Noninvasive measurement of subsurface tissue temperatures with microwave radiometry.

Format:

Book

Thesis/Dissertation

Author/Creator:

Leonard, Jonathan Bartoo.

Contributor:

University of Pennsylvania.

Language:

English

Subjects (All):

Diagnostic imaging.

Radiology.

Biomedical engineering.

0541.

0574.

Local Subjects:

0541.

0574.

Physical Description:

356 pages

Contained In:

Dissertation Abstracts International 51-08B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The potential of microwave radiometry as a non-invasive probe for subsurface tissue temperature measurements in biological heat transfer studies was investigated. The study consisted of two parts: a theoretical and experimental characterization of the radiometer, and a thermal analysis of an isolated, perfused tissue.

The initial portion of the study demonstrated the suitability of the radiometer for non-invasive thermal measurements. The Dicke-switched radiometer system operating at 4.7 GHz was modeled using microwave and antenna theory. This model was evaluated by using it to predict the radiometer response during thermal clearance experiments with unperfused gelatin phantoms. Lacking perfusion, heat transfer processes could be modeled using the Fourier heat diffusion equation. The radiometer model was demonstrated to successfully predict radiometer performance in the unperfused gelatin phantoms. Radiometer penetration depth and spatial resolution were determined from the model, and verified by experiment.

The radiometer was then used to investigate basic heat transfer processes in a specific tissue--the renal cortex. The kidney was chosen as the experimental system for the perfused tissue experiments, because it is the most highly perfused organ in mammals. The model of radiometer response previously developed was combined with biological heat transfer theories to analyze thermal clearance measurements in the kidney.

Two biological heat transfer models were applied to the renal cortex: the isotropic heat sink, as expressed by the bioheat transfer equation (BHTE); and enhanced (effective) thermal conductivity. The BHTE failed to adequately predict the thermal clearance of the cortex at high or low perfusion. The effective conductivity model provided an excellent fit to experimental data, with the effective conductivity parameter showing only modest increases over a broad range of perfusion. The use of histological data from the renal cortex with the Weinbaum-Jiji equation for effective conductivity predicted comparable changes in this parameter. These results strongly support recent theoretical heat transfer analyses which place the site for blood-tissue thermal equilibration in vessels $>$100 micrometer diameter--not in the capillary bed.

Notes:

Source: Dissertation Abstracts International, Volume: 51-08, Section: B, page: 3957.

Supervisors: Kenneth R. Foster; Daniel K. Bogen.

Thesis (Ph.D.)--University of Pennsylvania, 1990.

Local Notes:

School code: 0175.

Access Restriction:

Restricted for use by site license.