Author: Jingyao Chen, Yingli Yang, Jie Zhang π¨βπ¬
Affiliation: Department of Radiology, Ruijin Hospital, Shanghai Ruijin Hospital, Shanghai United imaging Healthcare Advanced Technology Research Institute π
Purpose: Magnetic Resonance Electrical Properties Tomography (MR EPT) is a method to spatially mapping the conductivity and permittivity based on small B1 field changes after the imaged object was introduced into the field. Itβs been nearly three decades since MR EPT was invented, technical and clinical implementations of MR EPT are still lacking. The aim of this study is to design a dedicated EPT coil, in a simulation environment, to achieve improved visualization and accurate quantification of MR EPT phenomena and understand its technical limits.
Methods: A human head model with assigned electrical properties for different tissue compartments, including tumors, was integrated into COMSOL Multiphysics for electromagnetic simulations. A custom RF coil was designed to generate a uniform B1 field under ambient conditions. Phase-based Helmholtz (PB) EPT reconstruction algorithm was employed to derive tissue conductivity (Ο) maps from micro RF-distorted signals. The coil's radius, number of excitation ports, and resonant frequency were systematically varied to identify the optimal configuration.
Results: The simulations demonstrated that the optimized RF coil achieved a highly uniform B1 field while effectively maximizing RF-distorted signals caused by electrical property differences between tumor and healthy tissues. A smaller coil radius, an increased number of excitation ports, and a higher resonant frequency were identified as key factors contributing to improved performance. The PB-EPT algorithm successfully reconstructed conductivity maps, highlighting distinct electrical properties of tumor tissues compared to healthy tissues. The optimal coil design balanced field uniformity, sensitivity, and signal amplification, achieving a reduction in the relative error of conductivity reconstruction by 0.43.
Conclusion: The proposed dedicated head coil design, combined with PB-EPT reconstruction, provides a robust framework for non-invasive mapping of tumor electrical properties. This approach holds significant potential to bring EPT, an unique quantitative MRI technique, one step closer to routine clinical application.