ONLINE ESTIMATION OF CAPILLARY PERMEABILITY AND CONTRAST AGENT CONCENTRATION IN RAT TUMORS

This paper presents a two-compartment model for the transfer of optical contrast agent, namely indocyanine green (ICG), in the presence of tumors between the plasma and extracellular extravascular space (EES) compartments. An adaptive extended Kalman filter (EKF) has been derived to estimate the quantities that are transferred between the compartments, Moreover, in order to validate the proposed EKF, real data have been utilized and the experimentally obtained ICG concentration data quantitatively analyzed through the estimation of physiological parameters related to capillary permeability and the optical contrast agent concentration in the compartments concurrently. The proposed method produces the estimate of tissue permeability, independent of the initial permeability values, without resorting to computationally expensive nonlinear fitting algorithms. Considering the fact that the change in the tissue permeability occurs usually due to a disease such as cancer, an estimated value of the permeability could be used to extract valuable information about tumor cell behavior patterns.