Magnetic Resonance Based Electrical Properties Tomography (Ept) Using Multi-Channel Transmission For Imaging Human Brain And Animal Cancer Models

Abstract

Electrical properties (EPs) of biological tissues are determined by tissue constituents, and therefore may provide novel biomarkers for characterization of diseased tissues such as cancer. In addition, accurate quantification of tissue EPs is essential for understanding the biological effects of electromagnetic radiation involved in MRI exams as well as wireless communication. In this dissertation, non-invasive EP imaging methods are proposed based on inverse problems using a plurality of radiofrequency electromagnetic field maps (B1 maps) acquired with ultra-high-field MRI. For human brain imaging, an automatic seed selection strategy is developed for gradient-based Electrical Properties Tomography (gEPT) to provide objective EP values. Reconstruction results of twelve healthy subjects demonstrate that considerable intra- and inter- subject EP heterogeneity resides in the normal brain, which may provide rationale for subject-specific mapping of EPs for improved accuracy in electromagnetic safety evaluation. Furthermore, a generalized technology called “CONtrast Conformed Electrical Properties Tomography (CONCEPT)” is developed based on transmit B1 maps and image sparsity. Numerical simulations and phantom experiments have been performed to quantify its accuracy and sensitivity. For rodent cancer model imaging, Boundary Informed Electrical Properties Tomography (BIEPT) technology is proposed based on a constrained inverse problem that exploits prior information and image sparsity. The imaging platform and BIEPT reconstruction method have been evaluated using simulations, phantom experiments and in vivo cancer xenograft imaging experiments. The reconstructed EPs are compared to multiple conventional MR contrasts as well as histopathology slides to demonstrate their potential value for cancer diagnosis and staging.