Microwave and millimeter wave nondestructive measurement in biomedical engineering

Recent microwave and millimeter wave nondestructive measurement in biomedical engineering are reviewed. Millimeter wave reflection from the human skin was studied in the frequency range of 37-74 GHz in steps of 1 GHz. The forearm and palm data were used to model the skin with thin and thick stratum corneum (SC), respectively. To fit the reflection data, a homogeneous unilayer and three multilayer skin models were tested. A novel in vitro test of blood analysis based on the measurement of the dielectric properties at microwave frequencies is reported. The measurements were made using rectangular cavity perturbation technique at the S-band of microwave frequency with the different samples of blood obtained from healthy donors as well as from patients. The measurements are in good agreement with clinical analysis. Noncontact measurement of heart rate variability using a compact 24 GHz microwave radar is developed, without large scale equipment and placing a heavy burden on the monitored individual. This method appears to be promising for future monitoring of stress induced autonomic activation of operators and may reduce stress induced accidents. Finally the technical challenges of microwave and millimeter wave nondestructive measurement in biomedical engineering are discussed.