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Gravier, Erwan, Yongyi Yang et Mingwu Jin. « Tomographic Reconstruction of Dynamic Cardiac Image Sequences ». IEEE Transactions on Image Processing 16, no 4 (avril 2007) : 932–42. http://dx.doi.org/10.1109/tip.2006.891328.
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Gravier, E. J., et Yongyi Yang. « Motion-compensated reconstruction of tomographic image sequences ». IEEE Transactions on Nuclear Science 52, no 1 (février 2005) : 51–56. http://dx.doi.org/10.1109/tns.2004.843092.
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Siedlecki, Damian, Waldemar Kowalik et Henryk Kasprzak. « Optical Coherence Tomography as a Tool for Ocular Dynamics Estimation ». BioMed Research International 2015 (2015) : 1–8. http://dx.doi.org/10.1155/2015/293693.
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Purpose. The aim of the study is to demonstrate that the ocular dynamics of the anterior chamber of the eye can be estimated quantitatively by means of optical coherence tomography (OCT).Methods. A commercial high speed, high resolution optical coherence tomographer was used. The sequences of tomographic images of the iridocorneal angle of three subjects were captured and each image from the sequence was processed in MATLAB environment in order to detect and identify the contours of the cornea and iris. The data on pulsatile displacements of the cornea and iris and the changes of the depth of the gap between them were retrieved from the sequences. Finally, the spectral analysis of the changes of these parameters was performed.Results. The results of the temporal and spectral analysis manifest the ocular microfluctuation that might be associated with breathing (manifested by 0.25 Hz peak in the power spectra), heart rate (1–1.5 Hz peak), and ocular hemodynamics (3.75–4.5 Hz peak).Conclusions. This paper shows that the optical coherence tomography can be used as a tool for noninvasive estimation of the ocular dynamics of the anterior segment of the eye, but its usability in diagnostics of the ocular hemodynamics needs further investigations.
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Nielsen, Lars, Hans Thybo et Martin Glendrup. « Seismic tomographic interpretation of Paleozoic sedimentary sequences in the southeastern North Sea ». GEOPHYSICS 70, no 4 (juillet 2005) : R45—R56. http://dx.doi.org/10.1190/1.1996908.
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Seismic wide-angle data were recorded to more than 300-km offset from powerful airgun sources during the MONA LISA experiments in 1993 and 1995 to determine the seismic-velocity structure of the crust and uppermost mantle along three lines in the southeastern North Sea with a total length of 850 km. We use the first arrivals observed out to an offset of 90 km to obtain high-resolution models of the velocity structure of the sedimentary layers and the upper part of the crystalline crust. Seismic tomographic traveltime inversion reveals 2–8-km-thick Paleozoic sedimentary sequences with P-wave velocities of 4.5–5.2 km/s. These sedimentary rocks are situated below a Mesozoic-Cenozoic sequence with variable thickness: ∼2–3 km on the basement highs, ∼2–4 km in the Horn Graben and the North German Basin, and ∼6–7 km in the Central Graben. The thicknesses of the Paleozoic sedimentary sequences are ∼3–5 km in the Central Graben, more than 4 km in the Horn Graben, up to ∼4 km on the basement highs, and up to 8 km in the North German Basin. The Paleozoic strata are clearly separated from the shallower and younger sequences with velocities of ∼1.8–3.8 km/s and the deeper crystalline crust with velocities of more than 5.8–6.0 km/s in the tomographic P-wave velocity model. Resolution tests show that the existence of the Paleozoic sediments is well constrained by the data. Hence, our wide-angle seismic models document the presence of Paleozoic sediments throughout the southeastern North Sea, both in the graben structures and in deep basins on the basement highs.
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Santarelli, Chiara, Fabrizio Argenti, Francesca Uccheddu, Luciano Alparone et Monica Carfagni. « Volumetric interpolation of tomographic sequences for accurate 3D reconstruction of anatomical parts ». Computer Methods and Programs in Biomedicine 194 (octobre 2020) : 105525. http://dx.doi.org/10.1016/j.cmpb.2020.105525.
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Santarelli, Chiara, Monica Carfagni, Luciano Alparone, Alberto Arienzo et Fabrizio Argenti. « Multimodal fusion of tomographic sequences of medical images : MRE spatially enhanced by MRI ». Computer Methods and Programs in Biomedicine 223 (août 2022) : 106964. http://dx.doi.org/10.1016/j.cmpb.2022.106964.
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Puķīte, J., S. Kühl, T. Deutschmann, S. Dörner, P. Jöckel, U. Platt et T. Wagner. « The effect of horizontal gradients and spatial measurement resolution on the retrieval of global vertical NO<sub>2</sub> ; distributions from SCIAMACHY measurements in limb only mode ». Atmospheric Measurement Techniques Discussions 3, no 3 (11 mai 2010) : 2055–105. http://dx.doi.org/10.5194/amtd-3-2055-2010.
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Abstract. Limb measurements provided by the Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale. Combining measurements of the same air volume from different viewing positions along the orbit, a tomographic approach can be applied and 2-D distribution fields of stratospheric trace gases can be acquired in one inversion. With this approach, it is possible to improve the accounting for the effect of horizontal gradients in the trace gas distribution on the profile retrieval. This was shown in a previous study for the retrieval of NO2 and OClO profiles in the Arctic region near the polar vortex boundary. In this study, the tomographic retrieval is applied on measurements during special limb-only orbits performed on 14 December 2008. For these orbits the distance between consecutive limb scanning sequences was reduced to ~3.3° of the orbital circle (i.e. more than two times with respect to the nominal operational mode). Thus, the same air volumes are scanned successively by more than one scanning sequence also for midlatitudes and the tropics. It is found that the profiles obtained by the tomographic 2-D approach show significant differences to those obtained by the 1-D approach. In particular, for regions close to stratospheric transport barriers (i.e. near to the edge of the polar vortex and subtropical transport barrier) up to 50% larger or smaller NO2 number densities (depending on the sign of the gradient along the line of sight) for altitudes below the peak of the profile (around 20 km) are obtained. The limb-only measurements allow examining the systematic error if the horizontal gradient is not accounted for, and studying the impact of the gradient strength on the profile retrieval on a global scale. The findings for the actual SCIAMACHY observations are verified by sensitivity studies for simulated data for which the NO2 distributions to be retrieved are known in advance. In addition, the impact of the horizontal distance between consecutive limb scanning sequences on the quality of the tomographic 2-D retrieval is investigated and a possibility to take into account the horizontal gradients by an interpolation approach is studied.
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Puķīte, J., S. Kühl, T. Deutschmann, S. Dörner, P. Jöckel, U. Platt et T. Wagner. « The effect of horizontal gradients and spatial measurement resolution on the retrieval of global vertical NO<sub>2</sub> ; distributions from SCIAMACHY measurements in limb only mode ». Atmospheric Measurement Techniques 3, no 4 (30 août 2010) : 1155–74. http://dx.doi.org/10.5194/amt-3-1155-2010.
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Abstract. Limb measurements provided by the Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale. Combining measurements of the same air volume from different viewing positions along the orbit, a tomographic approach can be applied and 2-D distribution fields of stratospheric trace gases can be acquired in one inversion. With this approach, it is possible to improve the accounting for the effect of horizontal gradients in the trace gas distribution on the profile retrieval. This was shown in a previous study for the retrieval of NO2 and OClO profiles in the Arctic region near the polar vortex boundary. In this study, the tomographic retrieval is applied on measurements during special limb-only orbits performed on 14 December 2008. For these orbits the distance between consecutive limb scanning sequences was reduced to ~3.3° of the orbital circle (i.e. more than two times with respect to the nominal operational mode). Thus, the same air volumes are scanned successively by more than one scanning sequence also for midlatitudes and the tropics. It is found that the profiles obtained by the tomographic 2-D approach show significant differences to those obtained by the 1-D approach. In particular, for regions close to stratospheric transport barriers (i.e. near to the edge of the polar vortex and subtropical transport barrier) up to 50% larger or smaller NO2 number densities (depending on the sign of the gradient along the line of sight) for altitudes below the peak of the profile (around 20 km) are obtained. The limb-only measurements allow examining the systematic error if the horizontal gradient is not accounted for, and studying the impact of the gradient strength on the profile retrieval on a global scale. The findings for the actual SCIAMACHY observations are verified by sensitivity studies for simulated data for which the NO2 distributions to be retrieved are known in advance. In addition, the impact of the horizontal distance between consecutive limb scanning sequences on the quality of the tomographic 2-D retrieval is investigated and a possibility to take into account the horizontal gradients by an interpolation approach is studied.
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Valeev, A. I., et A. A. Malov. « The role of magnetic resonance imaging in the diagnosis of malignant bone neoplasms. Current state of an issue ». Russian Journal of Pediatric Hematology and Oncology 7, no 4 (7 janvier 2021) : 77–81. http://dx.doi.org/10.21682/2311-1267-2020-7-4-77-81.
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The review article is about clinical experience in the use of modern tomographic methods (magnetic resonance imaging (MRI) and X-ray computed tomography (CT)) in the diagnosis and assessment of the progression of malignant bone neoplasms, summarizing the results of the largest studies demonstrating the comparative characteristics of the methods. Numerous data demonstrate high sensitivity of MRI and form the following diagnostic tasks that can be solved by this method: the involvement degree of soft tissues in the pathological process, damage to the neurovascular bundle, the articular surface, assessment of the extent of tumor in the bone marrow canal. At the same time, CT shows a higher sensitivity in assessing cortical destruction and the degree of matrix mineralization. The article discusses the variety of program sequences and modes of MRI scanning, the prospects of the method in assessing the prevalence, staging, and differential diagnosis of bone tumors.
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BAIMPAS, NIKOLAOS, MENGYIN XIE, XU SONG, FELIX HOFMANN, BRIAN ABBEY, JAMES MARROW, MAHMOUD MOSTAFAVI, JIAWEI MI et ALEXANDER M. KORSUNSKY. « RICH TOMOGRAPHY TECHNIQUES FOR THE ANALYSIS OF MICROSTRUCTURE AND DEFORMATION ». International Journal of Computational Methods 11, no 03 (juin 2014) : 1343006. http://dx.doi.org/10.1142/s0219876213430068.
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Until very recently, the three-dimensionality of the material world presented numerous challenges in terms of characterization, data handling, visualization, and modeling. For this reason, 2D representation of sections, projections, or surfaces remained the mainstay of most popular imaging techniques, such as optical and electron microscopy and X-ray radiography. However, the advent of faster computers with greater memory capacity ensured that large 3D matrices can now not only be stored and manipulated efficiently, but also that advanced algorithms such as algebraic reconstruction techniques (ART) can be used to interpret redundant datasets containing multiple projections or averages across the object obtained by some suitable analytical measurement technique. These tools open up unprecedented opportunities for numerical simulation. Model formulation can be accomplished semi-automatically on the basis of microstructurally-informed 3D imaging, while model validation can be achieved by direct comparison of 3D maps of complex quantities, such as displacement vectors or strain tensor components. In this paper, we review several modalities of what can be referred to as "rich" tomography: strain tomography in the bulk of a load bearing structural component; Laue orientation tomography for nondestructive mapping of grain orientation within a polycrystal, and the use of sequences of tomographic reconstructions for digital volume correlation (DVC) analysis of in situ deformation.
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Yamamoto, Tokua, Tom Nye et Murat Kuru. « Porosity, permeability, shear strength : Crosswell tomography below an iron foundry ». GEOPHYSICS 59, no 10 (octobre 1994) : 1530–41. http://dx.doi.org/10.1190/1.1443542.
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Crosswell tomography of a sedimentary foundation at an iron foundry was affected by very high background noise; nevertheless, high‐resolution velocity images were obtained between wells separated by long distances (120 to 250 m). A piezoelectric source in a water‐filled well used long sequences (4095 cycles) of pseudorandom binary codes at high carrier frequencies (1 to 10 kHz). A 24‐channel hydrophone array in another well received the signal. Beamforming of common‐source data selected the directions and arrival times of multiple raypaths and tube waves and further enhanced the signal‐to‐noise ratio. Inversion of first‐arrival times by damped least squares imaged the compressional wave velocities. Assuming the normal consolidation condition, the porosity and shear strength images are predicted from the compressional wave velocity image. The direct measurements of porosity and shear strength conducted on the cores and boreholes were used to verify the tomographic predictions. The slight differences in the compressional wave velocity images obtained using different carrier frequencies can be used to determine the permeability image of sediments based on the Biot theory.
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Suh, Daniel Y., Patricia C. Davis, Katherine L. Hopkins, Nancy N. Fajman et Timothy B. Mapstone. « Nonaccidental Pediatric Head Injury : Diffusion-weighted Imaging Findings ». Neurosurgery 49, no 2 (1 août 2001) : 0148–396. http://dx.doi.org/10.1097/00006123-200108000-00011.
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Abstract OBJECTIVE Diffusion-weighted imaging (DWI) reveals nonhemorrhagic posttraumatic infarction hours to days before conventional computed tomographic scanning or magnetic resonance imaging (MRI). We evaluated the diagnostic utility of DWI in children with nonaccidental head trauma. METHODS The medical records and imaging examinations obtained between January 1998 and May 2000 for all children less than 2 years of age with presumed or suspected nonaccidental head injury were reviewed retrospectively. Twenty children who had undergone DWI within 5 days of presentation were included in the study. Computed tomographic scans, conventional MRI sequences, and DWI combined with apparent diffusion coefficient (ADC) maps were evaluated. RESULTS Eleven girls and nine boys (median age, 5 mo) were studied. Eighteen children had presumed nonaccidental head trauma, and two children had suspected nonaccidental head trauma. Of the 18 children with presumed nonaccidental trauma, 16 (89%) demonstrated abnormalities on DWI/ADC, as compared with neither of the two children with suspected nonaccidental trauma. In 13 (81%) of 16 positive cases, DWI revealed more extensive brain injury than was demonstrated on conventional MRI sequences or showed injuries not observed on conventional MRI. DWI combined with ADC maps allowed better delineation of the extent of white matter injury. DWI/ADC abnormalities in the nonaccidental head-injured children were likely to involve posterior aspects of the cerebral hemispheres, with relative sparing of the frontal and temporal poles. Severity on DWI correlated significantly with poor outcome (P < 0.005). CONCLUSION DWI has broad applications in the early detection of infarction in children with nonaccidental head injury and enhances the sensitivity of conventional MRI. In the patients in this study, early DWI provided an indicator of severity that was more complete than any other imaging modality. The use of DWI may help to identify children at high risk for poor outcome and to guide management decisions.
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Vasquez, Dionicio, Jacob Scharcanski et Alexander Wong. « Automatic Framework for Extraction and Characterization of Wetting Front Propagation Using Tomographic Image Sequences of Water Infiltrated Soils ». PLOS ONE 10, no 1 (20 janvier 2015) : e0115218. http://dx.doi.org/10.1371/journal.pone.0115218.
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Säring, D., H. Handels et J. Ehrhardt. « Structure-preserving Interpolation of Temporal and Spatial Image Sequences Using an Optical Flow-based Method ». Methods of Information in Medicine 46, no 03 (2007) : 300–307. http://dx.doi.org/10.1160/me9047.
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Summary Objectives: Modern tomographic imaging devices enable the acquisition of spatial and temporal image sequences. But, the spatial and temporal resolution of such devices is limited and therefore image interpolation techniques are needed to represent images at a desired level of discretization. This paper presents a method for structure-preserving interpolation between neighboring slices in temporal or spatial image sequences. Methods: In a first step, the spatiotemporal velocity field between image slices is determined using an optical flow-based registration method in order to establish spatial correspondence between adjacent slices. An iterative algorithm is applied using the spatial and temporal image derivatives and a spatiotemporal smoothing step. Afterwards, the calculated velocity field is used to generate an interpolated image at the desired time by averaging intensities between corresponding points. Three quantitative measures are defined to evaluate the performance of the interpolation method. Results: The behaviorand capability of the algorithm is demonstrated by synthetic images. A population of 17 temporal and spatial image sequences are utilized to compare the optical flow-based interpolation method to linear and shape-based interpolation. The quantitative results show that the optical flow-based method outperforms the linear and shape-based interpolation statistically significantly. Conclusions: The interpolation method presented is able to generate image sequences with appropriate spatial or temporal resolution needed for image comparison, analysis or visualization tasks. Quantitative and qualitative measures extracted from synthetic phantoms and medical image data show that the new method definitely has advantages over linear and shape-based interpolation.
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DeFilipp, Gary J., et William A. Buchheit. « Magnetic Resonance Imaging of Acoustic Neuromas ». Neurosurgery 16, no 6 (1 juin 1985) : 763–65. http://dx.doi.org/10.1227/00006123-198506000-00004.
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Abstract Ten patients with neurosensory hearing loss and computed tomographic (CT) evidence of acoustic neuromas were evaluated with magnetic resonance imaging (MRI). Tumors ranged in size from 0.8 to 3.7 cm. With the use of spin echo pulse sequences, all tumors were identified by MRI and appeared as masses with signal intensities greater than that of cerebrospinal fluid and equal to or greater than that of brain stem. Two patients who previously had undergone operation for acoustic neuromas were evaluated with MRI. In one patient with CT evidence of tumor recurrence, the lesion could not be identified by MRI. MRI holds promise of becoming a primary diagnostic modality for the evaluation of acoustic neuromas.
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Rusche, Thilo, Hanns-Christian Breit, Michael Bach, Jakob Wasserthal, Julian Gehweiler, Sebastian Manneck, Johanna Maria Lieb, Gian Marco De Marchis, Marios Nikos Psychogios et Peter B. Sporns. « Potential of Stroke Imaging Using a New Prototype of Low-Field MRI : A Prospective Direct 0.55 T/1.5 T Scanner Comparison ». Journal of Clinical Medicine 11, no 10 (16 mai 2022) : 2798. http://dx.doi.org/10.3390/jcm11102798.
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Objectives: Ischemic stroke is a leading cause of mortality and acquired disability worldwide and thus plays an enormous health-economic role. Imaging of choice is computed-tomographic (CT) or magnetic resonance imaging (MRI), especially diffusion-weighted (DW) sequences. However, MR imaging is associated with high costs and therefore has a limited availability leading to low-field-MRI techniques increasingly coming into focus. Thus, the aim of our study was to assess the potential of stroke imaging with low-field MRI. Material and Methods: A scanner comparison was performed including 27 patients (17 stroke cohort, 10 control group). For each patient, a brain scan was performed first with a 1.5T scanner and afterwards with a 0.55T scanner. Scan protocols were as identical as possible and optimized. Data analysis was performed in three steps: All DWI/ADC (apparent diffusion coefficient) and FLAIR (fluid attenuated inversion recovery) sequences underwent Likert rating with respect to image impression, resolution, noise, contrast, and diagnostic quality and were evaluated by two radiologists regarding number and localization of DWI and FLAIR lesions in a blinded fashion. Then segmentation of lesion volumes was performed by two other radiologists on DWI/ADC and FLAIR. Results: DWI/ADC lesions could be diagnosed with the same reliability by the most experienced reader in the 0.55T and 1.5T sequences (specificity 100% and sensitivity 92.9%, respectively). False positive findings did not occur. Detection of number/location of FLAIR lesions was mostly equivalent between 0.55T and 1.5T sequences. No significant difference (p = 0.789–0.104) for FLAIR resolution and contrast was observed regarding Likert scaling. For DWI/ADC noise, the 0.55T sequences were significantly superior (p < 0.026). Otherwise, the 1.5T sequences were significantly superior (p < 0.029). There was no significant difference in infarct volume and volume of infarct demarcation between the 0.55T and 1.5T sequences, when detectable. Conclusions: Low-field MRI stroke imaging at 0.55T may not be inferior to scanners with higher field strengths and thus has great potential as a low-cost alternative in future stroke diagnostics. However, there are limitations in the detection of very small infarcts. Further technical developments with follow-up studies must show whether this problem can be solved.
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Lopatin, A. V., N. G. Solomonov, N. V. Serdyuk, E. N. Maschenko, D. V. Mukha et A. K. Agadjanyan. « A finding of a frozen mummy of a lemming (Rodentia, Cricetidae, Lemmus) in the upper pleistocene of Yakutia ». Доклады Академии наук 489, no 1 (10 novembre 2019) : 108–12. http://dx.doi.org/10.31857/s0869-56524891108-112.
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External morphological, X‑ray and tomographic study of the rodent frozen mummy from the Upper Pleistocene Yedoma deposits on the Tirekhtyakh River (tributary of the Semyulyakh River, Abyi District, Republic of Sakha (Yakutia)) showed its belonging to Lemmus sp. The radiocarbon age of the find is 41 305-41 885 cal BP. This is the first Pleistocene discovery of a frozen mummy of the representative of the genus Lemmus. In terms of body and skull size, coat color, length of the lower incisor and the structure of the molars, the specimen studied is closed to the Recent Lemmus sibiricus (Kerr, 1792). Comparison of the mitochondrial COI gene sequence with the DNA sequences presented in the GenBank database demonstrates maximum similarity with the Recent Siberian brown lemming too.
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De Nolf, Wout, Frederik Vanmeert et Koen Janssens. « XRDUA : crystalline phase distribution maps by two-dimensional scanning and tomographic (micro) X-ray powder diffraction ». Journal of Applied Crystallography 47, no 3 (29 mai 2014) : 1107–17. http://dx.doi.org/10.1107/s1600576714008218.
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Imaging of crystalline phase distributions in heterogeneous materials, either plane projected or in virtual cross sections of the object under investigation, can be achieved by scanning X-ray powder diffraction employing X-ray micro beams and X-ray-sensitive area detectors. Software exists to convert the two-dimensional powder diffraction patterns that are recorded by these detectors to one-dimensional diffractograms, which may be analysed by the broad variety of powder diffraction software developed by the crystallography community. However, employing these tools for the construction of crystalline phase distribution maps proves to be very difficult, especially when employing micro-focused X-ray beams, as most diffraction software tools have mainly been developed having structure solution in mind and are not suitable for phase imaging purposes.XRDUAhas been developed to facilitate the execution of the complete sequence of data reduction and interpretation steps required to convert large sequences of powder diffraction patterns into a limited set of crystalline phase maps in an integrated fashion.
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Petrescu, Stelian-Mihai-Sever, Mihaela Țuculină, Dragoș Popa, Alina Duță, Alex Sălan, Ruxandra Voinea Georgescu, Oana Diaconu et al. « Modeling and Simulating an Orthodontic System Using Virtual Methods ». Diagnostics 12, no 5 (23 mai 2022) : 1296. http://dx.doi.org/10.3390/diagnostics12051296.
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Cone beam computed tomography (CBCT) is a modern imaging technique that uses X-rays to investigate the structures of the dento-maxillary apparatus and obtain detailed images of those structures. The aim of this study was to determine a functional mathematical model able to evaluate the elastic force intensity on each bracket and tube type element and the ways in which those components act on the orthodontic system being used. To analyze a real orthodontic system, we studied the case of a 13-year-old female patient. To transfer geometric information from tomographic images, we used the InVesalius software. This software can generate three-dimensional reconstructions based on sequences and files in the DICOM format and was purchased from CBCT equipment. We analyzed and processed the geometries of the converted tissues in InVesalius using the Geomagic software. After using the Geomagic software, we exported the resulting model to the SolidWorks software used in computer-aided design. In this software, the model is transformed into a virtual solid. After making the geometric model, we analyzed the model using the Ansys Workbench software, which incorporates finite element analysis techniques. Following the simulations, we obtained result maps, which showed the complete mechanical behavior of the analyzed structures.
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Delalande, Olivier, Diana Rodriguez, Catherine Chiron et Martine Fohlen. « Successful Surgical Relief of Seizures Associated with Hamartoma of the Floor of the Fourth Ventricle in Children : Report of Two Cases ». Neurosurgery 49, no 3 (1 septembre 2001) : 726–31. http://dx.doi.org/10.1097/00006123-200109000-00037.
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Abstract OBJECTIVE AND IMPORTANCE To discuss the physiopathology and surgical handling of seizures due to hamartoma of the floor of the fourth ventricle in two children. CLINICAL PRESENTATION Two girls aged 3 years at the time of their operations presented with seizures due to a lesion of the floor of the fourth ventricle. The seizures began within the first days of life and consisted of hemifacial contraction, then head deviation, blinking of the eyelids, and intermittent dysautonomic manifestations. The interictal neurological condition seemed normal in one patient and showed a slight development delay in the other. An ictal electroencephalogram showed slow waves in the posterior areas. A magnetic resonance imaging scan revealed a mass that remained unchanged on serial examinations bordering the fourth ventricle, with an isointense signal on T1-weighted sequences and high-intensity signals on T2-weighted sequences without gadolinium enhancement. An ictal single-photon emission computed tomographic scan showed hyperperfusion in the lesion in both girls. INTERVENTION The operation consisted of resection and disconnection of the lesion. An electrical recording was obtained in one patient during the operation while she was anesthetized; the recording, made by means of a depth electrode with five contacts inside the lesion, indicated that repetitive θ rhythmic discharges were present. Neuropathology was consistent with a hamartoma. In both girls, the seizures disappeared after their operations, and antiepileptic drugs were withdrawn (follow-up periods, 8 and 3 yr, respectively). CONCLUSION Considering the results of single-photon emission computed tomography, the intralesional electrical record, and the relief of seizures after the operation, we postulate that the seizures arose from inside the lesion. This particular kind of noncortical seizure is similar to gelastic seizure due to hypothalamic hamartoma.
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Cai, Yiheng, Dan Liu, Jin Xie, Jingxian Yang, Xiangbin Cui et Shinan Lang. « Attention Multi-Scale Network for Automatic Layer Extraction of Ice Radar Topological Sequences ». Remote Sensing 13, no 12 (21 juin 2021) : 2425. http://dx.doi.org/10.3390/rs13122425.
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Analyzing the surface and bedrock locations in radar imagery enables the computation of ice sheet thickness, which is important for the study of ice sheets, their volume and how they may contribute to global climate change. However, the traditional handcrafted methods cannot quickly provide quantitative, objective and reliable extraction of information from radargrams. Most traditional handcrafted methods, designed to detect ice-surface and ice-bed layers from ice sheet radargrams, require complex human involvement and are difficult to apply to large datasets, while deep learning methods can obtain better results in a generalized way. In this study, an end-to-end multi-scale attention network (MsANet) is proposed to realize the estimation and reconstruction of layers in sequences of ice sheet radar tomographic images. First, we use an improved 3D convolutional network, C3D-M, whose first full connection layer is replaced by a convolution unit to better maintain the spatial relativity of ice layer features, as the backbone. Then, an adjustable multi-scale module uses different scale filters to learn scale information to enhance the feature extraction capabilities of the network. Finally, an attention module extended to 3D space removes a redundant bottleneck unit to better fuse and refine ice layer features. Radar sequential images collected by the Center of Remote Sensing of Ice Sheets in 2014 are used as training and testing data. Compared with state-of-the-art deep learning methods, the MsANet shows a 10% reduction (2.14 pixels) on the measurement of average mean absolute column-wise error for detecting the ice-surface and ice-bottom layers, runs faster and uses approximately 12 million fewer parameters.
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Marti, David, Ignacio Marzan, Jana Sachsenhausen, Joaquina Alvarez-Marrón, Mario Ruiz, Montse Torne, Manuela Mendes et Ramon Carbonell. « 3-D seismic travel-time tomography validation of a detailed subsurface model : a case study of the Záncara river basin (Cuenca, Spain) ». Solid Earth 10, no 1 (21 janvier 2019) : 177–92. http://dx.doi.org/10.5194/se-10-177-2019.
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Abstract. A high-resolution seismic tomography survey was acquired to obtain a full 3-D P-wave seismic velocity image in the Záncara river basin (eastern Spain). The study area consists of lutites and gypsum from a Neogene sedimentary sequence. A regular and dense grid of 676 shots and 1200 receivers was used to image a 500 m×500 m area of the shallow subsurface. A 240-channel system and a seismic source, consisting of an accelerated weight drop, were used in the acquisition. Half a million travel-time picks were inverted to provide the 3-D seismic velocity distribution up to 120 m depth. The project also targeted the geometry of the underground structure with emphasis on defining the lithological contacts but also the presence of cavities and fault or fractures. An extensive drilling campaign provided uniquely tight constraints on the lithology; these included core samples and wireline geophysical measurements. The analysis of the well log data enabled the accurate definition of the lithological boundaries and provided an estimate of the seismic velocity ranges associated with each lithology. The final joint interpreted image reveals a wedge-shaped structure consisting of four different lithological units. This study features the necessary key elements to test the travel time tomographic inversion approach for the high-resolution characterization of the shallow subsurface. In this methodological validation test, travel-time tomography demonstrated to be a powerful tool with a relatively high capacity for imaging in detail the lithological contrasts of evaporitic sequences located at very shallow depths, when integrated with additional geological and geophysical data.
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Hao, Da-Peng, Jian-Zhong Zhang, Wen-Jian Xu, Zhen-Chang Wang et Xue-Na Wang. « Pigmented Villonodular Synovitis of the Ankle ». Journal of the American Podiatric Medical Association 101, no 3 (1 mai 2011) : 252–58. http://dx.doi.org/10.7547/1010252.
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Background: Pigmented villonodular synovitis (PVNS) of the ankle is a rare benign proliferative growth of the synovium. Studies of the radiologic characteristics of ankle PVNS are sparse. Methods: To characterize the radiologic features of ankle PVNS, five patients with histologically proven ankle PVNS were retrospectively studied. The features of their radiographs, computed tomographic scans, and magnetic resonance images were reviewed, with emphasis on the morphological features, extension, margin, bone involvement, signal intensity, and degree of magnetic resonance enhancement. Results: All five lesions were diffuse, affecting the ankle and distal tibiofibular joint; three lesions also involved the subtalar joint. Radiography demonstrated extrinsic bone erosions with marginal sclerosis of the involved joints in all of the patients, but computed tomography identified this much better than did radiography. Magnetic resonance imaging revealed multiple lobulated soft-tissue masses in all of the cases. These soft-tissue masses surrounded the flexor hallux longus tendon and were hypointense on T1-weighted images, with a heterogeneous signal in two cases and homogenous hypointensity in three cases on fat-suppressed T2-weighted images. In one patient who underwent gadolinium-enhanced imaging, the masses showed intense enhancement. Conclusions: Magnetic resonance imaging is the best way to reveal ankle PVNS. Magnetic resonance imaging findings of predominant hypointensity on all pulse sequences and standard radiography findings of bone erosion with marginal sclerosis are characteristic. (J Am Podiatr Med Assoc 101(3): 252–258, 2011)
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SCHILLO, DOROTHEE, BENJAMIN WIPFLER, NANI UNDAP, ADELFIA PAPU, NILS BÖHRINGER, JAN-HENDRIK EISENBARTH, FONTJE KALIGIS et al. « Description of a new Moridilla species from North Sulawesi, Indonesia (Mollusca : Nudibranchia : Aeolidioidea)—based on MicroCT, histological and molecular analyses ». Zootaxa 4652, no 2 (8 août 2019) : 265–95. http://dx.doi.org/10.11646/zootaxa.4652.2.3.
Texte intégralRésumé :
We describe a new species, Moridilla jobeli sp. nov., belonging to the marine heterobranch group Aeolidioidea. Up to now, it is only recorded from Bunaken National Park, North Sulawesi, Indonesia. A combination of histological, computer tomographic and scanning electron microscopic methods was applied in order to describe and illustrate the anatomy of Moridilla jobeli sp. nov. in detail. Furthermore, we conducted molecular analyses which include available partial COI and 16S rRNA sequences, as well as the nuclear gene Histone 3 (H3) of Facelinidae and Aeolidiidae. NeighborNet analyses, species delimitation tests and phylogenetic reconstruction methods show the distinctiveness of the new species from the type species Moridilla brockii Bergh, 1888 and the two recently described species Moridilla fifo Carmona & Wilson, 2018 and Moridilla hermanita Carmona & Wilson, 2018, as well as the monophyly of the genus. A phylogenetic analysis of the Facelinidae and Aeolidiidae does not result in a resolved tree, therefore relationship of former assumed closely related genera, Noumeaella Risbec, 1937 and Palisa Edmunds, 1964, cannot be discussed in detail.
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James, Jeyanthan Charles, Daniel Richter, Laura Tomaske, Ruth Schneider, Carsten Lukas, Felix Kaemmerer, Ralf Gold et Christos Krogias. « Usefulness of Computed Tomographic Perfusion Imaging for Appropriate Diagnosis of Acute Cerebral Vessel Occlusion in Case of Anatomic Variations of the Circle of Willis ». Neurointervention 16, no 2 (1 juillet 2021) : 190–93. http://dx.doi.org/10.5469/neuroint.2021.00136.
Texte intégralRésumé :
Mechanical thrombectomy (MT) is an effective treatment in patients with acute ischemic stroke (AIS) due to emergent large-vessel occlusion in the anterior circulation. Occlusion of the anterior cerebral artery (ACA) affects up to 15% of these patients. Here we report a case of an elderly patient with an successful MT of an embolic A2-segment occlussion with the anatomic variation of a triplication. Triplication of ACA is a rare anatomical variation, and the occlusion could have been easily overlooked in case of not performing the CT-perfusion (CTP) sequences. As anatomical variations of the circle of Willis are present in most subjects, CTA alone might be limited in the acute setting, particularly for young residents performing the first view on call. This case highlights the importance of including CTP in the initial CT-diagnostic algorithm in AIS patients who are basically eligible for recanalization therapies, irrespective of inconspicuous initial findings in CTA.
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Salem, Mohamed, El-Sayed El-Shafaey, Alshimaa M. M. Farag, Sabry El-khodery, Zakriya Al Mohamad et Marwa Abass. « A Descriptive Study of the Carpal Joint of Healthy Donkeys Using Ultrasonography, Computed Tomography, and Magnetic Resonance Imaging ». Veterinary Sciences 9, no 5 (23 mai 2022) : 249. http://dx.doi.org/10.3390/vetsci9050249.
Texte intégralRésumé :
This study was conducted to establish a detailed anatomic reference for the carpal joint of apparently healthy donkeys using ultrasonography (US), computed tomographic (CT), and magnetic resonance imaging (MRI). Ten orthopedically sound adult donkeys were used for US examination of the carpal joint in each forelimb. Additionally, the carpi of ten donkey cadavers were subjected to CT and MRI examinations. The carpal joint was divided into four zones to simplify examination. US assessment of the carpal joint included transverse and longitudinal sonograms. CT was performed using three planes: axial, sagittal, and coronal. MRI was performed using axial and sagittal planes with two sequences: gradient-echo T1-weighted and proton density. The donkeys’ carpus US, CT, and MRI images were labeled and serially interpreted based on references and anatomical cross-sections. The anatomical characteristics of the carpal joint and the surrounding soft tissue structures were thoroughly described and precisely differentiated on US, CT, and MRI scans. It can be concluded that US, CT, and MRI are effective noninvasive diagnostic imaging tools for evaluating the carpal joint in donkeys. Moreover, these imaging modalities can aid in establishing a reference database for the carpal joint of donkeys, which differs from that of horses.
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Martin, Thomas G., Tanmay A. M. Bharat, Andreas C. Joerger, Xiao-chen Bai, Florian Praetorius, Alan R. Fersht, Hendrik Dietz et Sjors H. W. Scheres. « Design of a molecular support for cryo-EM structure determination ». Proceedings of the National Academy of Sciences 113, no 47 (7 novembre 2016) : E7456—E7463. http://dx.doi.org/10.1073/pnas.1612720113.
Texte intégralRésumé :
Despite the recent rapid progress in cryo-electron microscopy (cryo-EM), there still exist ample opportunities for improvement in sample preparation. Macromolecular complexes may disassociate or adopt nonrandom orientations against the extended air–water interface that exists for a short time before the sample is frozen. We designed a hollow support structure using 3D DNA origami to protect complexes from the detrimental effects of cryo-EM sample preparation. For a first proof-of-principle, we concentrated on the transcription factor p53, which binds to specific DNA sequences on double-stranded DNA. The support structures spontaneously form monolayers of preoriented particles in a thin film of water, and offer advantages in particle picking and sorting. By controlling the position of the binding sequence on a single helix that spans the hollow support structure, we also sought to control the orientation of individual p53 complexes. Although the latter did not yet yield the desired results, the support structures did provide partial information about the relative orientations of individual p53 complexes. We used this information to calculate a tomographic 3D reconstruction, and refined this structure to a final resolution of ∼15 Å. This structure settles an ongoing debate about the symmetry of the p53 tetramer bound to DNA.
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Puķīte, J., S. Kühl, T. Deutschmann, U. Platt et T. Wagner. « Accounting for the effect of horizontal gradients in limb measurements of scattered sunlight ». Atmospheric Chemistry and Physics 8, no 12 (20 juin 2008) : 3045–60. http://dx.doi.org/10.5194/acp-8-3045-2008.
Texte intégralRésumé :
Abstract. Limb measurements provided by the SCanning Imaging Absorption spectrometer for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale, among them BrO for the first time. For limb observations in the UV/VIS spectral region the instrument measures scattered light with a complex distribution of light paths: the light is measured at different tangent heights and can be scattered or absorbed in the atmosphere or reflected by the ground. By means of spectroscopy and radiative transfer modelling these measurements can be inverted to retrieve the vertical distribution of stratospheric trace gases. The fully spherical 3-D Monte Carlo radiative transfer model "Tracy-II" is applied in this study. The Monte Carlo method benefits from conceptual simplicity and allows realizing the concept of full spherical geometry of the atmosphere and also its 3-D properties, which is important for a realistic description of the limb geometry. Furthermore it allows accounting for horizontal gradients in the distribution of trace gases. In this study the effect of horizontally inhomogeneous distributions of trace gases along flight/viewing direction on the retrieval of profiles is investigated. We introduce a tomographic method to correct for this effect by combining consecutive limb scanning sequences and utilizing the overlap in their measurement sensitivity regions. It is found that if horizontal inhomogenity is not properly accounted for, typical errors of 20% for NO2 and up to 50% for OClO around the altitude of the profile peak can arise for measurements close to the Arctic polar vortex boundary in boreal winter.
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Shumaker, Niven, Daniel Haymond et Joe Martin. « Kinematic linkage between minibasin welds and extreme overpressure in the deepwater Gulf of Mexico ». Interpretation 2, no 1 (1 février 2014) : SB69—SB77. http://dx.doi.org/10.1190/int-2013-0104.1.
Texte intégralRésumé :
A geopressure interpretation technique known as the seismic velocity method is a common workflow in which shale compaction functions are characterized at offset control wells, matched to interval seismic velocities, and then used to predictively calculate geopressure away from well control. The seismic velocity method is used to interpret the expected geopressure profile at the Deep Blue subsalt exploration well in Green Canyon 723 in the deep water Gulf of Mexico. The Deep Blue prospect is distinct from other prospects in the play fairway in that the prospective section is overlain by a salt withdrawal minibasin, whereas the offsetting fields are positioned either along the flanks of minibasins or under a thick allochthonous salt canopy. Predrill geopressure interpretations using numerous tomographic imaging velocity data sets shows a large degree of consistency with the magnitude of geopressure encountered in offsetting supra salt and subsalt fields. Results from the Deep Blue 1 exploration well indicate the predrill geopressure interpretation from interval seismic velocities failed to anticipate the extreme degree overpressure encountered in the subsalt section of the well due to poor deep velocity resolution and an “unloaded” compaction signature. The magnitude of overpressure in the primary section is attributed to the emplacement of an unconformable halokinetic sequence over the primary subsalt basin. An interpretive paradigm is described in which the Deep Blue pressure cell is created through two halokinetic episodes: (1) rapid progradation of a salt canopy followed by (2) subsequent salt withdrawal and emplacement of an overlying minibasin. The linkage between halokinetic sequences, burial history, and the development of overpressure can be used to predictively characterize subsalt geopressure environments.
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Khury, Farouk, Michael Fuchs, Hassan Awan Malik, Janina Leiprecht, Heiko Reichel et Martin Faschingbauer. « Validation of joint space narrowing on plain radiographs and its relevance to partial knee arthroplasty ». Bone & ; Joint Research 10, no 3 (1 mars 2021) : 173–87. http://dx.doi.org/10.1302/2046-3758.103.bjr-2020-0216.r1.
Texte intégralRésumé :
Aims To explore the clinical relevance of joint space width (JSW) narrowing on standardized-flexion (SF) radiographs in the assessment of cartilage degeneration in specific subregions seen on MRI sequences in knee osteoarthritis (OA) with neutral, valgus, and varus alignments, and potential planning of partial knee arthroplasty. Methods We retrospectively reviewed 639 subjects, aged 45 to 79 years, in the Osteoarthritis Initiative (OAI) study, who had symptomatic knees with Kellgren and Lawrence grade 2 to 4. Knees were categorized as neutral, valgus, and varus knees by measuring hip-knee-angles on hip-knee-ankle radiographs. Femorotibial JSW was measured on posteroanterior SF radiographs using a special software. The femorotibial compartment was divided into 16 subregions, and MR-tomographic measurements of cartilage volume, thickness, and subchondral bone area were documented. Linear regression with adjustment for age, sex, body mass index, and Kellgren and Lawrence grade was used. Results We studied 345 neutral, 87 valgus, and 207 varus knees. Radiological JSW narrowing was significantly (p < 0.01) associated with cartilage volume and thickness in medial femorotibial compartment in neutral ( r = 0.78, odds ratio (OR) 2.33) and varus knees ( r = 0.86, OR 1.92), and in lateral tibial subregions in valgus knees ( r = 0.87, OR 3.71). A significant negative correlation was found between JSW narrowing and area of subchondral bone in external lateral tibial subregion in valgus knees ( r = −0.65, p < 0.01) and in external medial tibial subregion in varus knees ( r = −0.77, p < 0.01). No statistically significant correlation was found in anterior and posterior subregions. Conclusion SF radiographs can be potentially used for initial detection of cartilage degeneration as assessed by MRI in medial and lateral but not in anterior or posterior subregions. Cite this article: Bone Joint Res 2021;10(3):173–187.
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Zabramski, Joseph M., Robert F. Spetzler et Benjamin Kaufman. « Magnetic Resonance Imaging : Comparative Study of Radiofrequency Pulse Techniques in the Evaluation of Focal Cerebral Ischemia ». Neurosurgery 16, no 4 (1 avril 1985) : 502–10. http://dx.doi.org/10.1097/00006123-198504000-00012.
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Abstract The recently developed technique of magnetic resonance (MR) imaging utilizes radiofrequency (RF) radiation in the presence of a strong magnetic field to provide cross sectional displays of body anatomy similar to computed tomography, When utilizing MR, the operator alters tissue contrast electronically by changing RF pulse sequences. The three most frequently used RF pulse sequences are partial-saturation (PS), inversion-recovery (IR), and spin-echo (SE). We evaluated the sensitivity of these RF sequences to detect ischemic changes in our primate model. Serial MR scans were carried out using all three pulse formats 5 to 60 hours after middle cerebral artery occlusion (MCAO) in four animals. SE- and IR-sequenced proton MR images readily identified areas of evolving infarct 5 to 6 hours after MCAO, whereas PS scans that were performed during this acute period appeared normal. From 24 to 60 hours after MCAO, PS-sequenced scans showed focal areas of progressively decreasing signal intensity. However, SE and IR scans performed at the same intervals always demonstrated more extensive tissue changes. The basis of MR imaging, the effects of altering RF pulse sequences, and the resulting interpretation of changes observed in MR sections are presented. (Neurosurgery 16: 502-510, 1985)
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Kızıloğlu, Hüseyin Alper, Adem Karaman, Okan Dilek, Kamber Kasali et Fatih Alper. « Evaluation of pulmonary nodules by magnetic resonance imaging sequences : which sequence will replace computed tomography ? » Revista da Associação Médica Brasileira 68, no 11 (novembre 2022) : 1519–23. http://dx.doi.org/10.1590/1806-9282.20220215.
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Zhang, Li. « Evaluation of Incision Margin and Radiotherapy Adjustment in Breast Cancer-Conserving Surgery Based on VR Pathology 3D Reconstruction ». Journal of Healthcare Engineering 2021 (16 août 2021) : 1–11. http://dx.doi.org/10.1155/2021/2709461.
Texte intégralRésumé :
At present, the incidence of breast cancer is high worldwide and the most effective way to treat breast cancer is surgery. This study mainly explores the application of pathological three-dimensional reconstruction based on VR technology in the evaluation of the margins of breast-conserving surgery and the adjustment of radiotherapy for breast cancer. In the process of making pathological large slices, the slice markers are counted and the upper and outer cutting edges are located and placed in a large embedding box to prevent tissue deformation. ACDSEE6.0 is used to convert the aligned image BMP format into JPG format, the JPG images of each breast are cropped in batches under the same range and size, and then 3DDOCTOR1.0 is imported to edit the images. The boundary edit tool is activated to segment the target area layer by layer to create a boundary data set of the target structure. The stored file is opened and 3D rendering simple surface and volume rendering on the computer is run to display the surface data 3D display and the volume data 3D display. During VR image processing, the data are imported into the VR image workstation and the Radio Dexter software system is used for image adjustment, trimming, and sequence extraction. Then, the preliminary processed CT and MRI data are displayed in pairs. Through multiplane comparison, manual or automatic fusion tools are used to reduce the gap between image sequences. The surgical process is simulated under VR: by changing the window size and viewing angle; using virtual electric drills, cutting tools, and other virtual instruments; ad selecting the operating microscope perspective; and simulating steps such as breast opening, visual field exposure, and tumor resection. The breast tomographic image was reconstructed in multiple planes, and two-dimensional images of any plane could be observed. 10 cases showed high-density shadows and 5 cases showed isodensity shadows. This research contributes to the precise treatment of breast-conserving surgery.
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Thariat, Juliette, Joel Castelli, Stephane Chanalet, Serge Marcie, Hamid Mammar et Pierre-Yves Bondiau. « CYBERKNIFE STEREOTACTIC RADIOTHERAPY FOR SPINAL TUMORS ». Neurosurgery 64, suppl_2 (1 février 2009) : A60—A66. http://dx.doi.org/10.1227/01.neu.0000339129.51926.d6.
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Abstract OBJECTIVE For para- and intraspinal tumors, precise spinal cord delineation is critical for CyberKnife (Accuray, Inc., Sunnyvale, CA) stereotactic radiotherapy. We evaluated whether computed tomographic (CT) myelography is superior to magnetic resonance imaging (MRI) for accurate spinal cord delineation. Treatment parameters and short-term outcome and toxicity are also presented. METHODS The planning CT scan, the gadolinium-enhanced, T1-weighted, 3-dimensional (3D) fast imaging employing steady-state acquisition MRI scan, and the CT myelogram were fused before volume-of-interest delineation. The planning target volume margin was less than 1 mm using the Xsight Spine tracking system (Accuray). We present data from 11 heavily pretreated patients who underwent CyberKnife stereotactic radiosurgery between November 2006 and January 2008. RESULTS Spatial resolution was 0.46 and 0.93 mm/pixel for CT myelography and 3D-fast imaging employing steady-state acquisition MRI, respectively. The contrast between cerebrospinal fluid and spinal cord was excellent with CT myelography. A transient postmyelography headache occurred in 1 patient. The mean gross tumor volume was 51.1 mL. The mean prescribed dose was 34 Gy in 4 fractions (range, 2–7 fractions) with 147 beams (range, 79–232 beams) to the 75% reference isodose line (range, 68–80%), covering 95% (range, 86–99%) of the gross tumor volume with a mean conformity index of 1.4 (range, 1.1–1.8). No short-term toxicity on the spinal cord was noted at 1- to 6-months of follow-up. CONCLUSION CT myelography was more accurate for spinal cord delineation than 3D-fast imaging employing steady-state acquisition MRI (used for its myelographic effect), particularly in the presence of ferromagnetic artifacts in heavily pretreated patients or in patients with severe spinal compression. Because other MRI sequences (T2 and gadolinium-enhanced T1) provide excellent tumor characterization, we suggest trimodality imaging for spinal tumor treatment to yield submillimetric delineation accuracy. Combined with CyberKnife technology, CT myelography can improve the feasibility of dose escalation or reirradiation of spinal tumors in selected patients, thereby increasing local control while avoiding myelopathy. Further follow-up and prospective studies are warranted.
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Jiang Peng, 蒋鹏, 吴迪 Wu Di, 谢菲 Xie Fei, 高树辉 Gao Shuhui et 蔡能斌 Cai Nengbin. « 光学相干层析技术在打印文书朱墨时序判别中的实验研究 ». Laser & ; Optoelectronics Progress 59, no 10 (2022) : 1011005. http://dx.doi.org/10.3788/lop202259.1011005.
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Boecker, H., A. O. Ceballos-Baumann, P. Bartenstein, A. Dagher, K. Forster, B. Haslinger, D. J. Brooks, M. Schwaiger et B. Conrad. « A H215O Positron Emission Tomography Study on Mental Imagery of Movement Sequences—The Effect of Modulating Sequence Length and Direction ». NeuroImage 17, no 2 (octobre 2002) : 999–1009. http://dx.doi.org/10.1006/nimg.2002.1139.
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Kostova-Lefterova, D., et A. Partenova. « Тechnical aspects of cardiac magnetic resonance tomography ». Bulgarian Cardiology 28, no 4 (30 décembre 2022) : 7–28. http://dx.doi.org/10.3897/bgcardio.28.e97065.
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Cardiac magnetic resonance tomography (CMRT) is a method of high diagnostic value in the assessment of cardiac vitality through the application of various perfusion techniques, as well as in the evaluation and diagnosis of early myocardial ischemic changes. The aim of this article is to review the different technical aspects of CMRT. A major problem in CMRT studies is the deterioration of image quality due to the presence of motion artefacts. This necessitates the development of ECG-gated and respiratory triggered or breath-holding techniques and their implementation in practice. In contrast to most other applications of MRT, the planes used in CMRT are defined with respect to the orientation of the heart so that they are parallel and orthogonal to the cardiac axes. Two main groups of sequences are used in CMRT: 1) to determine morphology, function, and blood flow and 2) to provide good tissue contrast of the heart. Technological development of the method has not stopped, and techniques and pulse sequences continue to be developed to improve the diagnostic capabilities of CMRT. Through proper planning, a thorough understanding of the cardiac planes, and appropriate selection of technical parameters for the respective sequences depending on the clinical finding being addressed, a successful performance of each CMRT study is achieved.
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Popovtzer, Aron, Mohannad Ibrahim, Daniel Tatro, Felix Y. Feng, Randall K. Ten Haken et Avraham Eisbruch. « MRI to delineate the gross tumor volume of nasopharyngeal cancers : which sequences and planes should be used ? » Radiology and Oncology 48, no 3 (1 septembre 2014) : 323–30. http://dx.doi.org/10.2478/raon-2014-0013.
Texte intégralRésumé :
Abstract Background. Magnetic resonance imaging (MRI) has been found to be better than computed tomography for defining the extent of primary gross tumor volume (GTV) in advanced nasopharyngeal cancer. It is routinely applied for target delineation in planning radiotherapy. However, the specific MRI sequences/planes that should be used are unknown. Methods. Twelve patients with nasopharyngeal cancer underwent primary GTV evaluation with gadolinium-enhanced axial T1 weighted image (T1) and T2 weighted image (T2), coronal T1, and sagittal T1 sequences. Each sequence was registered with the planning computed tomography scans. Planning target volumes (PTVs) were derived by uniform expansions of the GTVs. The volumes encompassed by the various sequences/planes, and the volumes common to all sequences/planes, were compared quantitatively and anatomically to the volume delineated by the commonly used axial T1-based dataset. Results. Addition of the axial T2 sequence increased the axial T1-based GTV by 12% on average (p = 0.004), and composite evaluations that included the coronal T1 and sagittal T1 planes increased the axial T1-based GTVs by 30% on average (p = 0.003). The axial T1-based PTVs were increased by 20% by the additional sequences (p = 0.04). Each sequence/plane added unique volume extensions. The GTVs common to all the T1 planes accounted for 38% of the total volumes of all the T1 planes. Anatomically, addition of the coronal and sagittal-based GTVs extended the axial T1-based GTV caudally and cranially, notably to the base of the skull. Conclusions. Adding MRI planes and sequences to the traditional axial T1 sequence yields significant quantitative and anatomically important extensions of the GTVs and PTVs. For accurate target delineation in nasopharyngeal cancer, we recommend that GTVs be outlined in all MRI sequences/planes and registered with the planning computed tomography scans.
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Harrison, Tyler, Peng Shao et Roger J. Zemp. « S-sequence patterned illumination iterative photoacoustic tomography ». Journal of Biomedical Optics 19, no 9 (9 septembre 2014) : 096004. http://dx.doi.org/10.1117/1.jbo.19.9.096004.
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Yang, Nathaniel. « Inner Ear Hemorrhage : A Cause of Sensorineural Hearing Loss in Leukemia ». Philippine Journal of Otolaryngology Head and Neck Surgery 37, no 1 (5 juin 2022) : 55. http://dx.doi.org/10.32412/pjohns.v37i1.1955.
Texte intégralRésumé :
A 25-year-old male who was recently diagnosed with chronic myelogenous leukemia developed bilateral tinnitus and hearing loss. The hearing loss progressed rapidly but asymmetrically, with the right ear being subjectively worse than the left. Pneumatoscopy revealed bilaterally intact and mobile tympanic membranes and no visual evidence of middle ear pathology. Audiometry confirmed the presence of a profound hearing loss in the right ear and a moderate sensorineural hearing loss in the left ear. In relation to evaluating the cause of hearing loss, the radiologic interpretation of a contrast-enhanced cranial MRI performed to evaluate other neurological symptoms that predated the hearing loss only stated that the cerebellopontine angle cisterns were unremarkable. No mention was made about the status of the inner ears. When asked to comment on the inner ears in the MR study, the radiologist opined that the cranial MRI did not have the proper fine-cut imaging sequences necessary to evaluate this region adequately, and indicated the need for a dedicated MR study of the temporal bones. An independent review of the DICOM imaging data of the patient’s cranial MRI revealed the presence of three imaging sequences with information pertinent to the evaluation of the inner ears. These sequences are shown below, with a sequential narration of the descriptive imaging findings and their clinical significance that helps to arrive at a conclusive diagnosis.
1. FIESTA (Fast imaging employing steady-state acquisition) – a thin-slice heavily T2- weighted imaging sequence specific to GE MRI machines.
Beginning the MR evaluation of the inner ear by viewing a T2-weighted sequence allows one to immediately visualize the fluid-filled compartments of the cochlea, vestibule and semicircular canals in a depiction most similar to that of computerized tomographic imaging of the temporal bones. In a T2-weighted imaging sequence, the normal inner ear contains fluid that gives it a bright, intrinsically high signal intensity similar to that of cerebrospinal fluid.1 In this particular case, it can be visually discerned in the axial image (Figure 1A) that the right cochlea (white diagonal farrow) has a lower signal intensity compared to the left cochlea (white diagonalgarrow). The signal intensity in the left cochlea is similar in brightness to the CSF in the cerebellopontine angle cistern (white *). This difference in signal intensity can also be visually discerned in the coronal image (Figure 1B).
A lower T2-weighted signal intensity within the cochlea indicates a change in its normal fluid content. Several conditions can lead to this change, including intralabyrinthine hemorrhage, labyrinthitis, labyrinthine fibrosis and intralabyrinthine mass lesions like a schwannoma or a lipoma.2,3 As such, this T2-weighted imaging abnormality needs to be correlated with the clinical setting and the imaging characteristics in the other MR sequences in order to discern the true nature of the condition.
2. 3D LAVA (Liver acquisition with volume acceleration) – a thin- slice T1-weighted gradient echo sequence specific to GE MRI machines. The imaging study contained both non-contrast (Figure 2) and contrast- enhanced (Figure 3) series.
In a non-contrast T1-weighted imaging sequence, the normal inner ear would have the same low signal intensity as cerebrospinal fluid.1 In this particular case, it can be seen in the axial image (Figure 2A) that the left cochlea (white diagonalgarrow) is similar in brightness to the CSF in the cerebellopontine angle cistern (white *) and is barely discernible . On the other hand, the right cochlea (white diagonal f arrow) can be easily identified and has a high signal intensity compared to the contralateral side. This same pattern of high signal intensity is reciprocated on the coronal image as well (Figure 2B).
An intrinsically high signal intensity (hyperintense) in the cochlea in a non-contrast T1-weighted imaging sequence is an abnormal finding and is one of the main imaging characteristics that defines the presence of intralabyrinthine hemorrhage.4 However, this finding can also be seen in the presence of fat, and in conditions where the inner ear fluid has an elevated protein content.5 Rare intralabyrinthine lipomas have been reported,3 and differentiation of this condition will depend on the contrast-enhanced, fat suppressed T1-weighted imaging sequence. Elevated protein in perilymph fluid has been reported in patients with acoustic neuromas, in otitis media, and in bacterial labyrinthitis,5 all of which would present with other readily apparent MR findings in the middle ear or in the region of the internal auditory canal and cerebellopontine angle.
Thus, based on the imaging characteristics of the T2-weighted and non-contrast T1-weighted imaging sequences, the differential diagnoses have been narrowed down to intralabyrinthine hemorrhage and a specific type of mass lesion, an intralabyrinthine lipoma.
In a contrast-enhanced T1-weighted imaging sequence, the normal inner ear would maintain the same low signal intensity as CSF. In this particular case, it can be seen in the axial image (Figure 3A) that the left cochlea (white diagonalgarrow) maintains this same signal characteristic. The right cochlea (white diagonal f arrow) also maintains its intrinsically high signal intensity, with no additional increase in signal intensity from the contrast medium. Additionally, this high signal was maintained in this fat-suppressed sequence. This same pattern is present in the coronal image (Figure 2B).
When the imaging characteristics in the contrast-enhanced T1- weighted imaging sequence are taken in isolation, it can be determined that the lack of enhancement negates the diagnosis of labyrinthitis or an intralabyrinthine schwannoma. When the T2-weighted and non- contrast T1-weighted imaging characteristics are factored in, the lack of signal intensity loss in this fat-suppressed sequence effectively removes the intralabyrinthine lipoma from the list of differentials. As such, one is left with intralabyrinthine hemorrhage as the only possible diagnosis.
3. 3D FLAIR (fluid-attenuated inversion recovery) – a thin slice heavily T2-weighted imaging sequence with suppression of the cerebrospinal fluid signal that makes recognition of various pathologies near the CSF space easier.6
The FLAIR sequence is a common component of MR imaging of the brain that has, in recent years, received attention in the scientific literature as an imaging sequence that could provide more information on inner ear pathologies. In the non-contrast FLAIR sequence, the normal inner ear has a low signal intensity, similar to the suppressed signal from cerebrospinal fluid. In this particular case, the axial image (Figure 4A) the left vestibule (white diagonal g arrow) has a very low signal intensity and is barely discernible. On the other hand, the right vestibule (white diagonal f arrow) is hyperintense. This same pattern is also demonstrated in the coronal image (Figure 4B).
A high signal intensity in the inner ear on non-contrast FLAIR imaging has been identified in intracochlear hemorrhage, in vestibular schwannomas, and in labyrinthitis.4 Since the presence of a vestibular schwannoma or labyrinthitis have already been ruled out in this particular case by the findings in the preceding imaging sequences, then the inner ear FLAIR hyperintensity serves to corroborate the diagnosis of inner ear hemorrhage.
Sensorineural hearing loss has been reported in the medical literature as one of the otological manifestations of leukemia.7 Various pathophysiologic mechanisms have been ascribed to this symptom including leukostasis, leukemic infiltration of the cochlea, hyperviscosity syndrome, inner ear hemorrhage and infections.8 Magnetic resonance imaging plays a significant diagnostic and prognostic role in this situation, as it can help to determine the presence or absence of several of these conditions, and elevate the case from the realm of mere conjecture and speculation. In this particular case, inner ear hemorrhage was recognized to be the pathophysiologic basis for hearing loss in leukemia. Inner ear hemorrhage has also been identified in hearing loss related to other hematologic conditions like pernicious anemia, sickle cell anemia, hyperviscosity disorders, and in patients taking anticoagulation drugs like aspirin or warfarin.4 As such, searching for the characteristic imaging findings on MR studies done in these clinical situations would be appropriate.
It must be acknowledged that the ability to detect abnormalities on MR imaging depends on the presence of imaging sequences that allows one to adequately visualize the minute structures of the inner ear. Although it would be intuitive to think that these structures would always require a dedicated MR imaging study of the inner ear and temporal bones, one must be cognizant of the possibility of the inclusion of newer, thin-slice imaging sequences in an institution- specific brain MR imaging protocol that would allow appropriate evaluation of the inner ear in the absence of a dedicated study.
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Wadbro, Eddie. « Microwave tomographic imaging as a sequence of topology optimization problems ». Optimization and Engineering 11, no 4 (17 décembre 2008) : 597–610. http://dx.doi.org/10.1007/s11081-008-9075-x.
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Ding, W., et B. Liu. « Tomographic image sequence reconstruction by edge-preserving interslice MAP methods ». IEEE Transactions on Image Processing 5, no 1 (janvier 1996) : 178–83. http://dx.doi.org/10.1109/83.481687.
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Barber, Quinn M., et Roger J. Zemp. « Photoacoustic–Ultrasound Tomography With S-Sequence Aperture Encoding ». IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 64, no 4 (avril 2017) : 688–93. http://dx.doi.org/10.1109/tuffc.2017.2661238.
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Lum, Edward S., et Chad L. Pope. « Matlab enhanced multi-threaded tomography optimization sequence (MEMTOS) ». Annals of Nuclear Energy 91 (mai 2016) : 127–34. http://dx.doi.org/10.1016/j.anucene.2015.12.020.
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Kawashima, R., J. Tanji, K. Okada, Motoaki Sugiura, Kazunori Sato, Shigeo Kinomura, Kentaro Inoue, Akira Ogawa et Hiroshi Fukuda. « Oculomotor sequence learning : a positron emission tomography study ». Experimental Brain Research 122, no 1 (3 septembre 1998) : 1–8. http://dx.doi.org/10.1007/s002210050485.
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Zhang Pin, Liang Yan-Mei, Chang Sheng-Jiang et Fan Hai-Lun. « Kidney segmentation in computed tomography sequences based on energy minimization ». Acta Physica Sinica 62, no 20 (2013) : 208701. http://dx.doi.org/10.7498/aps.62.208701.
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Mo, Weirong, et Nanguang Chen. « Fast time-domain diffuse optical tomography using pseudorandom bit sequences ». Optics Express 16, no 18 (20 août 2008) : 13643. http://dx.doi.org/10.1364/oe.16.013643.
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Gong, Jian, Kangjian He, Lisiqi Xie, Dan Xu et Tao Yang. « A Fast Image Guide Registration Supported by Single Direction Projected CBCT ». Electronics 11, no 4 (18 février 2022) : 645. http://dx.doi.org/10.3390/electronics11040645.
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Image registration is an important research topic in medical image-guided therapy, which is dedicated to registering the high-dose imaging sequences with low-dose/faster means. Registering computer tomography (CT) scanning sequences with cone beam computer tomography (CBCT) scanning sequences is a typical application and has been widely used in CBCT-guided radiotherapy. The main problem is the difference in image clarity of these two image sequences. To solve this problem, for the single projection image sequence matching tasks encountered in medical practice, a novel local quality based curved section encoding strategy is proposed in this paper, which is called the high-quality curved section (HQCS). As an optimized cross-section regularly encoded along the sequence of image, this curved section could be used in order to solve the matching problem. Referencing the independent ground truth provided by medical image physicians, with an experiment combined with the four most widely used indicators used on image registration, matching performance of HQCS on CT/CBCT datasets was tested with varying clarity. Experimental results show that the proposed HQCS can register the CT/CBCT effectively and outperforms the commonly used methods. Specifically, the proposed HQCS has low time complexity and higher scalability, which indicates that the application enhanced the task of diagnosis.
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Yashiro, Tabane. « DISCRETE TOMOGRAPHY FOR THE POINT SEQUENCE GENERATED BY THE ADJACENT TERMS OF A SEQUENCE ». JP Journal of Algebra, Number Theory and Applications 40, no 4 (31 août 2018) : 461–94. http://dx.doi.org/10.17654/nt040040461.
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Jenkins, IH, DJ Brooks, PD Nixon, RS Frackowiak et RE Passingham. « Motor sequence learning : a study with positron emission tomography ». Journal of Neuroscience 14, no 6 (1 juin 1994) : 3775–90. http://dx.doi.org/10.1523/jneurosci.14-06-03775.1994.
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