Design of Pulse Sequences for Low-Field Cardiac MRI Using Bloch Simulations
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2024
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Abstract
The recent development of high-end scanners offers the potential to make cardiac Magnetic Resonance Imaging (MRI) more accessible and affordable. However, adapting cardiac imaging sequences from higher fields such as to presents significant challenges.To address these challenges, we employed MRI simulations, which have proven effective for optimizing imaging parameters at novel field strengths. Nevertheless, current MRI simulators have performance, ease of use, and extensibility problems. Consequently, a new open-source MRI simulator with GPU acceleration, written in Julia, was developed. Its speed, accuracy, extensibility, and ease of use were demonstrated to be superior to currently available alternatives.This simulator was used to adapt two sequences, previously implemented at traditional field strengths, to . These sequences are for free-breathing 3D whole-heart cardiac MRI: (1) CMRA for cardiac angiography and (2) iprep-BOOST for simultaneous angiography and vessel wall imaging. Image navigators (iNAVs) were employed for non-rigid respiratory motion correction to enable 100% respiratory scan efficiency, while patch-based denoising techniques were used to mitigate the reduced signal-to-noise ratio at and accelerate the scans. As explained, for both sequences, the parameters were adjusted using MRI simulations and in-vivo experiments, focusing on improving SNR, contrast, and fat suppression. Both sequences were assessed using quantitative and qualitative scores, achieving excellent image quality and vessel sharpness comparable to previous studies.Finally, a comparison between the optimized sequences and their counterparts was conducted by acquiring images from the same cohort of healthy subjects. Image quality was comparable, with improvements observed in regions of high susceptibility, such as the lung vessels.In conclusion, this work successfully developed cardiac MRI sequences at using MRI simulations, demonstrating image quality comparable to their counterparts. Further evaluation of these sequences in patients with cardiovascular diseases will be necessary to determine the diagnostic quality provided.
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Tesis (Doctor of Philosophy in Biological and Medical Engineering)--Pontificia Universidad Católica de Chile, 2024
Tesis (Doctor of Philosophy in Biological and Medical Engineering)--King’s College London, 2024
Tesis (Doctor of Philosophy in Biological and Medical Engineering)--King’s College London, 2024