Novel techniques and innovative designs for the RF chain of magnetic resonance imaging scanners

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buir.advisorAtalar, Ergin
dc.contributor.authorTarakameh, Alireza Sadeghi
dc.date.accessioned2020-08-31T07:46:21Z
dc.date.available2020-08-31T07:46:21Z
dc.date.copyright2020-07
dc.date.issued2020-07
dc.date.submitted2020-08-27
dc.departmentDepartment of Electrical and Electronics Engineeringen_US
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (Ph.D.): Bilkent University, Department of Electrical and Electronics Engineering, İhsan Doğramacı Bilkent University, 2020.en_US
dc.descriptionIncludes bibliographical references (leaves 93-112).en_US
dc.description.abstractIn this dissertation, novel techniques and innovative designs are proposed to serve one of the main goals of MRI, which is achieving the best image quality by improving signal-to-noise ratio (SNR) while confined to the patient’s safety restrictions determined by specific absorption rate (SAR) limits. This dissertation comprises five different contributions to the field. First, the co-simulation method is accelerated using the equivalent circuit model of the intended coil and introduced as a compact novel technique for the fast design of transmit array (TxArray) coils. It is shown that the existing co-simulation method can be accelerated by more than 20-fold for different types of TxArray coils. In another study, a simple strategy is introduced for optimizing the topography of transmit elements to reduce the local SAR at ultra-high field (UHF, B0 ≥ 7 T) MRI. It is shown that the peak local 10g-averaged SAR can be reduced more than 20% for different types of transmit elements at two different field strengths (i.e., 7 T and 10.5 T). As another contribution, confining to the safety limits, the first in vivo human head images at 10.5 T is acquired. To ensure the safety of subjects, the EM simulation model of the radiofrequency (RF) coil is validated using an expanded validation workflow, then, safe RF power levels were calculated. In another study, a novel short dipole-like element with improved SAR performance, non-unform dielectric substrate (NODES) antenna, is introduced which provides an opportunity to design highly-dense TxArray coils for UHF-MRI. Eventually, a nine-channel transmit/receive coil is built and human cadaver spine images are acquired at 10.5 T. In the final study, a new parameter, ultimate intrinsic SAR efficiency (UISARE), is introduced and calculated as the upper bound for SAR performance of the transmit coils at different field strengths. Overall, this dissertation proposes novel techniques and innovative structures for designing the TxArray coils, which mainly contribute to enhancing image quality and patient safety by improving SNR and reducing SAR.en_US
dc.description.degreePh.D.en_US
dc.description.statementofresponsibilityby Alireza Sadeghi Tarakamehen_US
dc.format.extentxvii, 112 leaves : illustrations (color), charts (color) ; 30 cm.en_US
dc.identifier.itemidB160409
dc.identifier.urihttp://hdl.handle.net/11693/53984
dc.language.isoEnglishen_US
dc.publisherBilkent Universityen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectTransmit arrayen_US
dc.subjectCo-simulationen_US
dc.subjectUltra-high fielden_US
dc.subjectRF safetyen_US
dc.titleNovel techniques and innovative designs for the RF chain of magnetic resonance imaging scannersen_US
dc.title.alternativeManyetik resonans görüntüleme cihazlarının RF tarafı için yeni teknikler ve yaratıcı tasarımlaren_US
dc.typeThesisen_US

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