Background
Photon-counting detector computed tomography (PCD-CT) has the potential to provide superior image quality compared to energy-integrating detector computed tomography (EID-CT). We compared ...the two systems for elbow imaging in off-center arm positioning, 90° flexion, and cast fixation in a simulated post-trauma setting.
Methods
The institutional review board approved the study protocol. In a cadaver study, an olecranon fracture was artificially created in ten whole arm specimens. Two different scanning positions were evaluated: (a) arm overhead; and (b) arm on top of the abdomen of a whole-body phantom. The ultra-high resolution mode with three dose protocols and two reconstruction kernels was applied. Two blinded radiologists independently evaluated fracture and trabecular bone delineation. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and cortical sharpness measurements were performed. Cohen κ correlations, Mann-Whitney
U
and Wilcoxon signed rank tests were used. A
p
value lower than 0.05 was considered statistically significant.
Results
Dose-equivalent PCD-CT scans were rated better for fracture and trabecular bone evaluation (
p
< 0.001). SNR, CNR, and cortical sharpness were higher for all diagnostic (Br76) PCD-CT images (
p
< 0.001). The arm position had less effect on image quality in the PCD-CT compared to the EID-CT. The use of a sharp bone kernel (Br89) improved image quality ratings for PCD-CT. In the low-dose scan mode, PCD-CT resulted in more diagnostic scans (75%) compared to EID-CT (19%).
Conclusions
PCD-CT provided superior objective and subjective image quality for fracture and trabecular bone structures delineation of the elbow compared to EID-CT in a typical post-trauma setting.
Key points
• Photon-counting detector computed tomography (PCD-CT) preserved high image quality in elbow imaging with off-center positions.
• PCD-CT was advantageous for bone evaluation in trauma elbows.
• PCD-CT ultra-high-resolution mode and very sharp reconstruction kernels facilitated higher image quality.
Biodiversity conservation in rangeland environments is often addressed by removing livestock, but inconsistent responses by biota mean that the efficacy of this form of management is hotly debated. ...Reasons for this inconsistency include the usually short duration and small spatial scale of manipulations compared to the area of grazing properties, as well as divergent responses amongst biota. In low-productivity arid environments, the pulse-reserve dynamic also complicates the outcome of manipulations. Here, we tested and extended these ideas in a heterogeneous desert environment in central Australia that consists of small patches of open woodland (gidgee) in a grassland (spinifex) matrix. Taking advantage of a controlled property-scale removal of cattle, and a rain event that stimulated productivity, we first quantified differences in the vegetation and small vertebrates of these two habitats, and then tracked the diversity, composition, and abundance of these biota for 6-19 months post-rain. We predicted that the two habitats would differ in the structure, composition, and reproductive output of their constituent plant species. We predicted also that the effects of cattle removal would interact with these habitat differences, with the abundance, richness, and diversity of small mammals and reptiles differing across habitats and grazing treatments. As anticipated, plant species composition in woodland was distinct from that in grassland and varied over time. The effects of cattle removal were habitat specific: Plant composition responded to de-stocking in woodland, but not in grassland; flowers were more abundant, and palatable plant cover also was greater following cessation of grazing pressure. The responses of small mammals but not reptiles showed some accord with our predictions, varying over time but inconsistently with treatment, and perhaps reflected high variability in capture success. We conclude that the timing and length of sampling are important when evaluating the responses of biota to livestock removal, as is the inclusion of all key habitats in the sampling regime.
To test the hypothesis of equal or even superior applicability and accuracy of a fully integrated, laser-based computed tomography (CT) navigation system compared with conventional CT guidance for ...percutaneous interventions.
CT-guided punctures were first performed in phantoms. Four radiologists with different experience levels (2 residents (L.B., C.D.) and 2 board-certified radiologists (B.M., K.R.) performed 48 punctures using both conventional image-guided and laser-guided approaches. Subsequently, 12 punctures were performed in patients during a clinical pilot trial. Phantom targets required an in-plane or a single-/double-angulated, out-of-plane approach. Planning and intervention time, control scan number, radiation exposure, and accuracy of needle placement (measured by deviation of the needle tip to the designated target) were assessed for each guidance technique and compared (Mann-Whitney U test and t test). Patient interventions were additionally analyzed for applicability in a clinical setting.
The application of laser guidance software in the phantom study and in 12 human patients in a clinical setting was both technically and clinically feasible in all cases. The mean planning time (P = .009), intervention time (P = .005), control scan number (P < .001), and radiation exposure (P = .013) significantly decreased for laser-navigated punctures compared with those for conventional CT guidance and especially in punctures with out-of-plane-trajectories. The accuracy significantly increased for laser-guided interventions compared with that for conventional CT (P < .001).
Interventional radiologists with differing levels of experience performed faster and more accurate punctures for out-of-plane trajectories in the phantom models, using a new, fully integrated, laser-guided CT software and demonstrated excellent clinical and technical success in initial clinical experiments.
Government is the custodian of the most critical (and limited) factor of production, namely, land. Assuring the security of tenure, arbitrating disputes, and facilitating the transfer or sales of ...titles renders the land market more efficient and less volatile, attracting investors and promoting sustainable urban development. Land tenure security is also a critical government service that has repercussions on agricultural productivity, housing development, business investment, and the development of urban areas. However, land administration is mired in corruptive practices, elite capture, and inefficient allocation. Globally, only 24% of rural areas are mapped (46 in urban areas), with approximately the same percentage registered, that is, 22%. In Africa, only about 14% of rural land is formally recorded in a public register. Land tenure security can take a variety of forms depending on national regulatory frameworks that allocate land and specify its use. Success stories include transferable user certificates in China and individual land titles in Rwanda. Systematic evaluation of the evidence on tenure programs demonstrates that improved tenure security increases agricultural output (40% on average), increases urban land values (25% on average), and increases household welfare (15% on average). Other observed country-specific benefits include additional years of schooling, better academic performance, access to credit, reforestation, and improved household nutrition. The costs of establishing tenure security in Sub-Saharan Africa include the separate costs of rural (US$ 3 billion) and urban (US$ 2.2 billion) land registration; the cost of digitizing land registries and information to improve efficiency and transparency (US$ 880 million), the cost of strengthening institutions and systems to resolve land disputes and manage expropriations (US$ 960 million) over a ten-year implementation period, and land administration operations and land records maintenance over 30 years (US$ 64 billion). The net present value (8%) of costs is US$ 21.7 billion for rural land tenure and US$ 5.3 billion for urban areas. The benefits of rural land registration were based on the observed 15% household wealth effect noted in the literature. The net present value (8%) of a 30-year benefits stream is US$ 396 billion. The benefit–cost ratio of completing and modernizing land registration and improving land administration coverage and effectiveness in rural Sub-Saharan Africa is 18. The benefits of urban land registration were based on the average 25% increase in property values observed in the literature. Using housing prices for the 20 largest, Sub-Saharan African countries, the net present value (8%) of the benefits over a 30-year period is US$ 237 billion, yielding a benefit–cost ratio of 45 when the average housing price is used. When the population-weighted housing price is used, benefits are valued at US$ 160 billion, yielding a benefit–cost ratio of 30.
The primary mechanism for eliminating synaptically released glutamate is uptake by astrocytes. In the present study, we examined whether traumatic brain injury (TBI) affects the cellular expression ...of glutamate transporters EAAT1 and EAAT2. Morphometrical immunohistochemical analysis demonstrated a predominant expression of EAAT1 and EAAT2 in astrocytes of normal human neocortex (n = 10). Following traumatic injury of human brain (n = 55), the number of EAAT2-positive cells was decreased for a prolonged survival period within the traumatized neocortex and the pericontusional region. GFAP-positive astrocytes decreased in number within the first 24 h. Thereafter, the number of GFAP-positive astrocytes increased again, indicating formation of reactive gliosis. Double immunofluorescence examinations revealed a reduction in absolute numbers of GFAP-positive astrocytes coexpressing EAAT1 or EAAT2 at survival times up to 7 days. In addition, the relative fractions of astrocytes coexpressing glutamate transporters decreased following TBI. We conclude that the posttraumatic reduction in cellular EAAT 1 and EAAT2 expression is predominantly due to degeneration of astrocytes and to downregulation in surviving astrocytes. Our results support the view that reduced glutamate uptake by astrocytes contributes to posttraumatic elevation of extracellular glutamate in humans.
Deep Neural Network (DNN), which can model a long-span, intricate transform compactly with a deep-layered structure, has recently been investigated for parametric TTS synthesis with a fairly large ...corpus (33,000 utterances) 6. In this paper, we examine DNN TTS synthesis with a moderate size corpus of 5 hours, which is more commonly used for parametric TTS training. DNN is used to map input text features into output acoustic features (LSP, F0 and V/U). Experimental results show that DNN can outperform the conventional HMM, which is trained in ML first and then refined by MGE. Both objective and subjective measures indicate that DNN can synthesize speech better than HMM-based baseline. The improvement is mainly on the prosody, i.e., the RMSE of natural and generated F0 trajectories by DNN is improved by 2 Hz. This benefit is likely from the key characteristics of DNN, which can exploit feature correlations, e.g., between F0 and spectrum, without using a more restricted, e.g. diagonal Gaussian probability family. Our experimental results also show: the layer-wise BP pre-training can drive weights to a better starting point than random initialization and result in a more effective DNN; state boundary info is important for training DNN to yield better synthesized speech; and a hyperbolic tangent activation function in DNN hidden layers yields faster convergence than a sigmoidal one.
A cycle analysis model for an airbreathing, rotating detonation wave engine (RDE) is presented. The engine consists of a steady inlet system with an isolator which delivers air into an annular ...combustor. A detonation wave continuously rotates around the combustor with side relief as the flow expands towards the nozzle. A model for the side relief is used to find the pressure distribution around the combustor. Air and fuel enter the combustor when the rarefaction wave pressure behind the detonation front drops to the inlet supply pressure. To create a stable RDE, the inlet pressure is matched in a convergence process with the average combustor pressure by increasing the annulus channel radial width with respect to the isolator channel. Performance of this engine is considered using several parametric studies and compared with rocket-mode computational results. A hydrogen–air RDE reaches a specific impulse of 3800 s and can reach a flight speed of Mach 5.
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