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MR technology

Research group 8.11

UWB radar as a medical sensor system


The interdisciplinary research project ultraMEDIS within the DFG priority programme 1202 "Ultra-wideband radio technologies for communication, localisation and sensor technology" is aimed at using ultra-wideband (UWB) radar techniques (spectral bandwidth up to 10 GHz) for the detection of tumours, as well as for navigation technology in magnetic resonance (MR) imaging.

The high temporal and spatial resolution of radar sensors, their compatibility to existing narrow-band systems, the low integral power of the probing signals and their ability to penetrate objects are exploited for this purpose. Especially the last one is the very property which makes UWB radar so attractive for medical applications.

Ultra-wideband electromagnetic pulses (spectral bandwidth up to 10 GHz) generated by an UWB radar and transmitted by an antenna are able to probe the human body with low integral power (~ 1 mW), because electromagnetic waves can propagate through the body and are reflected at interfaces between materials with different dielectric properties (s. Fig. 1).

Fig. 1: Probing the human body with broadband electromagnetic pulses. Top: Transmitted pulse and received pulse (impulse response function, IRF) modulated by physiological processes. Bottom: Reconstructed physiological signature, breathing with superimposed heartbeat, reconstructed from ultra-wideband radar data. Anatomic slice taken from "The Visible Human Project", U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894, http://www.nlm.nih.gov/research/visible/visible_human.html.


The receiving antenna detects the reflected signals from different interfaces within the body. Physiological processes like respiration and heartbeat displace and deform these interfaces and thus affect the reflected signal. For the reconstruction of such spatially dependent displacements, special algorithms are currently being developed.

Fig. 2: Demonstrator set-up inside the MR scanner. The insert shows an enlarged view of the phantom/antenna/head coil arrangement .


For the evaluation of the principal feasibility of an MR-UWB combination a demonstrator setup has been realized [1, 3] (s. Fig. 2). Using an MR-compatible UWB radar, the characteristic landmarks of the heart muscle during breathing could be followed without disturbing the actual MR measurement. Thus, both, a real-time adjustment of the MR frequency according to the current position of the heart or a retrospective position correction of the MR data, can be carried out (s. Fig. 3).

Fig. 3: Top: Set-up for simultaneous UWB-MRI acquisition of physiological signatures. Bottom: Breathing with superimposed cardiac signal simultaneously recorded with both modalities. Upper trace: Normalized 1-D MRI signal. Lower trace: Normalized corresponding surface UWB time series.


A model representation of the whole system is crucial for a sound understanding of the propagation of electromagnetic waves in layered dielectric media as well as for studying the variation of the reflected signal induced by well-defined layer displacements. To this end, an analytic channel model was developed including the antennas, the human body and the signal processing part of the UWB unit [3]. Especially the frequency dependence of the complex dielectric properties of individual biological tissues was incorporated. The continuous motion of individual intra-thoracic layers was also included in the simulation of physiological signatures. In this way, the influence of physiological processes like breathing and cardiac motion on the reflection coefficient, and therefore the reflected signal, can be modeled and studied independently or in superposition. Using these artificial signals, different motion reconstruction algorithms can now be tested and improved. Furthermore, the robustness of the algorithms to perturbations which can be deliberately built into the model can be evaluated.

The Project is carried out in cooperation with the Ilmenau University of Technology and with medical partners from Jena University, who are especially interested in tumour detection.

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Topics

  • Radar based detection of breathing and myocardial deformation for the reduction of motion artifacts in MRI [1]
  • Development of UWB/MR phantoms [2]
  • Modeling the propagation of electromagnetic waves in biological tissue [3]
  • Signal decomposition of physiological signatures acquired by UWB radar

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Selected references

Reviews

F. Thiel, O. Kosch, F. Seifert
Ultra-wideband Sensors for Improved Magnetic Resonance Imaging, Cardiovascular Monitoring and Tumour Diagnostics,
Sensors, Special Issue "Sensors in Biomechanics and Biomedicine", 10(12), 10778-10802, doi:10.3390/s101210778, ISSN 1424-8220, 25 pages, (2010).
Abstract Full Text: [ PDF (1228 kB) ].

F. Thiel, M. Helbig, U. Schwarz, C. Geyer, G. Rimkus, W. A. Kaiser, I. Hilger, M. Hein, J. Sachs, F. Seifert
Implementation of ultra-wideband sensors for biomedical applications
Frequenz, Journal of RF-Engineering and Telecomunications, vol. 63, no. 9-10, pp.221-224, (2009).
Full Text: [ PDF (3352 kB) ].

Combination of MRI and UWB radar

F. Thiel, M. Hein, J. Sachs, U. Schwarz, F. Seifert
Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging
Rev. Sci. Instrum., Vol. 80, Issue 1, 014302, Melville, NY: AIP (2009), (10 pages).
Abstract Full Text: [ PDF (1271 kB) ].

F. Thiel, W. Hoffmann, F. Wojcik, M. Hein, J. Sachs, U. Schwarz, M. Helbig, F. Seifert
Evaluation of a combined magnetic resonance (MR)/ultra-wideband (UWB) radar technique
Proc.Intl. Soc. Mag. Reson. Med. 16, p. 349, ISSN 1545-4428, (2008).

F. Thiel, M. Hein, J. Sachs, U. Schwarz, F. Seifert
Fusion of magnetic resonance and ultra-wideband radar for medical applications
IEEE Int. Conf. on Ultra-Wideband (ICUWB), Vol. 1, pp. 97-100, ISBN 978-1-4244-2216-6, (2008)
Abstract.

F. Thiel, M. Hein, J. Sachs, U. Schwarz, T. D. Lindel, F. Seifert
Exploring the benefits of ultra-wideband radar for high- and ultra-high field magnetic resonance imaging
Eur. Microwave Conf. (39th EuMC 2009), Rom, Italy, 28.09-02.10., pp. 866-69, ISBN 978-2-87487-010-1, referenced at IEEE Xplore, (2009).

 

Modelling of wave propagation

F. Thiel, F. Seifert
Reflection Coefficient of the Human Thorax: Sensitivity to Intrathoracic Displacements and Incorporation into an Ultra-Wideband Channel
Proc. Eur. Conf. on Antennas and Propagation (EuCAP 2009), pp. 268 - 272, 23-27.03.2009, Berlin, Germany, ISBN 978-1-4244-4753-4, referenced at IEEE Xplore, (2009)
Abstract.

F. Thiel, F. Seifert
Non-invasive probing of the human body with electromagnetic pulses: Modelling of the signal path
J. Appl. Phys., Vol.105, Issue 4, 044904, ISSN 0021-8979, Melville, NY: American Institute of Physics (2009)
Abstract
Full Text Link
Full Text [ PDF (924 kB) ].

F. Thiel, F. Seifert
Modeling of physiological signatures in ultrawideband radar signals
in H.Malberg, T. Sander-Thömmes, N. Wessel, W. Wolf (Eds.), "Biosignalverarbeitung: Innovationen bei der Erfassung und Analyse bioelektrischer und biomagnetischer Signale" , pp. 130-2, ISBN 978-3-9810021-7-1, (2008).

F. Thiel, F. Seifert
Reconstruction of physiological signatures from synthetic biomedical ultra-wideband signals
Eur. Microwave Conf. (39th EuMC 2009), Rom, Italy, 28.09-02.10., pp.1579 - 82, ISBN 978-2-87487-010-1, referenced at IEEE Xplore, (2009).

F. Thiel, O. Kosch, F. Seifert
Intracranial pulsation detected by ultra-wideband radar: Detectability analysis using synthetic signals
Proc. Eur. Conf. on Antennas and Propagation (EuCAP 2010), 12-16.04.2010, Barcelona, Spain, ISBN 978-3-8007-3152-7, referenced at IEEE Xplore, (2010).

F. Thiel, O. Kosch, F. Seifert
Contrast agent based tumour detection by ultra-wideband radar: A model approach
Proc. Eur. Conf. on Antennas and Propagation (EuCAP 2010), 12-16.04.2010, Barcelona, Spain, ISBN 978-3-8007-3152-7, referenced at IEEE Xplore, (2010).

Detection of physiological signitures and signal decomposition methods

F. Thiel, D. Kreiseler, F. Seifert
Non-contact detection of myocardium's mechanical activity by ultra-wideband rf-radar and interpretation applying electrocardiography
Rev. Sci. Instrum., vol. 80, 11, 114302, Doi:10.1063/1.3238506, ISSN 0034-6748, Melville, NY:
American Institute of Physics (AIP), (2009).
Abstract Full Text: [ PDF (1749 kB) ].

F. Thiel, M. Hein, J. Sachs, U. Schwarz, F. Seifert
Physiological signatures monitored by ultra-wideband-radar validated by magnetic resonance imaging
IEEE Int. Conf. on Ultra-Wideband (ICUWB), Vol. 1, pp. 105-8, ISBN 978-1-4244-2216-6, (2008).
Abstract.

F. Thiel, T. Lindel, M. Hein, U. Schwarz, F. Seifert
Multimodal biomedical sensing applying ultra-wideband electromagnetic excitation:
Ultra-wideband sounding of the human myocardium from different radiographic standard positions and simultaneous high resolution electrocardiography

IEEE Intl. Conf. on Ultra-Wideband (ICUWB), Vancouver, Canada, 09-11.09.2009, pp. 495-500, ISBN 978-1-4244-2931-8, (2009).

O. Kosch ,   F. Thiel,    F. Scotto di Clemente ,   M.A. Hein,    F. Seifert
Monitoring of human cardio-pulmonary activity by multi-channel UWB-radar
IEEE Intl. Conf. on Antennas and Propagation in Wireless Communications(APWC), Torino, 2011, pp. 382-385,
ISBN: 978-1-4577-0046-0
Abstract Full Text: [ PDF (1088 kB) ].

 

Phantoms

F. Thiel, F. Schubert, W. Hoffmann, F. Seifert
Tissue-mimicking phantoms for a combined magnetic resonance (MR)/ultra-wideband (UWB) radar technique
Proc. Intl. Soc. Mag. Reson. Med. 16, p. 1054, ISSN 1545-4428, (2008).

Ultra-wideband antennas for biomedical applications

U. Schwarz, F. Thiel, F. Seifert, R. Stephan, M. Hein
Ultra-Wideband Antennas for Magnetic Resonance Imaging Navigator Techniques
IEEE Trans. on Antennas and Propagation, Vol. 58, 6, p. 2107-2112, (2010)
Abstract

M. Hein, C. Geyer, M. Helbig, I. Hilger, J. Sachs, U. Schwarz, F. Seifert, R. Stephan, F. Thiel
Antennas for Ultra-Wideband Medical Sensor Systems (invited)
Proc. Eur. Conf. on Antennas and Propagation (EuCAP 2009), pp. 1868 - 1872, 23-27.03.2009, Berlin, Germany, ISBN 978-1-4244-4753-4, referenced at IEEE Xplore, (2009)
Abstract.

U. Schwarz, F. Thiel, F. Seifert, M. Hein
Magnetic Resonance Imaging Compatible Ultra-Widebande Antennas
Proc. Eur. Conf. on Antennas and Propagation (EuCAP 2009), pp. 1102 - 1105, 23-27.03.2009, Berlin, Germany, ISBN 978-1-4244-4753-4, referenced at IEEE Xplore, (2009)
Abstract.

U. Schwarz, M. Helbig, J. Sachs, F. Seifert, R. Stephan, F. Thiel, M. Hein
Physically small and adjustable double ridged horn antenna for biomedical UWB radar applications
Int. Conf. on Ultra-Wideband (ICUWB), Vol. 1, pp. 5-8, ISBN 978-1-4244-2216-6, (2008)
Abstract.

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Related links

Cooperations

"Ultra-wideband Radio Technologies for Communication, Localisation and Sensor Technology" (UKoLoS) is the 6-year priority programme SPP1202 supported by Deutsche Forschungsgemeinschaft.
http://www-emt.tu-ilmenau.de/ukolos/

Technische Universiät Ilmenau, department of RF and microwave technique, faculty of electrical engineering and information technology.
http://www.tu-ilmenau.de/en/rf-and-microwave-research-laboratory/

Technische Universität Ilmenau, electronic measurement research lab.
http://www-emt.tu-ilmenau.de/WWW/Index.php?lang=ENG

University hospital Jena, institute for diagnostic and interventional radiology, experimental radiology group (in German):
http://www.idir.uk-j.de/Willkommen.html

 

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Contact

Address

Physikalisch-Technische Bundesanstalt
Abbestraße 2–12
10587 Berlin