Search Results (23)

A Labrador Retriever (4-year-old, castrated male) with signs of fatigue was diagnosed with an atrial septal defect at his primary veterinary clinic. Due to the uncertainty of this diagnosis, he was referred to the Tokyo University of Agriculture and Technology Animal Medical Center for further investigation. Transthoracic echocardiography performed on arrival showed an irregular blood flow from the left atrium (LA) to the right atrium (RA), yet no opening was found in the septum. An electrocardiogram (ECG)-gated computed tomography (CT) exam revealed a communication between the coronary sinus (CS) and the LA, causing a shunt between the LA and the RA. A diagnosis of unroofed coronary sinus syndrome (UCSS) was made. The dog’s condition was stable and plans to keep observations were made. This is the first case of UCSS diagnosed with an ECG-gated CT exam. Full article

Background: The burden of stroke is on the rise in low-income countries (LICs). Organized stroke care (OSC) is crucial for improving outcomes in LICs and is the very first step to reducing delays in diagnosis and treatment. We aim to evaluate delay times (DT) in accessing OSC at the national reference hospital of Mozambique, a LIC from southern Africa. Methods: An observational study based on consecutive case series of 59 stroke patients confirmed by computed tomography (CT) scans over a period of 3 months (May–July 2023). The total DT (from stroke onset to inward hospitalization) was the main outcome. Other specific DTs were analyzed including initial symptoms to arrival and admission (DT0), arrival to CT scans (DT1), arrival of laboratory results (DT2), and arrival to inward hospitalization (DT3). Results: The mean age was 61.9 (min 30–max 90) and 45.8% were female. The median total DT was 20 h. The median time DT0 was 10.6 h (interquartile range (IQR): 16.48). The median DT1 and DT2 were 4 h (IQR: 3.5) and 5 h (IQR: 2.6), respectively. The median DT3 was 10 h (IQR: 4). None of the patients were treated under a stroke code. Conclusions: This study reveals an unacceptable prehospital and in-hospital DT. Waiting for the CT scan contributed to a large proportion of the total DT, which among other factors can be explained by the absence of a stroke code and limited imaging capacity. These findings mirror disparities in stroke care seen in other LICs, where late presentation, scarce imaging, and limited specialized protocols are common. The urgent implementation of organized prehospital and in-hospital stroke pathways is needed in Maputo to improve outcomes. Full article

Preliminary tunnel surveys are essential for identifying geological hazards such as aquifers, faults, and karstic zones. While first-arrival tomography is effective for imaging shallow anomalies, traditional seismic sources face significant limitations in forested mountainous regions due to mobility, cost, and environmental impact. To address this, we deployed a seismic source delivered by an unmanned aerial vehicle (UAV) for a highway tunnel survey in Lijiang, China. The UAV system, paired with nodal geophones, enabled rapid, low-impact, and high-resolution data acquisition in rugged terrain. To enhance the weak far-offset refractions affected by near-surface attenuation, we applied supervirtual refraction interferometry (SVI), which significantly improved the signal-to-noise ratio and expanded the usable first-arrival dataset. The combined use of UAV excitation and SVI processing produced a high-precision P-wave velocity model through traveltime tomography, aligned well with borehole data. This model revealed the spatial distribution of weathered zones and bedrock interfaces, and allowed us to infer potential fracture zones. The results offer critical guidance for tunnel alignment and hazard mitigation in complex geological settings. Full article

Pavement materials like hot mix asphalt (HMA) and cold recycled mixes (CRMs) are typically considered isotropic. This study evaluates the anisotropy of a cold in-place recycled (CIR) material using the shear wave velocity (V_s) parameter. The piezoelectric ring actuator technique (P-RAT) is utilized to assess the V_s parameter in three directions in CIR slabs. Similarly, the ultrasonic pulse velocity (UPV) technique is employed to measure P-wave velocities. Both methods evaluate mechanical properties in multiple directions. Complex modulus tests are conducted to link velocities results to |E*| modulus. Finally, computed tomography (CT) scans are performed on the specimens in order to evaluate anisotropy resulting from aggregate alignment. The V_s obtained using P-RAT and the V_p from UPV indicate anisotropy, as the wave velocities differ across the three directions. Differences range from 0.6 to 11.6% in V_s, influenced by measurement location. UPV results are analysed in relation to the |E*| modulus master curves, demonstrating that the first peak arrival time for the P-wave corresponds with the master curve. CT scan analysis reveals that the aggregates tend to be more aligned in the direction of the compacting wheel’s displacement, which also highlights anisotropy. Full article

Seismic characterization of landslides offers the potential for developing high-resolution models on subsurface shear-wave velocity profile. However, seismic methods based on reflection processing are challenging to apply in such scenarios as a consequence of the disturbance to the often well-defined structural and stratigraphic layering by the landslide process itself. We evaluate the use of alternative seismic characterization methods based on elastic full waveform inversion (E-FWI) to probe the subsurface of a landslide complex in Majes, southern Peru, where recent agricultural development and irrigation activities have altered the hydrology and groundwater table and are thought to have contributed to increased regional landslide activities that present continuing sustainability community development challenges. We apply E-FWI to a 2D near-surface seismic data set for the purpose of better understanding the subsurface in the vicinity of a recent landslide location. We use seismic first-arrival travel-time tomography to generate the inputs required for E-FWI to generate the final high-resolution 2D compressional- and shear-wave (P- and S-wave) velocity models. At distances greater than 140 m from the cliff, the inverted models show a predominantly vertically stratified velocity structure with a low-velocity near-surface layer between 5–15 m depth. At distances closer than 140 m from the cliff, though, the models exhibit significantly reduced shear-wave velocities, stronger heterogeneity, and localized shorter wavelength structure in the top 20 m. These observations are consistent with those expected for a recent landslide complex; however, follow-on geotechnical analysis is required to confirm these assertions. Overall, the E-FWI seismic approach may be helpful for future landslide characterization projects and, when augmented with additional geophysical and geotechnical analyses, may allow for improved understanding of the hydrogeophysical properties associated with suspected ground-water-driven landslide activity. Full article

Subsurface characterization is crucial for geothermal energy exploration and production. Yet hydrothermal reservoirs usually reside in highly fractured and faulted zones where accurate characterization is very challenging because of low signal-to-noise ratios of land seismic data and lack of coherent reflection signals. We perform an active-source seismic characterization for the Blue Mountain geothermal field in Nevada using active seismic data to reveal the elastic medium property complexity and fault distribution at this field. We first employ an unsupervised machine learning method to attenuate groundroll and near-surface guided-wave noise and enhance coherent reflection and scattering signals from noisy seismic data. We then build a smooth initial P-wave velocity model based on an existing magnetotellurics survey result, and use 3D first-arrival traveltime tomography to refine the initial velocity model. We then derive a set of elastic wave velocities and anisotropic parameters using elastic full-waveform inversion, and obtain PP and PS images using elastic reverse-time migration. We identify major faults by analyzing the variations of seismic velocities and anisotropy parameters, and reveal mid- to small-scale faults by applying a supervised machine learning method to the seismic migration images. Our characterization reveals complex velocity heterogeneities and anisotropies, as well as faults, with a high spatial resolution. These results can provide valuable information for optimal placement of future injection and production wells to increase geothermal energy production at the Blue Mountain geothermal power plant. Full article

The ingestion of foreign bodies is a common cause for presentation in the emergency department by pediatric, adult, or elderly psychiatric patients. Swallowed foreign bodies sometimes represent a great challenge for surgeons due to the obstruction or perforation of the digestive tube’s upper or lower segments. Occasionally, the foreign bodies detected in the lower parts of the digestive tube (colon and rectum) could be introduced through the anal route with the risk of perforation of the rectum or sigmoid colon. In this report, we describe a unique case of a foreign body located in the sigmoid colon, where it arrived due to backstabbing and was retained for 7 years without acute symptoms. The 43-year-old male patient came to the emergency department with pain in the left iliac fossa. Before his presentation, a computerized tomography (CT) scan examination had suggested a foreign body. A surgical approach was decided. The surgery started as an exploratory laparoscopy and was converted to a xiphoid-pubic incision to extract the foreign body (a piece of glass about 8 cm long) through a sigmoid colotomy followed by a double-layer sigmoidorrhaphy. The postoperative evolution of the patient was uneventful. As far as we know, this is the first case of a patient with a foreign glass body positioned in the sigmoid colon that got there by stabbing and not by ingestion or introduced per anum. In conclusion, we suggest that aggressive behavior and abdominal wall penetration by different sharp objects should be considered when foreign bodies are detected in the abdomen. Full article

During the Development Phase of the U.S. Southwest Regional Partnership on Carbon Sequestration, supercritical CO₂ was continuously injected into the deep oil-bearing Morrow B formation of the Farnsworth Unit in Texas for Enhanced Oil Recovery (EOR). The project injected approximately 94 kilotons of CO₂ to study geologic carbon storage during CO₂-EOR. A three-dimensional (3D) surface seismic dataset was acquired in 2013 to characterize the subsurface structures of the Farnsworth site. Following this data acquisition, the baseline and three time-lapse three-dimensional three-component (3D-3C) vertical seismic profiling (VSP) data were acquired at a narrower surface area surrounding the CO₂ injection and oil/gas production wells between 2014 and 2017 for monitoring CO₂ injection and migration. With these VSP datasets, we inverted for subsurface velocity models to quantitatively monitor the CO₂ plume within the Morrow B formation. We first built 1D initial P-wave (V_p) and S-wave (V_s) velocity models by upscaling the sonic logs. We improved the deep region of the V_p and V_s models by incorporating the deep part of a migration velocity model derived from the 3D surface seismic data. We improved the shallow region of 3D V_p and V_s models using 3D traveltime tomography of first arrivals of VSP downgoing waves. We further improved the 3D baseline velocity models using elastic-waveform inversion (EWI) of the 3D baseline VSP upgoing data. Our advanced EWI method employs alternative tomographic and conventional gradients and total-variation-based regularization to ensure the high-fidelity updates of the 3D baseline V_p and V_s models. We then sequentially applied our 3D EWI method to the three time-lapse datasets to invert for spatiotemporal changes of V_p and V_s in the reservoir. Our inversion results reveal the volumetric changes of the time-lapse V_p and V_s models and show the evolution of the CO₂ plume from the CO₂ injection well to the oil/gas production wells. Full article

Although serious accidents remain the leading cause of pediatric mortality, protocols to orient diagnostic procedures towards a certain type of initial imaging are widely needed. Since 2007, we have performed whole-body magnetic resonance imaging (WBMR) and whole-body computed tomography (WBCT) for diagnoses of severely injured children. We retrospectively reviewed 134 WBMR and 158 WBCT in patients younger than 16 years that were performed at two trauma centers between 2007 and 2018. A higher Injury Severity Score (ISS) was found in WBCT vs. WBMR (10.6 vs. 5.8; p = 0.001), but without any significant difference in mortality. The WBMR was significantly preferred at younger ages (9.6 vs. 12.8 years; p < 0.001). The time between patient’s arrival until diagnosis was 2.5 times longer for WBCT (92.1 vs. 37.1 min; p < 0.001). More patients in the CT group received analgesic sedation and/or intubation at 37.3% vs. 21.6% in the MRI group. Of these patients, 86.4% (CT) and 27.6% (MRI) were already preclinically sedated (p < 0.001). Correspondingly, 72.4% of the patients were first sedated in-hospital for MRIs. In conclusion, WBMR is an alternative and radiation-free imaging method for high-energy-traumatized children. Although the selected diagnostics seemed appropriate, limitations regarding longer duration or additional analgesic sedation are present, and further studies are needed. Full article

Seismic imaging is now a well-established method in mineral exploration with many successful case studies. Seismic data are usually imaged in the time domain (post-stack or pre-stack time migration), but recently pre-stack depth imaging has shown clear advantages for irregular/sparse acquisitions and very complex targets. Here, we evaluate the effectiveness of both ray-based and wave-equation-based pre-stack depth imaging methodologies applied to crooked-line 2D seismic reflection profiles. Seismic data were acquired in the Kylylahti mining area in eastern Finland over severely folded, faulted and subvertical Kylylahti structure, and associated mineralization. We performed 3D ray-based imaging, i.e., industry-standard Kirchhoff migration and its improved version (coherency migration, CM), and wave-equation-based migration, i.e., reverse time migration (RTM) using a velocity model built from first-arrival traveltime tomography. Upon comparing the three different migrations against available geological data and models, it appeared that CM provided the least noisy and well-focused image, but failed to image the internal reflectivity of the Kylylahti formation. RTM was the only method that produced geologically plausible reflections inside the Kylylahti formation including a direct image of the previously known shallow massive sulfide mineralization. Full article

Accurate picking of seismic first arrivals is very important for first arrival travel time tomography, but the first arrivals appearing at far offsets are often more difficult to pick accurately due to the low signal-to-noise ratio (SNR). The conventional supervirtual refraction interferometry (SVI) method can improve the SNR of first arrivals to a certain extent; however, it is not suitable for seismic data that interfered by strong noise. In order to better process the first arrivals at far offsets with serious noise interference, we propose a modified method, in which SVI implemented in the Radon domain (RDSVI) due to the cross-correlation in the Radon domain have a better effect. According to the kinematic characteristics of first arrival refractions, SVI is performed in the linear Radon domain. Both synthetic data and field data demonstrate the proposed method can enhance the effective signal and attenuate the strong noise simultaneously, so as to significantly improve the SNR of the first arrival data. Meanwhile, the RDSVI method is tested on the first arrival data with missing traces, which proves that this method can overcome the influence of abnormal traces and is suitable for the reconstruction of sparsely sampled seismic data. Full article

Deep reflection seismic data are usually accompanied by large-offset data, and the accurate and rapid identification of the first arrivals of seismic records plays an important role in eliminating the effects of topography and other factors that increase with the increasing offsets. In this paper, we propose a method based on convolutional neural networks (CNNs) that can accurately identify the first arrivals of large-offset seismic data. A time window for linear dynamic correction was established to convert the raw seismic data into rectangular images so as to reduce the amount of invalid sample data and improve the training efficiency. In order to enhance the prediction effect of the far-offset first arrivals, we propose the strategy of adjusting the weight of the far-offset data to increase the weight of the far-offset data in the training dataset and, thus, to improve the first arrival accuracy. The manually picked first arrivals are used as labels and the input to the CNNs for training, and the full-offset first arrivals are the output. The travel time tomography velocity is modeled and compared based on the first arrivals obtained through manual picking, industrial software automatic picking, and CNN prediction. The results show that the application of CNNs to large-offset seismic datasets can help researchers to obtain the first arrivals at different offsets, while the inclusion of far-offset weights can effectively improve the modeling depth of the tomography inversion, and the accuracy of the results is high. Full article

In conventional cross-correlation (CC)-based wave-equation travel-time tomography, wrong source wavelets can result in inaccurate velocity inversion results, which is known as the source–velocity trade-off. In this study, an envelope travel-time objective function is developed for wave-equation tomography to alleviate the non-uniqueness and uncertainty due to wrong source wavelets. The envelope of a seismic signal helps reduce the waveform fluctuations/distortions caused by variations of the source time function. We show that for two seismic signals generated with different source wavelets, the travel-time shift calculated by cross-correlation of their envelopes is more accurate compared to that obtained by directly cross-correlating their waveforms. Then, the CC-based envelope travel-time (ET) objective function is introduced for wave-equation tomography. A new adjoint source has also been derived to calculate the sensitivity kernels. In the numerical inversion experiments, a synthetic example with cross-well survey is first given to show that compared to the traditional CC travel-time objective function, the ET objective function is relatively insensitive to source wavelet variations and can reconstruct the elastic velocity structures more reliably. Finally, the effectiveness and advantages of our method are verified by inversion of early arrivals in a practical seismic survey for recovering near-surface velocity structures. Full article

In this article, we describe in detail three seismic measurement campaigns based on refraction methods that we conducted at different sites in Bavaria, Germany. The measured data is published as an open data set. The particularity of this data set lies in its available ground truth information about each measurement site. Acquiring seismic data from sites with ground truth information is important for validation of seismic inversion algorithms. Since near-surface seismic field data with ground truth information is rather limited, we anticipate this data set to be a valuable contribution to the research community. For the measurements, three sites have been selected: (1) a gravel pit with a ground water layer, (2) a site above a highway tunnel and (3) a surface over underground tubes. The measurements have been conducted using line arrays of geophones, the Geode Seismograph from Geometrics Inc. and hammer strikes as seismic source. To obtain inversion results a travel time tomography based on first-arrivals within the software SeisImager is used. The inversion results show that we are able to image the ground water layer in the gravel pit, the highway tunnel and partly features of underground tubes. Furthermore, the results coincide with available ground truth information about the measurement sites. This paper summarizes the measurement campaigns and the respective data sets obtained through these campaigns. The data have been published by the authors as an open data set under the license CC BY 4.0 on figshare to make it available to the research community for validation of seismic data processing and inversion techniques. Full article

The genesis of deeply buried deposits in the Duobaoshan ore district, the largest porphyry-related Cu-Mo-Au ore field in northeastern China, is not well understood and their exploration is lacking because the fine velocity structure of this region is not comprehensively understood. Herein, first-arrival seismic travel times were picked along a deep seismic reflection profile and inverted using the tomographic method to obtain a detailed velocity profile of the upper 2900 m of the crust beneath this region. The profile showed that the velocity varied from 1900 to 6100 m/s and that the crust was subdivided into five parts by two low-velocity (2500–4000 m/s) blocks. Based on previous studies, the boundaries between the high-speed and low-speed bodies were interpreted as hidden fractures, and the 5000–6100 m/s parts were interpreted as concealed granite bodies in these sections. Porphyry copper deposits in the Duobaoshan ore district were related to the occulted granite bodies, and epithermal Au deposits were associated with the occulted fracture zones. Comprehensive evaluation of hydrothermal activity, regional magnetic anomalies, and deposit distribution indicated that the hidden fractures served as channels for ore-related magmas. Combining previous research on the Duobaoshan ore district with our results of the high-velocity interface, we infer that the prospecting range of the Tongshan deposit is below the depth of 1000 m. Full article