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4. Signal processing for impedance spectroscopy of dynamic objects

General aim is to develop effective methods, algorithms and electronic devices for frequency domain detecting and characterising of different time variant systems under test (SUT), as technical objects and materials, chemical solutions, electronic circuits and systems, living matters (cells and tissues, organs and organelles), on the bases of their measured impedance spectra. Achieving the goal requires novel results from the following research topics.

4.1. Methods for synthesis of broadband excitation signals.

The methods for mathematical synthesis of simple waveforms (chirp, multi-sine, binary and ternary sequences) for the excitation signals with predetermined frequency range and amplitude spectra have been developed [1, 2, 3]. The most informative response to the excitation is required for characterization of the dynamic system under test (SUT) with the highest accuracy [2, 3]. Specific requirements: short duration (avoids dynamic errors), maximal excitation energy in the desired frequency range (ensures high signal-to-noise ratio), low amplitude value at the maximal energy content, that is, effective energy packaging [2].  Achieved original results have been patented in the US and Europe, see [P1], [P2].

Publications:

1.      Min, M.; Paavle, T. (2014). Broadband discrete-level excitations for improved extraction of information in bioimpedance measurements. Physiological Measurement, 35(6), 997- 1010.

2.      Ojarand, J.; Min, M.; Annus, P. (2014). Crest factor optimization of the multisine waveform for bioimpedance spectroscopy. Physiological Measurement, 35(6), 1019-1033.

3.      Ojarand, J.; Min, M.; Annus, P.; Gorev, M.; Ellervee, P. (2014). Optimization of Multisine Excitation for a Bioimpedance Measurement Device. Proc. 2014 IEEE Instrumentation and Measurement Tech. Conf. (I2MTC 2014), Montevideo, Uruguay, May 12-15, 2014. Hoboken, NJ, USA: IEEE Pub., 829 - 832.

Patents:

P1.     Patent EE05668B1 (Estonia, granted 15.08.2013) and Patent Applications EP2565654A2 (Europe, publ. 06.03.2013), and US 2013/0054178 A1 (USA, publ. Feb. 28, 2013). Method and device for broadband analysis of systems and substances.  Authors: R. Land, P. Annus, M. Min, O. Märtens, J. Ojarand.

P2.     Patents EP2314217B1 (Europe, 13.03.2013) and US8674680B2 (USA, Mar.18, 2014). Method and device for fast measurement of frequency response with scalable short chirp signals. Authors: M. Min, T. Paavle, R. Land, P. Annus, T. Parve.

 

4.2.Principles for the design of electronic circuits and software tools for impedance spectroscopy.

Principles for using of digital electronics for generation and analysis of analog signals was developed [1]. Effective circuit design (simple, fast operating, low energy consuming) for signal processing units was worked out [1, 2]. An original digital system for the processing of response signals was patented in the US [P1].

PhD Thesis: Juri Mihhailov (2013).

PhD student: Georgios Giannoukos (expected defending in October 2015); Marek Rist (defending is expected in 2017);

Publications:

1.        Annus, Paul; Land, Raul; Reidla, Marko; Ojarand, Jaan; Mughal, Yar and Min, Mart (2013). Simplified signal processing for impedance spectroscopy with spectrally sparse sequences. XV. International Conference on Electrical Bio-Impedance (ICEBI) and XIV. Conference on Electrical Impedance Tomography (EIT) in Heilbad Heiligenstadt, Germany, April 22–25, 2013.

2.        Mart Min, Toomas Parve, Uwe F. Pliquett (2014). Impedance detection. In: Encyclopedia of Microfluidics and Nanofluidics (Prof. D. Li, Ed.), DOI: 10.1007/SpringerReference_367827 http://www.springerreference.com/index/chapterdbid/367827Springer-Verlag Berlin Heidelberg (12. Sept. 2014), 28 pp.

Patents:

P1.   US8773151B2 (USA, Jul. 08, 2014). Method and device for multichannel and multi-frequency analysis of an object. M. Min, P. Annus, A. Haapalainen, A. Kuusik, R. Land, T. Parve, A. Ronk.

 

4.3.Solutions for digitizing and digital processing of analog response signals.

Simple but effective algorithms and electronic solutions have been developed for processing of analog signals. Digitizing (sampling and quantizing), fighting with aliasing (at lower sampling rates), and reconstruction and digital processing of analog signals were highlighted [1]. As a result, an original method and device for frequency domain measurement and identification of dynamic objects have been developed [P1].

Publications:

Bilinskis, I.; Sudars, K.; Min, M. (2014). Method for Wideband Signal Digitizing and their Real-time Reconstruction in Enlarged Dynamic Range. Electronics and Electrical Engineering, 20(6), 110 - 113.

Patents:

P1.   US8854030B2 (USA, Oct. 07, 2014). Method and device for frequency response measurement. Authors: O. Märtens, M. Min, R. Land, P. Annus, T. Saar, M. Reidla.

Implementations

The results have been implemented in developing of the prototyped and tested impedance spectroscopy device Quadra (2014) with frequency range from 1 kHz to 350 kHz [1]. Duration of the shortest spectral analysis is 1ms, which makes possible the frequency domain medical diagnosing of breathing lungs (pulmonary analysis), beating heart (cardiac diagnosing) and the organs with pulsating blood (vascular analysis) [P1].

PhD thesis: Yar Muhammad (defending on May 5, 2015).

PhD students: Andres Kink (defending is expected in October 2015).

Publications:

1.      Rist, Marek; Reidla, Marko; Land, Raul; Parve, Toomas; Märtens, Olev; Annus, Paul; Ojarand, Jaan; Min, Mart (2014). Modular System for Spectral Analysis of Time-Variant Impedances.  858 IFMBE Proceedings 45: 6th Eur. Conf. of Int. Federation for Medical and Biological Engineering (MBEC 2014), Dubrovnik, 7-11 Sept., 2014. (Eds) I. Lacković, D. Vasić. Springer, 858 - 861.

Patents:

1.      Utility Model Application U201300075 (Estonia, filed 29.08.2013). Modular measurement system. Authors: Marek Rist, Mart Min, Paul Annus, Raul Land, Toomas Parve, Marko Reidla. 

Applications.

The technology of spectroscopy device Quadra has been used for the design of tissue analyser BZ-301 with deep injection needle (licensing agreement No. 12-1/581 with Injeq Oy, Finland, registrated 30.10.2014) and meat quality assessment device (licensing agreement No. 12-1/683 with Carometec A/S, Denmark, registrated 8.11.2013), also for the developing of central blood pressure analyser (in collaboration with JR Medical  OÜ and East-Tallinn Central Hospital, Estonia, 2013-2014).

PhD students: Hasso Uuetoa (defending is expected in 2017).

Publications:

1.      Krivoshei, A.; Lamp, J.; Min, M.; Uuetoa, T.; Uuetoa, H.; Annus, P. (2013). Wearable System for Non-Invasive and Continuous Monitoring Central Aortic Pressure Curve and Augment-ation Index. B. Blobel, P. Pharow, L. Parv (Eds.). In: pHealth 2013, IOS Press, 101 – 106.