Method for in situ characterization of radiofrequency heating in parallel transmit MRI

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

    Research output: Contribution to journalArticle

    Abstract

    In ultra-high-field magnetic resonance imaging, parallel radiofrequency (RF) transmission presents both opportunities and challenges for specific absorption rate management. On one hand, parallel transmission provides flexibility in tailoring electric fields in the body while facilitating magnetization profile control. On the other hand, it increases the complexity of energy deposition as well as possibly exacerbating local specific absorption rate by improper design or delivery of RF pulses. This study shows that the information needed to characterize RF heating in parallel transmission is contained within a local power correlation matrix. Building upon a calibration scheme involving a finite number of magnetic resonance thermometry measurements, this work establishes a way of estimating the local power correlation matrix. Determination of this matrix allows prediction of temperature change for an arbitrary parallel transmit RF pulse. In the case of a three transmit coil MR experiment in a phantom, determination and validation of the power correlation matrix were conducted in less than 200 min with induced temperature changes of <4°C. Further optimization and adaptation are possible, and simulations evaluating potential feasibility for in vivo use are presented. The method allows general characteristics indicative of RF coil/pulse safety determined in situ.

    Original languageEnglish (US)
    Pages (from-to)1457-1465
    Number of pages9
    JournalMagnetic resonance in medicine
    Volume69
    Issue number5
    DOIs
    StatePublished - May 2013

    Keywords

    • global specific absorption rate
    • local specific absorption rate
    • radiofrequency heating
    • radiofrequency power deposition
    • specific absorption rate
    • ultra-high-field MRI

    ASJC Scopus subject areas

    • Radiology Nuclear Medicine and imaging

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