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Scientific Reports Jan 2023A novel laboratory platform has been designed and built for the irradiation of a plasma crystal (PC) with an electron beam (e-beam) having an energy around 10 keV and a...
A novel laboratory platform has been designed and built for the irradiation of a plasma crystal (PC) with an electron beam (e-beam) having an energy around 10 keV and a current of tens of milliamperes. The pulsed e-beam collimated to a few millimeter-size spot is aimed at a crystal made of dust particles levitated in a radio-frequency (RF) plasma. The platform consists of three vacuum chambers connected in-line, each with different utility: one for generating free electrons in a pulsed hollow-anode Penning discharge, another for the extraction and acceleration of electrons at [Formula: see text] kV and for focusing the e-beam in the magnetic field of a pair of circular coils, and the last one for producing PCs above a RF-driven electrode. The main challenge is to obtain both a stable e-beam and PC by insuring appropriate gas pressures, given that the e-beam is formed in high vacuum ([Formula: see text] Torr), while the PC is produced at much higher pressures ([Formula: see text] Torr). The main diagnostics include a high speed camera, a Faraday cup and a Langmuir probe. Two applications concerned with the creation of a pair of dust flow vortices and the rotation of a PC by the drag force of the e-beam acting on the strongly coupled dust particles are presented. The dust flow can become turbulent as demonstrated by the energy spectrum, featuring vortices at different space scales.
PubMed: 36653432
DOI: 10.1038/s41598-023-28152-8 -
Optics Letters Jan 2023A photoelectrochemical (PEC) cell produces hydrogen energy using solar energy and an electrochemical reaction. In the hydrogen production process with water...
A photoelectrochemical (PEC) cell produces hydrogen energy using solar energy and an electrochemical reaction. In the hydrogen production process with water decomposition, electrons move from the anode to the cathode, and by measuring the current value at this time, the PEC cell can generate hydrogen and function as an image sensor at the same time. Due to the characteristics of the PEC cell that can perform both functions simultaneously, it can be applied as a device that can detect and respond to the surrounding environment without the need for an observation system such as a camera. We present the imaging performance of PEC cells. The effectiveness of the experiment was confirmed by applying the PEC cells to integral imaging, one of the three-dimensional (3D) imaging techniques.
Topics: Electrochemical Techniques; Imaging, Three-Dimensional; Solar Energy; Hydrogen
PubMed: 36638454
DOI: 10.1364/OL.476115 -
Journal of Structural Biology: X 2023Advances in electron detection have been essential to the success of high-resolution cryo-EM structure determination. A new generation of direct electron detector called...
Advances in electron detection have been essential to the success of high-resolution cryo-EM structure determination. A new generation of direct electron detector called the Apollo, has been developed by Direct Electron. The Apollo uses a novel event-based MAPS detector custom designed for ultra-fast electron counting. We have evaluated this new camera, finding that it delivers high detective quantum efficiency (DQE) and low coincidence loss, enabling high-quality electron counting data acquisition at up to nearly 80 input electrons per pixel per second. We further characterized the performance of Apollo for single particle cryo-EM on real biological samples. Using mouse apoferritin, Apollo yielded better than 1.9 Å resolution reconstructions at all three tested dose rates from a half-day data collection session each. With longer collection time and improved specimen preparation, mouse apoferritin was reconstructed to 1.66 Å resolution. Applied to a more challenging small protein aldolase, we obtained a 2.24 Å resolution reconstruction. The high quality of the map indicates that the Apollo has sufficiently high DQE to reconstruct smaller proteins and complexes with high-fidelity. Our results demonstrate that the Apollo camera performs well across a broad range of dose rates and is capable of capturing high quality data that produce high-resolution reconstructions for large and small single particle samples.
PubMed: 36578473
DOI: 10.1016/j.yjsbx.2022.100080 -
Annals of Nuclear Cardiology 2022The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic... (Review)
Review
The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic coronary artery disease (CAD). One of the implications of this trial is the importance of close patient follow-up. To improve patient prognosis, evaluation of the residual extent of ischemia after treatment may be important because several studies have shown a close relationship between residual ischemia and cardiac events. For this assessment, myocardial perfusion single-photon emission computed tomography (MPS) has been utilized and is almost the only modality. Among the participants in the ISCHEMIA trial, more than 10% were excluded due to the absence of obstructive CAD. The pathophysiology of ischemia without non-obstructive coronary artery disease (INOCA) is gaining recognition; however, diagnosis is difficult, except for the assessment of myocardial flow reserve (MFR). Myocardial perfusion positron emission tomography (PET) is the most common modality for noninvasive evaluation of MFR; however, its availability in Japan is limited. For a breakthrough in this situation, a novel gamma camera with a cadmium zinc telluride (CZT) semiconductor might be one of the solutions that enables the evaluation of MFR with a commercially available perfusion tracer, similar to PET. Another solution is a novel PET tracer with a longer half-life. Clinical trials with F labeled perfusion agents have been initiated in Japan, and in a few years, delivery of this perfusion tracer will result in more frequent and easier assessment of MFR.
PubMed: 36540172
DOI: 10.17996/anc.22-00168 -
Radiological Physics and Technology Mar 2023
Topics: Gamma Cameras; Nuclear Medicine; Radionuclide Imaging; Physics; Positron-Emission Tomography
PubMed: 36534344
DOI: 10.1007/s12194-022-00693-z -
Cancer Imaging : the Official... Dec 2022With the rapid emergence of extended Field-of-View PET-cameras several new applications for radiopharmaceuticals become within reach. Main reason is the significant... (Review)
Review
With the rapid emergence of extended Field-of-View PET-cameras several new applications for radiopharmaceuticals become within reach. Main reason is the significant increase of the sensitivity of the PET-camera so that much less radioactivity can be administered. Issues that that hampered development or use of PET-radiopharmaceuticals become realistic again. Molar activity requirements can become less strict. New low-yielding radiochemistry methods may become applicable. Carbon-11 labelled compounds can revive and potentially be shipped to nearby PET-facilities. PET-radiopharmaceuticals with slow kinetics in comparison to their half life can still be used. As additional infrastructure and equipment will likely remain unchanged and keep the same sensitivity therefore there will be issues with kinetic modelling requiring analysis of plasma or metabolites samples with lower count rate. Besides the potential revival of failed radiopharmaceuticals, novel challenges are ahead to develop novel radiochemistry based on thus far unsuitable (low yielding or time consuming) reactions.
Topics: Humans; Radiopharmaceuticals; Positron Emission Tomography Computed Tomography; Cemeteries; Positron-Emission Tomography
PubMed: 36529738
DOI: 10.1186/s40644-022-00510-1 -
Advances in Experimental Medicine and... 2022Solid tumours may present hypoxic sub-regions of increased radioresistance. Hypoxia quantification requires of clinically implementable, non-invasive and reproducible...
Solid tumours may present hypoxic sub-regions of increased radioresistance. Hypoxia quantification requires of clinically implementable, non-invasive and reproducible techniques as positron emission tomography (PET). PET-based dose painting strategies aiming at targeting those sub-regions may be limited by the resolution gap between the PET imaging resolution and the smaller scale at which hypoxia occurs. The ultimate benefit of the usage of dose painting may be reached if the planned dose distribution can be performed and delivered consistently. This study aimed at assessing the feasibility of two PET-based dose painting strategies using two beam qualities (photon or proton beams) in terms of tumour control probability (TCP), accounting for underlying oxygen distribution at sub-millimetre scale.A tumour oxygenation model at submillimetre scale was created consisting of three regions with different oxygen partial pressure distributions, being hypoxia decreasing from core to periphery. A published relationship between uptake and oxygen partial pressure was used and a PET image of the tumour was simulated. The fundamental effects that limit the PET camera resolution were considered by processing the uptake distribution with a Gaussian 3D filter and re-binning to a PET image voxel size of 2 mm. Prescription doses to overcome tumour hypoxia were calculated based on the processed images, and planned using robust optimisation.Normal tissue complication probabilities and TCPs after the delivery of the planned doses were calculated for the nominal plan and the lowest bounds of the dose volume histograms resulting from the robust scenarios planned, taking into account the underlying oxygenation at submillimetre scale. Results were presented for the two beam qualities and the two dose painting strategies: by contours (DPBC) and by using a voxel grouping-based approach (DPBOX).In the studied case, DPBOX outperforms DPBC with respect to TCP regardless the beam quality, although both dose painting strategy plans demonstrated robust target coverage.
Topics: Humans; Radiotherapy Planning, Computer-Assisted; Protons; Feasibility Studies; Oxygen; Positron-Emission Tomography; Neoplasms; Hypoxia; Probability; Radiotherapy Dosage
PubMed: 36527641
DOI: 10.1007/978-3-031-14190-4_37 -
Optics Express Nov 2022A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of...
A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 10 W/cm, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.
PubMed: 36523045
DOI: 10.1364/OE.475945 -
JACC. Cardiovascular Imaging Dec 2022For molecular imaging of atherosclerotic vessel wall activity, tracer kinetic analysis may yield improved contrast versus blood, more robust quantitative parameters, and...
BACKGROUND
For molecular imaging of atherosclerotic vessel wall activity, tracer kinetic analysis may yield improved contrast versus blood, more robust quantitative parameters, and more reliable characterization of systems biology.
OBJECTIVES
The authors introduce a novel dynamic whole-body positron emission tomography (PET) protocol that is enabled by rapid continuous camera table motion, followed by reconstruction of parametric data sets using voxel-based Patlak graphical analysis.
METHODS
Twenty-five subjects were prospectively enrolled and underwent dynamic PET up to 90 minutes after injection of 2-[F]fluoro-2-deoxy-D-glucose (FDG). Two sets of images were generated: 1) the established standard of static standardized uptake value (SUV) images; and 2) parametric images of the metabolic rate of FDG (MR) using the Patlak plot-derived influx rate. Arterial wall signal was measured and compared using the volume-of-interest technique, and its association with hematopoietic and lymphoid organ signal and atherosclerotic risk factors was explored.
RESULTS
Parametric MR images provided excellent arterial wall visualization, with elimination of blood-pool activity, and enhanced focus detectability and reader confidence. Target-to-background ratio (TBR) from MR images was significantly higher compared with SUV images (2.6 ± 0.8 vs 1.4 ± 0.2; P < 0.0001), confirming improved arterial wall contrast. On MR images, arterial wall signal showed improved correlation with hematopoietic and lymphoid organ activity (spleen P = 0.0009; lymph nodes P = 0.0055; and bone marrow P = 0.0202) and increased with the number of atherosclerotic risk factors (r = 0.49; P = 0.0138), where signal from SUV images (SUVP = 0.9754; TBRP = 0.8760) did not.
CONCLUSIONS
Absolute quantification of MR is feasible for arterial wall using dynamic whole-body PET imaging. Parametric images provide superior arterial wall contrast, and they might be better suited to explore the relationship between arterial wall activity, systemic organ networks, and cardiovascular risk. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of arterial wall disease.
Topics: Humans; Kinetics; Predictive Value of Tests; Positron-Emission Tomography
PubMed: 36481078
DOI: 10.1016/j.jcmg.2022.05.008 -
The Review of Scientific Instruments Nov 2022The Gamma Ray Imager (GRI) is a pinhole camera providing 2D imaging of MeV hard x-ray (HXR) bremsstrahlung emission from runaway electrons (REs) over the poloidal cross...
The Gamma Ray Imager (GRI) is a pinhole camera providing 2D imaging of MeV hard x-ray (HXR) bremsstrahlung emission from runaway electrons (REs) over the poloidal cross section of the DIII-D tokamak. We report a series of upgrades to the GRI expanding the access to RE scenarios from the diagnosis of a trace amount of REs to high flux HXR measurements during the RE plateau phase. We present the implementation of novel gamma ray detectors based on LYSO and YAP crystals coupled to multi-pixel photon counters, enabling a count rate in excess of 1 MHz. Finally, we highlight new insights into the RE physics discovered during the current quench and RE plateau phase experiments as the result of these upgrades.
PubMed: 36461541
DOI: 10.1063/5.0101690