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 “"pulse design"”.
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Improvements in magnetic resonance imaging excitation pulse design
This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) simultaneous sparse approximation problem. The contributions are both …
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Pulse Design for Two-Qubit Gates in Superconducting Circuits
… gates. In this thesis, we formulate the design of the control trajectory for baseband controlled phase gates in superconducting circuits into a pulse design problem. Our research indicates that the Chebyshev trajectories – the trajectories based on the Chebyshev pulse and weighted …
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Local and global SAR constrained large tip angle 3D kT̳-points parallel transmit pulse design at 7 T
… can be mitigated through radio frequency (RF) pulse design with conventional single-channel RF systems, but at the cost of impractically long pulses. Parallel transmit (pTx) systems with multiple independent and simultaneous RF transmit channels achieve transmit field inhomogeneity mitigation …
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Design of multidimensional radiofrequency pulses in magnetic resonance imaging
Multidimensional radiofrequency (RF) pulses have wide applications in magnetic resonance imaging and spectroscopy experiments. These applications include reduced field-of-view (FOV) imaging of region-of-interest (ROI), B1 inhomogeneity correction, and simultaneous spatial-spectral selective …
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Parallel radiofrequency transmission for 3 Tesla and 7 Tesla magnetic resonance imaging
… both of these challenges by optimization of RF pulses transmitted from multiple independent channels simultaneously. However, both the RF pulse design and RF safety management become more complicated with pTx. In this work, a framework to apply pTx to 3T fetal and 7T brain imaging is developed …
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Development of Optimised Pulse Sequences for Magnetic Resonance Imaging of Tumour Metabolism
Development of efficient pulse sequences for hyperpolarised 13C imaging: Dynamic nuclear spin polarization of 13C-labeled cell substrates has enabled dynamic measurements of tissue metabolism in vivo using 13C MRSI. The principal limitation of the technique is the short lifetime of the …
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Slice-selective parallel transmit magnetic resonance imaging at 7T
… transmit channels to dynamically control RF pulses, is a promising solution to overcome these limitations. While pTx has shown maturity in 3D neuroimaging with universal pulses, its application to 2D imaging suffers from optimisation complexities, scanner integration hurdles, and specific …
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Excitation and readout Designs for high field spectroscopic imaging
… single-channel transmission. We address two design problems that need to be solved before this emerging technology can be deployed in the clinical and research domain of human imaging at high field. First, we demonstrate a method for rapid and robust acquisition of the non-uniform fields of …
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Integral Equation-Based Inverse Scattering and Coil Optimization in Magnetic Resonance Imaging
… undesirable from the point of view of coil and pulse design, this dependence on EP opens the door to new imaging modalities using the same MR data. In this thesis, I detail how we applied highly accurate integral equation formulations to the tasks of 3D electrical properties estimation (inverse …
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Optimal control in an open quantum system : selecting DNP pathways in an electron-nuclear system
… for spin-based systems. Previous control pulse finding efforts have primarily optimized pulses to a desired unitary control. Non-unitary dynamics are unavoidable in quantum systems, and, to improve current control techniques, interactions with the environment and stochastic noise processes …
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Parallel transmission for magnetic resonance imaging on a 9.4 Tesla Human System.
… Multidimensional spatially selective RF pulses have been proposed as a method to mitigate B1+ inhomogeneity. However, those RF pulses are typically very long and are impractical at high field. Parallel transmission, an emerging technique, makes it possible to design sufficiently short …
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Bilateral Ortohogonality Generative Acquisitions Method for Transmit Field Inhomogeneity Correction in Magnetic Resonance Imaging
… utilization. In literature, radiofrequency pulse design and multi-acquisition methods with and without parallel transmission systems have been demonstrated for addressing the transmit field inhomogeneity. While substantial improvements have been demonstrated with these methods, they can be …
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Variation in wing area and prey detection volume of Rhinolophus Capensis in response to different climates
… conditions also influence echolocation pulse design. Echolocation pulses must successfully reach a target and generate an audible echo despite atmospheric attenuation. High-duty cycle (HDC) pulses, calls with longer durations than the interval between them, are particularly useful in …
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Optimal Control of Inhomogeneous Ensembles
This dissertation is concerned with formulating the problem and developing methods for the synthesis of optimal, open-loop inputs for large numbers of identically structured dynamical systems that exhibit variation in the values of characteristic parameters across the collection, or ensemble. Our …
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Habitat correlates of pulse parameters in the highly specialised acoustic system of Chiroptera
… bats use high frequency echolocation pulses that have limited range but are clutter resistant i.e. can detect targets in dense clutter (the number of echoes produced other than those from the target of interest). A specialised echolocation pulse design (consisting of a constant …
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Waveform design and processing techniques in OFDM radar
… for the case of a train of wideband OFDM pulses. In this, our first so-called time domain solution consists in applying a matched filter to compress the received echoes in the fast time before applying a fast Fourier transform in the slow time to form the range Doppler image. We motivate …