In situ chamber for studying battery failure using high-speed synchrotron radiography.

The investigation of lithium-ion battery failures is a major challenge for personnel and equipment due to the associated hazards (thermal reaction, toxic gases and explosions). To perform such experiments safely, a battery abuse-test chamber has been developed and installed at the microtomography beamline ID19 of the European Synchrotron Radiation Facility (ESRF). The chamber provides the capability to robustly perform in situ abuse tests through the heat-resistant and gas-tight design for flexible battery geometries and configurations, including single-cell and multi-cell assemblies. High-speed X-ray imaging can be complemented by supplementary equipment, including additional probes (voltage, pressure and temperature) and thermal imaging. Together with the test chamber, a synchronization graphical user interface was developed, which allows an initial interpretation by time-synchronous visualization of the acquired data. Enabled by this setup, new meaningful insights can be gained into the internal processes of a thermal runaway of current and future energy-storage devices such as lithium-ion cells.

Fractal analysis reveals functional unit of ventilation in the lung.

Ventilation is inhomogeneous in the lungs across species. It has been hypothesized that ventilation inhomogeneity is largely determined by the design of the airway branching network. Because exchange of gases at the alveolar barrier is more efficient when gas concentrations are evenly distributed at subacinar length scales, it is assumed that a 'functional unit' of ventilation exists within the lung periphery, where gas concentration becomes uniform. On the other hand, because the morphology of pulmonary airways and alveoli, and the distribution of inhaled fluorescent particles show self-similar fractal properties over a wide range of length scales, it has been predicted that fractal dimension of ventilation approaches unity within an internally homogeneous functional unit of ventilation. However, the existence of such a functional unit has never been demonstrated experimentally due to lack of in situ gas concentration measurements of sufficient spatial resolution in the periphery of a complex bifurcating network. Here, using energy-subtractive synchrotron radiation tomography, we measured the distribution of an inert gas (Xe) in the in vivo rabbit lung during Xe wash-in breathing manoeuvres. The effects of convective flow rate, diffusion and cardiac motion were also assessed. Fractal analysis of resulting gas concentration and tissue density maps revealed that fractal dimension was always smaller for Xe than for tissue density, and that only for the gas, a length scale existed where fractal dimension approached unity. The length scale where this occurred was seen to correspond to that of a rabbit acinus, the terminal structure comprising only alveolated airways. KEY POINTS: Gas ventilation is inhomogeneous in the lung of many species. However, it is not known down to what length scales this inhomogeneity persists. It is generally assumed that ventilation becomes homogeneous at subacinar length scales, beyond the spatial resolution of commonly available imaging techniques, hence this has not been demonstrated experimentally. Here we measured the distribution of inhaled Xe gas in the rabbit lung using synchrotron radiation energy-subtractive imaging and used fractal analysis to show that ventilation becomes internally uniform within regions about the size of rabbit lung acini.

Individual Airway Closure Characterized In Vivo by Phase-Contrast CT Imaging in Injured Rabbit Lung.

OBJECTIVES: Airway closure is involved in adverse effects of mechanical ventilation under both general anesthesia and in acute respiratory distress syndrome patients. However, direct evidence and characterization of individual airway closure is lacking. Here, we studied the same individual peripheral airways in intact lungs of anesthetized and mechanically ventilated rabbits, at baseline and following lung injury, using high-resolution synchrotron phase-contrast CT. DESIGN: Laboratory animal investigation. SETTING: European synchrotron radiation facility. SUBJECTS: Six New-Zealand White rabbits. INTERVENTIONS: The animals were anesthetized, paralyzed, and mechanically ventilated in pressure-controlled mode (tidal volume, 6 mL/kg; respiratory rate, 40; FIO2, 0.6; inspiratory:expiratory, 1:2; and positive end-expiratory pressure, 3 cm H2O) at baseline. Imaging was performed with a 47.5 × 47.5 × 47.5 µm voxel size, at positive end-expiratory pressure 12, 9, 6, 3, and 0 cm H2O. The imaging sequence was repeated after lung injury induced by whole-lung lavage and injurious ventilation in four rabbits. Cross-sections of the same individual airways were measured. MEASUREMENTS AND MAIN RESULTS: The airways were measured at baseline (n = 48; radius, 1.7 to 0.21 mm) and after injury (n = 32). Closure was observed at 0 cm H2O in three of 48 airways (6.3%; radius, 0.35 ± 0.08 mm at positive end-expiratory pressure 12) at baseline and five of 32 (15.6%; radius, 0.28 ± 0.09 mm) airways after injury. Cross-section was significantly reduced at 3 and 0 cm H2O, after injury, with a significant relation between the relative change in cross-section and airway radius at 12 cm H2O in injured, but not in normal lung (R = 0.60; p < 0.001). CONCLUSIONS: Airway collapsibility increases in the injured lung with a significant dependence on airway caliber. We identify "compliant collapse" as the main mechanism of airway closure in initially patent airways, which can occur at more than one site in individual airways.

Synchrotron Imaging Shows Effect of Ventilator Settings on Intrabreath Cyclic Changes in Pulmonary Blood Volume.

Despite the importance of dynamic changes in the regional distributions of gas and blood during the breathing cycle for lung function in the mechanically ventilated patient, no quantitative data on such cyclic changes are currently available. We used a novel gated synchrotron computed tomography imaging to quantitatively image regional lung gas volume (Vg), tissue density, and blood volume (Vb) in six anesthetized, paralyzed, and mechanically ventilated rabbits with normal lungs. Images were repeatedly collected during ventilation and steady-state inhalation of 50% xenon, or iodine infusion. Data were acquired in a dependent and nondependent image level, at zero end-expiratory pressure (ZEEP) and 9 cm H2O (positive end-expiratory pressure), and a tidal volume (Vt) of 6 ml/kg (Vt1) or 9 ml/kg (Vt2) at an Inspiratory:Expiratory ratio of 0.5 or 1.7 by applying an end-inspiratory pause. A video showing dynamic decreases in Vb during inspiration is presented. Vb decreased with positive end-expiratory pressure (P = 0.006; P = 0.036 versus Vt1-ZEEP and Vt2-ZEEP, respectively), and showed larger oscillations at the dependent image level, whereas a 45% increase in Vt did not have a significant effect. End-inspiratory Vb minima were reduced by an end-inspiratory pause (P = 0.042, P = 0.006 at nondependent and dependent levels, respectively). Normalized regional Vg:Vb ratio increased upon inspiration. Our data demonstrate, for the first time, within-tidal cyclic variations in regional pulmonary Vb. The quantitative matching of regional Vg and Vb improved upon inspiration under ZEEP. Further study is underway to determine whether these phenomena affect intratidal gas exchange.

Characterization of a sCMOS-based high-resolution imaging system.

The detection system is a key part of any imaging station. Here the performance of the novel sCMOS-based detection system installed at the ID17 biomedical beamline of the European Synchrotron Radiation Facility and dedicated to high-resolution computed-tomography imaging is analysed. The system consists of an X-ray-visible-light converter, a visible-light optics and a PCO.Edge5.5 sCMOS detector. Measurements of the optical characteristics, the linearity of the system, the detection lag, the modulation transfer function, the normalized power spectrum, the detective quantum efficiency and the photon transfer curve are presented and discussed. The study was carried out at two different X-ray energies (35 and 50 keV) using both 2× and 1× optical magnification systems. The final pixel size resulted in 3.1 and 6.2 µm, respectively. The measured characteristic parameters of the PCO.Edge5.5 are in good agreement with the manufacturer specifications. Fast imaging can be achieved using this detection system, but at the price of unavoidable losses in terms of image quality. The way in which the X-ray beam inhomogeneity limited some of the performances of the system is also discussed.

Dynamic Mechanical Interactions Between Neighboring Airspaces Determine Cyclic Opening and Closure in Injured Lung.

OBJECTIVES: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. DESIGN: Experimental animal study. SETTING: International synchrotron radiation laboratory. SUBJECTS: Four anesthetized rabbits, ventilated in pressure controlled mode. INTERVENTIONS: The lung was consecutively imaged at ~ 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end-expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (Fderecruited, Frecruited) were computed based on the comparison of the aerated volumes at successive time points. MEASUREMENTS AND MAIN RESULTS: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of Fderecruited and Frecruited when mechanical interdependence was included, while its exclusion gave Frecruited values of zero at positive end-expiratory pressure greater than or equal to 3 cm H2O. CONCLUSIONS: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage.

Pressure-regulated volume control vs. volume control ventilation in healthy and injured rabbit lung: An experimental study.

BACKGROUND: It is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung. OBJECTIVES: We compared respiratory mechanics, lung aeration and regional specific ventilation ((Equation is included in full-text article.)) distributions in healthy and surfactant-depleted rabbits ventilated with pressure-regulated volume control (PRVC) mode with a decelerating inspiratory flow or with volume control (VC) mode. DESIGN: Randomised experimental study. ANIMALS AND INTERVENTIONS: New Zealand white rabbits (n = 8) were anaesthetised, paralysed and mechanically ventilated either with VC or PRVC mode (tidal volume: 7 ml kg; rate: 40 min; positive end-expiratory pressure (PEEP): 3 cmH2O), at baseline and after lung injury induced by lung lavage. MAIN OUTCOME MEASURES: Airway resistance (Raw), respiratory tissue damping (G) and elastance (H) were measured by low-frequency forced oscillations. Synchrotron radiation computed tomography during stable xenon wash-in was used to measure regional lung aeration and specific ventilation and the relative fraction of nonaerated, trapped, normally, poorly and hyperinflated lung regions. RESULTS: Lung lavage significantly elevated peak inspiratory pressure (PIP) (P < 0.001). PIP was lower on PRVC compared with VC mode (-12.7 ±â€Š1.7%, P < 0.001). No significant differences in respiratory mechanics, regional ventilation distribution, strain or blood oxygenation could be detected between the two ventilation modes. CONCLUSION: A decelerating flow pattern (PRVC) resulted in equivalent regional ventilation distribution, respiratory mechanics and gas exchange, in both normal and mechanically heterogeneous lungs with, however, a significantly lower peak pressure. Our data suggest that the lower PIP on PRVC ventilation was because of the decelerating flow pattern rather than the ventilation distribution.

Optimising 4D imaging of fast-oscillating structures using X-ray microtomography with retrospective gating.

Imaging the internal architecture of fast-vibrating structures at micrometer scale and kilohertz frequencies poses great challenges for numerous applications, including the study of biological oscillators, mechanical testing of materials, and process engineering. Over the past decade, X-ray microtomography with retrospective gating has shown very promising advances in meeting these challenges. However, breakthroughs are still expected in acquisition and reconstruction procedures to keep improving the spatiotemporal resolution, and study the mechanics of fast-vibrating multiscale structures. Thereby, this works aims to improve this imaging technique by minimising streaking and motion blur artefacts through the optimisation of experimental parameters. For that purpose, we have coupled a numerical approach relying on tomography simulation with vibrating particles with known and ideal 3D geometry (micro-spheres or fibres) with experimental campaigns. These were carried out on soft composites, imaged in synchrotron X-ray beamlines while oscillating up to 400 Hz, thanks to a custom-developed vibromechanical device. This approach yields homogeneous angular sampling of projections and gives reliable predictions of image quality degradation due to motion blur. By overcoming several technical and scientific barriers limiting the feasibility and reproducibility of such investigations, we provide guidelines to enhance gated-CT 4D imaging for the analysis of heterogeneous, high-frequency oscillating materials.

Synchrotron X-ray imaging of the onset of ultrasonic horn cavitation.

High-power ultrasonic horns operating at low frequency are known to generate a cone-shaped cavitation bubble cloud beneath them. The exact physical processes resulting in the conical structure are still unclear mainly due to challenges associated with their visualization. Herein, we address the onset of the cavitation cloud by exploiting high-speed X-ray phase contrast imaging. It reveals that the cone formation is not immediate but results from a three-step phenomenology: (i) inception and oscillation of single bubbles, (ii) individual cloud formation under splitting or lens effects, and (iii) cloud merging leading to the formation of a bubble layer and, eventually, to the cone structure due to the radial pressure gradient on the horn tip.

Preliminary study of all-solid-state batteries: Evaluation of blast formation during the thermal runaway.

All-solid-state batteries have been developed to increase energy density by replacing the lithiated graphite negative electrode by a lithium metal foil and to increase safety by removing the organic compounds. However, the safety issues of these batteries have received little attention up to now. The behavior of a reassembled all-solid-state battery under thermal stress was recorded by X-ray radiography and a high-speed camera. The thermal runaway (TR) lasted about 5 ms, thus extremely fast reaction kinetics. In comparison, the TR of a lithium-ion battery is about 500 ms. Furthermore, a 188-mbar aerial overpressure was measured using a piezoelectric sensor. Although this cell is not an explosive, 2.7 g TNT equivalent was calculated for it. This atypical behavior could have an impact on the casing or the battery pack. Therefore, it must be studied in greater detail.