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Robust assessment of quantitative magnetic resonance imaging as an imaging biomarker at 7 Tesla

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dc.contributor.advisor Cho, Hyungjoon -
dc.contributor.author Lee, Dongkyu -
dc.date.accessioned 2020-04-01T08:57:33Z -
dc.date.available 2020-04-01T08:57:33Z -
dc.date.issued 2020-02 -
dc.identifier.other 200000289402 -
dc.identifier.uri http://unist.dcollection.net/common/orgView/200000289402 en_US
dc.identifier.uri https://scholarworks.unist.ac.kr/handle/201301/31822 -
dc.description Department of Biomedical Engineering -
dc.description.abstract Magnetic susceptibility contrast MRI using local magnetic field gradients or inhomogeneities is expected to provide low-resolution quantification of tissue microarchitecture, as magnetic resonance (MR) transverse relaxation times (T2 and T2*) are influenced by field inhomogeneity arising from susceptibility mismatch of tissues. By aid of ultra-high field MRI scanner, MR transverse relaxation times is promising to further increase their sensitivity to detecting subtle structural changes in tissue microstructures. However, one of the main technical difficulty of ultra-high field MRI is unwanted variations of signal and contrast, or even worse, nullify the MR signal due to increased macroscopic static magnetic field inhomogeneities which are prone to misinterpretation and loss of structural information. This study focuses on improving the sensitivity and the robustness of ultra-high field MRI (particularly for 7 T) from unwanted signal variations due to magnetic field inhomogeneities and shortened MR transverse relaxation times. MR transverse relaxation times were investigated for the low-resolution assessment of tissue microstructures, such as trabecular bone microstructure and cerebral microvasculature. As a result, T2 relaxation time without having an effect of macroscopic field inhomogeneities may be suitable for the assessment of trabecular structural indices and robust with degrading spatial resolution with reduced scan time at 7 T. For the assessment of cerebral microvasculature, the diffusion-time-dependent stimulated-echo-based MR relaxation-rates was demonstrated as robust measures for assessing small (diameter < 5 μm) cerebral microvasculature, where macroscopic field inhomogeneities from bone (air)-tissue interfaces and influences of large vessels in cortical region are significant. Finally, the quantification of MR longitudinal relaxation time (T1) was optimized by variable repetition-delay turbo-spin echo method with sparse encoding technique. -
dc.description.statementofresponsibility close -
dc.language ENG -
dc.publisher Graduate School of UNIST -
dc.subject magnetic resonance relaxations -
dc.subject magnetic resonance spatial resolution -
dc.subject trabecular structure -
dc.subject vessel size imaging (VSI) -
dc.subject stimulated echo (STE) -
dc.subject compressed sensing -
dc.subject T1 measurements -
dc.subject turbo-spin echo (TSE) -
dc.subject rapid acquisition with refocused echoes (RARE) -
dc.title Robust assessment of quantitative magnetic resonance imaging as an imaging biomarker at 7 Tesla -
dc.title.alternative 7 Tesla에서 이미징 바이오 마커로서 정량적 자기 공명 영상법의 강력한 평가 -
dc.type Doctoral thesis -
dc.administration.regnum 200000289402 -
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