Aminzadeh, Reza

De Geeter, Nele

Descamps, Benedicte

Dupré, Luc

Joseph, Wout

Parappurath Vasudevan, Prakash

Van Holen, Roel

Ghent University Academic Bibliography

       ELECTRICAL CONDUCTIVITY IMAGING WITH 7T PRECLINICAL MRI USING MR ELECTRICAL PROPERTIES TOMOGRAPHY   Prakash Parappurath Vasudevan*1, Reza Aminzadeh2, Nele De Geeter3, Benedicte Descamps1, Luc Dupré 3,  Wout Joseph2, Roel Van Holen1  1Dept. of Electronics and Information Systems (ELIS), Ghent University, Ghent, Belgium   2Dept. of Information Technology (INTEC), Ghent University, Ghent, Belgium   3Dept. of Electrical Energy, Metals, Mechanical Constructions and Systems (EEMMeCS), Ghent University, Ghent, Belgium  Keywords: Electrical properties tomography; EPT; MRI; conductivity; tumor imaging  1. INTRODUCTION The accurate assessment of dielectric properties of human tissue is important for radio-frequency (RF) absorption measurements and has significant impact on medical applications and diagnosis. Magnetic Resonance Electrical Properties Tomography (MREPT) is a method to assess the Electrical Properties of tissues in vivo from the RF magnetic field (B1+) at Larmor frequency. This method uses standard magnetic resonance imaging (MRI) equipment without the need of any additional hardware. Studies have shown the feasibility of phase-based conductivity reconstruction, which uses only B1+ phase for the conductivity mapping [1,2]. This study evaluates the phase only conductivity imaging at 7T using preclinical MRI.  2. MATERIALS AND METHODS The experimental studies were carried out on phantom and a mouse tumor model. A mouse bearing breast tumor on hindlimb was then used for in vivo studies. The mouse was euthanized, and the tumor region was extracted. Measurements were performed on the extracted tumor and electrical conductivity was reconstructed at 300MHz.  The experiments were performed on a 7T MR scanner at Ghent University, Belgium with a quadrature birdcage RF coil with 40 mm diameter. Two 2D spin echo (SE) images with Repetition Time (TR) of 1600ms, Echo Time (TE) of 12ms, resolution of 0.3x0.3x0.9 mm3 and four averages on five axial slices were used to obtain eddy current corrected B1+ phase images. The conductivity was calculated from the transmit phase 𝜑+ using [2]:  σ(r) =∇2φ+(r)ω μ (2)   Reconstructed Conductivity (S/m) 3. RESULTS AND DISCUSSION Average conductivities determined for the breast tumor is 0.53 ± 0.41 S/m.  The results are in good agreement with the expected values. The standard deviation represents the spatial variation of conductivity in ROI. The results show that the conductivity mapping using only the transmit phase is possible in piece-wise constant conductivity regions, which confirms the possibility of conductivity assessment in different pathological conditions. References  [1] T. Voigt et al. Quantitative conductivity and permittivity imaging of the human brain using electric properties tomography, Magn. Reson. Med., vol. 66, no. 2, pp. 456-466, 2011. [2] A. L. van Lier et al. B1+ phase mapping at 7T and its application for in vivo electrical conductivity mapping, Magn. Reson. Med., vol. 67, no. 2, pp. 555-561, 2012. 

Electrical conductivity imaging with 7T preclinical MRI using electrical properties tomography

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Electrical conductivity imaging with 7T preclinical MRI using electrical properties tomography

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