Manipulating transmit and receive sensitivities of radiofrequency surface coils using shielded and unshielded high-permittivity materials

Manushka V. Vaidya, Cem M. Deniz, Christopher M. Collins, Daniel K. Sodickson, Riccardo Lattanzi

    Research output: Contribution to journalArticle

    Abstract

    Objective: To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns. Materials and methods: A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil. Finally, we evaluated the increase in transmit homogeneity for a four-channel array with HPM discs interposed between adjacent coil elements. Results: Various configurations of HPM increased SNR, transmit/receive efficiency, excitation/reception sensitivity overlap, and FOV when positioned near a surface coil. For a four-channel array driven in quadrature, shielded HPM discs enhanced the field below the discs as well as at the center of the sample as compared with other configurations with or without unshielded HPM discs. Conclusion: Strategically positioning HPM at a distance from a surface coil or array can increase the overlap between excitation/reception sensitivities, and extend the FOV of a single coil for reduction of the number of channels in an array while minimally affecting the SNR.

    Original languageEnglish (US)
    Pages (from-to)355-366
    Number of pages12
    JournalMagnetic Resonance Materials in Physics, Biology and Medicine
    Volume31
    Issue number3
    DOIs
    StatePublished - Jun 1 2018

    Keywords

    • Computer Simulation
    • Electromagnetic Fields
    • Magnetic Resonance Imaging

    ASJC Scopus subject areas

    • Biophysics
    • Radiological and Ultrasound Technology
    • Radiology Nuclear Medicine and imaging

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