Diffusion weighted magnetic resonance imaging for detection of tissue electroporation in vivo

Abstract

Electroporation is advancing toward the treatment of non-superficial cancers. With this an increased demand of noninvasive methods for verification of electroporation-based treatments has emerged. Brownian motion of water is present everywhere in the organism and, as such, indirectly reveals the microscopic structure of the tissue, the main components of which are the intracellular space, the cell membrane, and the extracellular space. Any change in the tissue structure may inflict a change in the diffusivity of the water. Electroporationinduced cell membrane permeabilization is believed to cause a number of morphological changes of the tissue components, therefore potentially detectable through water diffusion measurements. Diffusion-weighted magnetic resonance imaging (DW-MRI) is a sophisticated MRI technique that utilizes the differences in water diffusivity within the tissue to generate image contrast. From DW-MRI so-called apparent diffusion coefficient (ADC) maps can be derived providing a quantitative tool for water diffusivity assessment. Investigations of electroporated tissue using DW-MRI in vivo show biomarker potential. Following irreversible electroporation, the ADC shows a characteristic temporal evolution. Reversible electroporation studies are limited but show that the ADC is increased during the first 24 h after treatment. The complexity of biological tissue does not allow DW-MRI to provide a detailed characterization of the electroporated tissue or the membrane permeabilization itself. Nonetheless, bulk tissue features are accessible through quantitative DW-MRI, yet more advanced signal processing isnecessary if someday DW-MRI is to be used for "virtual histology" of electroporated tissue.