Pneumothorax is the medical condition caused by the air concentration inside the pleural cavity, the space between the lung and the chest wall. Apart from traditional diagnostic methods, it can be detected by using microwave sensors that capture variations in reflected electromagnetic field (EMF). Sex and obesity, related to the internal composition of the biological tissues, can influence the reflected EMF and therefore the sensor diagnostic ability. This paper investigates the effect on the performance of a proposed on-body dual-patch antenna sensor for pneumothorax diagnosis, due to inter-subject variability in underlying tissue structure. The sensor operates at frequency range of 1-4 GHz. The challenge of the paper is to propose frequency bands for robust and safe sensor operation. S12 parameter alternation versus frequency is assessed for healthy and pathological cases. Implemented thorax numerical models include modified (i) closed rectangular multilayered and (ii) MRI-based anatomical ones. In rectangular models, thickness and configuration of muscle, fat and bone tissues are varied, according to literature. Additionally, sex-related anatomical differences are taken into account in MRI-based models. All scenarios are solved using Finite Difference Time Domain method. Results revealed that the proposed frequency bands lie within 1-2.7 and 2.9-3.5 GHz, for muscle, 1.4-3.5 GHz for fat and 1-2.2 and 2.8-3.5 GHz, for bone variations. Numerical evaluations for accurate anatomical models verify the findings.
2. Conceicao, R. C., M. O’Halloran, M. Glavin, and E. Jones, "Comparison of planar and circular antenna configurations for breast cancer detection using microwave imaging," Progress In Electromagnetics Research, Vol. 99, 1-20, 2009. doi:10.2528/PIER09100204
3. Mohammed, B. J., A. M. Abbosh, D. Ireland, and M. E. Bialkowski, "Compact wideband antenna for microwave imaging of brain," Progress In Electromagnetics Research C, Vol. 27, 27-39, 2012. doi:10.2528/PIERC11102708
4. Christopoulou, M. and S. Koulouridis, "Dual patch antenna sensor for pneumothorax diagnosis: Sensitivity and performance study," Proceedings of IEEE Annual International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE EMBC 2014, 4827-4830, Chicago, USA, Aug. 2014.
5. Gabriel, S., R. W. Lau, and C. Gabriel, "The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues," Phys. Med. Biol., Vol. 41, No. 11, 2231-2293, 1996. doi:10.1088/0031-9155/41/11/001
6. Frank, M., V. Schorge, K. Hegenscheid, A. Angermaier, A. Ekkernkamp, N. Hosten, R. Puls, and S. Langner, "Sturdivan’s formula revisited: MRI assessment of anterior chest wall thickness for injury risk prediction of blunt ballistic impact trauma," Forensic. Sci. Int., Vol. 212, 110-114, 2011. doi:10.1016/j.forsciint.2011.05.022
7. British Thoracic Society, Pleural Disease Guidelines, Sep. 2010.
8. Christopoulou, M. and S. Koulouridis, "Design requirements of microwave sensor for pneumothorax diagnosis," Proceedings of IEEE International Symposium on AP/URSI, 2052-2053, Florida, USA, Jul. 2013.
9. Taflove, A. and S. C. Hagness, Computational Electrodynamics: The Finite-difference Time-domain Method, 2nd Ed., Artech House, 2000.
10. Reddy, J. N., An Introduction to the Finite Element Method, 3rd Ed., McGraw-Hill, 2005.
14. Christ, A., et al., "The virtual family --- Development of surface-based anatomical models of two adults and two children for dosimetric simulations," Phys. Med. Biol., Vol. 55, No. 2, N23-N38, 2010. doi:10.1088/0031-9155/55/2/N01
15. Christopoulou, M., M. Capstick, B. Reumer, S. Koulouridis, and N. Kuster, "Experimental thorax prototype for multistage pneumothorax diagnosis," Proceedings of Joint Meeting of The Bioelectromagnetics Society (BEMS) and the European BioElectromagnetics Association (EBEA), BioEM2015, Asilomar Conference Center, California, USA, Jun. 14-19, 2015.
16. Kim, Y. S., M. J. Park, H. Rhim, M. W. Lee, and H. K. Lim, "Sonographic analysis of the intercostal spaces for the application of high-intensity focused ultrasound therapy to the liver," Am. J. Roentgenol., Vol. 203, No. 1, 201-208, 2014. doi:10.2214/AJR.13.11744
17., Advanced Trauma life Support Program for Doctors, 6th Ed., American College of Surgeons, Chicago, IL, 1997.
18. IEEE Standard C95.1-2005, IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, 2005.