rdf-syntax-grammar
mods:
  schema location: http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
  title info:
    title: Three Studies in High-Field MR Engineering: SAR Reduction Through Sequential RF Pulses, A System for B1+ Steering, and A Low-Complexity Multi-Nuclei Array Coil
  name:
    name part: Sun, Chenhao
    role:
      role term: creator
    role:
      role term: author.
  name:
    name part: Wright, Steven
    role:
      role term: thesis advisor.
  name:
    name part: Texas A&M University
    role:
      role term: degree granting institution.
  type of resource: text
  genre: bibliography
  origin info:
    place:
      place term: txu
    date issued: 2023
    issuance: monographic
  language:
    language term: eng
  physical description:
    form: remote
    extent: 1 online resource.
  abstract: Recent years have seen great development in ultra-high-field (UHF) magnetic resonance imaging (MRI). In particular, the advantage of increased sensitivity available at UHF and the scan time acceleration enabled by parallel imaging can together offer unprecedented imaging detail. However, technical challenges, such as B1+ inhomogeneity and specific absorption rate (SAR) also come with the UHF scanner. A head coil array at 9.4T using a novel transmit approach of serial transit parallel receive (STxPRx) is modeled and analyzed in this doctoral work. By transmitting each coil element in an array sequentially rather than simultaneously, a 25.7% peak SAR reduction can be found. For MRI applications with significant SAR concerns, such as lower-gamma nuclei imaging, this work provides a potential alternative approach. To mitigate the image inhomogeneity issue at 7T, an add-on B1+ steering system is reported in this doctoral work. By using a house-designed phase shifter array and associated circuitry, 8 transmit channels with independent phase control can be created to drive an 8-channel transmit coil array, yet with only two transmitters installed on the scanner. By using the conjugate-phase steering method, an approximately 2.6x4.2cm2 very homogenous B1+ region and approximately 5.9x8.9cm2 fairly homogenous B1+ region can be generated at any targeting point in phantom. This work suggests a different hardware approach to gain the new degree of freedom of controllable transmit B1+ pattern in parallel imaging. Along with the development of higher B0 strength, multi-nuclei MRI have become increasingly popular since both the anatomical detail from proton and the physiological process from X-nuclei can be acquired simultaneously. As the essential tool in multi-nuclei MRI, the multi-tuned RF array coil suffers from the excessive complexity of the multi-tuned retrofit of the current decoupling mechanism. A novel strategy aimed at simplifying multi-nuclei array coil⁰́₉s decoupling …
  note: by Chenhao Sun.
  note: "Major Subject: Electrical Engineering"
  note: Includes vita.
  note: Doctor of Philosophy Texas A&M University 2022 https://hdl.handle.net/1969.1/197342
  note: Includes bibliographical references.
  note: Text (Dissertation)
  subject:
    topic: Major Electrical Engineering
  subject:
    topic: SAR
  subject:
    topic: Array
  subject:
    topic: B1+ Steering
  subject:
    topic: Multi Nuclei
  subject:
    topic: Decoupling
  subject:
    topic: RF Coil
  identifier: https://hdl.handle.net/1969.1/197342
  record info:
    record content source: TXA
    record creation date: 240819
    record change date: 20240820145900.7
    record identifier: in00005463664
    language of cataloging:
      language term: eng