 15 ± 3 was achieved for an X-ray fluence of less than 3 photons/mm 2 .
Effect of betamethasone, surfactant, and positive end-expiratory pressures on lung aeration at birth in preterm rabbits
Publisher: American Physiological Society
Date: 09-2016
DOI: 10.1152/JAPPLPHYSIOL.01043.2015
Abstract: Antenatal glucocorticoids, exogenous surfactant, and positive end-expiratory pressure (PEEP) ventilation are commonly provided to preterm infants to enhance respiratory function after birth. It is unclear how these treatments interact to improve the transition to air-breathing at birth. We investigated the relative contribution of antenatal betamethasone, prophylactic surfactant, and PEEP (3 cmH 2 O) on functional residual capacity (FRC) and dynamic lung compliance (C DL ) in preterm (28 day GA) rabbit kittens at birth. Kittens were delivered by cesarean section and mechanically ventilated. FRC was calculated from X-ray images, and C DL was measured using plethysmography. Without betamethasone, PEEP increased FRC recruitment and C DL . Surfactant did not further increase FRC, but significantly increased C DL . Betamethasone abolished the benefit of PEEP on FRC, but surfactant counteracted this effect of betamethasone. These findings indicate that low PEEP levels are insufficient to establish FRC at birth following betamethasone treatment. However, surfactant reversed the effect of betamethasone and when combined, these two treatments enhanced FRC recruitment irrespective of PEEP level.
Argand-plane vorticity singularities in complex scalar optical fields: An experimental study using optical speckle
Publisher: The Optical Society
Date: 12-03-0001
DOI: 10.1364/OE.22.006495
2D and 3D X-ray phase retrieval of multi-material objects using a single defocus distance
Publisher: Optica Publishing Group
Date: 15-03-2010
DOI: 10.1364/OE.18.006423
Spectral propagation-based X-ray phase-contrast imaging
Publisher: SPIE
Date: 09-09-2021
DOI: 10.1117/12.2596158
A new design for high stability pressure-controlled ventilation for small animal lung imaging
Publisher: IOP Publishing
Date: 26-02-2010
Speckle-Based X-Ray Dark-Field Tomography of an Attenuating Object
Publisher: SPIE
Date: 09-09-2021
DOI: 10.1117/12.2597722
Tomographic reconstruction using tilted Laue analyser-based X-ray phase-contrast imaging
Publisher: International Union of Crystallography (IUCr)
Date: 2021
DOI: 10.1107/S1600577520013995
Abstract: Analyser-based phase-contrast imaging (ABPCI) is a highly sensitive phase-contrast imaging method that produces high-contrast images of weakly absorbing materials. However, it is only sensitive to phase gradient components lying in the diffraction plane of the analyser crystal [ i.e. in one dimension (1-D)]. In order to accurately account for and measure phase effects produced by the wavefield-s le interaction, ABPCI and other 1-D phase-sensitive methods must achieve 2-D phase gradient sensitivity. An inclined geometry method was applied to a Laue geometry setup for X-ray ABPCI through rotation of the detector and object about the optical axis. This allowed this traditionally 1-D phase-sensitive phase-contrast method to possess 2-D phase gradient sensitivity. Tomographic datasets were acquired over 360° of a multi-material phantom with the detector and s le tilted by 8°. The real and imaginary parts of the refractive index were reconstructed for the phantom.
A feasibility study of X-ray phase-contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron
Publisher: International Union of Crystallography (IUCr)
Date: 16-10-2015
DOI: 10.1107/S160057751501766X
Abstract: Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low-dose high-sensitivity three-dimensional mammographic phase-contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X-ray energy, source size, detector resolution, s le-to-detector distance, scanning and data processing strategies in the case of propagation-based phase-contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast-tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation-based phase contrast and demonstrated significant improvement of the quality of phase-contrast CT imaging compared with conventional (absorption-based) CT, at medically acceptable radiation doses.
A high precision recipe for correcting images distorted by a tapered fiber optic
Publisher: IOP Publishing
Date: 29-09-2010
Generalised Cornu spirals: An experimental study using hard x-rays
Publisher: The Optical Society
Date: 05-05-2016
DOI: 10.1364/OE.24.010620
An improvement to the diffraction-enhanced imaging method that permits imaging of dynamic systems
Publisher: Elsevier BV
Date: 08-2005
The role of lung inflation and sodium transport in airway liquid clearance during lung aeration in newborn rabbits
Publisher: Springer Science and Business Media LLC
Date: 26-12-2013
DOI: 10.1038/PR.2012.197
Abstract: Recent phase-contrast X-ray imaging studies suggest that inspiration primarily drives lung aeration and airway liquid clearance at birth, which questions the role of adrenaline-induced activation of epithelial sodium channels (ENaCs). We hypothesized that pressures generated by inspiration have a greater role in airway liquid clearance than do ENaCs after birth. Rabbit pups (30 d of gestation) were delivered and sedated, and 0.1 ml of saline (S) or amiloride (Am an ENaC inhibitor) was instilled into the lungs before mechanical ventilation. Two other groups (30 d of gestation) were treated similarly but were also given adrenaline (S/Ad and Am/Ad) before mechanical ventilation. Amiloride and adrenaline did not affect functional residual capacity (FRC) recruitment (P > 0.05). Amiloride increased the rate of FRC loss between inflations (Am: -5.2 ± 0.6 ml/kg/s), whereas adrenaline reduced the rate of FRC loss (S/Ad: -1.9 ± 0.3 ml/kg/s) as compared with saline-treated controls (S: -3.5 ± -0.6 ml/kg/s P < 0.05). These data indicate that inspiration is a major determinant of airway liquid clearance and FRC development during positive pressure ventilation. Although ENaC inhibition and adrenaline administration had no detectable effect on FRC development, ENaC may help to prevent liquid from re-entering the airways during expiration.
Combined lung imaging and respiratory physiology research at SPring-8
Publisher: Informa UK Limited
Date: 12-04-2011
Unification of analyser-based and propagation-based X-ray phase-contrast imaging
Publisher: Elsevier BV
Date: 08-2005
Ventilation/perfusion mismatch during lung aeration at birth
Publisher: American Physiological Society
Date: 09-2014
DOI: 10.1152/JAPPLPHYSIOL.01358.2013
Abstract: At birth, the transition to newborn life is triggered by lung aeration, which stimulates a large increase in pulmonary blood flow (PBF). Current theories predict that the increase in PBF is spatially related to ventilated lung regions as they aerate after birth. Using simultaneous phase-contrast X-ray imaging and angiography we investigated the spatial relationships between lung aeration and the increase in PBF after birth. Six near-term (30-day gestation) rabbits were delivered by caesarean section, intubated and an intravenous catheter inserted, before they were positioned for X-ray imaging. During imaging, iodine was injected before ventilation onset, after ventilation of the right lung only, and after ventilation of both lungs. Unilateral ventilation increased iodine levels entering both left and right pulmonary arteries (PAs) and significantly increased heart rate, iodine ejection per beat, diameters of both left and right PAs, and number of visible vessels in both lungs. Within the 6th intercostal space, the mean gray level (relative measure of iodine level) increased from 68.3 ± 11.6 and 70.3 ± 7.5%·s to 136.3 ± 22.6 and 136.3 ± 23.7%·s in the left and right PAs, respectively. No differences were observed between vessels in the left and right lungs, despite the left lung not initially being ventilated. The increase in PBF at birth is not spatially related to lung aeration allowing a large ventilation erfusion mismatch, or pulmonary shunting, to occur in the partially aerated lung at birth.
High spatiotemporal resolution measurement of regional lung air volumes from 2D phase contrast x-ray images
Publisher: Wiley
Date: 19-03-2013
DOI: 10.1118/1.4794926
Abstract: Described herein is a new technique for measuring regional lung air volumes from two-dimensional propagation-based phase contrast x-ray (PBI) images at very high spatial and temporal resolution. Phase contrast dramatically increases lung visibility and the outlined volumetric reconstruction technique quantifies dynamic changes in respiratory function. These methods can be used for assessing pulmonary disease and injury and for optimizing mechanical ventilation techniques for preterm infants using animal models. The volumetric reconstruction combines the algorithms of temporal subtraction and single image phase retrieval (SIPR) to isolate the image of the lungs from the thoracic cage in order to measure regional lung air volumes. The SIPR algorithm was used to recover the change in projected thickness of the lungs on a pixel-by-pixel basis (pixel dimensions ≈ 16.2 μm). The technique has been validated using numerical simulation and compared results of measuring regional lung air volumes with and without the use of temporal subtraction for removing the thoracic cage. To test this approach, a series of PBI images of newborn rabbit pups mechanically ventilated at different frequencies was employed. Regional lung air volumes measured from PBI images of newborn rabbit pups showed on average an improvement of at least 20% in 16% of pixels within the lungs in comparison to that measured without the use of temporal subtraction. The majority of pixels that showed an improvement was found to be in regions occupied by bone. Applying the volumetric technique to sequences of PBI images of newborn rabbit pups, it is shown that lung aeration at birth can be highly heterogeneous. This paper presents an image segmentation technique based on temporal subtraction that has successfully been used to isolate the lungs from PBI chest images, allowing the change in lung air volume to be measured over regions as small as the pixel size. Using this technique, it is possible to measure changes in regional lung volume at high spatial and temporal resolution during breathing at much lower x-ray dose than would be required using computed tomography.
Accurate measures of changes in regional lung air volumes from chest x-rays of small animals
Publisher: IOP Publishing
Date: 07-10-2022
Abstract: Objective . To develop a robust technique for calculating regional volume changes within the lung from x-ray radiograph sequences captured during ventilation, without the use of computed tomography (CT). Approach . This technique is based on the change in transmitted x-ray intensity that occurs for each lung region as air displaces the attenuating lung tissue. Main results . Lung air volumes calculated from x-ray intensity changes showed a strong correlation ( R 2 = 0.98) against the true volumes, measured from high-resolution CT. This correlation enables us to accurately convert projected intensity data into relative changes in lung air volume. We have applied this technique to measure changes in regional lung volumes from x-ray image sequences of mechanically ventilated, recently-deceased newborn rabbits, without the use of CT. Significance . This method is suitable for biomedical research studies,enabling quantitative regional measurement of relative lung air volumes at high temporal resolution, and shows great potential for future clinical application.
Functional Imaging to Understand Biomechanics: A Critical Tool for the Study of Biology, Pathology and the Development of Pharmacological Solutions
Publisher: Bentham Science Publishers Ltd.
Date: 08-2012
DOI: 10.2174/138920112802502060
Abstract: We present four case studies of the literature discussing the effects of physical forces on biological function. While the field of biomechanics has existed for many decades, it may be considered by some a poor cousin to biochemistry and other traditional fields of medical research. In these case studies, including cardiovascular and respiratory systems, we demonstrate that, in fact, many systems historically believed to be controlled by biochemistry are dominated by biomechanics. We discuss both the previous paradigms that have advanced research in these fields and the changing paradigms that will define the progressions of these fields for decades to come. In the case of biomechanical effects of flowing blood on the endothelium, this has been well understood for decades. In the cases of platelet activation and liquid clearance from the lungs during birth, these discoveries are far more recent and perhaps not as universally accepted. While only a few specific ex les are examined here, it is clear that not enough attention is paid to the possible mechanical links to biological function. The continued development of these research areas, with the inclusion of physical effects, will hopefully provide new insight into disease development, progression, diagnosis and effective therapies.
Optimizing lung aeration at birth using a sustained inflation and positive pressure ventilation in preterm rabbits
Publisher: Springer Science and Business Media LLC
Date: 18-03-2016
DOI: 10.1038/PR.2016.59
Quantitative material decomposition using linear iterative near-field phase retrieval dual-energy x-ray imaging
Publisher: IOP Publishing
Date: 18-09-2020
Measurement of absolute regional lung air volumes from near-field x-ray speckles
Publisher: The Optical Society
Date: 06-11-2013
DOI: 10.1364/OE.21.027905
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