Specific absorption rate benefits of including measured electric field interactions in parallel excitation pulse design

Cem Murat Deniz, Leeor Alon, Ryan Brown, Daniel K. Sodickson, Yudong Zhu

    Research output: Contribution to journalArticle

    Abstract

    Specific absorption rate management and excitation fidelity are key aspects of radiofrequency pulse design for parallel transmission at ultra-high magnetic field strength. The design of radiofrequency pulses for multiple channels is often based on the solution of regularized least-squares optimization problems for which a regularization term is typically selected to control the integrated or peak pulse waveform amplitude. Unlike single-channel transmission, the specific absorption rate of parallel transmission is significantly influenced by interferences between the electric fields associated with the individual transmission elements, which a conventional regularization term does not take into account. This work explores the effects upon specific absorption rate of incorporating experimentally measurable electric field interactions into parallel transmission pulse design. Results of numerical simulations and phantom experiments show that the global specific absorption rate during parallel transmission decreases when electric field interactions are incorporated into pulse design optimization. The results also show that knowledge of electric field interactions enables robust prediction of the net power delivered to the sample or subject by parallel radiofrequency pulses before they are played out on a scanner.

    Original languageEnglish (US)
    Pages (from-to)164-174
    Number of pages11
    JournalMagnetic resonance in medicine
    Volume67
    Issue number1
    DOIs
    StatePublished - Jan 2012

    Keywords

    • RF power deposition
    • RF shimming
    • SAR
    • parallel transmission
    • pulse design
    • ultra-high-field MRI

    ASJC Scopus subject areas

    • Radiology Nuclear Medicine and imaging

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