Robust high-resolution reduced field-of-view MRI with sheared 2D RF excitation

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buir.advisorÇukur, Emine Ülkü Sarıtaş
dc.contributor.authorBarlas, Bahadır Alp
dc.date.accessioned2022-08-19T11:09:05Z
dc.date.available2022-08-19T11:09:05Z
dc.date.copyright2022-07
dc.date.issued2022-07
dc.date.submitted2022-08-18
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (Master's): Bilkent University, Department of Electrical and Electronics Engineering, İhsan Doğramacı Bilkent University, 2022.en_US
dc.descriptionIncludes bibliographical references (leaves 54-60).en_US
dc.description.abstractReduced field-of-view (FOV) single-shot echo-planar imaging (ssEPI) is a widely applied imaging technique for diffusion-weighted magnetic resonance imaging (MRI), due to its robustness against in-plane off-resonance artifacts. Two-dimensional echo-planar RF (2D RF) excitation is a popular approach for reduced-FOV imaging due to its fat suppression capability and sharp slab profiles. However, long pulse durations render 2D RF pulses sensitive to through-plane off-resonance effects, causing local signal losses in reduced-FOV images. The standard 2D RF pulses also generate excitation replicas along the slice stack, limiting the slice coverage during multislice imaging. This thesis proposes a sheared 2D RF design for reduced-FOV imaging for significant reduction in pulse duration, leading to significant improvement in through-plane off-resonance ro-bustness. The proposed design also provides unlimited slice coverage and high fidelity fat suppression. Sheared k-space trajectories are designed such that the excitation replicas are positioned outside the slice stack to guarantee unlimited slice coverage, while ensuring identical k-space coverage as that of a standard 2D RF pulse. The efficacy of the sheared design is demonstrated by extensive simulations in terms of pulse duration, fat suppression capability, and signal com-parisons under off-resonance effects for a range of design parameters and hardware limits. The sheared and standard 2D RF pulses are then compared via imaging experiments on a custom head and neck phantom, and in vivo imaging experi-ments in the spinal cord at 3 T. The results show that in regions with high off-resonance effects, the sheared 2D RF pulse improves the signal by more than 50%when compared to the standard 2D RF pulse while preserving profile sharpness. Lastly, the benefits of the sheared design are demonstrated for low-cost low-field MRI systems via simulations and phantom experiments, making reduced-FOV imaging applicable on these systems. The proposed sheared 2D RF design will be especially beneficial in regions suffering from a variety of off-resonance effects, such as spinal cord and breast.en_US
dc.description.provenanceSubmitted by Betül Özen (ozen@bilkent.edu.tr) on 2022-08-19T11:09:05Z No. of bitstreams: 1 B161176.pdf: 8237327 bytes, checksum: 4a0ade71befc67ab7e469ae02c09f01d (MD5)en
dc.description.provenanceMade available in DSpace on 2022-08-19T11:09:05Z (GMT). No. of bitstreams: 1 B161176.pdf: 8237327 bytes, checksum: 4a0ade71befc67ab7e469ae02c09f01d (MD5) Previous issue date: 2022-07en
dc.description.statementofresponsibilityby Bahadır Alp Barlasen_US
dc.embargo.release2023-03-01
dc.format.extentxxii, 60 leaves : illustrations, charts (color) ; 30 cm.en_US
dc.identifier.itemidB161176
dc.identifier.urihttp://hdl.handle.net/11693/110458
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subject2D RF pulseen_US
dc.subjectSheared trajectoryen_US
dc.subjectReduced field-of-view imagingen_US
dc.subjectOff-resonance robustnessen_US
dc.subjectFat suppressionen_US
dc.subjectMultislice imagingen_US
dc.titleRobust high-resolution reduced field-of-view MRI with sheared 2D RF excitationen_US
dc.title.alternativeKesimli 2D RF eksitasyon ile gürbüz yüksek çözünürlüklü indirgenmiş görüş alanlı MRGen_US
dc.typeThesisen_US
thesis.degree.disciplineElectrical and Electronic Engineering
thesis.degree.grantorBilkent University
thesis.degree.levelMaster's
thesis.degree.nameMS (Master of Science)

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