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Journal articles on the topic 'Tomografo'
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1
Cartolari, R., L. Perugini, L. Vocino, and S. Boni. "Costruzione di trasparenti tridimensionali in tomografia computerizzata." Rivista di Neuroradiologia 9, no. 1 (February 1996): 81–87. http://dx.doi.org/10.1177/197140099600900110.
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Viene presentata una tecnica che, partendo da normali acquisizioni TC, con la sola utilizzazione dei programmi di base del tomografo («on-the-scanner») consente di produrre modelli tridimensionali (3D) con visualizzazione, in trasparenza, di aree di interesse specifico (bersagli). La tecnica prevede la produzione di una serie di «immagini-maschera» alle quali vengono sovrapposte «immagini-bersaglio» nella stessa prospettiva, ottenute sia con semplice campionamento attraverso l'u-so della soglia ( thresholding) che attraverso segmentazione manuale. La costruzione dei trasparenti, oltre a rappresentare un potente mezzo di sintesi delle informazioni contenute nell' esame, può consentire valutazioni diagnostiche originali in pazienti portatori di voluminose protesi metalliche, sia grazie alla visione d'insieme del volume esaminato, sia riducendo in parte gli artefatti da effetto Hounsfield.
2
Durlak, Wojciech, and Edyta Górska-Drabik. "Ocena przydatności tomografu dźwiękowego w diagnozowaniu zdrowotności drzew zasiedlonych przez szkodniki owadzie." Agronomy Science 76, no. 2 (July 21, 2021): 37–50. http://dx.doi.org/10.24326/as.2021.2.4.
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W badaniach określono przydatność tomografii dźwiękowej do oceny stanu zdrowotnego sosny pospolitej i olszy czarnej zasiedlonych przez szkodniki owadzie. Phaenops cyanea, Rhagium inquisitor, Arhopalus rusticus żerujące na sośnie oraz monofagiczny gatunek Synanthedon mesiaeformis występujący na olszy to szkodniki wtórne, które zasiedlają drzewa osłabione przez różne czynniki środowiskowe. Do badań wybrano dwie sosny pospolite i dwie olsze czarne rosnące na terenie leśnictwa Macoszyn w kompleksie lasu świeżego. Zastosowano urządzenie Picus 3 bazujące na metodzie tomografii akustycznej. Wykorzystuje ona właściwości fali dźwiękowej, generowanej po obwodzie pnia, dostarczając informacji o stanie zdrowotnym drewna. Oceniane sosny zasiedlone przez szkodniki wtórne były już martwe, jednak otrzymane wyniki z tomografu sugerowały 100% sprawność techniczną drewna, nie wykazując przy tym uszkodzeń spowodowanych przez owady. U olszy czarnej analiza tomograficzna wykazała znaczne uszkodzenia wewnętrznych struktur drewna (25 i 49%), ale nie były one spowodowane żerowaniem szkodnika a raczej rozkładem próchniczym. Tomografia dźwiękowa nie odzwierciedla rzeczywistego obrazu uszkodzeń spowodowanych przez owady, ale może być narzędziem do typowania drzew osłabionych, które mogą być atakowane przez szkodniki wtórnie.
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Rust, Steffen. "Accuracy and Reproducibility of Acoustic Tomography Significantly Increase with Precision of Sensor Position." Journal of Forest and Landscape Research 2, no. 1 (November 6, 2017): 1–6. http://dx.doi.org/10.13141/jflr.v2i1.449.
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Acoustic tomograms are widely used in tree risk assessment. They should be accurate,repeatable and comparable between consecutive measurements. Previous work has failed to address the effects of different approaches to record sensor positions, operators and models of tomograph on the resulting tomograms.In this study, three operators used the two most common sonic tomographmodels to measure seven cross-sections of Norway spruce trees, whichwere felled after the measurement. We evaluated the effects of model, operator, and different approaches to measure sensor positions on the quality of the tomograms.The largest source of error was the position of sensors, affectingestimated stress wave velocity, the shape of the tomogram, and the sizeof the defect.To produce accurate and repeatable tomograms of trees with complex shapes,it is essential to measure the sensor positions precisely.
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Терещенко, С. А., and А. Ю. Лысенко. "Реконструкция пространственного распределения источников излучения в пропорциональной рассеивающей среде." Журнал технической физики 91, no. 5 (2021): 732. http://dx.doi.org/10.21883/jtf.2021.05.50683.294-20.
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A new method of image reconstruction for single-photon emission computed tomography in a proportional scattering medium is investigated. The detector counts were obtained using Monte Carlo simulation with the Geant4 nuclear physics software system, which eliminates the need for a real tomograph, radiopharmaceuticals and a phantom under study. In this case, the detector counts obtained with the Geant4 do not practically differ from those that would have been obtained in a full-scale experiment for the real scattering medium. The influence of the absorbing and scattering properties of thirteen different substances as a medium, in which the spatial distribution of radiation sources is immersed, on the accuracy of the tomogram reconstruction is investigated. The significant advantage of the proposed algorithm for reconstruction of emission tomograms in comparison with the traditional one is shown.
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Терещенко, С. А., and А. Ю. Лысенко. "Реконструкция пространственного распределения источников излучения в пропорциональной рассеивающей среде." Журнал технической физики 91, no. 5 (2021): 732. http://dx.doi.org/10.21883/jtf.2021.05.50683.294-20.
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A new method of image reconstruction for single-photon emission computed tomography in a proportional scattering medium is investigated. The detector counts were obtained using Monte Carlo simulation with the Geant4 nuclear physics software system, which eliminates the need for a real tomograph, radiopharmaceuticals and a phantom under study. In this case, the detector counts obtained with the Geant4 do not practically differ from those that would have been obtained in a full-scale experiment for the real scattering medium. The influence of the absorbing and scattering properties of thirteen different substances as a medium, in which the spatial distribution of radiation sources is immersed, on the accuracy of the tomogram reconstruction is investigated. The significant advantage of the proposed algorithm for reconstruction of emission tomograms in comparison with the traditional one is shown.
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Righini, A., O. De Divitiis, A. Prinster, D. Spagnoli, I. Apollonio, L. Bello, G. Tomei, R. Villani, F. Fazio, and M. Leonardi. "Risonanza magnetica funzionale: Localizzazione dell'area motoria primaria in pazienti portatori di lesioni espansive cerebrali Risultati preliminari." Rivista di Neuroradiologia 8, no. 3 (June 1995): 371–81. http://dx.doi.org/10.1177/197140099500800304.
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La Risonanza Magnetica Funzionale (RMF) ha dimostrato di poter localizzare la sede di aree corticali funzionali in numerosi protocolli su volontari sani. La identificazione prechirurgica di aree corticali eloquenti è molto importante al fine della realizzazione di un intervento il meno lesivo possibile per la funzione. Il sowertimento più o meno grossolano della regione anatomica da parte di un processo espansivo rende spesso difficile la identificazione di determinati reperi anatomici. Ci siamo proposti di studiare con RMF, su tomografo convenzionale, pazienti affetti da neoplasie intra ed extrassiali che interessavano il lobo frontale posteriore o quello parietale. Sono stati studiati quindici pazienti, tutti destrimani, di età compresa tra i 15 ed i 64 anni. Sono state ottenute mappe di attivazione, che hanno evidenziato aree di significativo aumento del segnale in regione parieto-frontale posteriore. La morfologia delle aree di significativo aumento di segnale era il più delle volte di tipo serpiginoso. Quando l'effetto massa era netto, l'area attivata nell'emisfero patologico appariva dislocata rispetto a quella nell'emisfero controlaterale. Sino ad ora sono stati ripetuti gli esami di RMF dopo l'intervento chirurgico in tre pazienti che non presentavano deficit motori significativi all'arto superiore. Neoplasms compressing or infiltrating cerebral cortex often alter the normal anatomy in such a way that the neurosurgeon can not easily localize and spare functional areas. Moreover, the results of mass effect on brain functional anatomy have not been extensively investigated in vivo yet.
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Rector, James W., and John K. Washbourne. "Characterization of resolution and uniqueness in crosswell direct‐arrival traveltime tomography using the Fourier projection slice theorem." GEOPHYSICS 59, no. 11 (November 1994): 1642–49. http://dx.doi.org/10.1190/1.1443553.
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The process of acquiring a crosswell seismic direct‐arrival traveltime data set can be approximated by a series of truncated plane‐wave projections through an interwell slowness field. Using this approximation, the resolution and uniqueness of crosswell direct‐arrival traveltime tomograms can be characterized by invoking the Fourier projection slice theorem, which states that a plane‐wave projection through an object constitutes a slice of the object’s spatial spectrum. The limited vertical aperture of a crosswell survey introduces a small amount of nonuniqueness into the reconstructed tomogram by truncating the plane‐wave projection. By contrast, the limitations on angular aperture have a significant effect on resolution. The reconstructed tomogram is smeared primarily along the limiting projection angles, with the amount of smearing dependent upon the well spacing and the angular aperture. The amount of smearing was found to be inversely proportional to tan Δϕ, where Δϕ is the angular aperture illuminating a sector of the interwell plane. Consequently, the amount of smearing can be large where the angular aperture becomes small, such as at the top and bottom of the tomogram. For interwell sectors illuminated by large angular apertures, Fresnel zone effects will generally be the limiting factor in crosswell tomogram resolution. However, in some circumstances, angular aperture effects may control the tomogram resolution. The effects of angular aperture and direct‐arrival Fresnel zones produce tomograms with spatial resolution that is dependent upon the well spacing. This study indicates that direct‐arrival traveltime tomography will not usually produce tomograms with substantially greater resolution than surface seismic techniques for normal oil and gas well spacings.
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Makarov, A. Y., А. V. Kholin, and D. V. Gurevich. "The place of magnetic resonance tomography in diagnosis of discogenic cervical myelopathy." Neurology Bulletin XXVII, no. 1-2 (May 15, 1995): 21–24. http://dx.doi.org/10.17816/nb78235.
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The data on complex examination using MRT techniques (T1 and T2 weighted sagittal and cross section tomograms in the tomograph with 0,04 T field strength) for examination of 45 patients suspected in cervical ische mic myelopathy are given. In 27 patients with clinically confirmed diagnosis of myelopathy the compression of spinal marrow was found. MRT is the most informative techique allowing the objective detection of the causes of compressive ischemic myelopathy with cervical loca tion. It is advantageous to use expressed T2 weighted sa gittal tomograms better detecting osteochondrosis and posterior herniae. T1 weighted tomograms are important when determining the direction of disc protruding and the extent of spinal marrow compression.
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Zhou, Changxi, Gerard T. Schuster, Sia Hassanzadeh, and Jerry M. Harris. "Elastic wave equation traveltime and waveform inversion of crosswell data." GEOPHYSICS 62, no. 3 (May 1997): 853–68. http://dx.doi.org/10.1190/1.1444194.
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A method is presented for reconstructing P‐ and S‐velocity distributions from elastic traveltimes and waveforms. The input data consist of crosswell hydrophone records generated by a piezoelectric borehole source. Borehole effects are partially accounted for by using a low‐frequency Green's function to simulate the pressure generated in the fluid‐filled receiver well. The tube waves in the borehole are ignored, on the assumption that they can be removed from the field data by median filtering. In addition, the source‐radiation pattern is partially taken into account by inverting for the equivalent stress components acting on the earth at the source location. The elastic wave equation traveltime and waveform inversion (WTW) method is applied to both synthetic crosswell data and the McElroy field crosswell data. As predicted by theory, results show that elastic WTW tomograms provide a sharper interface image than delineated in the traveltime tomograms. The spatial resolution of the McElroy traveltime tomogram is about 20 m compared to about 3 m and 1.5 m, respectively, for the associated P‐ and S‐velocity WTW tomograms. From these tomograms, detailed porosity maps of the interwell geology are constructed. There is a very good correlation between the P‐velocity tomograms and the P‐velocity log profiles, and there is a good correlation between the smooth parts of the S‐velocity tomogram and the S‐velocity logs. Unfortunately, the high‐wavenumber parts of the S‐velocity tomograms do not correlate well with the high‐wavenumber parts of the S‐velocity logs. We believe this problem is partly caused by not taking into account attenuation effects in the WTW algorithm.
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Brazaitis, Andrius, Algirdas Tamošiūnas, Vytautas Tutkus, and Janina Tutkuvienė. "Patelofemoralinio skausmo sindromo vaizdinimas." Medicinos teorija ir praktika 21, no. 3.2 (June 10, 2015): 438–44. http://dx.doi.org/10.15591/mtp.2015.069.
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Reikšminiai žodžiai: kelio sąnarys, girnelės-šlaunikaulio sąnarys, patelofemoralinio skausmo sindromas, magnetinio rezonanso tomografija. Skausmas priekinėje kelio sąnario dalyje yra dažnas pacientų skundas. Ši problema turi didelę socialinę ir ekonominę reikšmę, nes dažniausiai paveikia jaunus ir aktyvius žmones [1]. Dažnis siekia 15–33 proc. suaugusiųjų populiacijoje, 21–45 proc. – paauglių [2, 3]. Nepaisant susirgimo dažnumo ir klinikinių simptomų gausumo, jo etiologija ir diferencinė diagnostika, remiantis tik klinikiniais požymiais, išlieka sudėtinga. Dalies etiologiją pavyksta išsiaiškinti lengvai – tai trauma, raiščių ar sausgyslių plyšimas, tepalinių maišelių uždegimas, likusių diferencinei diagnostikai reikalingi įvairūs radiologiniai tyrimai. Radiologinis kelio sąnario ištyrimas prasideda nuo rentgenogramų – greito, pigaus ir gana efektyvaus tyrimo metodo. Jose galima nustatyti lūžimus, osteoartritą, osteochondrinį pažeidimą, patinimą [2]. Daugiasluoksnio kompiuterinio tomografo ir trimačių rekonstrukcijų pagalba galima nustatyti smulkius lūžimus, kurių nesimato rentgeno nuotraukose [3]. Magnetinio rezonanso tomografija (MRT) yra pasirinkimo metodas įtariant meniskų, raiščių, kremzlės, raumenų ir sausgyslių pažeidimą arba jei nepakanka informacijos paprastesniuose tyrimuose [3]. MRT laikomas auksiniu standartu kelio sąnario radiologiniuose tyrimuose ir mūsų praktikoje sudaro per 50 proc. visų raumenų ir skeleto MRT tyrimų. Vis daugiau pacientų kreipiasi dėl kelio sąnario MRT tyrimo, todėl detalios kelio sąnario anatomijos ir patologijos žinios svarbios tinkamam tyrimui ir gydymui pasirinkti. Skausmo priekinėje sąnario dalyje klasifikacijos yra įvairios. Jackson ir kolegos [4] skausmo priežastis suskirstė į aiškias (židininiai pažeidimai nustatomi kliniškai ir radiologiškai) ir neaiškias (funkcines/dinamines). Tuo tarpu Post [5] skausmą priekinėje sąnario dalyje suskirstė pagal pobūdį: pastovų, susijusį su fiziniu krūviu, aštrų, nepastovų. Anatominis suskirstymas yra praktiškiausias, nes sujungia visas struktūras į vieną mechanizmą [6]. Priežastys gali būti ekstrasąnarinės ir intrasąnarinės. Šio straipsnio tikslas – apžvelgti skausmo priekinėje kelio sąnario dalyje priežastis, apibūdinti pakitimus, matomus magnetinio rezonanso tomografijos vaizduose.
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Pershyna, Iuliia. "MODELING A DYNAMIC THREE-DIMENSIONAL BODY USING INTERFLATATION AND BLENDING APPROXIMATION." Bulletin of the National Technical University "KhPI". Series: Mathematical modeling in engineering and technologies, no. 1 (March 5, 2021): 83–95. http://dx.doi.org/10.20998/2222-0631.2020.01.08.
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The paper deals with the problem of reconstruction of the internal structure (density, absorption or attenuation coefficient) of a three-dimensional body by the information about it in the form of tomograms, given on a certain system of planes intersecting the object of study. This problem arises in practice in cases where there is no plane among the planes that are included in the experimental data, which consists of one or another set of points that are of interest to the researcher. For example, such a problem may arise after a patient has undergone examinations on a medical tomograph. After analyzing the obtained tomograms, it becomes necessary to find with their help one or more tomograms in the planes intersecting the body, but not coinciding with any of the given planes. It is noted that the operators of interflatation of functions is a natural generalization of the interpolation operators for the functions of three variables. Therefore, as in the case of interpolation, errors in the experimental data (in this case, in tomograms) are also introduced into the interflatation operators. In mathematics, there is an alternative to interpolation operators, namely approximation operators. These are operators constructed by smoothing experimental data using polynomials, rational functions, trigonometric polynomials, wavelets, and the like. An operator of mixed approximation of a function of three variables is constructed using Bernstein polynomials; the general form of the approximation error by the constructed operator and the estimate of this error are given. In the paper a four-dimensional mathematical model of a three-dimensional body that changes over time is also built and studied. A computational experiment is presented to restore the internal structure of the human heart from tomograms lying on a system of mutually perpendicular planes, which come from an actually operating computer tomograph. The article presents some possibilities of working with tomograms when restoring the internal structure of a three-dimensional body from the known projections of this body (tomograms).
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Błachnio, Józef, Artur Kułaszka, Marek Chalimoniuk, and Piotr Woźny. "Egzemplifikacja Tomograficznej Metody Do Oceny Jakości Połączeń Spawanych Ze Stopu EN 5754 H22." Research Works of Air Force Institute of Technology 39, no. 1 (December 1, 2016): 51–64. http://dx.doi.org/10.1515/afit-2016-0017.
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Streszczenie Jakość połączeń spawanych zależna jest od wielu czynników. Przedmiotowe normy określają warunki techniczne oceny jakościowej spawów, co stanowi podstawę do uznania połączenia za zgodne z wymaganiami lub wadliwe. W praktyce wykonanie połączenia spawanego całkowicie pozbawionego wad jest trudne. Do kontroli wewnętrznej struktury połączenia wykorzystać można nieniszczącą metodę z zastosowaniem przemysłowego tomografu komputerowego. Ta nowoczesna metoda diagnozowania łączy badanie rentgenowskie z zaawansowaną technologią komputerową. Podstawową zaletą tomografii komputerowej jest badanie obiektów w trzech wymiarach oraz możliwość wykonania rekonstrukcji przestrzennych. Celem artykułu jest omówienie wykorzystania tej metody do oceny jakości połączeń spawanych stopów aluminium. Możliwości tomografii komputerowej przedstawiono na przykładzie próbek spawalniczych wykonanych metodą TIG przy różnych parametrach procesu. Dokonano analizy jakości próbek wykazujących najmniejsze i największe zewnętrzne, jak również wewnętrzne wady spawalnicze.
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Cotroneo, R., M. Dazi, R. Gigli, C. Guidetti, A. Pingi, G. Cantore, and F. Chiappetta. "Studio Angio-RM degli aneurismi intracranici embolizzati con GDC." Rivista di Neuroradiologia 10, no. 2_suppl (October 1997): 142. http://dx.doi.org/10.1177/19714009970100s256.
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Gli autori presentano 18 casi di pazienti portatori di aneurismi cerebrali sottoposti ad embolizzazione mediante uso di spirali a distacco elettrolitico (GDC), controllati a distanza di tre e sei mesi con Angio-RM 3D TOF. Come è noto il protocollo internazionale prevede controlli angiografici a distanza di una settimana, tre mesi, sei mesi, un anno, per gli aneurismi spiralizzati con GDC. Il fine è di controllare una eventuale riabilitazione dell'aneurisma o un aumento delle dimensioni del colletto qualora questi non fosse stato totalmente obliterato. Gli autori hanno suddiviso gli aneurismi in base alle dimensioni della sacca (<1 cm, 1–2.5 cm, >2.5 cm) e in base alle dimensioni del colletto (<4 mm o >4 mm). Inoltre gli aneurismi sono stati suddivisi, dopo il trattamento, in totalmente embolizzati, parzialmente embolizzati, ed embolizzati con residuo di colletto. Al fine di evitare ai pazienti ripetuti esami angiografici con i rischi connessi alla somministrazione di m.d.c. iodato ed a ripetuti traumatismi nelle sedi di puntura, gli AA. hanno ipotizzato di verificare possibilità alternative di immagine. La presenza delle spirali di platino rende, per i noti artefatti, di difficile interpretazione l'Angio-TC con ricostruzione tridimensionale. L'Angio-RM presenta limiti per artefatti dovuti a caduta di segnale proprio in prossimità del colletto dell'aneurisma per turbolenze di flusso. Tale turbolenza è un aspetto fisico che si presenta quanto la sacca aneurismatica è pervia; una volta obliterata il flusso dovrebbe risultare più regolare. Per confermare tale ipotesi, sono state confrontate le Angiografie digitali eseguite a tre e sei mesi dalla spiralizzazione con le Angio-RM eseguite nello stesso periodo tutte con il medesimo tomografo a RM di media intensità di campo (0,5T). Gli autori illustrano i risultati, i limiti e discutono le indicazioni di un protocollo di Angio-RM per alcuni aneurismi sottoposti a embolizzazione.
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Revil, A., Y. Qi, A. Ghorbani, M. Gresse, and D. M. Thomas. "Induced polarization of volcanic rocks. 5. Imaging the temperature field of shield volcanoes." Geophysical Journal International 225, no. 3 (January 28, 2021): 1492–509. http://dx.doi.org/10.1093/gji/ggab039.
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SUMMARY Kilauea is an active shield volcano located in Hawaiʻi. An induced polarization survey was performed in 2015 at the scale of the caldera. The data were acquired with a 2.5 km cable with 64 electrodes and a spacing of 40 m between the electrodes. A total of 6210 measurements were performed. The apparent chargeability data were inverted using a least square technique to obtain a chargeability tomogram. The normalized chargeability tomogram is obtained by multiplying cell-by-cell the chargeability by the conductivity. Once the conductivity and normalized chargeability tomograms are obtained, they are jointly interpreted using a dynamic Stern layer conduction/polarization model, which explains the low-frequency polarization spectra of volcanic rocks. This conductivity/polarization model is tested here on new laboratory experiments performed on 24 samples from a drill-hole located on the Kilauea East Rift Zone (Hole SOH-2). We show that for Kilauea, the ratio between the normalized chargeability and the conductivity is equal to a dimensionless number R = 0.10 ± 0.02 proving that the conductivity and the normalized chargeability are both controlled by the alteration products of the volcanic rocks with a minor role of magnetite except close to the ground surface. In turn, the degree of alteration is controlled by temperature and therefore normalized chargeability and electrical conductivity can both be used as a non-intrusive temperature sensor. This approach is then applied to the field data. Meaningful temperature tomograms can be produced from both electrical conductivity and normalized chargeability tomograms.
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Kotze, E. J., and S. B. Potter. "New Insights from Inside-Out Doppler Tomography." Acta Polytechnica CTU Proceedings 2, no. 1 (February 23, 2015): 170–73. http://dx.doi.org/10.14311/app.2015.02.0170.
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We present preliminary results from our investigation into using an “inside-out” velocity space for creating a Doppler tomogram. The aim is to transpose the inverted appearance of the Cartesian velocity space used in normal Doppler tomography. In a comparison between normal and inside-out Doppler tomograms of cataclysmic variables, we show that the inside-out velocity space has the potential to produce new insights into the accretion dynamics in these systems.
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Bellos, Dimitrios, Mark Basham, Tony Pridmore, and Andrew P. French. "A convolutional neural network for fast upsampling of undersampled tomograms in X-ray CT time-series using a representative highly sampled tomogram." Journal of Synchrotron Radiation 26, no. 3 (April 23, 2019): 839–53. http://dx.doi.org/10.1107/s1600577519003448.
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X-ray computed tomography and, specifically,time-resolvedvolumetric tomography data collections (4D datasets) routinely produce terabytes of data, which need to be effectively processed after capture. This is often complicated due to the high rate of data collection required to capture at sufficient time-resolution events of interest in a time-series, compelling the researchers to perform data collection with a low number of projections for each tomogram in order to achieve the desired `frame rate'. It is common practice to collect a representative tomogram with many projections, after or before the time-critical portion of the experiment without detrimentally affecting the time-series to aid the analysis process. For this paper these highly sampled data are used to aid feature detection in the rapidly collected tomograms by assisting with the upsampling of their projections, which is equivalent to upscaling the θ-axis of the sinograms. In this paper, a super-resolution approach is proposed based on deep learning (termed an upscaling Deep Neural Network, or UDNN) that aims to upscale the sinogram space of individual tomograms in a 4D dataset of a sample. This is done using learned behaviour from a dataset containing a high number of projections, taken of the same sample and occurring at the beginning or the end of the data collection. The prior provided by the highly sampled tomogram allows the application of an upscaling process with better accuracy than existing interpolation techniques. This upscaling process subsequently permits an increase in the quality of the tomogram's reconstruction, especially in situations that require capture of only a limited number of projections, as is the case in high-frequency time-series capture. The increase in quality can prove very helpful for researchers, as downstream it enables easier segmentation of the tomograms in areas of interest, for example. The method itself comprises a convolutional neural network which through training learns an end-to-end mapping between sinograms with a low and a high number of projections. Since datasets can differ greatly between experiments, this approach specifically develops a lightweight network that can easily and quickly be retrained for different types of samples. As part of the evaluation of our technique, results with different hyperparameter settings are presented, and the method has been tested on both synthetic and real-world data. In addition, accompanying real-world experimental datasets have been released in the form of two 80 GB tomograms depicting a metallic pin that undergoes corruption from a droplet of salt water. Also a new engineering-based phantom dataset has been produced and released, inspired by the experimental datasets.
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Ustinin, M. N., Yu V. Maslennikov, S. D. Rykunov, and V. A. Krymov. "Reconstruction of the Human Heart Functional Structure Based On a Few-Channel Magnetocardiogram." Mathematical Biology and Bioinformatics 13, no. 2 (October 3, 2018): 392–401. http://dx.doi.org/10.17537/2018.13.392.
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The new method of magnetocardiography data analysis is proposed. The method is based on the Fourier transform of prolonged time series and on the massive inverse problem solution for all spectral components. Magnetocardiograms (MCG) were registered in the plane above the subject’s chest in the nodes of the “rectangular” (6×6) grid with the step 40 mm at usual laboratory conditions without any additional magnetic shielding. The 9-channel MCG-system “MAG-SCAN-09” with dc-SQUID-based axial second order gradiometers was used. The MCG-recording was performed in four positions of investigated subjects under the instrument to get all 36 MCGs. For each of four positions of the MCG-recording the partial functional tomogram was calculated, which is the spatial distribution of elementary magnetic dipoles, observed in this position. The complete functional tomogram of the thorax was obtained by the summation of four partial functional tomograms, containing the data about the same object, observed from various positions. Filtering and contrasting of the complete functional tomogram made it possible to extract the 3D-object, representing the functional structure of the heart. The method was used for five subjects and provided consistent results. It is possible to use this method in cardiography, because the functional tomogram contains all measured information about individual heart.
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von Ketelhodt, Julius K., Thomas Fechner, Musa S. D. Manzi, and Raymond J. Durrheim. "Elastic Parameters from Compressional and Shear Wave Tomographic Survey: A Case Study from Kuala Lumpur, Malaysia." Journal of Environmental and Engineering Geophysics 22, no. 4 (December 2017): 427–34. http://dx.doi.org/10.2113/jeeg22.4.427.
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An integrated P- and S-wave cross-borehole tomographic survey was performed in the city center of Kuala Lumpur, Malaysia, with the aim of exploring a karstic limestone area near an area that previously encountered cavities. Horizontally polarized shear waves were generated with two opposing, perpendicular strike directions and recorded with a multi-level, three-component receiver array. This allowed a high quality picking of the traveltimes, whereby the wave train reverses at the time of the S-wave arrival. In addition, high quality sparker generated P-waves were recorded. The P- and S-wave traveltimes were used to invert for two co-located tomograms. These tomograms enabled a better interpretation capability than a P- or S-wave tomogram on its own. The tomograms enabled the calculation of the elastic parameters, i.e., P- to S-wave velocity (Vp/Vs) ratio, Poisson's ratio, bulk modulus, Young's modulus and the shear modulus, on a 2D surface between the boreholes. This further aided the interpretation, as areas with limited traveltime accuracy and thus, an increase in tomographic error, could be easily identified, and the extent of a large cavity could be estimated. The interpretation of the tomograms was constrained by two additional boreholes, which provided more confidence on the delineation and location of cavities at depths. The survey shows the benefit of co-locating P- and S-wave tomography surveys.
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Sharova, O. I., M. I. Agafonov, E. A. Karitskaya, N. G. Bochkarev, S. V. Zharikov, G. Z. Butenko, and A. V. Bondar. "Doppler Tomography in 2D and 3D of the X-ray Binary Cyg X-1 for June 2007." Proceedings of the International Astronomical Union 7, S282 (July 2011): 201–2. http://dx.doi.org/10.1017/s1743921311027359.
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AbstractThe 2D and 3D Doppler tomograms of X-ray binary system Cyg X-1 (V1357 Cyg) were reconstructed from spectral data for the line HeII 4686Å obtained with 2-m telescope of the Peak Terskol Observatory (Russia) and 2.1-m telescope of the Mexican National Observatory in June, 2007. Information about gas motions outside the orbital plane, using all of the three velocity components Vx, Vy, Vz, was obtained for the first time. The tomographic reconstruction was carried out for the system inclination angle of 45°. The equal resolution (50 × 50 × 50 km/s) is realized in this case, in the orbital plane (Vx, Vy) and also in the perpendicular direction Vz. The checkout tomograms were realized also for the inclination angle of 40° because of the angle uncertainty. Two versions of the result showed no qualitative discrepancy. Details of the structures revealed by the 3D Doppler tomogram were analyzed.
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Sinha, Mrinal, and Gerard T. Schuster. "Interferometric full-waveform inversion." GEOPHYSICS 84, no. 1 (January 1, 2019): R45—R60. http://dx.doi.org/10.1190/geo2018-0047.1.
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Velocity errors in the shallow part of the velocity model can lead to erroneous estimates of the full-waveform inversion (FWI) tomogram. If the location and topography of a reflector are known, then such a reflector can be used as a reference reflector to update the underlying velocity model. Reflections corresponding to this reference reflector are windowed in the data space. Windowed reference reflections are then crosscorrelated with reflections from deeper interfaces, which leads to partial cancellation of static errors caused by the overburden above the reference interface. Interferometric FWI (IFWI) is then used to invert the tomogram in the target region, by minimizing the normalized waveform misfit between the observed and predicted crosscorrelograms. Results with synthetic and field data with static errors above the reference interface indicate that an accurate tomogram can be inverted in areas lying within several wavelengths of the reference interface. IFWI can also be applied to synthetic time-lapse data to mitigate the nonrepeatability errors caused by time-varying overburden variations. The synthetic- and field-data examples demonstrate that IFWI can provide accurate tomograms when the near surface is ridden with velocity errors.
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Kilina, O. Yu, V. D. Zavadovskaya, R. V. Danilchuk, Ye M. Tretyakov, O. V. Rodionova, and O. V. Baranova. "Assessment of bone tissue architectonics with digital analysis of computed tomograms for osteoporosis diagnostics." Bulletin of Siberian Medicine 2, no. 2 (June 30, 2003): 94–100. http://dx.doi.org/10.20538/1682-0363-2003-2-94-100.
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Digital analysis potential of lumbar vertebra computed tomograms as a method of osteoporosis diagnostics has been investigated. Specific software designed for mineral weight and bone structure assessments has been developed. This software has been approved during the investigation of 10 lumbar vertebra anatomic preparations and 20 patients with chronic renal failure treated by hemodyalisis. Result comparison of computed tomogram digital analysis, mineral structure investigation and histomorphometry of lumbar vertebra anatomic preparations showed that the developed method allowed to perform a reliable analysis of trabecular bone structure and indirect assessment of mineral density.
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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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Sikora, Mateusz, Utz H. Ermel, Anna Seybold, Michael Kunz, Giulia Calloni, Julian Reitz, R. Martin Vabulas, Gerhard Hummer, and Achilleas S. Frangakis. "Desmosome architecture derived from molecular dynamics simulations and cryo-electron tomography." Proceedings of the National Academy of Sciences 117, no. 44 (October 16, 2020): 27132–40. http://dx.doi.org/10.1073/pnas.2004563117.
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Desmosomes are cell–cell junctions that link tissue cells experiencing intense mechanical stress. Although the structure of the desmosomal cadherins is known, the desmosome architecture—which is essential for mediating numerous functions—remains elusive. Here, we recorded cryo-electron tomograms (cryo-ET) in which individual cadherins can be discerned; they appear variable in shape, spacing, and tilt with respect to the membrane. The resulting sub-tomogram average reaches a resolution of ∼26 Å, limited by the inherent flexibility of desmosomes. To address this challenge typical of dynamic biological assemblies, we combine sub-tomogram averaging with atomistic molecular dynamics (MD) simulations. We generate models of possible cadherin arrangements and perform an in silico screening according to biophysical and structural properties extracted from MD simulation trajectories. We find a truss-like arrangement of cadherins that resembles the characteristic footprint seen in the electron micrograph. The resulting model of the desmosomal architecture explains their unique biophysical properties and strength.
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Durlak, Wojciech, Margot Dudkiewicz, Krystyna Pudelska, and Marek Dąbski. "Using Picus® Sonic Tomograph to assess the health state of trees of monumental sizes." Teka Komisji Architektury, Urbanistyki i Studiów Krajobrazowych 13, no. 2 (June 30, 2017): 73–82. http://dx.doi.org/10.35784/teka.1704.
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The aim of the study was to examine the usefulness of The Picus 3 Sonic Tomograph to assess the health state of trees of monumental sizes, which are an important part of the cultural landscape. In the study there were selected tree species Tilia cordata, Gingko biloba and Ulmus glabra growing in the vicinity of Lublin in different habitat conditions. Changes in the internal structure of the tree trunks were shown on the colour tomograms. Two tested specimens of Tilia cordata located in Radawiec Duży were intended to be cut down due to the construction of the ring road of Lublin. This made it possible to compare the obtained tomograms with the actual state of the inside of tree trunks after cutting down the examined trees. The results of Picus tomography Ulmus glabra and Gingko biloba growing in the historic park in Czesławice were confirmed by a visual assessment of trees. In each case the number of installed sensors influenced the image resolution and accuracy of the obtained tomograms. Diagnostics using sound waves is important in assessing the state of health of each tree, but it is especially recommended for testing of valuable trees. It allows for early diagnosis and selection of such protective actions to reduce to a minimum the destructive impact study on the body of the plant.
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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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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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Zhou, Changxi, Wenying Cai, Yi Luo, Gerard T. Schuster, and Sia Hassanzadeh. "Acoustic wave‐equation traveltime and waveform inversion of crosshole seismic data." GEOPHYSICS 60, no. 3 (May 1995): 765–73. http://dx.doi.org/10.1190/1.1443815.
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A hybrid wave‐equation traveltime and waveform inversion method is presented that reconstructs the interwell velocity distribution from crosshole seismic data. This inversion method, designated as WTW, retains the advantages of both full wave inversion and traveltime inversion; i.e., it is characterized by reasonably fast convergence which is somewhat independent of the initial model, and it can resolve detailed features of the velocity model. In principle, no traveltime picking is required and the computational cost of the WTW method is about the same as that for full wave inversion. We apply the WTW method to synthetic data and field crosshole data collected by Exxon at their Friendswood, Texas, test site. Results show that the WTW tomograms are much richer in structural information relative to the traveltime tomograms. Subtle structural features in the WTW Friendswood tomogram are resolved to a spatial resolution of about 1.5 m, yet are smeared or completely absent in the traveltime tomogram. This suggests that it might be better to obtain high quality (distinct reflections) crosshole data at intermediate frequencies, compared to intermediate quality data (good quality first arrivals, but the reflections are buried in noise) at high frequencies. Comparison of the reconstructed velocity profile with a log in the source well shows very good agreement within the 0–200 m interval. The 200–300 m interval shows acceptable agreement in the velocity fluctuations, but the tomogram’s velocity profile differs from the sonic log velocities by a DC shift. This highlights both the promise and the difficulty with the WTW method; it can reconstruct both the and high wavenumber parts of the model, but it can have difficulty recovering the very low wavenumber parts of the model.
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Rojas-Lazaro, Janet, Julio Crespo-Perauna, and Anibal Díaz-Lazo. "Cardiomiopatía dilatada periparto complicada con infarto renal." REVISTA PERUANA DE CIENCIAS DE LA SALUD 1, no. 3 (September 3, 2019): 146–50. http://dx.doi.org/10.37711/rpcs.2019.1.3.44.
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La cardiomiopatía periparto es una forma de miocardiopatía dilatada queafecta a mujeres en edad fértil, ocasionando elevada morbimortalidad. Sepresenta el caso de una paciente joven primípara con sintomatología deinsufciencia cardiaca que además súbitamente presentó dolor lumbar degran intensidad asociado a náuseas y vómitos. El examen de laboratorioreportó niveles altos de deshidrogenasa láctica sérica y tomografía de víasurinarias. El diagnóstico de insufciencia cardiaca con una severa disfunciónsistólica e infarto renal fueron realizados con evaluación clínica, delaboratorio, ecocardiográfco y tomográfco, donde se demostró una severadisfunción sistólica. Se realizó tratamiento con medidas convencionales parainsufciencia cardiaca, empleandose anticoagulación parenteral y oral. Laevolución del cuadro clínico fue favorable, con recuperación parcial de sufuncionalidad. Se presenta este caso debido a la complicación atípica de unapatología infrecuente o sub diagnosticada.
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Lee, Doo Sung, Veronica M. Stevenson, Phil F. Johnston, and C. E. Mullen. "Time‐lapse crosswell seismic tomography to characterize flow structure in the reservoir during the thermal stimulation." GEOPHYSICS 60, no. 3 (May 1995): 660–66. http://dx.doi.org/10.1190/1.1443805.
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Time‐lapse crosswell seismic tomography data, recorded with an interval of six months, indicate a strong directional thermal response in a fractured eolian sandstone reservoir at a five‐spot thermal stimulation site in the South Casper Creek oil field, Wyoming. The seismic thermal response depicted on the tomogram and in conjunction with the geological data from cores and a wireline log, reveals the multichannel flow mechanism in the reservoir formation. The three factors that control steam or heat propagation are the fractures, the directional permeability existing in the rock matrix, and the fault. Crosswell tomograms imply that the primary fluid flow is through fractures oriented north‐south, whereas the secondary fluid flow is through the matrix in the direction of maximum horizontal permeability. The thermal response expressed on the tomogram infers that a fault oriented N80°E offsets flow units and acts as a flow barrier or baffle. The flow structure implied by the crosswell seismic tomography is strikingly different from the initial conjecture, as deduced from engineering perception based on geological reasoning. However, the tomographic implications were supported by both a tracer test and fluid temperature measurements at the four producing wells around the injector.
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Liu, Zhaolun, Jing Li, Sherif M. Hanafy, Kai Lu, and Gerard Schuster. "3D wave-equation dispersion inversion of surface waves recorded on irregular topography." GEOPHYSICS 85, no. 3 (May 1, 2020): R147—R161. http://dx.doi.org/10.1190/geo2019-0537.1.
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Irregular topography can cause strong scattering and defocusing of propagating surface waves, so it is important to account for such effects when inverting surface waves for shallow S-wave velocity structures. We have developed a 3D surface-wave dispersion inversion method that takes into account the topographic effects modeled by a 3D spectral element solver. The objective function is the frequency summation of the squared wavenumber differences [Formula: see text] along each azimuthal angle of the fundamental mode or higher-order modes of Rayleigh waves in each shot gather. The wavenumbers [Formula: see text] associated with the dispersion curves are calculated using the data recorded along the irregular free surface. Numerical tests on synthetic and field data demonstrate that 3D topographic wave equation dispersion inversion (TWD) can accurately invert for the S-wave velocity model from surface-wave data recorded on irregular topography. Field data tests for data recorded across an Arizona fault demonstrate that, for this example, the 2D TWD model can be as accurate as the 3D tomographic model. This suggests that in some cases, the 2D TWD inversion is preferred over 3D TWD because of its significant reduction in computational costs. Compared to the 3D P-wave velocity tomogram, the 3D S-wave tomogram agrees much more closely with the geologic model taken from the trench log. The agreement with the trench log is even better when the [Formula: see text] tomogram is computed, which reveals a sharp change in velocity across the fault. The localized velocity anomaly in the [Formula: see text] tomogram is in very good agreement with the well log. Our results suggest that integrating the [Formula: see text] and [Formula: see text] tomograms can sometimes give the most accurate estimates of the subsurface geology across normal faults.
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D’Hondt, Olivier, Ronny Hänsch, Nicolas Wagener, and Olaf Hellwich. "Exploiting SAR Tomography for Supervised Land-Cover Classification." Remote Sensing 10, no. 11 (November 5, 2018): 1742. http://dx.doi.org/10.3390/rs10111742.
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In this paper, we provide the first in-depth evaluation of exploiting Tomographic Synthetic Aperture Radar (TomoSAR) for the task of supervised land-cover classification. Our main contribution is the design of specific TomoSAR features to reach this objective. In particular, we show that classification based on TomoSAR significantly outperforms PolSAR data provided relevant features are extracted from the tomograms. We also provide a comparison of classification results obtained from covariance matrices versus tomogram features as well as obtained by different reference methods, i.e., the traditional Wishart classifier and the more sophisticated Random Forest. Extensive qualitative and quantitative results are shown on a fully polarimetric and multi-baseline dataset from the E-SAR sensor from the German Aerospace Center (DLR).
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Błaszczyk, E., B. Bobek Billewicz, W. Windorbska, and P. Błaszczyk. "72/Porównanie wyników badań tomografii komputerowej i rezonansu magnetycznego z pozytonową emisyjną tomografią w ocenie wyników leczenia ziarnicy złośliwej." Reports of Practical Oncology & Radiotherapy 9 (2004): S298—S299. http://dx.doi.org/10.1016/s1507-1367(04)70928-1.
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Kłosowski, Grzegorz, Tomasz Rymarczyk, Tomasz Cieplak, Konrad Niderla, and Łukasz Skowron. "Quality Assessment of the Neural Algorithms on the Example of EIT-UST Hybrid Tomography." Sensors 20, no. 11 (June 11, 2020): 3324. http://dx.doi.org/10.3390/s20113324.
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The paper presents the results of research on the hybrid industrial tomograph electrical impedance tomography (EIT) and ultrasonic tomography (UST) (EIT-UST), operating on the basis of electrical and ultrasonic data. The emphasis of the research was placed on the algorithmic domain. However, it should be emphasized that all hardware components of the hybrid tomograph, including electronics, sensors and transducers, have been designed and mostly made in the Netrix S.A. laboratory. The test object was a tank filled with water with several dozen percent concentration. As part of the study, the original multiple neural networks system was trained, the characteristic feature of which is the generation of each of the individual pixels of the tomographic image, using an independent artificial neural network (ANN), with the input vector for all ANNs being the same. Despite the same measurement vector, each of the ANNs generates its own independent output value for a given tomogram pixel, because, during training, the networks get their respective weights and biases. During the tests, the results of three tomographic methods were compared: EIT, UST and EIT-UST hybrid. The results confirm that the use of heterogeneous tomographic systems (hybrids) increases the reliability of reconstruction in various measuring cases, which is used to solve quality problems in managing production processes.
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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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Zerbini, Talita. "Estimativa do intervalo postmortem por análise de imagens tomográfi cas das hipóstases viscerais torácicas." Saúde, Ética & Justiça 18, no. 2 (December 14, 2013): 173. http://dx.doi.org/10.11606/issn.2317-2770.v18i2p173.
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<p>Em casos de investigação criminal, a determinação do tempo de morte pode inocentar ou culpar algum suspeito. Atualmente, os estudos publicados relacionados ao advento da autópsia virtual não consideram a possibilidade da utilização dos exames complementares de imagem como auxílio à estimativa do intervalo <em>postmortem</em>, sendo esta uma das principais motivações para a realização do presente estudo, já que a tomografi a computadorizada é excelente método de medida de densidade. Diante desse cenário, o objetivo do trabalho foi aprimorar a estimativa do intervalo <em>postmortem </em>por meio da avaliação tomográfi ca das hipóstases viscerais torácicas. Foi realizado estudo prospectivo observacional com dados obtidos de 23 corpos de pacientes de ambos os sexos que foram encaminhados ao Serviço de Verifi cação de óbitos da Capital São Paulo. Foram obtidos cortes tomográfi cos do segmento torácico de modo sequencial utilizando-se o tomógrafo SOMATOM® Emotion syngo CT 2012E, com intervalo de uma hora entre os exames, a fi m de permitir a análise das modificações de densidade das hipóstases ao longo do tempo. Na janela de mediastino, foram selecionados os átrios direito e esquerdo para obtenção das medidas de densidade tecidual média. Foi possível concluir que a maioria das hipóstases pulmonares se estabiliza entre 8 e 12 horas e as hipóstases intracardíacas em torno de 12 horas. Além disso, o modelo estatístico de Mitscherlich pode ser utilizado para descrever o comportamento da hipóstase em função do intervalo de morte decorrido.</p>
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Zhou, Hau‐wei. "Traveltime tomography with a spatial‐coherency filter." GEOPHYSICS 58, no. 5 (May 1993): 720–26. http://dx.doi.org/10.1190/1.1443456.
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Spatially incoherent small wavelengths in a velocity tomogram are usually noise that could destabilize an iterative traveltime tomographic process. By defining the number of connected cells of similar values in an image as the spatial‐coherency (SC) value of these cells, an SC filtering is introduced in this paper to suppress incoherent features in an image. An SC filter first quantifies the SC value of all image cells and then conducts a discriminative moving‐average over cells of low SC values. It is demonstrated that such an SC filtering of the intermediate‐stage tomograms may enhance the robustness of the iterative tomographic process to noise. The SC values can be used in general to deconvolve an image of any dimension into components of different lengths in spatial connectivity.
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Kryszyn, Jacek. "Elektryczny tomograf pojemnościowy EVT4." ELEKTRONIKA - KONSTRUKCJE, TECHNOLOGIE, ZASTOSOWANIA 1, no. 7 (July 5, 2015): 14–17. http://dx.doi.org/10.15199/13.2015.7.2.
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Patel, Nimit J., Simon Toms, Fraser McDonald, Joanna Johnson, and Louis McArdle. "Unusual presentation of a tooth associated with an adenomatoid odontogenic tumour." Dental Update 46, no. 6 (June 2, 2019): 561–64. http://dx.doi.org/10.12968/denu.2019.46.6.561.
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Unilocular radiolucent lesions of the dental hard tissues can present regularly, however they are impossible to diagnose definitively without appropriate imaging and histopathology. A case is reported that involves a 14-year-old that presented with a history of an unerupted maxillary first premolar. An initial Dental Panoramic Tomograph (DPT) did not identify any localized opacities and was diagnosed as a dentigerous cyst. A Cone Bean Computed Tomogram (CBCT) identified calcified opacities resulting in a re-evaluated radiological interpretation. With the help of a multidisciplinary approach, the removal of the benign lesion allowed orthodontic traction to extrude the tooth and for it to be brought into alignment. CPD/Clinical Relevance: This report highlights the importance of three-dimensional imaging as an adjunct to aid diagnosis and highlights the importance of multidisciplinary teams in the management of clinical challenges.
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Ammanna, Susan, Anisha Rodrigues, N. Sridhar Shetty, and Karunakar Shetty. "A Tomographic Study of the Mandibular Condyle Position in Partially Edentulous Population." Journal of Contemporary Dental Practice 16, no. 1 (January 2015): 68–73. http://dx.doi.org/10.5005/jp-journals-10024-1637.
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ABSTRACT Background and objectives The influence of the loss of teeth on the condylar position and on temporomandibular joint (TMJ) dysfunction syndrome remains a controversial issue. This study analyses the condylar position by means of a tomogram in partially dentate subjects which serves as a guide to predict which of the partially dentate statuses is prone to develop TMJ dysfunction syndrome in personnel without symptoms of the same. Methodology Eighty personnel were enrolled in this study consisting of Kennedy's class I, II, III, IV and control to analyze the condylar position by means of a tomogram. In all the five groups TMJ sectional tomogram programmed in a panoramic radiographic machine (PLANMECA PM 2002 CC PROLINE) was taken with the subjects at maximal intercuspal position and rest position. Tomograms were evaluated using linear measurements of the anterior and posterior intra-articular joint spaces on the basis of drawings and tracings. Results The results of the study revealed a predominance of reduced posterior condylar space in Kennedy's class I and II. A disparity was seen between the maximum intercuspal position and rest position, where the posterior joint space was reduced in the rest position. Conclusion Within the limitations of this study, it has been revealed that in Kennedy's classes I and II, for partially dentate personnel, a posterior displacement of the condyles was seen. This predisposition would suggest towards the necessity of restoring the missing dentition in order to maintain the harmony of the stomatognathic system. How to cite this article Ammanna S, Rodrigues A, Shetty NS, Shetty K, Augustine D, Patil S. A Tomographic Study of the Mandibular Condyle Position in Partially Edentulous Population. J Contemp Dent Pract 2015;16(1):68-73.
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Michałowski, Piotr. "Tomografia wiersza." Poznańskie Studia Polonistyczne. Seria Literacka, no. 19 (January 1, 2012): 199. http://dx.doi.org/10.14746/pspsl.2012.19.14.
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WEBB, S. "Inverse tomograph." Nature 344, no. 6264 (March 1990): 284. http://dx.doi.org/10.1038/344284d0.
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Yu, Han, Sherif M. Hanafy, and Gerard T. Schuster. "Wave-equation traveltime inversion with multifrequency bands: Synthetic and land data examples." GEOPHYSICS 83, no. 6 (November 1, 2018): B305—B315. http://dx.doi.org/10.1190/geo2018-0070.1.
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We have developed a wave-equation traveltime inversion method with multifrequency bands to invert for the shallow or intermediate subsurface velocity distribution. Similar to the classical wave-equation traveltime inversion, this method searches for the velocity model that minimizes the squared sum of the traveltime residuals using source wavelets with progressively higher peak frequencies. Wave-equation traveltime inversion can partially avoid the cycle-skipping problem by recovering the low-wavenumber parts of the velocity model. However, we also use the frequency information hidden in the traveltimes to obtain a more highly resolved tomogram. Therefore, we use different frequency bands when calculating the Fréchet derivatives so that tomograms with better resolution can be reconstructed. Results are validated by the zero-offset gathers from the raw data associated with moderate geometric irregularities. The improved wave-equation traveltime method is robust and merely needs a rough estimate of the starting model. Numerical tests on the synthetic and field data sets validate the above claims.
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KIZILDAĞ YIRGIN, İnci, Elif HOCAOĞLU, Hakan YIRGIN, Arda KAYHAN, Nurten TURAN GÜNER, Serpil KALKAN GÖMEÇ, Sibel BAYRAMOĞLU, and Tan CİMİLLİ. "Akut pankreatitli hastalarda, hastalığın şiddetini belirlemede bilgisayarlı tomografi ve modifiye bilgisayarlı tomografi şiddet indekslerinin karşılaştırılması." Marmara Medical Journal 27, no. 3 (October 15, 2014): 190. http://dx.doi.org/10.5472/mmj.2014.03530.1.
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Campos Carbo, Lito Danny, Karla Katiuska Wellington Criollo, Jazmín Mirella Sánchez Cevallos, and Alicia Yezenia Molina Pantoja. "Hemorragia cerebral no traumática en adulto como primera manifestación de hemofilia. Reporte de caso, hospital Teodoro Maldonado Carbo." Medicina 21, no. 3 (August 27, 2020): 138–41. http://dx.doi.org/10.23878/medicina.v20i4.1074.
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La hemorragia intracraneal en pacientes con hemofilia tiene una tasa de letalidad de aproximadamente 25%, y en hasta un 40% de los pacientes afectados no registran antecedentes desencadenantes de sangrado tales como hipertensión arterial o traumatismos. Se reporta el caso clínico de un paciente atendido en el área de emergencia del hospital de especialidades Teodoro Maldonado Carbo en la ciudad de Guayaquil. Se trata de un hombre de 39 años, con antecedente de hipertensión arterial, que ingresa al area de emergencia con deterioro del nivel de conciencia; la tomografia computarizada de cerebro evidencia hemorragia intraparenquimatosa, se establece una sospecha inicialmente de etiología hipertesiva, sin embargo la prolongación del Tiempo Parcial de Tromboplastina (TPT) canaliza el despistaje de trastornos de coagulación. Obteniéndose entre los resultados deficiencia leve de factor VIII. La hemorragia intracraneal es de fácil diagnóstico gracias a la disponibilidad de la tomografía axial computarizada (TAC) y se relaciona a trauma en ams del 50% de los casos por lo que su asociación como complicación de hemofilia puede pasar desapercibida.
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Cristini, Valentino, Jan Tippner, Barbora Vojáčková, and Vinko Paulić. "Comparison of variability in results of acoustic tomographs in pedunculate oak (Quercus robur L.)." BioResources 16, no. 2 (March 5, 2021): 3046–58. http://dx.doi.org/10.15376/biores.16.2.3046-3058.
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Tree acoustic tomography is a widely used device supported method for tree stability assessment. In this work, the results of the three most commonly used devices for acoustic tomography of standing trees (ARBOTOM®, ArborSonic®, and PiCUS®) were compared on selected individuals of sessile oak in Brno, Czech Republic. According to the statistical analysis, there was a significant difference between values measured by the PiCUS® acoustic tomograph and those measured by both the ARBOTOM and ArborSonic® acoustic tomographs. Based on the measured data, velocities measured by PiCUS® were considerably lower than those recorded by the other acoustic tomographs (ARBOTOM® and ARBORSONIC®). Measured radial and tangential velocities differed from each other. In data obtained from the defective cross-sections, this difference was attenuated. Image reconstructions (tomograms) from the acoustic tomographs differed from each other. Complex shapes of defects in standing trees can significantly influence acoustic tomography results. According to the statistical analysis, there was no significant relationship between sound velocity and density, while there was a relatively strong positive correlation between sound velocity and moisture content.
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Oliveira, Naiane Pereira de, and Amin Bassrei. "SEISMIC TRAVELTIME TOMOGRAPHY IN THE DOM JOÃO FIELD, RECÔNCAVO BASIN, BRAZIL." Revista Brasileira de Geofísica 33, no. 1 (November 19, 2015): 89. http://dx.doi.org/10.22564/rbgf.v33i1.604.
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ABSTRACT. Tomography was incorporated in Exploration Geophysics with the intention of providing high-resolution images of regions in Earth’s subsurface that are characterized as potential reservoirs. In this work, seismic traveltime tomography in the transmission mode was applied to real data from the Dom João Field, Recôncavo Basin, State of Bahia, Brazil. This basin represents a landmark of oil exploration in Brazil and has been intensively studied since the 1950’s. Today, the Recôncavo Basin is still the principal oil producer in the State of Bahia, but there is a demand for new technologies, especially for mature fields, to improve hydrocarbon recovery. Acoustic ray tracing for the computation of traveltimes was used for forward modeling, and the conjugate gradient algorithm with regularization through derivative matrices was used as the inverse procedure. The estimated tomograms were consistent with available data from a sonic log near the acquisition area in terms of the layer geometry, as well as the P-wave velocity range. The results showed that traveltime tomography is feasible for the characterization of reservoirs with a high rate of vertical change, similar to the Dom Jo˜ao Field.Keywords: traveltime tomography, seismic inversion, regularization, reservoir characterization, Recˆoncavo Basin.RESUMO. A tomografia foi incorporada na Geofísica de Exploração justamente para fornecer imagens de alta resolução de regiões do interior da Terra, consideradas como potenciais reservatórios. Neste trabalho aplicamos a tomografia sísmica de tempos de trânsito no modo de transmissão em dados reais do Campo de Dom João, Bacia do Recôncavo, Estado da Bahia, Brasil. Esta bacia representa um marco da exploração de petróleo no Brasil e vem sendo exaustivamente estudada desde a década de 1950. Embora haja uma demanda por novas tecnologias, em especial para campos maduros, com o propósito de se aumentar a recuperação de hidrocarbonetos, a Bacia do Recôncavo é ainda a principal produtora do Estado da Bahia. Para o procedimento da modelagem direta foi utilizado o traçado de raios acústicos e para o procedimento inverso foi utilizado o algoritmo do gradiente conjugado com regularização através de matrizes de derivadas. Os tomogramas estimados foram consistentes com os dados provenientes do perfil sõnico de um poço próximo ao levantamento tomográfico analisado, tanto em termos de geometria de camadas, como também na faixa de velocidades da onda P. Os resultados mostraram que a tomografia de tempos de trânsito é viável para a caracterização de reservatórios com elevada taxa de variação vertical, que é o caso do Campo de Dom João.Palavras-chave: tomografia de tempos de trânsito, inversão sísmica, regularização, caracterização de reservatórios, Bacia do Recôncavo.
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INABA, FUMIO. "Laser computed tomograph." Review of Laser Engineering 21, no. 1 (1993): 221–25. http://dx.doi.org/10.2184/lsj.21.221.
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Rodríguez Salvador, Jorge Juan. "Tomografía simultánea multipelícula." Imagen Diagnóstica 3, no. 1 (January 2012): 35–37. http://dx.doi.org/10.1016/s2171-3669(12)70050-1.
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Kucera, Martin. "Traumhimmel überm Tomografen." kma - Klinik Management aktuell 19, no. 01 (January 2014): 64–66. http://dx.doi.org/10.1055/s-0036-1577198.
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Kunstlicht, Apparate, Enge: In Diagnostikräumen ist die Angst von Patienten am größten. Und Angst beeinträchtigt die Heilungsgeschwindigkeit. Ein „Healing Environment” zu schaffen, kann hier eine Lösung sein. Krankenhäuser, Großgerätehersteller und Architekten arbeiten daran.
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Cabrera Villegas, Antonio. "Jornadas Sobre Tomografía." Revista Española de Medicina Nuclear 20, no. 6 (January 2001): 509–10. http://dx.doi.org/10.1016/s0212-6982(01)72002-2.
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