Development of methodologies for the estimation of blood perfusion using a minimally invasive thermal probe

Abstract

Parameter estimation techniques have been utilized in the development of methodologies for the noninvasive determination of blood perfusion using measurements from a new thermal surface probe. The basic concept behind this work is that heat flux and temperature measurements from the probe are combined with results from a mathematical model of the probe and tissue in an estimation procedure for the determination of the blood perfusion. The key element of the probe is a thin sensor, which is placed in contact with the tissue and provides time-resolved signals representing heat flux and temperature while the probe is cooled by air jets. This probe has been newly modified to enhance performance. Parameter estimation techniques were developed which incorporate measured heat flux and/or temperature data and corresponding calculated data from the model to estimate blood perfusion and also the thermal contact resistance between the probe and the tissue. The sensitivity coefficients associated with heat flux were found to be much higher than those associated with temperature such that the heat flux measurements were the most influential in the estimation of the parameters. Simultaneous estimates of blood perfusion and contact resistance were successfully obtained using the Gauss minimization method. The resulting estimates of blood perfusion were consistent with the range of values found in the literature.