Measurement of low level blood flow: instrumentation, methodology, and analysis

The authors extend the governing mathematical models for two separate thermal probe measurement procedures to produce a novel, integrated technique for the local quantification of tissue thermal conductivity, diffusivity, and perfusion. A theoretical analysis indicates the potential to quantify perfusion down to essentially zero-flow levels in small tissue volumes. These advances have been implemented in the enhanced thermal diffusion probe (ETDP), a versatile, microprocessor-based instrument capable of quantifying temperature (0.003 degrees C), thermal conductivity (0.2%), and thermal diffusivity (0.4%). Data collected in the isolated, perfused rat liver model demonstrate sensitivity to perfusion at flow levels of biological interest (0-60 ml/100 gm-min). Further in-vivo experiments in mice and rabbits, in tumor and normal tissue, demonstrate the sensitivity and clinical utility of this technique to monitor vascular response to various interventions in a realistic clinical setting.<>