title: In vivo and in situ measurement and modelling of intra-body effective complex permittivity.
abstract: Radio frequency tracking of medical micro-robots in minimally invasive medicine is usually investigated upon the assumption that the human body is a homogeneous propagation medium. In this Letter, the authors conducted various trial programs to measure and model the effective complex permittivity ε in terms of refraction ε', absorption ε″ and their variations in gastrointestinal (GI) tract organs (i.e. oesophagus, stomach, small intestine and large intestine) and the porcine abdominal wall under in vivo and in situ conditions. They further investigated the effects of irregular and unsynchronised contractions and simulated peristaltic movements of the GI tract organs inside the abdominal cavity and in the presence of the abdominal wall on the measurements and variations of ε' and ε''. They advanced the previous models of effective complex permittivity of a multilayer inhomogeneous medium, by estimating an analytical model that accounts for reflections between the layers and calculates the attenuation that the wave encounters as it traverses the GI tract and the abdominal wall. They observed that deviation from the specified nominal layer thicknesses due to non-geometric boundaries of GI tract morphometric variables has an impact on the performance of the authors' model. Therefore, they derived statistical-based models for ε' and ε'' using their experimental measurements.
authors.affiliation: Applied Statistical Signal Processing Group (πSeG), Faculty of Engineering , Maersk Mc-Kinney Moller Institute, University of Southern Denmark , Denmark.
authors.forename: Esmaeil S
authors.initials: ES
authors.lastname: Nadimi
authors.affiliation: Department of Chemical Engineering, Biotechnology and Environmental Technology , University of Southern Denmark , Denmark.
authors.forename: Victoria
authors.initials: V
authors.lastname: Blanes-Vidal
authors.affiliation: Biomedical Laboratory , Institute of Molecular Medicine, Odense University Hospital , Denmark.
authors.forename: Jakob L F
authors.initials: JL
authors.lastname: Harslund
authors.affiliation: Applied Statistical Signal Processing Group (πSeG), Faculty of Engineering , Maersk Mc-Kinney Moller Institute, University of Southern Denmark , Denmark.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Ramezani
authors.affiliation: Department for Gastroenterology , Institute of Clinical Research, Odense University Hospital , Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Kjeldsen
authors.affiliation: Aalborg University , Denmark.
authors.forename: Per Michael
authors.initials: PM
authors.lastname: Johansen
authors.affiliation: Center for Wireless Monitoring and Applications, School of Engineering , Griffith University , Australia.
authors.forename: David
authors.initials: D
authors.lastname: Thiel
authors.affiliation: School of Engineering and Applied Sciences , Harvard University , USA.
authors.forename: Vahid
authors.initials: V
authors.lastname: Tarokh
keywords: GI tract morphometric variables; abdominal cavity; absorption; bioelectric phenomena; biological organs; biomechanics; biomedical measurement; electromagnetic wave absorption; electromagnetic wave attenuation; electromagnetic wave refraction; gastrointestinal tract organs; homogeneous propagation medium; in situ measurement; in vivo measurement; intrabody effective complex permittivity; irregular unsynchronised contractions; large intestine; medical microrobots; medical robotics; microrobots; minimally invasive medicine; multilayer inhomogeneous medium; oesophagus; permittivity; porcine abdominal wall; radiofrequency measurement; radiofrequency tracking; refraction; simulated peristaltic movements; small intestine; statistical analysis; statistical based models; stomach; wave attenuation