IMS Presenters Address Healthcare Applications
Healthcare applications received considerable attention at the International Microwave Symposium held June 17 to 22 in Montréal. A session titled “RF Devices for Wireless Healthcare Applications and Biosensing” included papers addressing applications ranging from wireless implants for intraocular pressure sensing to advances in vital-sign Doppler radar for multisubject localization.
In the first paper of this session, authors representing the University of Tennessee and the School of Information and Electronics at the Beijing Institute of Technology described a low-cost ultrawideband (UWB) biometric radar sensor for respiration detection and monitoring applications that achieves 3-mm resolution, allowing it to detect breathing and heartbeat.1 The authors reported having conducted a variety of experiments, including detecting the respiration characteristics of a single person through a wall, the detection of two persons at different distances, and the detection of two humans at the same distance. The authors stated that the Doppler radar sensor exceeds CW radar for biomedical applications.
Similarly, authors representing National Chung Cheng University presented a tag-free 2-D wireless positioning system for human subject tracking that integrates a quadrature Doppler radar to sense respiration while a switched-beam phased antenna array determines a target’s angular information.2
Authors representing CNRS (Le Centre National de la Recherche Scientifique) and Université de Toulouse presented a demonstration of an accurate liquid-sensing technique in the nanoliter range using signals from 40 MHz to 40 GHz.3 They reported that their sensor is based on an “interdigitated capacitor” with a microfluidic channel placed on top to confine the liquid. The sending volume, they noted, corresponds to 0.9 nL. The 40-GHz operation, they concluded, derives rich information on the molecular content of a mixture, making it a strong contender for lab-on-a-chip applications.
In yet another paper, authors representing The University of Texas at Arlington, Med-Worx, The University of Mississippi, and The University of Texas Southwestern described a dual-sensor system that detects impedance and pH to monitor the symptoms of gastroesophageal reflux disease.4 The system consists of an implantable batteryless transponder and an external reader.
In the final paper of the session, authors from Purdue University and The Jackson Laboratory presented the measurement of intraocular pressure (IOP) within the eye of a mouse.5 Their paper describes the fabrication of an ultra-small Parylene tag containing a MEMS capacitive pressure sensor, a self-expandable Nitinol antenna, and a diode. From the implanted sensor, they reported being able to detect the frequency shift of a third-order harmonic signal with a sensitivity of approximately 1.5 MHz/mmHg at an 11.5-cm distance from the sensor.
An additional session on biomedical sensors included more papers on respiration detection, but it also addressed cancer detection, with results presented from investigations of colorectal and skin cancer cells. Authors representing XLIM and the Université de Limoges investigated the potential of using microwave frequencies for biological analysis.6 Microwaves, the authors noted, can derive an electromagnetic signature to determine the malignancy of colorectal cancer cells. An additional paper from authors representing the KTH Royal Institute of Technology described a millimeter-wave near-field measurement probe for skin-cancer diagnosis.7
A session on biomedical imaging also addressed cancer detection. Authors from McGill University described the performance of a time-domain microwave radar system fed with two different pulses and designed to detect breast-cancer tumors.8 The authors reported that they performed tests on a realistically shaped breast phantom with two tumor sizes, three tumor positions, and two antenna arrangements and found that a tumor could be easily detected in all scenarios.
In addition, authors representing the University of Arkansas, Miami University, and Ohio State University described terahertz measurements of excised formalin fixed paraffin embedded (FFPE) human breast cancer tissues.9 They collected data using a terahertz pulsed system operating from 0.1 THz to 3 THz.
Authors from McMaster University presented a sensitivity-based microwave imaging algorithm applied with measured data from raster scanning of tissue phantoms.10 They reported having tested the algorithm on measurements of breast tissue with initial results promising.
Authors from University of Minnesota addressed high-field MRI systems.11 They investigated the use of a TEM-based RF head coil with a double trapezoidal microstrip conductor shape to generate uniform fields that can provide high-quality images.
In the final paper, authors representing the University of Houston, the FDA, and the University of Southern California investigated the orthopedic implant heating that can occur because of MRI RF fields.12 They noted that recent advances in the numerical modeling of electromagnetic fields have made it possible to perform simulations of implant heating to determine the worst-case heating for an implant measuring 21 mm to 107 mm. They observed that the temperature rise is related to the length of the implant. Simulation, they said, makes it possible to determine the worst-case heating for an entire product family.
References
All the references can be found in the Proceedings of the International Microwave Symposium 2012.
1. Wang, Y., Liu, Q., and Fathy, A.E., “Simultaneous Localization and Respiration Detection of Multiple People Using Low Cost UWB Biometric Pulse Doppler Radar Sensor.”
2. Su, Y., Chang, C., Guo, J., and Chang, S., “2-D Wireless Human Subjects Positioning System Based on Respiration Detections.”
3. Chen, T., Dubuc, D., and Grenier, K., “Accurate Nanoliter Liquid Complex Admittance Characterization up to 40 GHz for Biomedical Applications.”
4. Cao, H., et al., “Remote Detection of Gastroesophageal Reflux Using an Impedance and pH Sensing Transponder.”
5. Ha, D., et al., “A Compact-Size Packaged Third-Order Harmonic Tag for Intraocular Pressure (IOP) Monitoring Inside a Mouse Eye.”
6. Zhang, L., et al., “Microwave Biosensors for Identifying Cancer Cell Aggressiveness Grade.”
7. Töpfer, F., Dodorov, S., and Oberhammer, J., “Micromachined 100-GHz Near-Field Measurement Probe for High-Resolution Microwave Skin-Cancer Diagnosis.”
8. Porter, E., et al., “Time-Domain Microwave Cancer Screening: Optimized Pulse Shaping Applied to Realistically Shaped Breast Phantoms.”
9. Hassan, A. M., et al., “Terahertz Imaging for Margin Assessment of Breast Cancer Tumors.”
10. Zhang, Y., et al., “Sensitivity-Based Microwave Imaging with Raster Scanning.”
11. Sohn, S., et al., “RF Multi-Channel Head Coil Design with Improved B1+ Fields Uniformity for High-Field MRI Systems.”
12. Liu, Y., et al., “Computational and Experimental Studies of Orthopedic Implants Heating under MRI RF Coils.”