Bibliografie tematiche / Motion correction

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Letteratura scientifica selezionata sul tema "Motion correction"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 8 giugno 2024

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Articoli di riviste sul tema "Motion correction"

Hagedorn, John G., Steven G. Satterfield, John T. Kelso, Whitney Austin, Judith E. Terrill e Adele P. Peskin. "Correction of Location and Orientation Errors in Electromagnetic Motion Tracking". Presence: Teleoperators and Virtual Environments 16, n. 4 (1 agosto 2007): 352–66. http://dx.doi.org/10.1162/pres.16.4.352.

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We describe a method for calibrating an electromagnetic motion tracking device. Algorithms for correcting both location and orientation data are presented. In particular, we use a method for interpolating rotation corrections that has not previously been used in this context. This method, unlike previous methods, is rooted in the geometry of the space of rotations. This interpolation method is used in conjunction with Delaunay tetrahedralization to enable correction based on scattered data samples. We present measurements that support the assumption that neither location nor orientation errors are dependent on sensor orientation. We give results showing large improvements in both location and orientation errors. The methods are shown to impose a minimal computational burden.

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Zhu, Z. "The understanding of the FK5 and Hipparcos proper-motion systems". Proceedings of the International Astronomical Union 3, S248 (ottobre 2007): 18–19. http://dx.doi.org/10.1017/s1743921308018553.

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AbstractComparing proper motions of the FK5 and Hipparcos, several authors declared that the two proper-motion systems are inconsistent with the value of the precession correction obtained from VLBI and LLR observations. Based on the proper-motion data from the PPM and ACRS catalogues which are constructed on the FK5 system, the inconsistent values of the precessional correction and of the time-dependent term of equinox correction, derived from the different subsets of stellar samples, have been found. One of the reasons for those discrepancies should be mostly due to the internally biased proper-motion system of the FK5.

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Choi, Hoon Sik, Ki Mun Kang, In Bong Ha, Bae Kwon Jeong, Jin Ho Song, Chul Hang Kim e Hojin Jeong. "Comprehensive Analysis of Set-Up Gain of 6-Dimensional Cone-Beam CT Correction Method in Radiotherapy for Head and Neck and Brain Tumors". Computational and Mathematical Methods in Medicine 2022 (20 ottobre 2022): 1–9. http://dx.doi.org/10.1155/2022/2964023.

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This study quantitatively analyzed the gain of the six-dimensional (6D) cone-beam CT (CBCT) correction method compared with the conventional set-up method in 60 patients who underwent radiation treatment of head and neck and brain tumors. The correction gain of CBCT was calculated for the translational and rotational motion components separately and in combination to evaluate the individual and overall effects of these motion components. Using a statistical simulation mimicking the actual set-up correction process, the effective gain of periodic CBCT correction during the entire treatment fraction was analyzed by target size and CBCT correction period under two different correction scenarios: translation alone and full 6D corrections. From the analyses performed in this study, the gain of CBCT correction was quantitatively determined for each situation, and the appropriate CBCT correction strategy was suggested based on treatment purpose and target size.

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Zahneisen, Benjamin, Brian Keating, Aditya Singh, Michael Herbst e Thomas Ernst. "Reverse retrospective motion correction". Magnetic Resonance in Medicine 75, n. 6 (3 luglio 2015): 2341–49. http://dx.doi.org/10.1002/mrm.25830.

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Miyamoto, Masanori. "Is the Vorticity Vector of the Galaxy Perpendicular to the Galactic Plane?" Symposium - International Astronomical Union 156 (1993): 219–30. http://dx.doi.org/10.1017/s0074180900173255.

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The modern astrometric catalogue ACRS invites attempts to re-examine the systematic stellar motions, together with the luni-solar precessional correction and the fictitious equinoctial motion correction to the FK5 system, and gives encouraging results.On the basis of the three-dimensional Ogorodnikov-Milne model for the overall pattern analysis of the proper motions, the systematic stellar velocity field of about 30000 K-M giants chosen from the ACRS is first examined in the heliocentric distance interval 0.5 to 1.0 kpc. We have found in an iterative fashion a solution for the K-M giants that yields neither deformation-nor vorticity-field other than the classical ones (the Oort constants A and B). The important point to note here is that the generally accepted idea such that the K-M giants are a steady-state constituent of the galaxy is compatible with the luni-solar precessional correction proposed by the VLBI and LLR observations. The K-M giants give the rational set of corrections to the FK5 system: the luni-solar precessional correction Δp = −0″.27 ± 0″.03 / cent and the equinoctial motion correction including the planetary precessional correction Δe + Δλ = −0″.12 ± 0″.03 / cent. Thus, the precessional correction previously proposed with the modern techniques has been confirmed by the pattern analysis of the proper motions.Next, applying the corrections obtained above, we have performed the overall pattern analysis of the proper motions of about 3000 O-B5 stars, supergiants, and bright giants, which are chosen again from the ACRS, and considered as an entity of the galactic warp. It is found that the kinematics of these stars is quite different from that of K-M giants. These stars show additional shears and rotations around two mutually orthogonal axes lying in the galactic plane, besides the classical ones. The present finding implies that the young stars are streaming around the galactic center in a tilted sheet (the warp) with the velocity of 225 km/s, and the sheet itself is simultaneously rotating around the nodal line of the warp (galactic center — sun — anticenter line) with the angular velocity of 4 km/s/kpc in increasing sense of the present inclination of the warp.

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Polycarpou, Irene, Georgios Soultanidis e Charalampos Tsoumpas. "Synergistic motion compensation strategies for positron emission tomography when acquired simultaneously with magnetic resonance imaging". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, n. 2204 (5 luglio 2021): 20200207. http://dx.doi.org/10.1098/rsta.2020.0207.

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Subject motion in positron emission tomography (PET) is a key factor that degrades image resolution and quality, limiting its potential capabilities. Correcting for it is complicated due to the lack of sufficient measured PET data from each position. This poses a significant barrier in calculating the amount of motion occurring during a scan. Motion correction can be implemented at different stages of data processing either during or after image reconstruction, and once applied accurately can substantially improve image quality and information accuracy. With the development of integrated PET-MRI (magnetic resonance imaging) scanners, internal organ motion can be measured concurrently with both PET and MRI. In this review paper, we explore the synergistic use of PET and MRI data to correct for any motion that affects the PET images. Different types of motion that can occur during PET-MRI acquisitions are presented and the associated motion detection, estimation and correction methods are reviewed. Finally, some highlights from recent literature in selected human and animal imaging applications are presented and the importance of motion correction for accurate kinetic modelling in dynamic PET-MRI is emphasized. This article is part of the theme issue ‘Synergistic tomographic image reconstruction: part 2’.

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Yang, Yongzhong, e Lingfeng Meng. "Physical Education Motion Correction System Based on Virtual Reality Technology". International Journal of Emerging Technologies in Learning (iJET) 14, n. 13 (15 luglio 2019): 105. http://dx.doi.org/10.3991/ijet.v14i13.10710.

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Compared with traditional physical education (PE), the computer virtual digital-based education system is convenient and efficient, which can effectively solve the shortcomings of traditional teaching mode, and correct the PE motions in real time. Thus, the athletes can master the motion technical skills as soon as possible and the training effect can be improved. For this, based on computer virtual reality technology, this paper constructs a PE motion correction system. Then, through the analysis for real-time motion data and human movement posture, it achieves the training objective of real-time PE teaching motion correction under the three-dimensional visualization. This shall provide a scientific basis for the evaluation of PE teaching and training methods.

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Cabas, Ashly, e Adrian Rodriguez-Marek. "VS-κ0 Correction Factors for Input Ground Motions Used in Seismic Site Response Analyses". Earthquake Spectra 33, n. 3 (agosto 2017): 917–41. http://dx.doi.org/10.1193/22315eqs188m.

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Input motions used in seismic site response analyses are commonly selected based on similarities between the shear wave velocity ( V S) at the recording station, and the reference depth at the site of interest (among other aspects such as the intensity of the expected ground motion). This traditional approach disregards the influence of the attenuation in the shallow crust on site response. Given that this attenuation (damping) can be characterized by the distance-independent high-frequency attenuation parameter κ0, a V S -κ0 correction framework for input motions is proposed to render them compatible with the assumed properties of the reference depth at the site. The proposed correction factors were applied to a subset of recordings from the KiK-net database, and compared to traditional deconvolution. Results indicate that V S -κ0 corrected motions outperform deconvolved motions in the characterization of the spectral energy in the high-frequency range. However, motions recorded at sites with soft deposits are not good candidates for the V S -κ0 correction approach. V S -κ0 corrections also affect amplification functions which are important in the assessment of site-specific seismic hazards.

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Wang, Tao, Hongbo Zhang e Guojian Tang. "Predictor-corrector guidance for entry vehicle based on fuzzy logic". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, n. 2 (3 novembre 2017): 472–82. http://dx.doi.org/10.1177/0954410017737574.

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With the development of aerospace industry, the guidance system of an entry vehicle will be more robust, reliable and autonomous in the future. Based on fuzzy logic, the paper designs a predictor-corrector guidance law. The trajectory prediction is realized by numerical integration. The correction system is based on two fuzzy controllers, which correct the longitudinal motion and lateral motion synergistically. The error of flight range is eliminated by correcting the magnitude of bank angle. The altitude error is eliminated by correcting the attack angle. The lateral error is eliminated by regulating the reversal time of bank angle. Comparing with the traditional corrector based on Newton-Raphson iteration, the method in this paper only needs a single trajectory prediction in one correction cycle, which is favorable for on-board calculation. Moreover, the longitudinal motion and lateral motion are synergistically corrected in the predictor-corrector, which makes the method more robust and flexible.

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Wang, Haiying. "Three-Dimensional Image Recognition of Athletes' Wrong Motions Based on Edge Detection". Journal Européen des Systèmes Automatisés 53, n. 5 (15 novembre 2020): 733–38. http://dx.doi.org/10.18280/jesa.530516.

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The traditional 3D visual motion amplitude tracking algorithms cannot acquire the complete contour features, not to mention the correction of wrong motions in sports training. To solve the problem, this paper designs a 3D visual image recognition method based on contourlet domain edge detection, and applies it to the recognition of athlete’s wrong motions in sports training. Firstly, the visual reconstruction and feature analysis of human motions were carried out, and the edge detection features were extracted by edge detection algorithm. Then, a 3D visual motion amplitude tracking method was proposed based on improved inverse kinematics. The simulation results show that the proposed algorithm can effectively realize the recognition of 3D visual images of athlete motions, and improve the correction and judgment ability of athlete motions.

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Più fonti

Tesi sul tema "Motion correction"

Smith, Rhodri. "Motion correction in medical imaging". Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841883/.

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It is estimated that over half of current adults within Great Britain under the age of 65 will be diagnosed with cancer at some point in their lifetime. Medical Imaging forms an essential part of cancer clinical protocols and is able to furnish morphological, metabolic and functional information. The imaging of molecular interactions of biological processes in vivo with Positron Emission Tomography (PET) is informative not only for disease detection but also therapeutic response. The qualitative and quantitative accuracy of imaging is thus vital in the extraction of meaningful and reproducible information from the images, allowing increased sensitivity and specificity in the diagnosis and precision of image guided treatment. Furthermore the utilization of complementary information obtained via Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) in integrated PET-CT and PET-MR devices offers the potential for the synergistic effects of hybrid imaging to provide increased detection and precision of diagnosis with reduced radiation dose in a fully comprehensive single imaging examination. With the increasing sophistication in imaging technology respiratory organ motion during imaging has demonstrated itself to be a major degrading factor of PET image resolution. A modest estimate of respiratory motion amplitude of 5mm, results in PET system resolution degrading from ≈ 5mm to ≈8.5mm. This evidently has an impact on cancer lesion detectability. Therefore accurate and robust methods for respiratory motion correction are required for both clinical effectiveness and economic justification for purchasing state of the art hybrid PET scanners with high resolution capabilities. In addition the judicious use of imaging resources from hybrid imaging devices coupled with advanced image processing / acquisition protocols will allow optimization of data used for improving quantitative accuracy of PET images and those used for clinical interpretation. In essence it would prove impractical to use the MR scanner purely for monitoring respiratory motion. Numerous methods exist to attempt to correct PET imaging for respiratory motion. As presented in this thesis many methods demonstrate themselves to be ineffective in the clinical setting where the patients breathing patterns appear irregular in comparison to the idealized situation of regular periodic motion. Advanced respiratory motion correction techniques utilize hybrid PET/CT, PET/MR scanners coupled with an external source of information which serves as a surrogate to build a static correspondence to the estimated internal respiratory motion. Static models however are unable to adapt to their external environment and do not consider time dependent changes in the state of a system. A further confounding factor in the development and assessment of motion correction schemes for medical imaging data is the inability to acquire volumetric data with high contrast and high spatial and temporal resolution which serves as a ground truth for quantifying model accuracy and confidence. This thesis addresses both problems by analysing respiratory motion correspondence modelling under a manifold learning and alignment paradigm which may be used to consolidate many of the respiratory motion estimation models that exist today. A Bayesian approach is adopted in this work to incorporate a-priori information into the model building stage for a more robust, flexible adaptive respiratory motion estimation / correction framework. This thesis constructs and tests the first proposed adaptive motion model to correlate a surrogate signal with internal motion. This adaptive approach allows the relationship between external surrogate signal and internal motion to change dependent upon breathing pattern and system noise. The adaptive model was compared to a state-of the-art static model and allows more accurate motion estimates to be made when the patient is breathing with an irregular pattern. Testing performed on MRI data from 9 volunteers demonstrated the adaptive model was statistically more significant (p < 0.001) in the presence of irregular motion in comparison to a static model. The adaptive Kalman model on average reduced the error in motion by 30% in comparison to the static model. Utilizing the adaptive model during a typical PET study would theoretically result in ≈ 10% increase in PET resolution in comparison to relying on a static model alone for motion correction. The adaptive Kalman model has the capability to increase the performance of PET system resolution from ≈ 8.5mm to ≈ 5.8mm, ≈ 30%. A simulated PET study also demonstrated ≈ 30% increase in tumour uptake when using motion correction. Also demonstrated in the thesis is the first method to acquire volumetric imaging data from sparse MR samples during free breathing to allow the realization of high contrast, high resolution 4D models of respiratory motion using limited acquired data. The developed framework facilitates greater freedom in the acquisition of free breathing respiratory motion sequences which may be used to inform motion modelling methods in a range of imaging modalities as well as informing the development of generalizable models of human respiration. It is shown that the developed approach can provide equivalent motion vector fields in comparison to fully sampled 4D dynamic data. The incorporation of the manifold alignment step into the sparse motion model reduces the error in motion estimates by ≈ 16%. Example images of propagated motion are also presented as supplementary information. The thesis concludes by generalizing the concepts in this work and looking to utilize the developed methods to other problems in the medical imaging arena.

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Sklyar, Andrey V. "Testing SPECT Motion Correction Algorithms". Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/419.

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Frequently, testing of Single Photon Emission Computed Tomography (SPECT) motion correction algorithms is done either by using simplistic deformations that do not accurately simulate true patient motion or by applying the algorithms directly to data acquired from a real patient, where the true internal motion is unknown. In this work, we describe a way to combine these two approaches by using imaging data acquired from real volunteers to simulate the data that the motion correction algorithms would normally observe. The goal is to provide an assessment framework which can both: simulate realistic SPECT acquisitions that incorporate realistic body deformations and provide a ground truth volume to compare against. Every part of the motion correction algorithm needs to be exercised: from parameter estimation of the motion model, to the final reconstruction results. In order to build the ground truth anthropomorphic numerical phantoms, we acquire high resolution MRI scans and motion observation data of a volunteer in multiple different configurations. We then extract the organ boundaries using thresholding, active contours, and morphology. Phantoms of radioactivity uptake and density inside the body can be generated from these boundaries to be used to simulate SPECT acquisitions. We present results on extraction of the ribs, lungs, heart, spine, and the rest of the soft tissue in the thorax using our segmentation approach. In general, extracting the lungs, heart, and ribs in images that do not contain the spine works well, but the spine could be better extracted using other methods that we discuss. We also go in depth into the software development component of this work, describing the C++ coding framework we used and the High Level Interactive GUI Language (HLING). HLING solved a lot of problems but introduced a fair bit of its own. We include a set of requirements to provide a foundation for the next attempt at developing a declarative and minimally restrictive methodology for writing interactive image processing applications in C++ based on lessons learned during the development of HLING.

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Sulikowska, Aleksandra. "Motion correction in high-field MRI". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33674/.

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The work described in this thesis was conducted at the University of Nottingham in the Sir Peter Mansfield Imaging Centre, between September 2011 and 2014. Subject motion in high- resolution magnetic resonance imaging (MRI) is a major source of image artefacts. It is a very complex problem, due to variety of physical motion types, imaging techniques, or k-space trajectories. Many techniques have been proposed over the years to correct images for motion, all looking for the best practical solution in clinical scanning, which would give cost- effective, robust and high accuracy correction, without decreasing patient comfort or prolonging the scan time. Moreover, if the susceptibility induced field changes due to head rotation are large enough, they will compromise motion correction methods. In this work a method for prospective correction of head motion for MR brain imaging at 7 T was proposed. It would employ innovative NMR tracking devices not presented in literature before. The device presented in this thesis is characterized by a high accuracy of position measurements (0.06 ± 0.04 mm), is considered very practical, and stands the chance to be used in routine imaging in the future. This study also investigated the significance of the field changes induced by the susceptibility in human brain due to small head rotations (±10 deg). The size and location of these field changes were characterized, and then the effects of the changes on the image were simulated. The results have shown that the field shift may be as large as |-18.3| Hz/deg. For standard Gradient Echo sequence at 7 T and a typical head movement, the simulated image distortions were on average equal to 0.5%, and not larger than 15% of the brightest voxel. This is not likely to compromise motion correction, but may be significant in some imaging sequences.

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Darwesh, Reem. "Motion correction in nuclear medicine imaging". Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664310.

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Patient motion either internal (organ motion) or external (body movement) can produce artefacts that can adversely affect nuclear medicine imaging. Motion artefacts can impair diagnostic information and potentially affect the image findings and prognosis for patients. The goal of this work was to investigate the effect of motion on nuclear medicine imaging and to improve image quality, lesion detectability, and tumour volume delineation by applying motion correction techniques. To investigate the effects of motion under controlled simulated conditions, a three dimensional phantom drive system was designed and constructed suitable for use with planar, SPECT, PET and CT scanners. The system was used with a range of nuclear medicine phantoms for testing proof of principle with planar, SPECT and PET imaging prior to undertake further work involving patients. Planar phantom and patient 99mTc_DMSA studies demonstrated improvements in image quality by the application of motion correction techniques. A comparison between the motion correction software using dynamic frame and list mode data showed that "MOCO" software with the use of the list mode data produced the best quantification results with phantom data, whereas determining the best approach was more difficult with patient data. The potential of using list mode data as an improved method of combining data into frames for subsequent analysis was demonstrated. Motion correction techniques would appear to offer great potential in lung imaging. Respiratory gated SPECT phantom studies have been carried out to simulate the visualisation of small defects in the lung. The CNRs and alternative free response receiver operating characteristic (AFROC) analysis have demonstrated that summing the gated data after the application of motion correction software significantly improved image quality, observer confidence and small defect detectability (less than 20 mm, p=O.0002). The results of these studies have shown the promising role of "MCFLIRT" software as a motion correction tool with gated SPECT data. Tumour volume delineation was investigated on PET images both with and without motion. The accuracy and consistency of the gradient-based software method for segmentation in PET images, which is commercially available from Mimvista Ltd was investigated. The results of comparing the measured volumes to the true volumes indicated significant differences (p=O.0005). It was found that the Signal:Background ratio and registering the PET to the CT data have significant effects on volume measurements, whereas, the effect of using different grey scale and plane of orientation were not found to have significant effects on the volume measurement. Motion correction techniques also showed to be potentially beneficial in PET imaging. Improvement in volume measurement as a result of summing the motion corrected gated data was demonstrated. The results of these studies have also shown the promising role of "MCFLIRT" as a motion correction tool with gated PET data.

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Bannister, Peter R. "Motion correction for functional magnetic resonance images". Thesis, University of Oxford, 2004. http://ora.ox.ac.uk/objects/uuid:f01d9fcb-e8bc-44ae-99a5-cc3e0bc12956.

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This work addresses the distortions in Functional Magnetic Resonance Images (FMRI) caused by subject motion. FMRI is a non-invasive technique which shows great promise in providing researchers and clinicians with neurological information both about healthy subjects and clinical patients by mapping functional activation within the brain using Echo Planar Imaging (EPI). If reliable information is to be obtained from these images, motion correction must be carried out in order to remove or suppress the artefacts arising from subject movement. This work begins by using exploratory data techniques to describe these artefacts so that they can be characterised according to their origin and spatio-temporal manifestation. Based on testing of the accuracy and consistency of existing rigid-body motion correction methods on FMRI data, a new registration algorithm Motion Correction using the FMRIB Linear Image Registration Tool (MCFLIRT) has been developed. It is shown that while MCFLIRT is both more accurate and more robust than previous methods, rigid-body registration schemes in general cannot completely remove the distortions associated with motion and so subsequent analysis of the images may still be inaccurate. Furthermore, it is demonstrated that failure to use a sufficiently detailed model of subject motion in FMRI can in fact lead to degradation of the images through the use of existing motion correction algorithms. Based on these findings, alternative schemes including non-rigid registration and adaptive real-time methods are evaluated. Leading on from this investigation, a framework for Temporally-Integrated Geometric EPI Realignment (TIGER), incorporating both spatial and temporal information about the images, is proposed. An implementation based on this novel modality-specific model is developed and tested against existing rigid-body registration methods. Results show that this new approach is able to achieve significantly more accurate results than previous methods. The quality of correction provided by this new approach brings more subtle artefacts in the data to the fore, suggesting a number of avenues of further research in this area. These are outlined in the final chapter of the thesis.

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Dikaios, Nikolaos. "Respiratory motion correction for positron emission tomography". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609967.

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Schleyer, Paul. "Respiratory motion correction in PET/CT imaging". Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/respiratory-motion-correction-in-petct-imaging(001f09fd-b405-4cbf-9ff7-9ba6541f3dab).html.

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In dual modality PET-CT imaging, respiratory motion can introduce blurring in PET images and create a spatial mismatch between the PET and CT datasets. Attenuation correction errors can result from this mismatch, which can produce severe artefacts that potentially alter the clinical interpretation of the images. Various approaches of reducing these effects have been developed. Many involve respiratory gated acquisitions which generally require a measure of the respiratory cycle throughout imaging. In this work, a retrospective respiratory gating technique was devel¬oped for both PET and CT which extracts the respiratory cycle from the acquired data itself, removing the requirement for hardware that measures respiration. This data-driven gating method was validated with phantom and patient data, and compared with a hardware based approach of gating. Extensions to the method facilitated the gating of multi-bed position, 3D clinical PET scans. Finally, 60 Ammonia cardiac PET/CT images were used to compare several different ap¬proaches of reducing respiratory induced attenuation correction errors and motion blur. The data-driven respiratory gating method accurately substituted a hardware based approach, and no significant difference was found between images gated with either methods. Gating 11 clinical 3D whole body PET images validated the extended data-driven gating methods and demonstrated successful combination of separate PET bed-positions. All evaluated approaches to reduce respiratory motion artefacts in cardiac imaging demonstrated an average improvement in PET-CT alignment. However, cases were found where alignment worsened and artefacts resulted. Fewer and less severe cases were produced when the 4D attenuation correction data was created from a 3D helical CT and PET derived motion fields. Full motion cor¬rection produced a small effect on average, however in this case no detrimental effects were found.

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Bai, Wenjia. "Respiratory motion correction in positron emission tomography". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:f73b144d-5287-4600-8b82-74229dc0eb31.

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In this thesis, we develop a motion correction method to overcome the degradation of image quality introduced by respiratory motion in positron emission tomography (PET), so that diagnostic performance for lung cancer can be improved. Lung cancer is currently the most common cause of cancer death both in the UK and in the world. PET/CT, which is a combination of PET and CT, providing clinicians with both functional and anatomical information, is routinely used as a non-invasive imaging technique to diagnose and stage lung cancer. However, since a PET scan normally takes 15-30 minutes, respiration is inevitable in data acquisition. As a result, thoracic PET images are substantially degraded by respiratory motion, not only by being blurred, but also by being inaccurately attenuation corrected due to the mismatch between PET and CT. If these challenges are not addressed, the diagnosis of lung cancer may be misled. The main contribution of this thesis is to propose a novel process for respiratory motion correction, in which non-attenuation corrected PET images (PET-NAC) are registered to a reference position for motion correction and then multiplied by a voxel-wise attenuation correction factor (ACF) image for attenuation correction. The ACF image is derived from a CT image which matches the reference position, so that no attenuation correction artefacts would occur. In experiments, the motion corrected PET images show significant improvements over the uncorrected images, which represent the acquisitions typical of current clinical practice. The enhanced image quality means that our method has the potential to improve diagnostic performance for lung cancer. We also develop an automatic lesion detection method based on motion corrected images. A small lung lesion is only 2 or 3 voxels in diameter and of marginal contrast. It could easily be missed by human observers. Our method aims to provide radiologists with a map of potential lesions for decision so that diagnostic efficiency can be improved. It utilises both PET and CT images. The CT image provides a lung mask, to which lesion detection is confined, whereas the PET image provides distribution of glucose metabolism, according to which lung lesions are detected. Experimental results show that respiratory motion correction significantly increases the success of lesion detection, especially for small lesions, and most of the lung lesions can be detected by our method. The method can serve as a useful computer-aided image analysing tool to help radiologists read images and find malignant lung lesions. Finally, we explore the possibility of incorporating temporal information into respiratory motion correction. Conventionally, respiratory gated PET images are individually registered to the reference position. Temporal continuity across the respiratory period is not considered. We propose a spatio-temporal registration algorithm, which models temporally smooth deformation in order to improve the registration performance. However, we discover that the improvement introduced by temporal information is relatively small at the cost of a much longer computation time. Spatial registration with regularisation yields similar results but is superior in speed. Therefore, it is preferable for respiratory motion correction.

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Weerasinghe, Arachchige Chaminda Perera. "Rotational Motion Artifact Correction in Magnetic Resonance Imaging". University of Sydney. Electrical and Information Engineering, 1999. http://hdl.handle.net/2123/357.

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The body motion of patients, during magnetic resonance (MR) imaging causes significant artifacts in the reconstructed image. Artifacts are manifested as a motion induced blur and ghost repetitions of the moving structures. which obscure vital anatomical and pathological detail. The techniques that have been proposed for suppressing motion artifacts fall into two major categories. Real-time techniques attempt to prevent the motion from corrupting the data by restricting the data acquisition times or motion of the patients, whereas the post-processing techniques use the information embedded in the corrupted data to restore the image. Most methods currently in widespread use belong to the real-time techniques, however with the advent of fast computing platforms and sophisticated signal processing algorithms, the emergence of post-processing techniques is clearly evident. The post-processing techniques usually demand an appropriate model of the motion. The restoration of the image requires that the motion parameters be determined in order to invert the data degradation process. Methods for the correction of translational motion have been studied extensively in the past. The subject of this thesis encompasses the rotational motion model and the effect of rotational motion on the collected MR data in the spatial frequency space (k-space), which is in general, more complicated than the translational model. Rotational motion artifacts are notably prevalent in MR images of head, brain and limbs. Post-processing techniques for the correction of rotational motion artifacts often involve interpolation and re-gridding of the acquired data in the k-space. These methods create significant data overlap and void regions. Therefore, in the past, proposed corrective techniques have been limited to suppression of artifacts caused by small angle rotations. This thesis presents a method of managing overlap regions, using weighted averaging of redundant data, in order to correct for large angle rotations. An iterative estimation technique for filling the data void regions has also been developed by the use of iterated application of projection operators onto constraint sets. These constraint sets are derived from the k-space data generated by the MR imager, and available a priori knowledge. It is shown that the iterative algorithm diverges at times from the required image, due to inconsistency among the constraint sets. It is also shown that this can be overcome by using soft. constraint sets and fuzzy projections. One of the constraints applied in the iterative algorithm is the finite support of the imaged object, marked by the outer boundary of the region of interest (ROI). However, object boundary extraction directly from the motion affected MR image can be difficult, specially if the motion function of the object is unknown. This thesis presents a new ROI extraction scheme based on entropy minimization in the image background. The object rotation function is usually unknown or unable to be measured with sufficient accuracy. The motion estimation algorithm proposed in this thesis is based on maximizing the similarity among the k-space data subjected to angular overlap. This method is different to the typically applied parameter estimation technique based on minimization of pixel energy outside the ROI, and has higher efficiency and ability to estimate rotational motion parameters in the midst of concurrent translational motion. The algorithms for ROI extraction, rotation estimation and data correction have been tested with both phantom images and spin echo MR images producing encouraging results.

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Maclaren, Julian Roscoe. "Motion Detection and Correction in Magnetic Resonance Imaging". Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1220.

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Magnetic resonance imaging (MRI) is a non-invasive technique used to produce high-quality images of the interior of the human body. Compared to other imaging modalities, however, MRI requires a relatively long data acquisition time to form an image. Patients often have difficulty staying still during this period. This is problematic as motion produces artifacts in the image. This thesis explores the methods of imaging a moving object using MRI. Testing is performed using simulations, a moving phantom, and human subjects. Several strategies developed to avoid motion artifact problems are presented. Emphasis is placed on techniques that provide motion correction without penalty in terms of acquisition time. The most significant contribution presented is the development and assessment of the 'TRELLIS' pulse sequence and reconstruction algorithm. TRELLIS is a unique approach to motion correction in MRI. Orthogonal overlapping strips fill k-space and phase-encode and frequency-encode directions are alternated such that the frequency-encode direction always runs lengthwise along each strip. The overlap between pairs of orthogonal strips is used for signal averaging and to produce a system of equations that, when solved, quantifies the rotational and translational motion of the object. Acquired data is then corrected using this motion estimation. The advantage of TRELLIS over existing techniques is that k-space is sampled uniformly and all collected data is used for both motion detection and image reconstruction. This thesis presents a number of other contributions: a proposed means of motion correction using parallel imaging; an extension to the phase-correlation method for determining displacement between two objects; a metric to quantify the level of motion artifacts; a moving phantom; a physical version of the ubiquitous Shepp-Logan head phantom; a motion resistant data acquisition technique; and a means of correcting for T2 blurring artifacts.

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Libri sul tema "Motion correction"

Gigengack, Fabian, Xiaoyi Jiang, Mohammad Dawood e Klaus P. Schäfers. Motion Correction in Thoracic Positron Emission Tomography. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-08392-6.

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Cronin, Meghan. Mooring motion correction of SYNOP central array current meter data. Narragansett, R.I: University of Rhode Island, Graduate School of Oceanography, 1992.

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(Firm), Avid Technology, a cura di. Color correction for Avid Xpress DV 3.5. Tewksbury, Mass: Avid Technology, 2002.

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Parker, David Baric. Optimal Correction of The Slice Timing Problem and Subject Motion Artifacts in fMRI. [New York, N.Y.?]: [publisher not identified], 2019.

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Dang, T. Q. An Euler correction method for two and three-dimensional transonic flows. New York: AIAA, 1987.

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Color correction handbook: Professional techniques for video and cinema. Berkeley, CA: Peachpit Press, 2011.

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Downing, George C. Evaluation of vertical motion sensors for potential application to heave correction in Corps hydrographic surveys. Vicksburg, Miss: US Army Corps of Engineers, Hydraulics Laboratory, 1987.

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Galper, Hal. Forward motion: From Bach to bebop : a corrective approach to jazz phrasing. [Bloomington, IN]: 1st Books Library, 2003.

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Groves, Penny. Correcting word reversals. Grand Rapids, Mich: LDA, 2002.

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Chamblee, Marie Brooks. Motor skill learning with pattern and error correction feedback. Eugene: Microform Publications, College of Human Development and Performance, University ofOregon, 1985.

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Capitoli di libri sul tema "Motion correction"

Gigengack, Fabian, Xiaoyi Jiang, Mohammad Dawood e Klaus P. Schäfers. "Motion Correction". In SpringerBriefs in Electrical and Computer Engineering, 65–74. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08392-6_3.

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Kraus, Martin F., e Joachim Hornegger. "OCT Motion Correction". In Optical Coherence Tomography, 459–76. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06419-2_16.

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Runge, Val M., e Johannes T. Heverhagen. "Abdomen: Motion Correction". In The Physics of Clinical MR Taught Through Images, 232–33. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-85413-3_105.

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Catana, Ciprian. "PET/MRI: Motion Correction". In PET/MRI in Oncology, 77–96. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-68517-5_5.

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Li, Ruijiang. "Image-Based Motion Correction". In Machine Learning in Radiation Oncology, 225–34. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18305-3_12.

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Bornstedt, Axel. "Introduction to motion suppression and motion correction". In Cardiovascular Magnetic Resonance, 43–48. Heidelberg: Steinkopff, 2004. http://dx.doi.org/10.1007/978-3-7985-1932-9_6.

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Talman, Richard. "Single particle motion". In Frontiers of Particle Beams; Observation, Diagnosis and Correction, 4–45. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/bfb0018280.

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Serrano-Sosa, Mario, e Chuan Huang. "Motion Correction in PET/MRI". In Hybrid PET/MR Neuroimaging, 27–34. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-82367-2_4.

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Brezov, Danail, e Michael Werman. "Camera Motion Correction with PGA". In Advances in Computer Graphics, 355–67. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-50078-7_28.

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Gigengack, Fabian, Xiaoyi Jiang, Mohammad Dawood e Klaus P. Schäfers. "Further Developments in PET Motion Correction". In SpringerBriefs in Electrical and Computer Engineering, 75–80. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08392-6_4.

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Atti di convegni sul tema "Motion correction"

Hong, Inki, Judson Jones e Michael Casey. "Ultrafast Elastic Motion Correction via Motion Deblurring". In 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). IEEE, 2014. http://dx.doi.org/10.1109/nssmic.2014.7430841.

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Ma, Xianglu, Xiaoshan Yao, Liming Ding, Tianshun Zhu e Guangming Yang. "Variable motion model for lidar motion distortion correction". In Conference on Optical Sensing and Imaging Technology, a cura di Yadong Jiang, Qunbo Lv, Bin Xue, Dengwei Zhang e Dong Liu. SPIE, 2021. http://dx.doi.org/10.1117/12.2606143.

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Yang, Zai, Cishen Zhang e Lihua Xie. "Sparse MRI for motion correction". In 2013 IEEE 10th International Symposium on Biomedical Imaging (ISBI 2013). IEEE, 2013. http://dx.doi.org/10.1109/isbi.2013.6556636.

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Mitra, Debasis, Daniel Eiland, Mahmoud Abdallah, Rostyslav Bouthcko, Grant T. Gullberg e Norberto S. Schechtmann. "SinoCor: motion correction in SPECT". In SPIE Medical Imaging, a cura di David R. Haynor e Sébastien Ourselin. SPIE, 2012. http://dx.doi.org/10.1117/12.911101.

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Wenjia Bai e S. M. Brady. "Motion correction and attenuation correction in thoracic PET imaging". In 2010 IEEE Nuclear Science Symposium and Medical Imaging Conference (2010 NSS/MIC). IEEE, 2010. http://dx.doi.org/10.1109/nssmic.2010.5874480.

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Shapiro, Ari, Marcelo Kallmann e Petros Faloutsos. "Interactive motion correction and object manipulation". In ACM SIGGRAPH 2008 classes. New York, New York, USA: ACM Press, 2008. http://dx.doi.org/10.1145/1401132.1401208.

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Stevendaal, Udo van, Tobias Klinder, Cristian Lorenz e Thomas Kohler. "Breathing-motion correction for helical CT". In 2008 IEEE Nuclear Science Symposium and Medical Imaging conference (2008 NSS/MIC). IEEE, 2008. http://dx.doi.org/10.1109/nssmic.2008.4774483.

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Jorgensen, Lasse Thurmann, Mikkel Schou, Matthias Bo Stuart e Jorgen Arendt Jensen. "Tensor Velocity Imaging with Motion Correction". In 2020 IEEE International Ultrasonics Symposium (IUS). IEEE, 2020. http://dx.doi.org/10.1109/ius46767.2020.9251661.

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Panin, V. Y., e H. Bal. "TOF data non-rigid motion correction". In 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). IEEE, 2015. http://dx.doi.org/10.1109/nssmic.2015.7582254.

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Shapiro, Ari, Marcelo Kallmann e Petros Faloutsos. "Interactive motion correction and object manipulation". In the 2007 symposium. New York, New York, USA: ACM Press, 2007. http://dx.doi.org/10.1145/1230100.1230124.

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Rapporti di organizzazioni sul tema "Motion correction"

Newsom, Rob, Gabriel Gibler, Krista Gaustad e Damao Zhang. Doppler Lidar Motion-Correction (DLMC) Value-Added Product Report. Office of Scientific and Technical Information (OSTI), febbraio 2024. http://dx.doi.org/10.2172/2318487.

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Ziock, Klaus-Peter, Chris Bensing Boehnen e Joseph Ernst. Advanced Demonstration of Motion Correction for Ship-to-Ship Passive Inspections. Office of Scientific and Technical Information (OSTI), settembre 2013. http://dx.doi.org/10.2172/1328268.

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Newsom, Rob, e Gabriel Gibler. Doppler Lidar Motion-Correction Wind Profiles (DLMCPROF-WIND) Value-Added Product Report. Office of Scientific and Technical Information (OSTI), gennaio 2024. http://dx.doi.org/10.2172/2301604.

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Wagner, Randall P., e Victor Nedzelnitsky. Determination of wave motion correction values required for comparison calibrations of a new working standard microphone. Gaithersburg, MD: National Institute of Standards and Technology, 2008. http://dx.doi.org/10.6028/nist.ir.7526.

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Smith, Horace, Carl Ekdahl, William Broste e Nicholas Kallas. Correcting Diamagnetic-Loop Measurements for Beam Corkscrew Motion. Office of Scientific and Technical Information (OSTI), aprile 2023. http://dx.doi.org/10.2172/1969201.

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Vlaicu, Razvan. Inequality Persistence and Policymaking Constraints: Explaining Regional Data Patterns. Inter-American Development Bank, ottobre 2023. http://dx.doi.org/10.18235/0005189.

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In well-functioning democracies, the policymaking process should in principle respond to persistent economic inequality with corrective policies. This process is set in motion through majority demands for redistributive taxation and spending that elected representatives eventually supply through policies designed to alleviate inequality. Policymaking constraints on both the demand side and the supply side have, however, considerably limited the extent of redistributive policies in Latin America. This paper explores recent data patterns from national and micro data to provide several process-centered explanations for the continuing high inequality observed in the region. Countries with stronger democracies have adopted more redistributive policies, even though post-tax inequality remains high in all of the region's democracies. Low citizen interpersonal and political trust both shape policy preferences away from effective redistribution. Electoral participation has risen in the more democratic countries, while economically motivated protests have increased in weakly institutionalized settings.

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Vlaicu, Razvan. Inequality Persistence and Policymaking Constraints: Explaining Regional Data Patterns. Inter-American Development Bank, maggio 2024. http://dx.doi.org/10.18235/0012973.

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Abstract (sommario):

In well-functioning democracies, the policymaking process should in principle respond to persistent economic inequality with corrective policies. This process is set in motion through majority demands for redistributive taxation and spending that elected representatives eventually supply through policies designed to alleviate inequality. Policymaking constraints on both the demand side and the supply side have, however, considerably limited the extent of redistributive policies in Latin America. This paper explores recent data patterns from national and micro data to provide several potential explanations for the continuing high inequality observed in the region. Countries with stronger democracies have adopted more redistributive policies, even though post-tax inequality remains high in all of the region's democracies. Low citizen interpersonal and political trust both lead to fiscal policy preferences that constrain effective redistribution. Electoral participation has risen in the more democratic countries, while economically motivated protests have increased in weakly institutionalized settings.

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Miller, Marcus, e Lei Zhang. Fear and Market Failure: Global Imbalances and ¿Self-Insurance¿. Inter-American Development Bank, dicembre 2007. http://dx.doi.org/10.18235/0010880.

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This paper proposes an integrated framework to analyze jointly two key issues: the emergence of global imbalances and the precautionary motive for accumulating reserves. Standard models of general equilibrium would predict modest current account surpluses in the emerging markets if they face higher risk than the US itself. But, with pronounced Loss Aversion in emerging markets, their precautionary savings can generate substantial global imbalances, especially if there is an inefficient supply of global insurance. In principle, lower real interest rates will ensure that aggregate demand equals supply at a global level (though the required real interest may be negative). While a precautionary savings glut appears to be a temporary phenomenon, a process of correction triggered by a Sudden Stop in capital flows to the United States might lead to a hard landing.

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Robinett, Fred. PR-471-14207-Z03 Evaluation of Field Pump Performance Testing Procedure. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto 2019. http://dx.doi.org/10.55274/r0011616.

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In situ pump performance testing was performed at the TransCanada pipeline Monitor station in Alberta Canada and Liebenthal station in Saskatchewan Canada in accordance with the Field Pump Performance Testing Procedure (PRCI report PR-471-14207-R01). Testing at the Monitor station was performed by Sulzer with two different batches of crude oil with slightly different viscosities and densities. Because of the pipeline operation limitations the flow could not be varied appreciably, however the flow points were near the pumps bep flow and therefore believed to be beneficial. To help validate field pump performance testing techniques measurements were taken using two methods to measure flow and two to measure pump power-in. Testing at the Liebenthal station was performed by TransCanada personnel on one fixed speed and one variable speed unit. All testing was performed with one batch of crude oil. The fixed speed unit power was measured with electrical power to the motor and the variable speed unit power was measured with a torque meter and electrical power. A full description of the Excel sheets used to calculate the field pump performance and the factory test data corrected to field conditions is made. The spreadsheet is included with this report. This work will benefit the liquids pipeline operators by validating the field test procedure, thereby providing assurance and acceptance of the methods. Using these field pump performance testing methods on additional pumps will help populate the database of measured viscous pump performances. This data can then be used to further improve the Hydraulic Institutes viscous correction calculations. Additionally, improved field pump performance measurements will allow the pipeline users to optimize their pipeline operation.

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Botero Mariaca, Paola María, Natalia Vélez Trujillo, Claudia Cecilia Restrepo Serna e Libbe Mariaca Cartagena. Manual de ortodoncia interceptiva: teoría y práctica. Ediciones Universidad Cooperativa de Colombia, novembre 2020. http://dx.doi.org/10.16925/gcgp.28.

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El proceso de transición dental para prevenir o interceptar las maloclusiones, es decir, el desarrollo de la dentición humana, se demora 12 años, por lo que muchos factores externos influyen en él. El grado de desarmonía oclusal que resulta luego del desarrollo es determinado por los cambios compensatorios que suceden con el crecimiento; las interferencias en el desarrollo de oclusión pueden llevar a una maloclusión. En la literatura se contemplan tres términos que importa diferenciar: ortodoncia preventiva, ortodoncia interceptiva y ortodoncia correctiva. La primera busca prevenir las interferencias potenciales que se presentan en el desarrollo de la oclusión para evitar que el problema se desarrolle, mientras que la ortodoncia interceptiva tiene como finalidad la eliminación de interferencias existentes durante el desarrollo de la oclusión. Muchas veces es difícil distinguir entre estos términos debido a que no siempre es posible discriminar un problema potencial de uno existente, motivo por el que se consideran ambos términos en conjunto. Entre los beneficios del tratamiento interceptivo se encuentran una mayor habilidad para modificar el crecimiento, el mejoramiento de la autoestima del paciente, la satisfacción de los padres, resultados óptimos y más estables, y una terapia posterior más corta. Los objetivos de la terapia son lograr un estado de normalidad lo más tempranamente posible para mejorar el crecimiento y desarrollo del paciente, obtener cambios esqueléticos, proveer la oportunidad de un cambio funcional, eliminar los factores externos y los hábitos dañinos, y tomar ventaja de las fuerzas oclusales del desarrollo para su corrección.

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