DEVELOPMENT OF METHODOLOGIES FOR THE ESTIMATION OF BLOOD PERFUSION USING A MINIMALLY INVASIVE THERMAL PROBE

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 p robe and tissue in an estimation procedure for the determination of th e blood perfusion. The key element of the probe is a thin sensor, whic h is placed in contact with the tissue and provides time-resolved sign als representing heat flux and temperature while the probe is cooled b y air jets. This probe has been newly modified to enhance performance. Parameter estimation techniques were developed which incorporate meas ured heat flux and/or temperature data and corresponding calculated da ta from the model to estimate blood perfusion and also the thermal con tact resistance between the probe and the tissue. The sensitivity coef ficients associated with heat flux were found to be much higher than t hose associated with temperature such that the heat flux measurements were the most influential in the estimation of the parameters. Simulta neous estimates of blood perfusion and contact resistance were success fully obtained using the Gauss minimization method. The resulting esti mates of blood perfusion were consistent with the range of values foun d in the literature.