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5 June 2003 Noninvasive quantitative mapping of conductivity and dielectric distributions using RF wave propagation effects in high-field MRI
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Abstract
In this paper I show with phantom and animal experiments a non-invasive and quantitative method for measuring the conductivity and dielectric distributions based on high field magnetic resonance imaging. High field MRI is accompanied by significant RF wave propagation effects. They are observed as phase and magnitude variations of the image that cannot be removed by optimizing the static field homogeneity, or by improving the RF coils. These variations reflect the RF field distribution in the sample, and in fact obey a modified Helmholtz equation. By mapping both the phase and magnitude of the field with MRI techniques, both the conductivity and the dielectric constant are determined non-invasively. In phantom experiments at 1.5 tesla, conductivity values were measured at 4 mm resolution to 0.5 S/m accuracy. At 4.7 tesla, the accuracy was improved to 0.2 S/m, and the dielectric constant was measured to an accuracy of 5 (relative to vacuum) for 2cm regions.
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Han Wen "Noninvasive quantitative mapping of conductivity and dielectric distributions using RF wave propagation effects in high-field MRI", Proc. SPIE 5030, Medical Imaging 2003: Physics of Medical Imaging, (5 June 2003); https://doi.org/10.1117/12.480000
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