High field MRI has been pursued with increasing interest and potential wide clinical applications due to its promise of improved signal-to-noise ratio, higher spatial resolution, and increased sensitivity for functional imaging using the blood oxygenation level-dependent contrast. However, the elevated thermal effect (due to tissue heating accompanied with an increased main magnetic field strength) poses a major safety concern in high field MRI applications. The Specific Absorption Rate (SAR) is directly related to radio frequency (RF) induced heating. An absence of quantification of the local SAR values on a subject specific basis yields a worse-case safety limit in current high field MRI RF power transmission, which may compromise the underlying improved signal-to-noise ratio and image contrast associated with high field. Therefore, there is a crucial need for real-time and subject-specific electrical property imaging, for the purpose of SAR quantification and subsequent tissue heating management in high field MRI applications. The goal of this R21 exploratory project is to explore and develop a novel magnetic resonance electrical property tomography (MR-EPT) technique for the quantitative prediction and proactive management of tissue heating in high-field MRI applications. To achieve this goal, we will address the following specific aims:
Aim 1) Development of MR electrical property tomography methods.
Aim 2) Experimental evaluation of MR electrical property tomography methods and heating quantification. We will develop novel theories and algorithms for electrical property imaging and local SAR quantification. We will conduct a series of computer simulations, and perform well controlled phantom experiments and experiments in post-mortem animal tissues to evaluate the performance of the proposed MR- EPT approach. Noninvasive imaging of the electrical property distribution is of significance for a variety of applications in biomedical research and clinical applications. The successful development of the proposed MR- EPT approach promises to provide a high-resolution noninvasive electrical property imaging modality, enabling the real-time and subject-specific quantification of tissue heating in high field MRI, and facilitating various applications including benign versus malignant tumor characterization and functional brain imaging.

Public Health Relevance

The proposed work is aimed at developing and evaluating a high resolution electrical property imaging technique using an MRI scanner. This novel technique promises to provide a noninvasive means of mapping tissue electrical properties, which are needed to quantify tissue heating in high field MRI. The successful development of such a novel imaging technique has the potential to greatly improve the safety and performance of high field MRI, thus making it available to a large population of patients who may suffer from various diseases such as brain cancer, epilepsy, etc.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Exploratory/Developmental Grants (R21)
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Special Emphasis Panel (ZRG1)
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Sastre, Antonio
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University of Minnesota Twin Cities
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United States
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Liu, Jiaen; Shao, Qi; Wang, Yicun et al. (2017) In vivo imaging of electrical properties of an animal tumor model with an 8-channel transceiver array at 7?T using electrical properties tomography. Magn Reson Med 78:2157-2169
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Liu, Jiaen; Zhang, Xiaotong; Schmitter, Sebastian et al. (2015) Gradient-based electrical properties tomography (gEPT): A robust method for mapping electrical properties of biological tissues in vivo using magnetic resonance imaging. Magn Reson Med 74:634-46
Zhang, Xiaotong; Liu, Jiaen; He, Bin (2014) Magnetic-resonance-based electrical properties tomography: a review. IEEE Rev Biomed Eng 7:87-96
Zhou, Lian; Zhu, Shanan; He, Bin (2014) A reconstruction algorithm of magnetoacoustic tomography with magnetic induction for an acoustically inhomogeneous tissue. IEEE Trans Biomed Eng 61:1739-46
Zhang, Xiaotong; Liu, Jiaen; Schmitter, Sebastian et al. (2014) Predicting temperature increase through local SAR estimation by B1 mapping: a phantom validation at 7T. Conf Proc IEEE Eng Med Biol Soc 2014:1107-10
Jiaen Liu; Xiaotong Zhang; Schmitter, Sebastian et al. (2014) Gradient-based magnetic resonance electrical properties imaging of brain tissues. Conf Proc IEEE Eng Med Biol Soc 2014:6056-9

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