Fast Scanning Research Articles

Updates on the clinical integration of point-of-care ultrasound in pediatric emergency medicine.

There is expanding evidence for point-of-care ultrasound (POCUS) use in pediatric emergency medicine - this review highlights the benefits and challenges in the clinical integration of high-yield POCUS applications. Specifically, it will delve into POCUS applications during resuscitations, controversies of Focused Assessment with Sonography for Trauma (FAST) in pediatric trauma, POCUS-guided procedures, and examples of clinical pathways where POCUS can expedite definitive care. POCUS can enhance diagnostic accuracy and aid in management of pediatric patients in shock and help identify reversible causes during cardiac arrest. The use of the FAST in pediatric blunt abdominal trauma remains nuanced - its proper use requires an integration with clinical findings and an appreciation of its limitations. POCUS has been shown to enhance safety and efficacy of procedures such as nerve blocks, incision & drainage, and intravenous access. Integrating POCUS into pathways for conditions such as intussusception and testicular torsion expedites downstream care. POCUS enhances diagnostic efficiency and management in pediatric patients arriving at the ED with undifferentiated shock, cardiac arrest, or trauma. Additionally, POCUS improves procedural success and safety, and is integral to clinical pathways for expediting definitive care for various pediatric emergencies. Future research should continue to focus on the impact of POCUS on patient outcomes, ensuring user competency, and the expansion of POCUS into diverse settings.

Ultra-thin sub-diffraction metalens with a wide field-of-view for UV focusing.

In recent years, wide field-of-view imaging technology based on a metasurface has been widely applied. However, works on the reported sub-diffraction metalens with a wide field-of-view indicate that multiple structures are essential to effectively eliminate aberrations, which results in a heavy device thickness and weakens the advantage of an ultra-thin metasurface. To solve this problem, according to the super-oscillation theory and the translational symmetry of quadratic phase, as well as the principle of virtual aperture diaphragm based on wave vector filter, this Letter demonstrates a sub-diffraction metalens combined with a single quadratic metalens and a wave vector filter. Our design not only realizes the super-resolution effects of 0.74 to 0.75 times the diffraction limit in the wide field-of-view of nearly 180° for the first time to our knowledge but also compresses the device thickness to the subwavelength order in principle. The proposed ultra-thin sub-diffraction metalens with a wide field-of-view is expected to be applied in the fields of super-resolution fast scanning imaging, information detection, small target recognition, and so on.

Chirped pulse upconversion for femtosecond mid-infrared spectroscopy at 100 kHz.

We demonstrate that chirped pulse up-conversion (CPU), a method routinely used with systems based on 1-kHz Titanium:Sapphire lasers, can be extended to a repetition rate of 100 kHz with an Ytterbium diode-pumped femtosecond amplifier. Individual mid-infrared spectra can thus be measured directly in the near infrared using a fast CMOS linescan camera. After an appropriate Fourier processing, a spectral resolution of 1.1 cm-1 is reported, currently limited by our spectrometer. Additionally, we demonstrate the application of CPU to a pump-probe measurement of the vibrational relaxation in carboxy-hemoglobin, and we show that the combination of fast scanning and fast acquisition enables a straightforward removal of pump scattering interference.

Physical aging of a biodegradable alicyclic polymer: poly (pentamethylene trans-1,4-cyclohexanedicarboxylate)

Physical aging of poly (pentamethylene trans-1,4-cyclohexanedicarboxylate) (PPeCE), a biodegradable alicyclic polyester, was investigated using Fast Scanning Calorimetry (FSC), a recent calorimetric technique allowing to accelerate physical aging and study the associated relaxation processes at different aging temperatures in an experimentally-reasonable time scale. Different mechanisms were highlighted by varying the aging temperature on a temperature range of more than 60 °C. At aging temperatures well below the glass transition temperature, several relaxation mechanisms were evidenced, probably related to secondary relaxation processes (β relaxations). When the aging temperature approaches the glass transition temperature, the primary relaxation process (α relaxation) becomes predominant.

Assessing the efficacy of simulation-based education for paramedics in extended focused assessment with sonography for trauma under physician guidance

We investigated the effectiveness of simulation-based education in Focused Assessment with Sonography for Trauma (FAST) to increase the number of Emergency Medical Technicians (EMTs) capable of performing ultrasound examinations in vehicles under the guidance of a physician. Twenty-eight paramedics watched a 14-min video on the features of the ultrasound system, its use, and the scanning method for each part of the body. Each participant performed four FAST examinations using a portable ultrasound device, and the task performance was rated using the Task Specific Checklist (TSC) and Global Rating Scale (GRS). The time required for visualizing each examination site and each FAST was assessed. The mean time required for the first and fourth FAST was 144.6 ± 52.4 s and 90.5 ± 31.0 s, respectively. The time required for each test significantly decreased with repeated testing (p < 0.001). The time to complete FAST was significantly shortened for the pericardial cavity (33.4 ± 23.1/15.3 ± 10.6 s, p < 0.01), right thoracic cavity (25.2 ± 11.8/12.1 ± 8.3 s, p < 0.01), Morrison fossa (19.1 ± 10.8/10.8 ± 6.3 s, p < 0.05), and left thoracic cavity (19.0 ± 8.3/15.6 ± 8.3 s, p < 0.05). TSC and GRS scores were elevated, and all EMTs could obtain valid images. The combination of a brief video lecture and hands-on training significantly reduced the time required for FAST performance. Moreover, repeated practice enabled the EMTs to efficiently obtain accurate and clinically useful images.

High-Throughput Two-Photon 3D Printing Enabled by Holographic Multi-Foci High-Speed Scanning.

The emerging two-photon polymerization (TPP) technique enables high-resolution printing of complex 3D structures, revolutionizing micro/nano additive manufacturing. Various fast scanning and parallel processing strategies have been proposed to promote its efficiency. However, obtaining large numbers of uniform focal spots for parallel high-speed scanning remains challenging, which hampers the realization of higher throughput. We report a TPP printing platform that combines galvanometric mirrors and liquid crystal on silicon spatial light modulator (LCoS-SLM). By setting the target light field at LCoS-SLM's diffraction center, sufficient energy is acquired to support simultaneous polymerization of over 400 foci. With fast scanning, the maximum printing speed achieves 1.49 × 108 voxels s-1, surpassing the existing scanning-based TPP methods while maintaining high printing resolution and flexibility. To demonstrate the processing capability, functional 3D microstructure arrays are rapidly fabricated and applied in micro-optics and micro-object manipulation. Our method may expand the prospects of TPP in large-scale micro/nanomanufacturing.

Prehospital Extended FAST Exams Improve Clinical Decision Making by Helicopter EMS Crews: A Retrospective Case Series

Point of Care Ultrasound (POCUS) has seen increasing use in the prehospital environment over the last decade, primarily with the extended focused assessment with sonography in trauma (eFAST) exam. Previous studies have shown prehospital eFAST exams are feasible in the helicopter transport environment but have yet to demonstrate effects on clinical care. This retrospective case series identified 655 patients with blunt thoraco-abdominal trauma or concern for pneumothorax due to penetrating injury transported by a single helicopter EMS (HEMS) program over a two-year period after introducing POCUS. Of those patients, 258 received prehospital ultrasound which was reported to change clinical care in seven cases (2.7%, 95%-CI [1.1–5.5]). This was primarily through preventing unnecessary needle thoracostomy and initiating blood transfusion for treatment of hemorrhagic shock in cases where the degree of shock was unclear due to inconsistent vital signs. This study highlights the improvements in clinical care that may result from the introduction of eFAST exams in the prehospital environment.

Batch Fabrication of Microelectrode Arrays with Glassy Carbon Microelectrodes and Interconnections for Neurochemical Sensing: Promises and Challenges.

Flexible multielectrode arrays with glassy carbon (GC) electrodes and metal interconnection (hybrid MEAs) have shown promising performance in multi-channel neurochemical sensing. A primary challenge faced by hybrid MEAs fabrication is the adhesion of the metal traces with the GC electrodes, as prolonged electrical and mechanical stimulation can lead to adhesion failure. Previous devices with GC electrodes and interconnects made of a homogeneous material (all GC) demonstrated exceptional electrochemical stability but required miniaturization for enhanced tissue integration and chronic electrochemical sensing. In this study, we used two different methods for the fabrication of all GC-MEAs on thin flexible substrates with miniaturized features. The first method, like that previously reported, involves a double pattern-transfer photolithographic process, including transfer-bonding on temporary polymeric support. The second method requires a double-etching process, which uses a 2 µm-thick low stress silicon nitride coating of the Si wafer as the bottom insulator layer for the MEAs, bypassing the pattern-transfer and demonstrating a novel technique with potential advantages. We confirmed the feasibility of the two fabrication processes by verifying the practical conductivity of 3 µm-wide 2 µm-thick GC traces, the GC microelectrode functionality, and their sensing capability for the detection of serotonin using fast scan cyclic voltammetry. Through the exchange and discussion of insights regarding the strengths and limitations of these microfabrication methods, our goal is to propel the advancement of GC-based MEAs for the next generation of neural interface devices.

Charge trapping-induced current–voltage hysteresis in a squaraine nanowire mesh enables synaptic memristive functionality

Nanowires (NWs) composed of 2,4-bis[(4-diethylamino)-2-hydroxyphenyl] squaraine were prepared by evaporation-induced self-assembly (EISA). NWs were ∼560 nm wide (aspect ratios: 10–90). X-ray diffraction analysis indicated polymorphism (monoclinic/triclinic). Optical data reported the triclinic phase with energetic disorder. Given the favorable alignment of the Au work function and squaraine HOMO energy, symmetric, unipolar metal–insulator–metal devices were formed by the EISA of NW meshes on inter-digitated Au electrodes. Room temperature DC I–V characteristics displayed hysteretic I–V loops, indicating memristive behavior. At low bias, data indicated Ohmic transport with carrier extraction facilitated by thermionic emission. At high biases, devices exhibited space-charge-limited conduction in the presence of shallow traps. At 77 K, data indicated Ohmic transport at low bias with carrier extraction by thermionic emission while, at high biases, trap-limited space-charge-limited conduction in the presence of traps distributed in energy, with carrier extraction by Fowler–Nordheim tunneling, was observed. The I–V hysteresis was eliminated at 77 K and attenuated by fast scan rates at room temperature, suggesting that carrier trapping/de-trapping underpinned the hysteresis. In impedance measurements, the device response fitted a Randles equivalent circuit indicating purely electronic conduction. By applying voltage waveforms, I–V hysteresis and analog resistive switching (memristive) functionality were observed. Device conductance could be increased sweep by sweep, giving conductance tuning through distinct states, with wait time- or voltage-erase options, consistent with trap filling/emptying effects. Repeated erase–write–read of multiple distinct states over many voltage cycles during continuous use in air was demonstrated. Finally, synaptic functions, e.g., pulse-dependent plasticity, and short- to long-term memory transition, were successfully emulated.

Detecting reorganization in semicrystalline polymers during heating: Insights from Fast Scanning Chip Calorimetry coupled with real-time optical microscopy

Thermal behavior of semicrystalline polymers is notoriously complex due to the metastable nature of polymer crystals. This complexity is evidenced in the multiple melting endotherms frequently observed in the heating traces of various plastics, a phenomenon known as ‘multiple melting behavior’. Extensive research indicates that calorimetric analysis alone may not suffice to fully elucidate the processes occurring during thermal experiments. In this study, we introduce an experimental setup that integrates Fast Scanning Chip Calorimetry, or nanocalorimetry, with real-time polarized optical microscopy. This combination enables in-situ morphological observations during rapid heating/cooling experiments. The setup not only complements thermal analysis but also rivals the capabilities of fast in situ X-ray scattering experiments conducted at synchrotron sources. Our findings show that the obtained data help in identifying melting/recrystallization processes and, therefore, enable the determination of the critical heating rate above which reorganization processes during heating are kinetically bypassed. This ensures that the thermal events detected in calorimetric curves are exclusively due to the initial sample structure, without being influenced by any reorganization that may occur during the heating process.

Parallel Diffractive Multi‐Beam Pulsed‐Laser Ablation in Liquids Toward Cost‐Effective Gram Per Hour Nanoparticle Productivity

Nanoparticles (NPs) generated by pulsed‐laser ablation in liquids (PLAL) have benefited many key applications due to their versatility, enlarged surface area, and high purity. However, scaling up NPs production represents one of the main requisites to commercialize this technology. The established upscaling strategy demands high power and repetition rate laser source with fast scanning systems, which are not widely available and costly. Herein, a cost‐effective alternative is proposed, the addition of static diffractive optical elements to achieve parallel processing through the multi‐beam PLAL (MB‐PLAL). In MB‐PLAL, the optimum repetition rate is reduced to compensate laser energy splitting, hence achieving a higher interpulse distance, reducing pulse shielding, and increasing NPs productivity. MB‐PLAL with 11 beams reached a factor 4 productivity increase for iron–nickel alloy (Fe50Ni50) NPs compared to the single‐beam setup (0.4–1.6 g h−1), and a factor 3 increase for gold (Au) NPs (0.32–0.94 g h−1). The scalability of the proposed MB‐PLAL technique setup is confirmed by Au and Fe50Ni50 NPs productivity experiments using 1, 6, and 11 beams, showing a linear increase in productivity.

High-Speed Near-Surface Tracking for Fast Atomic Force Microscope Scan Switching Based on the Squeeze Film Damping Effect

Atomic force microscope (AFM) is a crucial metrology tool in the semiconductor industry. However, the bottleneck of the AFM technique is its low efficiency, primarily owing to the time-consuming scanning point switching. The traditional method takes approximately one minute for a single switching. To shield the probe and sample, the switching should first lift the probe a considerable distance, move it to the next point, and finally engage the probe slowly to the sample surface. We propose a near-surface tracking method for use in fast scanning point switching. The probe-sample distance was sensed by the squeeze air film damping effect, and the probe was kept at a small constant height during the switching via feedback control. The method can decrease the lift and engage distance from approximately 1 mm to 5 μm, which was two order of reduction; thereby shortening the single switching time from 45 s to 6.1 s, which is an 87% reduction. Generally, the fast switching method can improve the measurement efficiency of the existing AFM working in the air, but it can not be used in liquid and vacuum. Furthermore, the proposed squeeze film damping effect based distance sensing method can be applied in various fields, such as vibration sensing and temperature drift measurement.

Correcting synthetic MRI contrast-weighted images using deep learning

Synthetic magnetic resonance imaging (MRI) offers a scanning paradigm where a fast multi-contrast sequence can be used to estimate underlying quantitative tissue parameter maps, which are then used to synthesize any desirable clinical contrast by retrospectively changing scan parameters in silico. Two benefits of this approach are the reduced exam time and the ability to generate arbitrary contrasts offline. However, synthetically generated contrasts are known to deviate from the contrast of experimental scans. The reason for contrast mismatch is the necessary exclusion of some unmodeled physical effects such as partial voluming, diffusion, flow, susceptibility, magnetization transfer, and more. The inclusion of these effects in signal encoding would improve the synthetic images, but would make the quantitative imaging protocol impractical due to long scan times. Therefore, in this work, we propose a novel deep learning approach that generates a multiplicative correction term to capture unmodeled effects and correct the synthetic contrast images to better match experimental contrasts for arbitrary scan parameters. The physics inspired deep learning model implicitly accounts for some unmodeled physical effects occurring during the scan. As a proof of principle, we validate our approach on synthesizing arbitrary inversion recovery fast spin-echo scans using a commercially available 2D multi-contrast sequence. We observe that the proposed correction visually and numerically reduces the mismatch with experimentally collected contrasts compared to conventional synthetic MRI. Finally, we show results of a preliminary reader study and find that the proposed method statistically significantly improves in contrast and SNR as compared to synthetic MR images.

Caged Zn2+ Photolysis in Zebrafish Whole Brains Reveals Subsecond Modulation of Dopamine Uptake.

Free, ionic zinc (Zn2+) modulates neurotransmitter dynamics in the brain. However, the sub-s effects of transient concentration changes of Zn2+ on neurotransmitter release and uptake are not well understood. To address this lack of knowledge, we have combined the photolysis of the novel caged Zn2+ compound [Zn(DPAdeCageOMe)]+ with fast scan cyclic voltammetry (FSCV) at carbon fiber microelectrodes in live, whole brain preparations from zebrafish (Danio rerio). After treating the brain with [Zn(DPAdeCageOMe)]+, Zn2+ was released by application of light that was gated through a computer-controlled shutter synchronized with the FSCV measurements and delivered through a 1 mm fiber optic cable. We systematically optimized the photocage concentration and light application parameters, including the total duration and light-to-electrical stimulation delay time. While sub-s Zn2+ application with this method inhibited DA reuptake, assessed by the first-order rate constant (k) and half-life (t1/2), it had no effect on the electrically stimulated DA overflow ([DA]STIM). Increasing the photocage concentration and light duration progressively inhibited uptake, with maximal effects occurring at 100 μM and 800 ms, respectively. Furthermore, uptake was inhibited 200 ms after Zn2+ photorelease, but no measurable effect occurred after 800 ms. We expect that application of this method to the zebrafish whole brain and other preparations will help expand the current knowledge of how Zn2+ affects neurotransmitter release/uptake in select neurological disease states.

Fast Ultrasound Scanning is a Rapid, Sensitive, Precise and Cost-Effective Method to Monitor Tumor Grafts in Mice

In preclinical studies, accurate monitoring of tumor dynamics is crucial for understanding cancer biology and evaluating therapeutic interventions. Traditional methods like caliper measurements and bioluminescence imaging (BLI) have limitations, prompting the need for improved imaging techniques. This study introduces a fast-scan high-frequency ultrasound (HFUS) protocol for the longitudinal assessment of syngeneic breast tumor grafts in mice, comparing its performance with caliper, BLI measurements and with histological analysis. The E0771 mammary gland tumor cell line, engineered to express luciferase, was orthotopically grafted into immunocompetent C57BL/6 mice. Tumor growth was monitored longitudinally at multiple timepoints using caliper measurement, HFUS, and BLI, with the latter two modalities assessed against histopathological standards post-euthanasia. The HFUS protocol was designed for rapid, anesthesia-free scanning, focusing on volume estimation, echogenicity, and necrosis visualization. All mice developed tumors, only 20.6% were palpable at day 4. HFUS detected tumors as small as 2.2 mm in average diameter from day 4 post-implantation, with an average scanning duration of 47 s per mouse. It provided a more accurate volume assessment than caliper, with a lower average bias relative to reference tumor volume. HFUS also revealed tumor necrosis, correlating strongly with BLI in terms of tumor volume and cellularity. Notable discrepancies between HFUS and BLI growth rates were attributed to immune cell infiltration. The fast HFUS protocol enables precise and efficient tumor assessment in preclinical studies, offering significant advantages over traditional methods in terms of speed, accuracy, and animal welfare, aligning with the 3R principle in animal research.

Accuracy of FAST in detecting intraabdominal bleeding in major trauma with pelvic and/or acetabular fractures: a retrospective cohort study

PurposeThe Focused Assessment with Sonography for Trauma (FAST) is a tool to rapidly detect intraabdominal and intrapericardial fluid with point-of-care ultrasound. Previous studies have questioned the role of FAST in patients with pelvic fractures. The aim of the present study was to assess the accuracy of FAST to detect clinically significant intraabdominal hemorrhage in patients with pelvic fractures.MethodsWe included all consecutive patients with pelvic and/or acetabular fractures treated our Level 1 trauma center from 2009–2020. We registered patient and fracture characteristics, FAST investigations and CT descriptions, explorative laparotomy findings, and transfusion needs. We compared FAST to CT and laparotomy findings, and calculated true positive and negative findings, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).ResultsWe included 389 patients. FAST had a sensitivity of 75%, a specificity of 98%, a PPV of 84%, and a NPV of 96% for clinically significant intraabdominal bleeding. Patients with retroperitoneal hematomas were at increased risk for laparotomy both because of True-negative FAST and False-positive FAST.ConclusionFAST is accurate to identify clinically significant intraabdominal blood in patients with severe pelvic fractures and should be a standard asset in these patients. Retroperitoneal hematomas challenge the FAST interpretation and thus the decision making when applying FAST in patients with pelvic fractures.

Mechanism and evaluation method of stress corrosion susceptibility of 904L stainless steel with optimized structure in seawater

The stress corrosion cracking (SCC) and the electrochemical behavior of 904 L stainless steel in a simulated seawater environment were investigated using slow strain rate testing (SSRT), electrochemical polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) curves. The sensitive potential range of 904 L stainless steel was determined by the fast and slow scan potential polarization curve, is − 950 mVSCE ∼ 270 mVSCE. Moreover, with the negative shift of applied potential, the toughness fracture characteristic of the three kinds of steel is reduced, and the sensitization state steel is the most obvious reduction. Finally, a practical formula for evaluating the SCC susceptibility of 904 L stainless steel was developed by integrating data from SSRT and fast and slow scan polarization curves.

Continuous cooling and isothermal solidification analysis of AlSi10Mg using differential fast scanning calorimetry

This study investigates the solidification process of individual micro-sized AlSi10Mg particles using continuous cooling and isothermal differential fast scanning calorimetry (DFSC) methods at a range of cooling rates (from 500 K/s to 50,000 K/s) and temperatures (from 562 °C to 502 °C). The solidification microstructure consists of fine α-Al dendrites and (α-Al + Si) eutectics. Both dendrite arm spacing and eutectic spacing decrease with increasing cooling rate, as well as decreasing solidification temperature. The continuous cooling treatment exhibits finer microstructures compared to those observed in the isothermal treatment in the similar solidification temperature range. Overall, this study highlights the effectiveness of the DFSC methods, along with microstructure characterization, in analyzing the solidification process of individual powder particles over a wide range of cooling rates and temperatures.

Investigation of the isothermal curing and glass transition behaviors of epoxy–imidazole systems

The isothermal curing behavior of an epoxy–imidazole system was investigated through thermal, mechanical, and compositional analyses. Precise control over temperature and time afforded the monitoring of the progression of the curing reaction and enthalpy relaxation via fast scanning calorimetry. The real-time tracking of the glass transition temperature (Tg) during isothermal curing revealed a temperature-dependent relationship between Tg and thermally estimated conversion, distinct from epoxy–amine systems. Unlike previous research suggesting plasticization through cyclic-compound formation in epoxy–imidazole systems, such compounds were not detected in the early curing stages in this study. Furthermore, an endothermic reaction from imidazole regeneration was suggested to overlap with the main exothermic reaction of polymerization. Therefore, assessing thermally estimated conversion in the intermediate curing stage through differential scanning calorimetry was deemed practically impossible for epoxy–imidazole systems. The Tg values of resins with different thermal histories were equal after complete curing under high-temperature/long-duration conditions.

Influence of cross-link density on the non-isothermal crystallization kinetics of polybutylene terephthalate

Kinetics of crystallization of the samples of cross-linked polybutylene terephthalate with different cross-link densities was studied experimentally using conventional differential scanning calorimetry (cooling rates 5 to 40 K·min–1) and fast scanning calorimetry (cooling rates 0.5 to 5000 K·s–1). The samples were obtained by copolycondensation of terephthaloyl chloride, 1,4-butanediol, and glycerol. The cross-linking degree was characterized using 1H NMR spectroscopy. An increase of the number of glycerol cross-links in polymer leads to a decrease in the crystallization and melting temperatures and suppression of crystallization process. The critical rate of crystallization decreases monotonically with increasing cross-linking degree from 2700 K·s–1 for linear polybutylene terephthalate to 110 K·s–1 for the sample with 270 mol·m–3 cross-link density. At the cross-link densities higher than 270 mol·m–3, the polymer does not crystallize even at 5 K·min–1 cooling rate. The observed dependence of the cold crystallization enthalpy on the previous cooling rate suggests that the homogeneous nuclei formation process also slows down with an increase in the cross-linking degree.