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Calcraft, Thomas, and Peter B. Rosenthal. "Cryogenic electron microscopy approaches that combine images and tilt series." Microscopy 71, Supplement_1 (February 18, 2022): i15—i22. http://dx.doi.org/10.1093/jmicro/dfab053.
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Abstract Cryogenic electron microscopy can be widely applied to biological specimens from the molecular to the cellular scale. In single-particle analysis, 3D structures may be obtained in high resolution by averaging 2D images of single particles in random orientations. For pleomorphic specimens, structures may be obtained by recording the tilt series of a single example of the specimen and calculating tomograms. Where many copies of a single structure such as a protein or nucleic acid assembly are present within the tomogram, averaging of the sub-volumes (subtomogram averaging) has been successfully applied. The choice of data collection method for any given specimen may depend on the structural question of interest and is determined by the radiation sensitivity of the specimen. Here, we survey some recent developments on the use of hybrid methods for recording and analysing data from radiation-sensitive biological specimens. These include single-particle reconstruction from 2D images where additional views are recorded at a single tilt angle of the specimen and methods where image tilt series, initially used for tomogram reconstruction, are processed as individual single-particle images. There is a continuum of approaches now available to maximize structural information obtained from the specimen.
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Verhey, Peter T., Marc V. Gosselin, Steven L. Primack, Paul L. Blackburn, and Alexander C. Kraemer. "The Right Mediastinal Border and Central Venous Anatomy on Frontal Chest Radiograph—Direct CT Correlation." Journal of the Association for Vascular Access 13, no. 1 (March 1, 2008): 32–35. http://dx.doi.org/10.2309/java.13-1-7.
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Abstract We describe a direct and accurate method for defining chest radiographic anatomy and use this method to delineate the anatomic composition of the right mediastinal border in an adult population. Intravenous contrast-enhanced computed tomographic scans of the chest and accompanying scout tomograms from 99 adults without previously known or detected cardiopulmonary disease that could potentially distort mediastinal, cardiac, or pulmonary anatomy were retrospectively evaluated. Transverse CT images through the mediastinum were directly referenced to the respective acquisition location on the scout tomogram via the acquisition reference line. The anatomic composition of the right mediastinal border on the scout tomogram was determined by drawing a vertical line tangential to the most lateral right mediastinal structure in each transverse CT image. The lengths and relationships of these structures were tabulated. These results will help to create a consensus among radiologists and other clinicians regarding radiographic anatomy, allowing improved localization of mediastinal pathology and enabling more optimal positioning of vascular and cardiac support devices.
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Yang, Mino, Jun-Ho Lee, Hee-Goo Kim, Euna Kim, Young-Nam Kwon, Jin-Gyu Kim, and Cheol-Woong Yang. "Meso-Scale Transmission Electron Microscope Tomography Applied for Wax Distribution in Toner Particles." Microscopy and Microanalysis 19, S5 (August 2013): 58–61. http://dx.doi.org/10.1017/s1431927613012336.
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AbstractDistribution of wax in laser printer toner was observed using an ultra-high-voltage (UHV) and a medium-voltage transmission electron microscope (TEM). As the radius of the wax spans a hundred to greater than a thousand nanometers, its three-dimensional recognition via TEM requires large depth of focus (DOF) for a volumetric specimen. A tomogram with a series of the captured images would allow the determination of their spatial distribution. In this study, bright-field (BF) images acquired with UHV-TEM at a high tilt angle prevented the construction of the tomogram. Conversely, the Z-contrast images acquired by the medium-voltage TEM produced a successful tomogram. The spatial resolution for both is discussed, illustrating that the image degradation was primarily caused by beam divergence of the Z-contrast image and the combination of DOF and chromatic aberration of the BF image from the UHV-TEM.
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Yedra, Lluís, Alberto Eljarrat, José Manuel Rebled, Lluís López-Conesa, Nico Dix, Florencio Sánchez, Sònia Estradé, and Francesca Peiró. "EELS tomography in multiferroic nanocomposites: from spectrum images to the spectrum volume." Nanoscale 6, no. 12 (2014): 6646–50. http://dx.doi.org/10.1039/c4nr01100g.
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Russell, Greg, Silvia N. W. Hertzberg, Natalia Anisimova, Natalia Gavrilova, Beáta É. Petrovski, and Goran Petrovski. "Digital Image Analysis of the Angle and Optic Nerve: A Simple, Fast, and Low-Cost Method for Glaucoma Assessment." Journal of Ophthalmology 2020 (October 28, 2020): 1–8. http://dx.doi.org/10.1155/2020/3595610.
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Purpose. To devise a simple, fast, and low-cost method for glaucoma assessment using digital image analysis of the angle and optic nerve in human subjects. Methods. Images from glaucoma and fundus assessment were used in this study, including color fundus photographs, standard optic nerve optical coherence tomography (OCT), and digital slit-lamp images of the angle/gonioscopy. Digital image conversion and analysis of the angle using ImageJ (NIH, USA) and adaptive histogram equalization contrast-limited AHE (CLAHE) to prevent noise amplification were implemented. Angle and optic nerve images were analyzed separately in the red, green, and blue (RGB) channels followed by 3D volumetric analysis of the degrees of angle depth and cup volume of the optic nerve. Horizontal tomogram reconstitution and nerve fiber detection methods were developed and compared to standard OCT images. Results. Digital slit-lamp angle images showed similar accuracy as standard anterior OCT measurements. Comparative analysis of RGB channels produced volumetric cup and horizontal tomogram, which closely resembled the 3D OCT appearance and B-scan of the cup, respectively. RGB channel splitting and image subtraction produced a map closely resembling that of the retinal nerve fiber layer (RNFL) thickness map on OCT. Conclusions. While OCT imaging is rapidly progressing in the area of optic disc and chamber angle assessment, rising healthcare costs and lack of availability of the technology open a demand for alternative and cost-minimizing forms of image analysis in glaucoma. Volumetric, geometric, and segmentational data obtained through digital image analysis correspond well to those obtained by OCT imaging.
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Lee, Doo Sung, Spyros K. Lazaratos, and Arthur F. Walden. "Crosswell seismic study in a seismically poor data area." GEOPHYSICS 60, no. 3 (May 1995): 758–64. http://dx.doi.org/10.1190/1.1443814.
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Crosswell traveltime tomography and reflection imaging assisted a reservoir characterization effort in an area of poor‐quality surface seismic data. Both the tomogram and the reflection image proved useful in the description of the fractured reservoir interval. The velocity tomogram shows that: (1) the vertical resolution was sufficient to identify and characterize a 50-ft (15 m) thick lithological unit of brittle rocks, which was the most important interval for the characterization of this fractured reservoir; (2) different lithological units present sufficient velocity contrast to be identifiable on the tomogram; and (3) the tomogram velocity is higher than the sonic velocity implying that the rocks in the interwell area may be anisotropic. Correlation of the lithologies with the tomogram implies that the major controlling factor of the anisotropy is the shale content in the formation. The crosswell reflection image, generated by a VSP‐CDP mapping technique, defines the fractured reservoir interval in terms of high‐frequency reflections. The lateral resolution of this reflection image is difficult to define because the survey coverage is nonuniform as a result of the receiver spacing being much larger than the source spacing. The dips of the reflections do not quite agree with the dips that are inferred from well log ties. We believe this disagreement is a result of the anisotropy of the medium and the use of an isotropic imaging algorithm. Improved data acquisition (finer spatial sampling) that would allow better wavefield separation techniques to be used would probably have produced higher quality crosswell reflection images.
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Jebelli, Mohammad, Kemp Kernstine, Mohammad Hossein Mandegar, Sam Chitsaz, and Hussein Rayatzadeh. "Left Ventricular Pseudoaneurysm Demonstrated by 64-Multislice Computed Tomography." Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 4, no. 4 (July 2009): 236. http://dx.doi.org/10.1097/imi.0b013e3181b01c36.
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A 50-year-old man with a history of left ventricular aneurysmectomy was evaluated with a 64-multislice computed tomogram, which demonstrated left ventricular enlargement and a pseudoaneurysm at the apicolateral side. The images were critical to our management. We resected the pseudoaneurysm with an excellent outcome.
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Argunova, T. S., V. G. Kohn, J. H. Lim, Z. V. Gudkina, and E. D. Nazarova. "Computer simulations of X-ray phase-contrast images and microtomographic observation of tubules in dentin." Journal of Synchrotron Radiation 27, no. 2 (January 27, 2020): 462–67. http://dx.doi.org/10.1107/s1600577519016503.
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An investigation of the problems of X-ray imaging of dentinal tubules is presented. Two main points are addressed. In the first part of this paper, the problem of computer simulating tubule images recorded in a coherent synchrotron radiation (SR) beam has been discussed. A phantom material which involved a two-dimensional lattice of the tubules with parameters similar to those of dentin was considered. By a comparative examination of two approximations, it was found that the method of phase-contrast imaging is valid if the number of tubules along the beam is less than 100. Calculated images from a lattice of 50 × 50 tubules are periodic in free space but depend strongly on the distance between the specimen and the detector. In the second part, SR microtomographic experiments with millimetre-sized dentin samples in a partially coherent beam have been described. Tomograms were reconstructed from experimental projections using a technique for incoherent radiation. The main result of this part is the three-dimensional rendering of the directions of the tubules in a volume of the samples. Generation of the directions is possible because a tomogram shows the positions of the tubules. However, a detailed tubule cross-section structure cannot be restored.
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Padgett, Elliot, Robert Hovden, Jessica C. DaSilva, Barnaby D. A. Levin, John L. Grazul, Tobias Hanrath, and David A. Muller. "A Simple Preparation Method for Full-Range Electron Tomography of Nanoparticles and Fine Powders." Microscopy and Microanalysis 23, no. 6 (December 2017): 1150–58. http://dx.doi.org/10.1017/s1431927617012764.
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AbstractElectron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a “missing wedge” of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.
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Gan, Lu, and Grant J. Jensen. "Electron tomography of cells." Quarterly Reviews of Biophysics 45, no. 1 (November 15, 2011): 27–56. http://dx.doi.org/10.1017/s0033583511000102.
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AbstractThe electron microscope has contributed deep insights into biological structure since its invention nearly 80 years ago. Advances in instrumentation and methodology in recent decades have now enabled electron tomography to become the highest resolution three-dimensional (3D) imaging technique available for unique objects such as cells. Cells can be imaged either plastic-embedded or frozen-hydrated. Then the series of projection images are aligned and back-projected to generate a 3D reconstruction or ‘tomogram’. Here, we review how electron tomography has begun to reveal the molecular organization of cells and how the existing and upcoming technologies promise even greater insights into structural cell biology.
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Modi, Jayesh, Pranshu Sharma, Alex Earl, Mark Simpson, J. Ross Mitchell, and Mayank Goyal. "iPhone-Based Teleradiology for the Diagnosis of Acute Cervico-Dorsal Spine Trauma." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 37, no. 6 (November 2010): 849–54. http://dx.doi.org/10.1017/s0317167100051556.
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AbstractObjective:To assess the feasibility of iPhone-based teleradiology as a potential solution for the diagnosis of acute cervico-dorsal spine trauma.Materials and Methods:We have developed a solution that allows visualization of images on the iPhone. Our system allows rapid, remote, secure, visualization of medical images without storing patient data on the iPhone. This retrospective study is comprised of cervico-dorsal computed tomogram (CT) scan examination of 75 consecutive patients having clinically suspected cervico-dorsal spine fracture. Two radiologists reviewed CT scan images on the iPhone. Computed tomogram spine scans were analyzed for vertebral body fracture and posterior elements fractures, any associated subluxation-dislocation and cord lesion. The total time taken from the launch of viewing application on the iPhone until interpretation was recorded. The results were compared with that of a diagnostic workstation monitor. Inter-rater agreement was assessed.Results:The sensitivity and accuracy of detecting vertebral body fractures was 80% and 97% by both readers using the iPhone system with a perfect inter-rater agreement (kappa:1). The sensitivity and accuracy of detecting posterior elements fracture was 75% and 98% for Reader 1 and 50% and 97% for Reader 2 using the iPhone. There was good inter-rater agreement (kappa: 0.66) between both readers. No statistically significant difference was noted between time on the workstation and the iPhone system.Conclusion:iPhone-based teleradiology system is accurate in the diagnosis of acute cervico-dorsal spinal trauma. It allows rapid, remote, secure, visualization of medical images without storing patient data on the iPhone.
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Dalal, Krishna, D. Elanchezhiyan, Raunak Das, Devjyoti Dalal, Ravindra Mohan Pandey, Subhamoy Chatterjee, Ashish Datt Upadhyay, V. Bharathi Maran, and Jyotirmoy Chatterjee. "Noninvasive Characterisation of Foot Reflexology Areas by Swept Source-Optical Coherence Tomography in Patients with Low Back Pain." Evidence-Based Complementary and Alternative Medicine 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/983769.
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Objective. When exploring the scientific basis of reflexology techniques, elucidation of the surface and subsurface features of reflexology areas (RAs) is crucial. In this study, the subcutaneous features of RAs related to the lumbar vertebrae were evaluated by swept source-optical coherence tomography (SS-OCT) in subjects with and without low back pain (LBP).Methods. Volunteers without LBP (n=6(male : female = 1 : 1)) and subjects with LBP (n=15(male : female = 2 : 3)) were clinically examined in terms of skin colour (visual perception), localised tenderness (visual analogue scale) and structural as well as optical attributes as per SS-OCT. From each subject, 6 optical tomograms were recorded from equidistant transverse planes along the longitudinal axis of the RAs, and from each tomogram, 25 different spatial locations were considered for recording SS-OCT image attributes. The images were analysed with respect to the optical intensity distributions and thicknesses of different skin layers by using AxioVision Rel. 4.8.2 software. The SS-OCT images could be categorised into 4 pathological grades (i.e., 0, 1, 2, and 3) according to distinctness in the visible skin layers.Results. Three specific grades for abnormalities in SS-OCT images were identified considering gradual loss of distinctness and increase in luminosity of skin layers. Almost 90.05% subjects were of mixed type having predominance in certain grades.Conclusion. The skin SS-OCT system demonstrated a definite association of the surface features of healthy/unhealthy RAs with cutaneous features and the clinical status of the lumbar vertebrae.
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Ghazali, L., MYP Mohd Yusof, and NH Norman. "Image Quality Optimization of Dental Panoramic Tomogram and Lateral Cephalogram: A Pilot Study on Human Skull." Compendium of Oral Science 8, no. 1 (September 1, 2021): 43–54. http://dx.doi.org/10.24191/cos.v8i0.17482.
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Purpose: The purpose of this study was to investigate the effects of varying scanning parameters of DPT and LC on diagnostic performance and quality of the images. Materials and Methods: Clinical evaluations of image quality were performed using an adult human skull with permanent dentition. Dental panoramic tomogram (DPT) and lateral cephalogram (LC) images were obtained using two different radiographic machines Instrumentarium 300OP taken at Sungai Buloh (SB) and Sirona Orthophos 3D taken at Puncak Perdana (PP) by varying tube voltages. Two orthodontic residents assessed images based on overall quality using a five-point rating scale and diagnostic performance by detection of anatomical landmarks. The correlations between radiation doses and diagnostic value of the images were analyzed using Pearson’s Correlation Test. Univariate analysis was calculated for the evaluation for image quality. Intra-class Correlation Coefficient (ICC) was used to test for intra-rater and inter-rater reliability. Results: Both modalities taken at both centers showed negative correlation between dosage and detection of anatomical landmarks except for LC SB. All images were rated at least with median of 3= more than adequately presented regardless of the radiation dosage except for DPT PP (median 5= inadequately presented). Conclusion: Lower dosage parameters should be used when taking DPT and LC as images appeared darker, lower in quality and less anatomical landmarks can be detected at higher scanning parameter.
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Mathisen, Mark E., Anthony A. Vasiliou, Paul Cunningham, J. Shaw, J. H. Justice, and N. J. Guinzy. "Time‐lapse crosswell seismic tomogram interpretation: Implications for heavy oil reservoir characterization, thermal recovery process monitoring, and tomographic imaging technology." GEOPHYSICS 60, no. 3 (May 1995): 631–50. http://dx.doi.org/10.1190/1.1443803.
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Time‐lapse crosswell seismic data acquired with a cemented receiver cable have been processed into P‐ and S‐wave tomograms which image heavy oil sand lithofacies and changes as a result of steam injection. Twenty‐seven crosswell surveys were acquired between two wells over a 3.5 month period before, during, and after a 34‐day, 30 MBBL [Formula: see text] steam injection cycle. Interpretation was based on correlations with reservoir data and models, observation well data, and engineering documentation of the production history and steam cycle. Baseline S‐ and P‐wave tomograms image reservoir sand flow units and areas affected by past cyclic steam injection. S‐wave tomograms define lithology and porosity contrasts between the excellent reservoir quality, “high flow” turbidite channel facies and the interbedded “low to moderate flow” bioturbated levee facies. The reservoir dip of approximately 20° is defined by the velocity contrast between lithofacies. P‐wave baseline tomograms image lithology, porosity, structure, and several low velocity zones caused by past steam injection. Previous steam‐heat injection caused the formation of gas which reduced velocities as much as several thousand ft/s (600 m/s), an amount which obscures the velocity contrast between lithofacies and smaller velocity reductions as a result of temperature alone. Time‐lapse and difference P‐wave tomograms document several areas with small decreases in velocity during steam injection and larger decreases after cyclic steam injection. Velocity reductions range from 300 to 900 ft/s (90 to 270 m/s) adjacent to and above injectors located 20 to 50 feet (6 to 15 m) from the tomogram cross‐section. Poisson’s ratio tomograms show a significant decrease (.10) in the same area, and include low values indicative of gas saturation. Continuous injectors located 50 to 350 feet (15 to 100 m) from the survey area also caused a progressive decrease in velocity of the “high flow” channel sands during the time‐lapse survey. Interdisciplinary interpretation indicates that tomograms not only complement other borehole‐derived reservoir characterization and temperature monitoring data but can be used to quantitatively characterize interwell reservoir properties and monitor changes as a result of the thermal recovery process. Monitoring results over 3.5 months confirms that stratification has controlled the flow of steam, in contrast to gravity override. This suggests that tomographic images of reservoir flow‐units and gas‐bearing high temperature zones should be useful for positioning wells and optimizing injection intervals, steam volumes, and producing well completions.
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Schankula, Christopher W., Christopher K. Anand, and Nabil D. Bassim. "Multi-Angle Plasma Focused Ion Beam (FIB) Curtaining Artifact Correction Using a Fourier-Based Linear Optimization Model." Microscopy and Microanalysis 24, no. 6 (December 2018): 657–66. http://dx.doi.org/10.1017/s1431927618015234.
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AbstractWe present a flexible linear optimization model for correcting multi-angle curtaining effects in plasma focused ion beam scanning electron microscopy (PFIB-SEM) images produced by rocking-polishing schemes. When PFIB-SEM is employed in a serial sectioning tomography workow, it is capable of imaging large three-dimensional volumes quickly, providing rich information in the critical 10–100 nm feature length scale. During tomogram acquisition, a “rocking polish” is often used to reduce straight-line “curtaining” gradations in the milled sample surface. While this mitigation scheme is effective for deep curtains, it leaves shallower line artifacts at two discretized angles. Segmentation and other automated processing of the image set requires that these artifacts be corrected for accurate microstructural quantification. Our work details a new Fourier-based linear optimization model for correcting curtaining artifacts by targeting curtains at two discrete angles. We demonstrate its capabilities by processing images from a tomogram from a multiphase, heterogeneous concrete sample. We present methods for selecting the parameters which meet the user’s goals most appropriately. Compared to previous works, we show that our model provides effective multi-angle curtain correction without introducing artifacts into the image, modifying non-curtain structures or causing changes to the contrast of voids. Our algorithm can be easily parallelized to take advantage of multi-core hardware.
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Menezes, Roberto B., João E. Steiner, Tiago V. Ricci, and Alexandre S. Oliveira. "The Active Nucleus in NGC 4579." Proceedings of the International Astronomical Union 5, S267 (August 2009): 123. http://dx.doi.org/10.1017/s1743921310005843.
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In this work, we present an analysis of a data cube obtained with the instrument IFU/GMOS Gemini North telescope centered on the nuclear region of the LINER galaxy NGC 4579. This galaxy is known to have a type 1 AGN (see Eracleous et al. 2002 for a review). The methodology used for the analysis of the data cube was PCA tomography (Steiner et al. 2009), which consists of applying the statistical tool known as principal component analysis (PCA) to extract information from data cubes. The analysis was performed in the following way: first, the data cube for this object was transformed into a data matrix, where each row corresponded to a spatial pixel and each column corresponded to a spectral pixel. We then applied the PCA to this matrix, obtaining eigenvectors as a function of spectral pixels (which correspond to the original coordinates). These eigenvectors, which have the appearance of spectra, are called eigenspectra. We also calculated the projection of the data corresponding to the spatial pixels on each one of the eigenvectors. These images were called tomograms. Figure 1 shows Eigenspectrum E2 and tomogram T2 superposed on T1.
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Boonyasiriwat, Chaiwoot, Gerard T. Schuster, Paul Valasek, and Weiping Cao. "Applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early-arrival windows." GEOPHYSICS 75, no. 6 (November 2010): R129—R136. http://dx.doi.org/10.1190/1.3507237.
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A recently developed time-domain multiscale waveform tomography (MWT) method is applied to synthetic and field marine data. Although the MWT method was already applied to synthetic data, the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging. This hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2D SEG/EAGE salt model. In the application of MWT to the field data, the inversion process is carried out using a multiscale method with a dynamic early-arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects. With the modified MWT method, reasonably accurate results as verified by comparison of migration images and common image gathers were obtained. The hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation. However, we believe it is applicable to field data applications.
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Richards, Mercedes T. "Doppler Tomography of Accretion Disks and Streams in Close Binaries." Proceedings of the International Astronomical Union 2, S240 (August 2006): 160–69. http://dx.doi.org/10.1017/s1743921307003973.
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AbstractThe application of tomography to the study of gas flows in interacting binaries has led to fascinating images of the Cataclysmic Variables and Algol-type binaries. Such detailed images are currently unachievable using direct-imaging techniques. Numerous images of accretion flows have now been derived from optical and ultraviolet spectra and they have been used to identify multiple emission sources including the gas stream, accretion disk, accretion annulus, shock regions, and the chromosphere of the mass loser. It was difficult to distinguish between the separate sources of emission since these sources have overlapping velocities in the Doppler tomogram. However, with the aid of a new spectral synthesis code, we can now systematically extract the individual emission sources to sequentially isolate the images of the disk and gas stream. With these new tools, we have begun to extract the critical properties of the disk and gas stream more accurately than previously possible.
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Dundamadappa, Sathish Kumar, Senthur Thangasamy, Nancy Resteghini, Srinivasan Vedantham, Andrew Chen, and Deepak Takhtani. "Skull fractures in pediatric patients on computerized tomogram: comparison between routing bone window images and 3D volume-rendered images." Emergency Radiology 22, no. 4 (February 20, 2015): 367–72. http://dx.doi.org/10.1007/s10140-015-1300-2.
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Lazaratos, Spyros K., Jerry M. Harris, James W. Rector, and Mark Van Schaack. "High‐resolution crosswell imaging of a west Texas carbonate reservoir: Part 4—Reflection imaging." GEOPHYSICS 60, no. 3 (May 1995): 702–11. http://dx.doi.org/10.1190/1.1443809.
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Reliable crosswell reflection imaging is a challenging task, even after the data have been wavefield‐separated in the time domain. Residual, strong coherent noise is still present in the data. Stacking is complicated by the wide range of reflection incidence angles available for imaging. With wavelengths of a few feet, small misalignments as a result of velocity or geometric errors produce destructive interference and degrade the quality of the stacked image. We present an imaging sequence that addressed these complications and allowed us to produce high‐quality stacked images for both P‐ and S‐waves from a large‐volume crosswell data set. A very good tie was achieved at both wells. Heterogeneities imaged from well to well included very thin beds [less than 5 ft (1.5 m) thick] within the reservoir, pinchouts, and a major angular unconformity—the Grayburg/San Andres—that could not be observed reliably with any other technique (log correlation, surface seismic imaging, or tomography). In fact, the produced crosswell reflection images exhibit dramatically higher resolution and continuity than the P‐wave traveltime tomogram.
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Soldatov, A. I., J. Chang, M. A. Kostina, A. A. Soldatov, and Sh Xu. "ULTRASOUND COMPUTED TOMOGRAPHY BY LINEAR ARRAYS WITH USED THROUGH TRANSMISSION TESTING METHOD." Kontrol'. Diagnostika, no. 273 (March 2021): 40–49. http://dx.doi.org/10.14489/td.2021.03.pp.040-049.
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The article describes few view through-transmission ultrasound tomography using linear gratings. Obtaining initial data is based on alternate radiation by each element of the emitting antenna array and simultaneous reception by all elements of the receiving antenna array. This results in a set of shadow images from different angles, the number of which is equal to the number of elements of the radiating array. The tomogram reconstruction process consists in calculating the signal amplitude in each pixel of the monitoring zone as the sum of signals from several sources passing to a specific receiver through this pixel. The defect decreases the signal amplitude at the receiver, which is linearly related to the area of the shadow at the receiver. To assess the magnitude of the signal attenuation, the defect detection coefficient was used, calculated as the ratio of the signal amplitude at the receiver that passed through the defect to the signal amplitude at the receiver in the absence of a defect. The use of a limited set of angles leads to a deterioration in the quality of the tomogram and, as a result, errors appear in the form of lines from emitters to receivers intersecting at the location of the defect. To improve the quality of the tomogram, a Gaussian filter was applied, after which the manifestation of artifacts was reduced, which made it possible to more accurately determine the coordinates and dimensions of the defect. In the article, a model study was carried out and the use of a filter with different parameters was tested on experimental data. The theoretical range of variation of the filter parameters is calculated and the optimal parameters are determined, at which the best tomogram quality is obtained. The simulation results are given for one and two reflectors located in the control zone. The resolving power of the system consisting of receiving and transmitting antenna arrays with 16 elements is determined. The resolution was 12 mm for arrays of circular piezoelectric elements 3 mm thick and 6 mm in diameter with a 10 mm distance between the centers of neighboring piezoelectric elements and 400 mm between the receiving and emitting gratings.
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Dehghan Khalili, A., J. Y. Y. Arns, F. Hussain, Y. Cinar, W. V. V. Pinczewski, and C. H. H. Arns. "Permeability Upscaling for Carbonates From the Pore Scale by Use of Multiscale X-Ray-CT Images." SPE Reservoir Evaluation & Engineering 16, no. 04 (October 10, 2013): 353–68. http://dx.doi.org/10.2118/152640-pa.
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Summary High-resolution X-ray-computed-tomography (CT) images are increasingly used to numerically derive petrophysical properties of interest at the pore scale—in particular, effective permeability. Current micro-X-ray-CT facilities typically offer a resolution of a few microns per voxel, resulting in a field of view of approximately 5 mm3 for a 2,0482 charge-coupled device. At this scale, the resolution is normally sufficient to resolve pore-space connectivity and calculate transport properties directly. For samples exhibiting heterogeneity above the field of view of such a single high-resolution tomogram with resolved pore space, a second low-resolution tomogram can provide a larger-scale porosity map. This low-resolution X-ray-CT image provides the correlation structure of porosity at an intermediate scale, for which high-resolution permeability calculations can be carried out, forming the basis for upscaling methods dealing with correlated heterogeneity. In this study, we characterize spatial heterogeneity by use of overlapping registered X-ray-CT images derived at different resolutions spanning orders of magnitude in length scales. A 38-mm-diameter carbonate core is studied in detail and imaged at low resolution—and at high resolution by taking four 5-mm-diameter subsets, one of which is imaged by use of full-length helical scanning. Fine-scale permeability transforms are derived by use of direct porosity/permeability relationships, random sampling of the porosity/permeability scatter plot as a function of porosity, and structural correlations combined with stochastic simulation. A range of these methods is applied at the coarse scale. We compare various upscaling methods, including renormalization theory, with direct solutions by use of a Laplace solver and report error bounds. Finally, we compare with experimental measurements of permeability at both the small-plug and the full-plug scale. We find that both numerically and experimentally for the carbonate sample considered, which displays nonconnecting vugs and intrafossil pores, permeability increases with scale. Although numerical and experimental results agree at the larger scale, the digital core-analysis results underestimate experimentally measured permeability at the smaller scale. Upscaling techniques that use basic averaging techniques fail to provide truthful vertical permeability at the fine scale because of large permeability contrasts. At this scale, the most accurate upscaling technique uses Darcy's law. At the coarse scale, an accurate permeability estimate with error bounds is feasible if spatial correlations are considered. All upscaling techniques work satisfactorily at this scale. A key part of the study is the establishment of porosity transforms between high-resolution and low-resolution images to arrive at a calibrated porosity map to constrain permeability estimates for the whole core.
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Oshiro, Osamu, Kumi Kamada, Masataka Imura, Kunihiro Chihara, Eiji Toyota, Yasuo Ogasawara, and Fumihiko Kajiya. "Kidney Glomerulus Observation in Interactive VR Space." International Journal of Image and Graphics 03, no. 04 (October 2003): 629–37. http://dx.doi.org/10.1142/s0219467803001226.
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This paper presents the system designed to observe kidney glomeruli interactively with conventional CCD cameras and immersive virtual reality (VR) space. First, we captured the X-ray transmitted images and converted them to computer tomogram (CT). Second, the three-dimensional (3D) image was reconstructed using various image processing, binarization, dilation, contraction, labeling and surface rendering. Third, we presented the 3D image on the immersive projection system (IPS) and installed the function of on-line counting of the number of glomeruli. This system provides an observer the immersive environment and enables him to count the kidney glomeruli interactively.
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Nussbaumer, Raphaël, Niklas Linde, Grégoire Mariethoz, and Klaus Holliger. "Simulation of fine-scale electrical conductivity fields using resolution-limited tomograms and area-to-point kriging." Geophysical Journal International 218, no. 2 (April 20, 2019): 1322–35. http://dx.doi.org/10.1093/gji/ggz185.
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SUMMARY Deterministic geophysical inversion approaches yield tomographic images with strong imprints of the regularization terms required to solve otherwise ill-posed inverse problems. While such tomograms enable an adequate assessment of the larger-scale features of the probed subsurface, the finer-scale details tend to be unresolved. Yet, representing these fine-scale structural details is generally desirable and for some applications even mandatory. To address this problem, we have developed a two-step methodology based on area-to-point kriging to generate fine-scale multi-Gaussian realizations from smooth tomographic images. Specifically, we use a co-kriging system in which the smooth, low-resolution tomogram is related to the fine-scale heterogeneity through a linear mapping operation. This mapping is based on the model resolution and the posterior covariance matrices computed using a linearization around the final tomographic model. This, in turn, allows us for analytical computations of covariance and cross-covariance models. The methodology is tested on a heterogeneous synthetic 2-D distribution of electrical conductivity that is probed with a surface-based electrical resistivity tomography (ERT) survey. The results demonstrate the ability of this technique to reproduce a known geostatistical model characterizing the fine-scale structure, while simultaneously preserving the large-scale structures identified by the smoothness-constrained tomographic inversion. Small discrepancies between the geophysical forward responses of the realizations and the reference synthetic data are attributed to the underlying linearization. Overall, the method provides an effective and fast alternative to more comprehensive, but computationally more expensive approaches, such as, for example, Markov chain Monte Carlo techniques. Moreover, the proposed method can be used to generate fine-scale multivariate Gaussian realizations from virtually any smoothness-constrained inversion results given the corresponding resolution and posterior covariance matrices.
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Zubareva, A. A., and Zh Y. Beiseyeva. "ANATOMICAL TOPOGRAPHIC FEATURES OF THE FACIAL NERVE ON CONE-BEAM CT." Folia Otorhinolaryngologiae et Pathologiae Respiratoriae 25, no. 3 (2019): 46–52. http://dx.doi.org/10.33848/foliorl23103825-2019-25-3-46-52.
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Introduction. Cone-beam computer tomography (CBCT) was introduced into the ENT practice more than 10 years ago. In recent years, it is actively used to visualize temporal bones in acute and chronic diseases of the middle ear (especially in visualizing implants of the middle and inner ear, shunts), but there is no precise description of anatomical features of the temporal bone’s structure. Materials and methods. A retrospective analysis of tomogram, made on a Sirona tomograph, Galaxis / Galileos software for the period from 08/04/2016 to 23/06/2017, in overall, there was analyzed 82 images, from which 71 images of temporal bones were selected from 41 people. Group 1 - CT of the temporal bone in patients with signs of acute inflammation of the middle ear, group 2 - CT of the temporal bone in patients with signs of chronic inflammation of the middle ear, group 3 - CT of the temporal bone in patients without signs of inflammation. Results. An algorithm for assessing the temporal bone according to the above parameters is(was) proposed. When three groups were compared, the length of the mastoid and drum part of the facial nerve, the canal of the facial nerve near the aditus ad antrum and the horizontal semicircular canal were revealed, and the distance between them, regardless to the progress of the disease, corresponds to the parameters of the norm. Conclusion. Thus, taking into account the data of the retrospective analysis, it should be noted that there was no significant difference between the quantitative indices of the facial nerve’s canal structure without inflammation and in the acute and chronic pathology of the middle ear
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Stone, James L., John R. Hughes, Arlene Barr, Walter Tan, Eric Russell, and Robert M. Crowell. "Neuroradiological and Electroencephalographic Features in a Case of Temporal Lobe Status Epilepticus." Neurosurgery 18, no. 2 (February 1, 1986): 212–16. http://dx.doi.org/10.1227/00006123-198602000-00019.
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Abstract A patient with medically intractable status epilepticus of temporal lobe origin is presented. A computed tomogram showed a low density area adjacent to the midbrain, possibly related to atrophy of the medial temporal lobe. Cerebral angiography revealed early filling veins and an anterior temporal blush. Magnetic resonance (MR) scanning (T2 weighted images) showed increased signal intensity in the region of the amygdala and anterolateral left temporal lobe. Ictal activity was recorded from scalp electrodes over the left temporal area, and many paroxysms were recorded from cortical surface electrodes. An anterior temporal lobectomy revealed only gliosis. The cerebral blood flow changes accompanying status epilepticus of focal origin are reviewed, and a possible relation of electroencephalographic, angiographic, and MR findings is discussed.
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Apkarian, Robert P. "Comments on Cryo High Resolution Scanning Electron Microscopy." Microscopy Today 12, no. 1 (January 2004): 45. http://dx.doi.org/10.1017/s1551929500051841.
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Stephen Carmichael wrote about Cryoelectron Tomography in the May 2003 issue of Microscopy Today. Citing new preparation methods, small cells can be vitrified, observed frozen in the TEM and a series of digital images captured while the specimen is being rotated around the axis perpendicular to the electron beam producing a 3-D tomogram. Gina Sosinski and Maryann Martone wrote about imaging big and messy biological structures using cryo-electron Tomography in the July issue of Microscopy Today. Cryo-HRSEM now also seeks to provide 3-D information approaching the molecular level from frozen hydrated cell and molecular systems. Vitrification procedures for small specimens such as platelets and biomolecules on grids are accomplished by plunge freezing in liquefied etiiane as is done with cryo-TEM procedures. Bulk specimens such as organic hydrogels and tissues are routinely high pressure frozen (HPF) in 3mm gold planchets. Employing an in-lens cryostage, identical to those used in cryo-TEM, cryo-HRSEM provides 3-D high-resolution images because secondary electrons are efficiently collected above the lens in a single scan thus minimizing specimen irradiation.
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Lock, Irene Sow Mei, Idris B. Ismail, Bawadi Abdullah, and Areeba Shafquet. "Evaluation of Electrical Capacitance Tomography Thresholding Techniques for Void Fraction Measurement of Gas-Liquid System." Applied Mechanics and Materials 625 (September 2014): 439–43. http://dx.doi.org/10.4028/www.scientific.net/amm.625.439.
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An analysis on the void fraction measurement for binary phase gas-liquid dielectric materials inside an Electrical Capacitance Tomography (ECT) sensor has been performed on the tomogram images by using different thresholding techniques. The analysis is pertinent to improve the accuracy of the application of thresholding technique for void fraction measurements in pipelines and reactors since the currently available information is limited in terms of accuracy. This preliminary investigation was performed to evaluate the accuracy of three different thresholding algorithms: Otsu’s, Niblack’s and Kuo’s Method based on the void fraction measurement for a binary phase oil-air system. The experimental and image processing analysis enables one to determine the optimal threshold method by selecting the threshold algorithm which produces the highest accuracy and consistency in the void fraction measurement as compared to the actual value.
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Skjønsfjell, Eirik Torbjørn Bakken, Yuriy Chushkin, Federico Zontone, and Dag Werner Breiby. "In situ coherent X-ray diffraction imaging of radiation-induced mass loss in metal–polymer composite spheres." Journal of Synchrotron Radiation 25, no. 4 (May 31, 2018): 1162–71. http://dx.doi.org/10.1107/s160057751800588x.
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A major limitation to the use of coherent X-ray diffraction imaging (CXDI) for imaging soft materials like polymers and biological tissue is that the radiation can cause extensive damage to the sample under investigation. In this study, CXDI has been used to monitor radiation-induced structural changes in metal-coated poly(methyl methacrylate) microspheres. Using a coherent undulator X-ray beam with 8.10 keV photon energy, 14 tomograms at a resolution of ∼30 nm were measured consecutively, which resulted in an accumulated dose of 30 GGy. The three-dimensional images confirmed that the polymer core was strongly affected by the absorbed dose, giving pronounced mass loss. Specifically, as the metal–polymer composite was exposed to the X-ray beam, a bubble-like region of reduced density grew within the composite, almost filling the entire volume within the thin metallic shell in the last tomogram. The bubble seemed to have its initiation point at a hole in the metal coating, emphasizing that the free polymer surface plays an important role in the degradation process. The irradiation of an uncoated polystyrene microsphere gave further evidence for mass loss at the free surface as the radius decreased with increased dose. The CXDI study was complemented by X-ray photon correlation spectroscopy, which proved efficient in establishing exposure dose limits. Our results demonstrate that radiation-induced structural changes at the tens of nanometer scale in soft materials can be followed as a function of dose, which is important for the further development of soft-matter technology.
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Greenhalgh, Stewart A., Iain M. Mason, and Cvetan Sinadinovski. "In‐mine seismic delineation of mineralization and rock structure." GEOPHYSICS 65, no. 6 (November 2000): 1908–19. http://dx.doi.org/10.1190/1.1444875.
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Significant progress has been made towards the goal of generating detailed seismic images as an aid to mine planning and exploration at the Kambalda nickel mines of Western Australia. Crosshole and vertical‐seismic‐profiling instrumentation, including a slimline multi‐element hydrophone array, three‐component geophone sensors, and a multishot detonator sound source, have been developed along with special seismic imaging software to map rock structure. Seismic trials at the Hunt underground mine established that high frequency (> 1 kHz) signals can be propagated over distances of tens of meters. Tomographic as well as novel 3-D multicomponent reflection imaging procedures have been applied to the data to produce useful pictures of the ore‐stope geometry and host rock. Tomogram interpretation remains problematic because velocity changes not only relate to differing rock types and/or the presence of mineralisation, but can also be caused by alteration/weathering and other rock condition variations. Ultrasonic measurements on rock core samples help in assigning velocity values to lithology, but geological assessment of tomograms remains ambiguous. Reflection imaging is complicated by the presence of strong tube‐wave to body‐wave mode conversion events present in the records, which obscure the weak reflection signatures. Three‐dimensional reflection data processing, especially three‐component analysis, is time consuming and difficult to perform. Notwithstanding the difficulties, the seismic migrations at the Hunt mine show a striking correlation with the known geology. Combined seismic and radar surveying from available underground boreholes and mine drivages is probably needed in the future to more confidently delineate mineralisation.
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Soto, Gabriel E., Stephen J. Young, Maryann E. Martone, Thomas J. Deerinck, Stephan Lamont, Bridget O. Carragher, and Mark H. Ellisman. "Tomographic methods for detailed examination of large structures in the nervous system." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 96–97. http://dx.doi.org/10.1017/s0424820100146321.
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One of the limitations of electron microscopy has been the requirement for very thin samples to allow penetration of the electron beam. It is often the case that structures of interest are not contained within a single thin section. In these cases, serial sectioning techniques are required to reconstruct the object in its entirety. The use of higher voltage electron microscopes has allowed researchers to examine specimens up to fifty times thicker than those suitable for a conventional TEM. However, images from thick sections are often difficult to interpret as the electron micrograph is essentially a projection of the overlapping material within the section. The method of computerized axial tilt electron microscopic tomography offers the potential to visualize and analyze information contained in a thick section by deriving a three dimensional volume from a series of projections acquired by collecting images of the specimen at successive tilt increments about the Y axis. Unfortunately there are practical limitations to the resolution that can be obtained using this technique with very thick sections. Resolution of the tomogram increases with finer tilt sampling and an increased range of tilts but decreases with section thickness.
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Beydoun, W. B., J. Delvaux, M. Mendes, G. Noual, and A. Tarantola. "Practical aspects of an elastic migration/inversion of crosshole data for reservoir characterization: A Paris basin example." GEOPHYSICS 54, no. 12 (December 1989): 1587–95. http://dx.doi.org/10.1190/1.1442626.
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The main obstacle for a detailed study of a reservoir is the lack of geophysical and petrophysical information between producing wells. Crosshole seismic data can aid reservoir geologists and engineers in (1) estimating the volume of oil in place, (2) mapping permeability/porosity barriers, and ultimately (3) monitoring and designing enhanced off‐recovery experiments. Due to their high‐frequency content, crosshole seismic data offer an ideal information link between conventional seismic data (surface reflection, VSPs, etc.) and full‐waveform sonic acoustic logs. Using a weightdrop downhole source located at one depth level, acoustic and multicomponent data at two different wells were collected in the Paris basin with interwell distances of about 100 m. The target zone includes three sand reservoir levels between depths of 575 and 600 m. A 2‐D elastic migration/inversion (M/I) of the scattered S‐S and S‐P crosshole field data produced high‐resolution S‐wave velocity and density depth images of the subsurface, extending information away from wells and identifying reservoirs. The residual energy reduction between synthetic seismograms derived from M/I images and field data is 18 percent, confirming that images contain elastic information. Structural dips obtained are very reasonable, the observed vertical spatial resolution being of the order of 3 m. We believe that this is the first time that such techniques have been applied to crosshole data. Elastic M/I images are generally better than elastic VSP‐CDP and migration images and have the advantage of producing global quality measures of images. Such a technique uses as input a background velocity, e.g., a tomogram obtained by traveltime tomography, and complements the background by recovering subsurface discontinuities and changes in elastic parameters within the signal bandwidth.
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Itoi, Eiji, Seok-Beom Lee, Kimberly K. Amrami, Doris E. Wenger, and Kai-Nan An. "Quantitative Assessment of Classic Anteroinferior Bony Bankart Lesions by Radiography and Computed Tomography." American Journal of Sports Medicine 31, no. 1 (January 2003): 112–18. http://dx.doi.org/10.1177/03635465030310010301.
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Background An anteroinferior osseous defect of the glenoid rim is sometimes encountered in patients with recurrent anterior dislocations of the shoulder. A defect of more than 21% of the glenoid length is reported to cause instability after Bankart repair. Hypothesis We can estimate the critical size of glenoid defects by using radiography or computed tomography. Study Design A controlled laboratory study. Methods Osseous defects of 0%, 9%, 21%, 34%, and 46% of the glenoid length were created stepwise in 12 cadaveric scapulae, and plain radiographs simulating the axillary and West Point views and computed tomographic images were obtained. The maximum width of the remnant glenoid was measured under each condition and expressed as a percentage of the width of the intact glenoid. Results A 21% defect appeared to be 18.6% of the intact glenoid on the West Point view. With computed tomography, a 21% defect resulted in loss of 50% of the width on a single slice across the lower one-fourth of the glenoid. Conclusions We can estimate the size of a glenoid defect by using the West Point radiographic view or computed tomogram. Clinical Relevance These images gave decisive information as to whether an osseous glenoid defect required bone grafting to achieve stability after Bankart repair.
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Márquez, G., A. Pinto, L. Alamo, B. Baumann, F. Ye, H. Winkler, K. Taylor, and R. Padrón. "A method for 3D-reconstruction of a muscle thick filament using the tilt series images of a single filament electron tomogram." Journal of Structural Biology 186, no. 2 (May 2014): 265–72. http://dx.doi.org/10.1016/j.jsb.2014.04.003.
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Srinivasan, Ashok, Mayank Goyal, Cheemun Lum, Thanh Nguyen, and William Miller. "Processing and Interpretation Times of CT Angiogram and CT Perfusion in Stroke." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 32, no. 4 (May 2005): 483–86. http://dx.doi.org/10.1017/s0317167100004480.
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ABSTRACT:Objective:To determine the mean time for acquiring computed tomogram perfusion (CTP) and CT angiogram (CTA) images in acute stroke. To determine and compare processing and interpretation times amongst three groups of radiologists with varying degree of expertise: two radiology residents (Group I), two neuroradiology fellows (Group II) and four consultant neuroradiologists (Group III).Methods:The mean time of acquisition of CTA and CTP studies was calculated among ten patients presenting with acute stroke. All readers had to process the CTA and CTP images, interpret them (for presence or absence of thrombus and penumbra) and save them on the GE Advantage Windows workstation. The mean time for processing and interpreting these studies was calculated.Results:The mean time for acquisition of CTA and CTP studies in the ten patients was 14.6 ± 5.9 minutes. The time taken for CTA processing and interpretation in Groups I, II and III was 2.3 ± 1.3 min, 1.6 ± 0.4 min and 1.5 ± 0.7 min respectively. The time required for CTP processing and interpretation by the same groups was 5.2 ± 1.7 min, 4.5 ± 1.5 min and 4.1 ± 1.1 min respectively. There was a statistically significant difference of means between Groups I and III in the CTA and CTP processing and interpretation times (p=0.02, p=0.01 respectively) but no statistical difference between Groups I and II (p=0.15, p=0.22 respectively) or Groups II and III (p=0.31, p=0.30 respectively).Conclusion:The CTA and CTP studies can be performed, processed and interpreted quickly in acute stroke.
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Hoversten, G. Michael, Paul Milligan, Joongmoo Byun, John Washbourne, Larry C. Knauer, and Paul Harness. "Crosswell electromagnetic and seismic imaging: An examination of coincident surveys at a steam flood project." GEOPHYSICS 69, no. 2 (March 2004): 406–14. http://dx.doi.org/10.1190/1.1707060.
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We studied crosswell electromagnetic and seismic images of three oil‐saturated intervals within a southern California heavy oil field undergoing steam flood. The crosswell survey is located in a portion of the field where one well is in a “cold spot,” resulting in differing steam propagation within the three units. Log analysis shows linear or second‐order polynomial relationships (with correlation coefficients greater than 0.7) between electrical conductivity and water saturation, porosity, and clay content; whereas only a weakly linear relationship can be found between velocity and temperature in the lower unit studied. Crosswell seismic data is used to produce a velocity tomogram and a reflection section, and crosswell electromagnetic data is used to produce a conductivity section and derived porosity and water saturation. The seismic velocities from the tomograms show lateral variations consistent with the lateral variations in temperature seen in observation wells on either side of the crosswell section. The continuity and disruption of seismic reflections coincide with zones of continuous and variable porosity and water saturation as produced from the crosswell electromagnetic inverted conductivity section, and the derived regression fits between conductivity and porosity/water saturation. Seismic velocities, reflections, electrical conductivity, and the derived porosity and water saturation sections all contribute to explaining the observed lateral temperature variations between the wells within the three reservoir units. The unit with high steam content has low water saturation, high porosity, and laterally continuous low‐velocity and seismic reflections, consistent with no barriers to flow. The upper unit, where steam breaks through later in the experiment, also has high porosity and laterally continuous seismic reflections. However, it shows a velocity gradient between the hot and cold wells consistent with the lack of steam in the cold well at the time of the experiment. The middle unit, in which steam never reaches the cold well during the experiment, has the highest water saturation and the largest zone of reduced porosity and disrupted seismic reflections, indicating a possible barrierto flow.
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Meng, Xu, Sixin Liu, Yi Xu, and Lei Fu. "Application of Laplace Domain Waveform Inversion to Cross-Hole Radar Data." Remote Sensing 11, no. 16 (August 7, 2019): 1839. http://dx.doi.org/10.3390/rs11161839.
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Full waveform inversion (FWI) can yield high resolution images and has been applied in Ground Penetrating Radar (GPR) for around 20 years. However, appropriate selection of the initial models is important in FWI because such an inversion is highly nonlinear. The conventional way to obtain the initial models for GPR FWI is ray-based tomogram inversion which suffers from several inherent shortcomings. In this paper, we develop a Laplace domain waveform inversion to obtain initial models for the time domain FWI. The gradient expression of the Laplace domain waveform inversion is deduced via the derivation of a logarithmic object function. Permittivity and conductivity are updated by using the conjugate gradient method. Using synthetic examples, we found that the value of the damping constant in the inversion cannot be too large or too small compared to the dominant frequency of the radar data. The synthetic examples demonstrate that the Laplace domain waveform inversion provide slightly better initial models for the time domain FWI than the ray-based inversion. Finally, we successfully applied the algorithm to one field data set, and the inverted results of the Laplace-based FWI show more details than that of the ray-based FWI.
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Sulaiman, M. I., P. A. Subakti, Haolia, D. Y. Fatimah, I. Madrinovella, A. Abdullah, D. A. Zaky, et al. "Early Results of Eastern Indonesia P-wave Tomography Study Using Regional Events." IOP Conference Series: Earth and Environmental Science 873, no. 1 (October 1, 2021): 012068. http://dx.doi.org/10.1088/1755-1315/873/1/012068.
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Abstract The tectonic system of Eastern Indonesia is controlled by several major and minor plates, such as Indo-Australian, Australian plate, and Pacific plates. This area is known for its complexity, and high seismic activity. This study tries to image the complex structures beneath this region by employing regional events data and seismic tomography methods. We used five years of regional events catalog provided by the Indonesian Agency of Meteorology, Climatology, and Geophysics. We have sorted 7336 events recorded between 120° – 136° longitude and 0° – 13°(-) latitude consisting of 46446 P and 15467 S wave arrival data. Relocated hypocenter map shows a better constrain location on seismicity along outer Bandar Arc. A dipping pattern of seismicity is seen that is going deeper to the Banda Sea. The seismicity map also images a steep angle pattern of seismicity that could be related to the subduction slab roll-back model at North of Wetar island. Interestingly, we spotted a seismicity gap in West Seram that could be linked with slab tear zone. The checker-board test suggests a proper resolution is still reliable to a depth of 200 km with a less interpretable model at a depth of 300 km. P-wave tomographic models image the high velocity dipping down going slab. The Banda slab is seen to subduct from south Timor Island to the north, from east Tanimbar and Aru Island to west part, and from north Seram Island to south. We observed the down-going slab meet from all directions at about 300 km beneath the Banda sea. P wave tomogram also shows the Timor Island slab has a steeper dip that agrees with the seismicity pattern. Near the Seram island, we identify a low-velocity anomaly zone infiltrate the Banda slab beneath the shallow part of West Seram, which was previously interpreted as slab tear zone. This study also noticed a higher velocity tomogram model at North of Wetar island that might indicate a back-arc thrust. Lastly, a low-velocity band is also exposed at a shallow depth close to the volcano chain along that Banda volcanic arc.
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Sanders, Toby, and Ilke Arslan. "Improved Three-Dimensional (3D) Resolution of Electron Tomograms Using Robust Mathematical Data-Processing Techniques." Microscopy and Microanalysis 23, no. 6 (November 16, 2017): 1121–29. http://dx.doi.org/10.1017/s1431927617012636.
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AbstractElectron tomography has become an essential tool for three-dimensional (3D) characterization of nanomaterials. In recent years, advances have been made in specimen preparation and mounting, acquisition geometries, and reconstruction algorithms. All of these components work together to optimize the resolution and clarity of an electron tomogram. However, one important component of the data-processing has received less attention: the 2D tilt series alignment. This is challenging for a number of reasons, namely because the nature of the data sets and the need to be coherently aligned over the full range of angles. An inaccurate alignment may be difficult to identify, yet can significantly limit the final 3D resolution. In this work, we present an improved center-of-mass alignment model that allows us to overcome discrepancies from unwanted objects that enter the imaging area throughout the tilt series. In particular, we develop an approach to overcome changes in the total mass upon rotation of the imaging area. We apply our approach to accurately recover small Pt nanoparticles embedded in a zeolite that may otherwise go undetected both in the 2D microscopy images and the 3D reconstruction. In addition to this, we highlight the particular effectiveness of the compressed sensing methods with this data set.
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Anggraini, Novia, Dwi Pujiastuti, and Atin Nur Aulia. "Tomografi Kecepatan Seismik 3D Daerah Danau Toba Menggunakan SimulPS12." Jurnal Fisika Unand 9, no. 4 (January 25, 2021): 457–64. http://dx.doi.org/10.25077/jfu.9.4.457-464.2020.
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Gunung Toba adalah salah satu gunung purba di Indonesia yang berada di Sumatera Utara. Terdapat dua aktivitas yang mempengaruhi gunung tersebut, yaitu aktivitas vulkanik yang berasal dari magma di bawahnya dan aktivitas tektonik yang berasal dari subduksi Lempang Indo-australia. Meskipun sudah lebih dari 70.000 tahun sejak terakhir kali erupsi dan menyebabkan terbentuknya kaldera vulkano-tektonik tersebar di dunia, yaitu Kaldera Toba, aktivitas-aktivitas tersebut masih ada. Salah satu hal yang dapat dilakukan untuk mengetahui keadaan di bawahnya adalah dengan melakukan tomografi kecepatan seismik 3D. Pada penelitian ini, program yang digunakan adalah SimulPS12 dan menghasilkan tomogram anomali Vp, Vs dan rasio Vp/Vs. Berdasarkan hasil tomografi tersebut diketahui bahwa zona lemah terdapat pada kedalaman 30 km di bagian tengah Danau Toba dan kedalaman 50 km. Adapun proses partial melting terjadi pada kedalaman sekitar 130 km hingga 50 km yang berasal dari slab subduksi di bawah Danau Toba. Pada kedalaman 30 km, selain anomali negatif, juga terlihat pola anomali Vp dan Vs positif yang mengindikasikan keberadaan bekas konduit dari intrusi magma yang membeku. Selain itu, aktivitas seismik juga terlihat tersebar pada beberapa titik di sekitar Kaldera Toba seperti di Gunung Pusuk Buhit dan Gunung Pardepur. Toba volcano is one of the ancient volcanoes in Indonesia located in Northern Sumatera. There were two activities having an affect on the volcano, the volcanic activity from the magma chamber beneath the Toba caldera complex and the tectonic activity from the subduction of Indo-Australia Plate. Despite the last eruption of Toba was about 70.000 years ago, the activities were still exist. The 3D seismic tomography could be carried out to understand the conditions beneath Toba Caldera. In this research, the data was processed using the SimulPS12 program, and tomography images obtained were from Vp, Vs, and Vp/Vs ratio. The results showed that the weak zones were found in the depth of 30 km in the middle part of Toba Caldera and the depth of 50 km. The partial melting process was in the depth of about 130 km to 50 km beneath Toba Caldera. The depth of 30 km was also found the high anomaly of Vp and Vs which indicated the existence of the remnant conduit of solidified magma. In addition, the other seismic activities could also be found in its vicinity, i. e., in Pusuk Buhit Volcano and Pardepur Volcano.
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Hauptmann, Edward, Kiran Batra, Asha Kandathil, Arzu Canan, Sergio Alvarado, Qiubai Li, Vishal Kukkar, Yin Xi, and Kemp H. Kernstine. "Using predictive models to determine the presence of non-small cell lung cancer metastasis to N2 and N3 regions." Journal of Clinical Oncology 39, no. 15_suppl (May 20, 2021): e20560-e20560. http://dx.doi.org/10.1200/jco.2021.39.15_suppl.e20560.
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e20560 Background: Accurate assessment of non-small cell lung cancer (NSCLC) mediastinal involvement is key to developing treatment plans and determining prognosis. To date, there is no reliable imaging-based means to determine the presence or absence of mediastinal involvement. Current computed tomogram (CT) and fluorodeoxyglucose-positron emission tomography/ computed tomogram (PET-CT) technologies provide numerous derived automated variables have not been sufficiently evaluated to determine the presence of metastasis to the mediastinum. We have developed predictive models to determine the presence or lack of metastatic NSCLC in N2 and N3 regions. Methods: Consecutive patients from 2012-2017 with biopsy-proven NSCLC who had CT and PET-CT, as well as biopsy of the mediastinum had their images reread by a team of blinded specialty radiologists and nuclear medicine specialists. Patients with no mediastinal malignancy on biopsy were followed for 6 months from the initial evaluation to confirm lack of mediastinal malignancy.278 regions (N2 and N3) from 139 patients were included. Logistic regression models were used to build a baseline model, as well as models with additional nodal station maximum standard uptake valuve (SUVm) measurements (SUVm, SUVm-SUVmeanbloodpool and SUV lymph node/tumor (LN/T)) for N2 and N3 regions, respectively. When nodal station SUVm was not measured, SUVmeanbloodpool was used. The SUVm within each region was used. Stepwise selection was used to select variables in the baseline model. Cross-validated ROC curve and area under the curve (AUC) were reported. All analyses were done in SAS 9.4 (SAS Institute, Inc., Cary, NC). Results: 40/139 N2 regions had malignancy, 4/139 N3 regions had malignancy. Baseline models for N2 regions selected lung laterality (OR right vs left: 4.84 (1.79, 13.05)) and nodal station short-axis diameter > 1 cm (OR yes vs no: 5.49 (1.71, 17.54)) while no variables were selected for the baseline model for N3 regions due to lack of statistical power. We used the same variables for the N3 baseline model. Conclusions: We have identified models that use a more advanced analysis of predicting the presence or absence of metastatic NSCLC in both N2 and N3 regions with respect to the primary lesion. All models perform better with SUVm related measurements. From this information, we are developing a clinical application to provide practitioners a better means of assessing the presence of mediastinal involvement of NSCLC. [Table: see text]
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Liu, Sixin, Xintong Liu, Xu Meng, Lei Fu, Qi Lu, and Li Deng. "Application of Time-Domain Full Waveform Inversion to Cross-Hole Radar Data Measured at Xiuyan Jade Mine, China." Sensors 18, no. 9 (September 15, 2018): 3114. http://dx.doi.org/10.3390/s18093114.
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Xiuyan Jade, produced in Xiuyan County, Liaoning Province, China is one of the four famous jade in China. King Jade, which is deemed the largest jade body of the world, was broken out from a hill. The local government planned to build a tourism site based on the jade culture there. The purpose of the investigation was to evaluate the stability of subsurface foundation, and the possible positions of mined-out zones to prevent the further rolling of the jade body. Cross-hole radar tomography is the key technique in the investigation. Conventional travel time and attenuation tomography based on ray tracing theory cannot provide high-resolution images because only a fraction of the measured information is used in the inversion. Full-waveform inversion (FWI) can provide high-resolution permittivity and conductivity images because it utilizes all the information provided by the radar signals. We deduce the gradient expression of the time-domain FWI with respect to the permittivity and conductivity using a method that is different from that of the previous work and realize the FWI algorithm that can simultaneously update the permittivity and conductivity by using the conjugate gradient method. Inverted results from synthetic data show that time-domain FWI can significantly improve the resolution compared with the ray-based tomogram methods. FWI can distinguish targets that are as small as one-half to one-third wavelength and the inverted physical values are closer to the real ones than those provided by the ray tracing method. We use the FWI algorithm to the field data measured at Xiuyan jade mine. Both the inverted permittivity and conductivity can comparably delineate four mined-out zones, which exhibit low-permittivity and low-conductivity characteristics. Furthermore, the locations of the interpreted mined-out zones are in good agreement with the existing mining channels recorded by geological data.
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Kumar S, Arun, and Meena Kumari S. "CT study of third and fourth ventricle size in South Indian subjects." National Journal of Clinical Anatomy 06, no. 03 (July 2017): 198–202. http://dx.doi.org/10.1055/s-0039-1700743.
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Abstract Background and aim: Assessment of normal dimension of cerebral ventricles is important for early detection of changes due to intrinsic and extrinsic pathology producing ventriculomegaly. Hence normal upper and lower limits of the cerebral ventricular system in various age groups and in both sexes are important for diagnosing it. Our aim is to establish a baseline reference value for the third and fourth ventricular width using Computed Tomogram [CT] for normal South Indian population. Materials and methods: 100 subjects aged between 5 to 90 years, comprising of 54 males and 46 females, with normal CT brain were analyzed. Subjects with intracranial and intraventricular pathology were excluded. Axial CT brain was obtained in Siemens Somatom scope multislice slice CT scanner. The widest diameter of the third and fourth ventricles on axial images using linear approach was measured. Student’s t test and one way analysis of variance was used. Results: Mean third ventricle size in male: 5.11 +/- 2.37 mm and in female: 4.35 +/- 2.08 mm. Mean fourth ventricle size in male: 13.40 +/- 1.66 mm and in female: 12.84 +/- 1.85 mm. Conclusion: The highest of the dimension in the third ventricle occurs in the highest age group of ≥60 years in both males and females. There was a steady rise in the third ventricle size across age groups until the seventh decade.
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White, James C. "Uncovering Flickering in Time-Resolved Spectroscopy for the Nova-like Variable UX Ursa Majoris." International Astronomical Union Colloquium 163 (1997): 834. http://dx.doi.org/10.1017/s0252921100044249.
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AbstractThe flickering phenomenon in cataclysmic variables (CVs) is manifest photometrically as variations in system brightness with amplitudes up to about 1 mag and on timescales from seconds to tens of minutes. Although a pronounced characteristic of CVs, flickering has been studied, in general, only tangentially and in the context of overall CV photometric properties. It is usually uncovered in CV photometry, yet my Doppler tomographic analysis of data collected on the KPNO 2.1-meter telescope in 1982 by Schlegel, Honeycutt, and Kaitchuck (1983) for the nova-like variable UX Ursa Majoris suggests that flickering also exists in this system’s spectroscopy.Using the integrated continuum flux from the UX UMa observations and Bruch’s (1992) methodology for classifying high- and low-flicker data, I constructed two data subsets corresponding to high- and low-flicker states. I generated Doppler tomograms of these high- and low-flicker states and interpret differences between the tomograms as spectroscopic signatures of flickering in the system.In UX UMa’s Hβ Doppler tomograms, a small, faint, incomplete ring of emission is visible for both flickering states. Dominating ring emission is strong emission in the (+Vx,+Vy) quadrant. The usual location for Swave emission, in the (−Vx,+Vy) quadrant, is here the region of faintest emission. Differenced Doppler tomograms, produced by subtracting from the tomograms the symmetric ring-emission component, show clear differences between the high- and low-flicker states. Further, these early results suggest Doppler tomography may be a useful technique for studying the secondary stars in CVs imaged in this manner. Enhanced chromospheric activity of the red dwarf companion is clearly visible in the high-flickering state tomogram at (0, Krd) and may, therefore, afford investigators the opportunity to estimate the chromospheric flux and radial velocity of the secondary star.
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Eggeman, Alexander, Robert Krakow, and Paul Midgley. "6D electron microscopy: combining real-space and reciprocal-space tomography." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C368. http://dx.doi.org/10.1107/s2053273314096314.
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STEM and TEM-based tomography has been used widely to study the 3D morphology of a wide range of materials. Similarly reciprocal space tomography in which a tilt-series of diffraction patterns are acquired offers a powerful method for the analysis of the atomic structure of crystalline materials. The natural progression is to combine these techniques into a complete three dimensional morphology and crystallography data set, allowing both features to be studied simultaneously. Using a tilt series of scanning precession electron diffraction measurements from a commercially available Ni-base superalloy as an example, the complete reciprocal lattice orientation for a number of components embedded within the matrix could be determined. It was straightforward to identify reciprocal lattice vectors that allowed dark-field images representing each phase to be produced post-acquisition. In turn these were combined using geometric tomography methods to yield a 3-D tomogram of the superalloy. Imaging these phases using conventional ADF STEM tomography would potentially be challenging given the compositional similarity between the different phases. From the combined dataset the spatial distribution of the component phases could be easily recovered but more importantly the orientational relationships between these different components could be unambiguously determined. In this way the thermo-mechanical history of the sample could be inferred from the arrangement of coherent and semi-coherent interfaces and a previously unreported crystallographic registry between metal carbide (MC) and the matrix f.c.c. phases could been identified. The possibilities for development and applications of this technique will be discussed further.
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Rosselin, Manon, Paula Nunes-Hasler, and Nicolas Demaurex. "Ultrastructural Characterization of Flashing Mitochondria." Contact 1 (January 2018): 251525641880142. http://dx.doi.org/10.1177/2515256418801423.
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Mitochondria undergo spontaneous transient elevations in matrix pH associated with drops in mitochondrial membrane potential. These mitopHlashes require a functional respiratory chain and the profusion protein optic atrophy 1, but their mechanistic basis is unclear. To gain insight on the origin of these dynamic events, we resolved the ultrastructure of flashing mitochondria by correlative light and electron microscopy. HeLa cells expressing the matrix-targeted pH probe mitoSypHer were screened for mitopHlashes and fixed immediately after the occurrence of a flashing event. The cells were then processed for imaging by serial block face scanning electron microscopy using a focused ion beam to generate ∼1,200 slices of 10 nm thickness from a 28 µm × 15 µm cellular volume. Correlation of live/fixed fluorescence and electron microscopy images allowed the unambiguous identification of flashing and nonflashing mitochondria. Three-dimensional reconstruction and surface mapping revealed that each tomogram contained two flashing mitochondria of unequal sizes, one being much larger than the average mitochondrial volume. Flashing mitochondria were 10-fold larger than silent mitochondria but with a surface to volume ratio and a cristae volume similar to nonflashing mitochondria. Flashing mitochondria were connected by tubular structures, formed more membrane contact sites, and a constriction was observed at a junction between a flashing mitochondrion and a nonflashing mitochondrion. These data indicate that flashing mitochondria are structurally preserved and bioenergetically competent but form numerous membrane contact sites and are connected by tubular structures, consistent with our earlier suggestion that mitopHlashes might be triggered by the opening of fusion pores between contiguous mitochondria.
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Popov, E. V., Zh Zh Anashbaev, A. N. Maltseva, and S. I. Sazonova. "Radiomic features of epicardial adipose tissue in coronary atherosclerosis." Complex Issues of Cardiovascular Diseases 10, no. 4 (December 20, 2021): 6–16. http://dx.doi.org/10.17802/2306-1278-2021-10-4-6-16.
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Aim. To investigate the association of the radiomic characteristics of epicardial adipose tissue (EAT) on contrast-free computed tomography (CT) of the heart with the severity of obstructive coronary lesion and myocardial ischemia.Methods. The study included 68 patients with coronary heart disease (mean age of 63.5±9.4, 45 men and 23 women), and 15 patients (mean age 30±4.8; 14 men and 1 woman) without cardiovascular disease as a control group. All the patients underwent multispiral computed coronary angiography, coronary calcium scores (CCS) determination and stress myocardial perfusion scintigraphy. Radiomic characteristics of EAT (texture analysis by gradations of gray color) were determined on non-contrast computer tomogram images of the heart using 3D-Sliser software and the SliserRadiomics module (version 4.10.2). The obtained indicators were compared between a control and under the study groups as well as between subgroups of patients divided according to the degree of obstruction of the coronary arteries, the size of the perfusion defect, and the value of the CCS.Results. The comparative analysis of radiomic indicators of EAT between patients with coronary artery disease and the control group showed the presence of statistically significant differences between them. At the same time, the correlation analysis in the study group did not reveal any correlations between the radiomic parameters and the size of the perfusion defect, CCS or degree of stenosis of the lumen of the coronary arteries.Conclusion. The textural characteristics of EAT in patients with coronary heart disease differ from those in individuals without cardiovascular pathology. At the same time, these indicators are not associated with the severity of obstructive lesions of the coronary arteries, the value of the CCS, and the size of the perfusion defect according to scintigraphy.
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Dantas, Renato R. S., and Walter E. Medeiros. "Resolution in crosswell traveltime tomography: The dependence on illumination." GEOPHYSICS 81, no. 1 (January 1, 2016): W1—W12. http://dx.doi.org/10.1190/geo2015-0119.1.
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The key aspect limiting resolution in crosswell traveltime tomography is illumination, a well-known result but not well-exemplified. We have revisited resolution in the 2D case using a simple geometric approach based on the angular aperture distribution and the Radon transform properties. We have analytically found that if an isolated interface had dips contained in the angular aperture limits, it could be reconstructed using just one particular projection. By inversion of synthetic data, we found that a slowness field could be approximately reconstructed from a set of projections if the interfaces delimiting the slowness field had dips contained in the available angular apertures. On the one hand, isolated artifacts might be present when the dip is near the illumination limit. On the other hand, in the inverse sense, if an interface is interpretable from a tomogram, there is no guarantee that it corresponds to a true interface. Similarly, if a body is present in the interwell region, it is diffusely imaged, but its interfaces, particularly vertical edges, cannot be resolved and additional artifacts might be present. Again, in the inverse sense, there is no guarantee that an isolated anomaly corresponds to a true anomalous body, because this anomaly could be an artifact. These results are typical of ill-posed inverse problems: an absence of a guarantee of correspondence to the true distribution. The limitations due to illumination may not be solved by the use of constraints. Crosswell tomograms derived with the use of sparsity constraints, using the discrete cosine transform and Daubechies bases, essentially reproduce the same features seen in tomograms obtained with the smoothness constraint. Interpretation must be done taking into consideration a priori information and the particular limitations due to illumination, as we have determined with a real data case.
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Sameer, Mohammed, and Li Sirui. "MDCT OF ABDOMINAL WALL LUMBAR HERNIAS." International Journal of Advanced Research 8, no. 10 (October 31, 2020): 890–95. http://dx.doi.org/10.21474/ijar01/11914.
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Purpose:To review the anatomical landmarks of the abdominal wall lumbar region and its normal appearance on multidetector computed tomography (MDCT) and to briefly describe the MDCT features of lumbar hernias.Diagnosis of traumatic diaphragmatic hernia due to blunt abdominal trauma requires a high index of suspicion. This study was conducted to assess the accuracy of multidetector computed tomogram (MDCT) in the diagnosis of traumatic diaphragmatic hernia.Diaphragmatic injuries remain a diagnostic challenge for both radiologists and surgeons. The detection of traumatic diaphragmatic rupture in the acute setting is problematic because specific clinical signs are usually not evident. Furthermore, the high frequency of associated injuries (52–100%) may distract from diaphragmatic injury. In conservatively managed patients, the rate of initially missed diaphragmatic injuries ranges from 12 to 66%, and they may even be overlooked at laparotomy. Diagnosis of a diaphragmatic injury requires a high index of suspicion, as delayed diagnosis increases the chance of visceral herniation and strangulation, which has mortality as high as 60%. Thus, the ability to detect diaphragmatic injuries with noninvasive techniques is increasingly important. Initial reports found CT to have sensitivity equal to that of chest radiography (i.e., 0–50%). Because of a dramatic reduction in motion and beam-hardening artifacts and significant improvement of spatial resolution, especially along the z-axis, helical CT and multisection CT allow better demonstration of most subtle signs of diaphragmatic herniation. In addition, these are also useful tools in the evaluation of patients with multiple traumatic injuries. Traumatic diaphragmatic hernias (TDHs) are sometimes difficult to identify at an early stage and can consequently result in diagnostic delays with life-threatening outcomes. It is the aim of this case study to highlight the difficulties encountered with the earlier detection of traumatic diaphragmatic hernias. Methods: We performed a retrospective search of the imaging report database from November 2007 to October 2011. We retrieved the clinical data and MDCT studies of patients suffering from abdominal wall lumbar hernias. We reviewed the imaging features of abdominal lumbar hernias and compared those with the normal appearance of the lumbar region in asymptomatic individuals.We assessed variables such as age, gender, mechanism of trauma, methods of diagnosis, herniated organs and associated lesions, time of evolution, morbidity, and mortality. Anteroposterior supine chest radiograph, which was performed in all patients, was also analyzed. Computed tomogram (CT) was performed on four-slice MDCT after an IV bolus of iodinated contrast agents. A slice thickness of 4 mm at a pitch of 1.5 was useful to evaluate thorax and abdomen with reconstruction at 1 mm reconstruction increment. An oral contrast agent was given whenever required. Multiplanar reconstruction was done in sagittal and coronal planes. Images were read in lung parenchyma, soft tissues, and bone windows. Findings were analyzed in a prospective manner to evaluate their use as a diagnostic modality as well as to determine their contribution to patient management. Results:We classified lumbar wall hernias as diffuse, superior (or Grynfelt–Lesshaft) and inferior (or Petit) lumbar hernias. We briefly describe the imaging features of each subtype and review the anatomy and MDCT appearance of normal lumbar region.Currently available MDCT provides an excellent opportunity for reviewing the normal anatomy of the wall lumbar region and may be considered a useful modality for evaluating lumbar hernias.Regarding Diaphragmatic hernia following blunt trauma:MDCT is a highly accurate modality for diagnosing traumatic diaphragmatic hernia. In addition, it is fast and compatible with various life-support systems hence, it can be used in acute trauma setting for making a diagnosis and helping in the management.Delayed traumatic diaphragmatic hernias are not common, but can lead to serious consequences once occurred. Early detection of diaphragmatic injuries is crucial to prevent the occurrence of dTDHs. Surgeons should maintain a high suspicion for injuries of the diaphragm in patients who had suffered abdominal or lower chest traumas, especially during the initial surgical explorations. The need for radiographical follow-ups is emphasized to detect diaphragmatic injuries at an earlier stage.
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Dai, Hongyi, Igor Shikhov, Rupeng Li, Ji-Youn Arns, and Christoph H. Arns. "Mechanisms of Confining Pressure Dependence of Resistivity Index for Tight Sandstones by Digital Core Analysis." SPE Journal 26, no. 02 (February 10, 2021): 883–96. http://dx.doi.org/10.2118/205026-pa.
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Summary Resistivity measurements are a major input into hydrocarbon reserve estimation and are usually described by Archie’s laws. In this study, we use digital rock physics to analyze the mechanisms of non-Archie and Archie behavior of formation factor (FF) and resistivity index (RI) of low-porosity Fontainebleau (FB) sandstone for ambient conditions and under high confining pressure, respectively. FB sandstone was imaged by micro-X-ray computed tomography (micro-CT) at a resolution of 1 µm. Subresolution details of the grain contact width distribution along with their length were extracted from a set of scanning electron microscope (SEM) images. The nanoscale aperture of grain contacts, which is below tomogram resolution, is accounted for in micro-CT-based numerical calculations by assigning effective porosity and conductivity to individual voxels of the extracted grain contact network. A porosity reduction of grain contacts and open pore space as a function of applied confining pressure is introduced, capturing the pressure dependence. The concept was implemented by grain contact labeling, introducing an additional phase derived from a Euclidean distance transform (EDT). Subvoxel stress-strain effects were incorporated by attributing all compressibility effects to the pore space (open pore space and grain contacts), treating the solid phase as perfectly rigid. Voxel-scale input conductivities are assigned using Archie’s law followed by solving the Laplace equation for sample-scale rock resistivity and RI directly on the segmented image using the finite element method. For the numerical modeling of the FF and RI of low-porosity FB sandstone as a function of confining pressure, which depends on subresolution features, a set of hypotheses were tested. These are based on two segmentation scenarios incorporating the measured contact aperture distribution from SEM analysis—a homogeneous aperture-based segmentation by assuming all grain contacts as an average constant value and a heterogeneous aperture-based segmentation assigning two groups of grain contact apertures. The segmentation scenarios enable homogeneous and heterogeneous morphological change of grain contacts due to confining pressure effects. Furthermore, partial saturation of grain contacts is considered. In all cases, strong water-wetness was assumed, and discretization effects were analyzed carefully. The numerical results highlight the relative contribution of each of two conductive components of FB sandstone (open pores vs. grain contacts) over the full range of partial saturations. Of importance is the connectivity of the system, with discretization effects having a significant effect on FF, but a small effect on the RI. Grain contacts and confining pressure are found to have a significant impact on RI behavior of low-porosity FB sandstone. Both the grain contact network with homogeneous aperture and the heterogeneous grain contact network are able to describe experimental observations. However, it is not sufficient to assume a homogeneous change in contact area, and an inhomogeneous deformation of grain contact zones is required to match the experiment.