Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 17 of 17 for “"attenuation correction"”.
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Improving Attenuation Correction In Hybrid Positron Emission to mography
… most critical component of PET quantification, attenuation correction in hybrid PET systems is challenged in several different aspects, including the spatial- temporal mismatch between the PET emission images and the associated attenuation images provided by the complementary modality, and the …
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The study and real-time implementation of attenuation correction for X-band dual-polarization weather radars
Attenuation of electromagnetic radiation due to rain or other wet hydrometeors along the propagation path has been studied extensively in the radar meteorology community. Recently, use of short range dual-polarization X-band radar systems has gained momentum due to lower system cost compared with …
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Evaluation of the effect of breast implants on the accuracy of the CT attenuation Correction (CTAC) map for SPECT/CT myocardial perfusion imaging: a phantom study
… such as ribs or breast tissue lead to gamma ray attenuation. Thisattenuation does not occur equally for all body regions. Photons emitted from deeper structureswill undergo more attenuation than superficial structures, causing artefacts within the imagethat can mimic pathology - such as …
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Fusion of observations from C-band polarimetric radar and S-band profiler radar during a convective storm
… discusses a procedure to measure and correct attenuation of the radar signals caused by the presence of partially melted ice hydrometeors (graupels and hails) in convective storms by utilizing simultaneous observations from a C-Band dual-polarization scanning radar and a vertically pointing …
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An investigation into the limitations of myocardial perfusion imaging
… the results so that many of the causes of the attenuation defects, when using MPI, could be identified. This was achieved by investigating the effect that the different anatomical parts of the thorax have on the attenuation defects caused. A further aspect investigated was the impact that …
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The assessment of biomechanical modelling and PET/MR imaging in coronary atherosclerosis
… and metabolic imaging. However, accurate attenuation correction is essential for quantitative PET reconstruction in the thorax, and the application of PET/MR in coronary imaging is limited due to the challenges of obtaining good quality images of the coronary vessels. The work presented in …
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Cross-validation of spaceborne radar and ground polarimetric radar observations
… into the intensity and distribution of rainfall. Attenuation effects on PR measurements, however, can be significant, which can be as high as 10-15 dB. This can seriously impair the accuracy of rain rate retrieval algorithms derived from PR signal returns, which makes it necessary to compensate …
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Radiation dose assessment : measurement, estimation and interpretation
… imaging raised questions as to the use of the attenuation correction data specifically. The question of should the cross sectional images be reviewed for pathology was has been the focus of debate. It was recognised that the quality of these images is poor due to the “low-dose” acquisition. The …
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MR-assisted PET data optimization for simultaneous dual-modality imaging in dementia
… is confounded by several factors. For example, attenuation correction is required to account for the interactions of the annihilation photons in the subject; motion correction is needed to minimize image degradation due to subject movements; partial volume effects correction is required due to …
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Bias and Variability In Image-Based Volumetric Yttrium-90 Dosimetry
… SPECT/CT (bSPECT/CT) images with CT attenuation correction and energy-window based background compensation. Although the volumetric quantitative accuracy of our bSPECT/CT images is limited by partial volume effect, the images can be used to accurately quantify the total 90Y activity …
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Novel positron emission tomography applications for imaging cardiovascular disease activity
… of respiratory-averaged computed tomography attenuation correction (RACTAC) compared to standard single-phase computed tomography attenuation correction (CTAC) map, on the quantitative measures of coronary atherosclerotic lesions of 18F-sodium fluoride in PET/CT. Twenty-three patients with …
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Imaging atherosclerotic plaque inflammation with [18F]- fluorodeoxyglucose positron emission tomography
… is currently unable to perform studies with attenuation correction. In summary, it has been shown, both in vitro and in vivo, that inflammation within atherosclerotic plaques can be successfully imaged by FDG-PET. In addition, pilot data from an experimental study of atherosclerosis in …
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Cardiac magnetic resonance imaging assessment of aortic stenosis to improve clinical care
… is feasible and well-tolerated. I tested novel attenuation correction and motion correction methods and showed that this technique can offer multiparametric imaging of valve, myocardium and coronary arteries in a single scan. Conclusion I have defined the longitudinal changes in hypertrophy and …
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Improved quantification in small animal PET/MR
… MR image segmentation method used to provide PET attenuation correction in mice was validated using the Cambridge split magnet PET/MR scanner’s transmission scanning capabilities. This work recommends that contributions from MR hardware in the PET field of view must be accounted forto gain …
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Ansätze zur Optimierung der Datenverarbeitung in der Positronen Emissions Tomographie
Die Positronen Emissions Tomographie (PET) ist ein nuklearmedizinisches <br>Schnittbildverfahren, mit dem die Möglichkeit der dreidimensionalen, <br>nicht-invasiven Darstellung und Quantifizierung von biochemischen und <br>physiologischen Prozessen im menschlichen Organismus besteht. Basierend …
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Myocardial Perfusion Imaging With Rb-82 PET
… SPECT scans and artifacts from soft tissue attenuation due to the routine application of attenuation correction. However 82Rb PET imaging is under-utilized clinically due to difficulty optimizing the imaging parameters. The major challenge of 82Rb imaging is determining when to begin the …
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Novel applications of fluorine-18 labelled radiotracers in cardiovascular disease
… Both standard (Dixon) and novel (radial GRE) MR attenuation correction (AC) maps were validated against PET/CT with results expressed as target-to-background ratios (TBRs). Visually, aortic valve 18F-fluoride uptake was similar on PET/CT and PET/MR. TBRMAX values were comparable with radial GRE …