Imaging conductivity using electric properties tomography — Initial clinical results in glioma patients

The electric properties of human tissue can potentially be used as an additional diagnostic parameter, e.g., in tumour diagnosis. In the framework of radiofrequency (RF) safety, the electric conductivity of tissue is needed to correctly estimate the local specific absorption rate (SAR) distribution during magnetic resonance imaging (MRI). In this study, a recently developed approach, called electric properties tomography (EPT) is applied to in vivo imaging in a clinical setting. It derives the patient´s electric conductivity and permittivity from the spatial sensitivity distributions of the RF coils in MRI. In contrast to other methods to measure the patient´s electric properties, EPT does not apply externally mounted electrodes, currents, or RF probes, which enhances the practicability of the approach. This work shows that conductivity distributions can be reconstructed from phase images of the RF transmit field. Using this approximation, three-dimensional in vivo conductivity maps of the human brain are obtained in 6 min. We report first practical experiences of conductivity imaging in patients with brain glioma in a real-world clinical environment. In vivo conductivity of glioma is measured for two patients and quantitative values are compared with white matter conductivities of healthy volunteers. Glioma conductivity was found to be significantly higher than healthy white matter conductivity.