Assessment of Tissue Impedance Postmortem Using Needle Measurement and Computation Modelling

There is a global shortage of organ transplants. Transplant preservation and diagnostic methods are being developed to ease the problem. This process requires understanding the degradation processes that take place in the transplant tissue as a function of time post-procurement. Good organ quality is the basis for successful long-term transplantation outcomes. This paper aims to look if electric bioimpedance measurement could provide a tool to assess organ quality. Needle-based bioimpedance measurement provides minimally invasive and safer real-time continuous data than traditional biopsies to assess kidney tissue condition. Additionally, it provides a controlled and small measurement area within the tissue. An electrode-based impedance measurement of a volume conductor target provides a value depending on the sensitivity distribution. In this study, we developed in COMSOL Multiphysics a homogeneous 3D computational model to translate experimental in-tissue impedance measurement time series (from procurement until 72 h post-procurement) from porcine kidneys into tissue conductivity, relative permittivity, and capacitance time series. The model determines the time-, temperature- and tissue depth-dependent changes in these electrical properties, facilitating characterization of tissue degradation processes. The value ranges and trends are useful for studying kidney function and the degradation processes for the clinically relevant post-procurement times.Clinical RelevanceThis study provides in-tissue impedance values for a porcine kidney as a function of time post-procurement during and after cooling at different depths in cortex. Thereafter, we provide a method to obtain electrical properties of the tissue using computational simulations to evaluate the kidney degradation process.