Poster Presentation 8
Electrical Conductivity Mapping at 21.1T
Ghoncheh Amouzandeh1,2, Samuel C. Grant1,3
1
CIMAR, National High Magnetic Field Laboratory
Physics and Chemical and Biomedical Engineering, The Florida State University
Tallahassee FL, USA
2
3
Magnetic Resonance electrical properties tomography (MR-EPT) is a recently introduced method to map
electrical properties of body tissues using a standard MRI machine [1], [2]. Mapping tissue electrical properties
like conductivity and permittivity can be used as an additional diagnostic parameter, e.g. in tumor diagnosis and
stroke therapy evaluation. According to ex vivo studies, breast tumors exhibit a significantly altered electrical
conductivity [3], [4]. The electrical conductivity of the tissue is also needed to correctly estimate the distribution
of local specific absorption rate (SAR) of the transmitted radio frequency (RF) wave in body tissues for RF
safety purposes.
Earlier studies have shown the feasibility of phase-based MR-EPT that uses only the phase data of the MR
image to infer the RF transmit field (B1+) map conductivity at low fields [5]. Although phase-based conductivity
mapping will benefit from higher field strength, which is related to increased signal-to-noise ratio (SNR), the
validity of the underlying assumptions will be affected by the higher dielectric properties of the object [6]. As a
result, the required Laplacian of the phase data for conductivity reconstruction is not straight forward at ultrahigh fields (> 3T).
This work shows the possibility of reconstructing conductivity distributions from phase images of the RF
transmit field in ultra-high field (21.1T). To be able to use phase-based MR-EPT, a new reconstruction
algorithm, based on fitting local parabolic functions to the local phase changes is developed. The average
conductivity values for tubes with different salt concentrations are evaluated. This phantom study can be used as
a step toward in vivo conductivity mapping at ultra-high fields.
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