Journal
IEEE JOURNAL OF ELECTROMAGNETICS RF AND MICROWAVES IN MEDICINE AND BIOLOGY
Volume 6, Issue 4, Pages 470-476Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JERM.2022.3171092
Keywords
Temperature measurement; Microwave radiometry; Microwave measurement; Biological system modeling; Antennas; Microwave antennas; Frequency measurement; Bioheat transfer; core body temperature; microwave radiometry; microwave thermometry
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Funding
- National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health [R03EB030286]
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This paper presents a novel method for retrieving core temperature using microwave radiometry when the complex permittivity and heat transfer parameters of the tissue layers of the human subject are unknown. The method accounts for population variation in the relevant electromagnetic and thermal parameters, resulting in a retrieval error within the clinically acceptable limit. The results of this study contribute to the advancement of medical microwave radiometry as a clinically viable and accurate noninvasive measurement for all patients.
This paper presents a novel method for core temperature retrieval using microwave radiometry when complex permittivity and heat transfer parameters of the tissue layers of the human subject are unknown. Previous works present methods for core temperature retrieval, but these methods do not account for population variation in the relevant electromagnetic and thermal parameters, which can increase measurement error beyond the clinically acceptable limit of 0.5 degrees C. Pennes' bioheat model of a six-tissue-layer human head model combined with a coherent electromagnetic model simulate experimental data. To retrieve core temperature, nonlinear least squares optimization is then used to minimize the difference between the simulated experimental data and an exponential model for physical temperature and the coherent electromagnetic model. By using 20 frequencies spanning from 1-5 GHz, core temperature is retrieved while accounting for population variation in the permittivity and thermal parameters. A Monte Carlo simulation in which the thermal parameters and permittivity vary according to literature derived, population-representative distributions and the core body temperature varies from 18 to 46 degrees C is used to assess the utility of the retrieval method. Different antenna patterns are tested to explore the effect on retrieval accuracy. The retrieval method has a retrieval error of <0.1 degrees C when only the thermal parameters are unknown and a retrieval error of <0.5 degrees C when the thermal parameters and permittivity are unknown, which is within the clinically acceptable error range of 0.5 degrees C. These results help progress the field of medical microwave radiometry toward being a clinically viable noninvasive measurement that is accurate when measuring all patients.
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