A simple approach to calculate active power of electrosurgical units
Monteiro, André Luiz Regis; Grande, Karin Cristine; Faria, Rubens Alexandre de; Schneider Junior, Bertoldo
http://dx.doi.org/10.1590/2446-4740.0776
Res. Biomed. Eng., vol.32, n1, p.14-27, 2016
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Abstract
Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods: This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables – frequency domain vectors – obtained through Discrete Fourier Transform (DFT) applied on time-sampled voltage and current vectors. Results: Comparative results between simulations and a practical experiment are presented – all being in accordance with the requirements of the applicable industry standards. Conclusion: An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.
Keywords
Active power, Power measurement, Electrosurgery, FFT-computing, DFT.
References
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Spangenberg SM, Scott I, Mclaughlin S, Povey GJR, Cruickshank DGM, Grant PM. An FFT-based approach for fast acquisition in spread spectrum communication systems. Wireless Personal Communications. 2000; 13(1-2):27-56. http://dx.doi.org/10.1023/A:1008848916834.
Tang X, Zeng X, Tu C. A sliding DFT algorithm for electric power measurement. In: Fang J, Wang Z, editors. Proceedings of SPIE 6357, 6th International Symposium on Instrumentation and Control Technology: Signal Analysis, Measurement Theory, Photo-Electronic Technology, and Artificial Intelligence; 2006 Oct 24; Beijing, China. Beijing: SPIE; 2006. p. 1-5. http://dx.doi.org/10.1117/12.717112.
Andria G, Savino M, Trotta A. Windows and interpolation algorithms to improve electrical measurement accuracy. IEEE Transactions on Instrumentation and Measurement. 1989; 38(4):856-63. http://dx.doi.org/10.1109/19.31004.
Associação Brasileira de Normas Técnicas - ABNT. NBR-IEC 60601-2-2: medical electrical equipment part 2-2: particular requirements for the safety of high frequency surgical equipment. Rio de Janeiro: ABNT; 2013.
Bernardi R. Desenvolvimento de um equipamento para estudo de eletrocirurgia com controle de potência ativa [dissertation]. Curitiba: Universidade Federal Tecnológica do Paraná; 2007.
Betta G, D’Apuzzo M, Liguori C, Pietrosanto A. An intelligent FFT-analyzer. IEEE Transactions on Instrumentation and Measurement. 1998; 47(5):1173-9. http://dx.doi.org/10.1109/19.746578.
Chen KF, Cao X, Li YF. Sine wave fitting to short records initialized with the frequency retrieved from Hanning windowed FFT spectrum. Measurement. 2009; 42(1):127-35. http://dx.doi.org/10.1016/j.measurement.2008.04.007.
De Santis V, Beeckman P, Lampasi DA, Feliziani M. Assessment of human body impedance for safety requirements against contact currents for frequencies up to 110 MHz. IEEE Transactions on Biomedical Engineering. 2011; 58(2):390-6. http://dx.doi.org/10.1109/TBME.2010.2066273. PMid:20709636.
Freescale Semiconductor, Inc. FFT-based algorithm for metering applications: AN4255. Eindhoven: NXP Semiconductors; 2015.
Fritz M, Schall H. inventors; ERBE Elektromedizin GmbH, assignee. Electrosurgical gerenator for the treatment of a biological tissue, method for regulating an output voltage of an electrosurgical generator, and corresponding use of the electrosurgical generator. United States patent US 8920412B2. 2014 Dec 30.
Grande KC. Análise da energia utilizada por bisturi elétrico na ablação de tecido orgânico [dissertation]. Curitiba: Universidade Federal Tecnológica do Paraná; 2014.
Harris FJ. On the use of windows for harmonic analysis with the discrete Fourier transform. Proceedings of the IEEE. 1978; 66(1):51-83. http://dx.doi.org/10.1109/PROC.1978.10837.
Hidalgo RM, Fernandez JG, Rivera RR, Larrondo HA. A simple adjustable window algorithm to improve FFT measurements. IEEE Transactions on Instrumentation and Measurement. 2002; 51(1):31-6. http://dx.doi.org/10.1109/19.989893.
Horton JW, VanRavenswaay AC. Electrical impedance of the human body. Journal of the Franklin Institute. 1935; 220(5):557-72. http://dx.doi.org/10.1016/S0016-0032(35)90038-2.
International Electrotechnical Commission. IEC 60990: methods of measurement of touch current and protective conductor current [internet]. 2nd ed. Geneva: IEC; 1999 [cited 2015 Mar 17]. Available from: http://webstore.iec.ch/preview/info_iec60990%7Bed2.0%7Db.pdf
International Electrotechnical Commission. IEC 60601-2-2:2009: medical electrical equipment – Part 2-2: particular requirements for the basic safety and essential performance of high frequency surgical equipment and high frequency surgical accessories [internet]. Geneva: IEC; 2009 [cited 2015 Mar 17]. Available from: http://www.iec.ch/index.htm
Jain VK, Collins WL, Davis DC. High-accuracy analog measurements via interpolated FFT. IEEE Transactions on Instrumentation and Measurement. 1979; 28(2):113-22. http://dx.doi.org/10.1109/TIM.1979.4314779.
Lyons RG. Understanding digital signal processing. 3rd ed. New York: Pearson Education; 2010.
Schneider B Jr, Abatti PJ. Desenvolvimento de um equipamento eletrocirúrgico com saída não chaveada. Revista Brasileira de Engenharia Biomédica. 2005; 21(1):15-24.
Schneider B Jr, Abatti PJ. Electrical characteristics of the sparks produced by electrosurgical devices. IEEE Transactions on Biomedical Engineering. 2008; 55(2 Pt 1):589-93. http://dx.doi.org/10.1109/TBME.2007.903525. PMid:18269994.
Schneider B Jr. Estudo teórico-prático de parâmetros técnicos e fisiológicos utilizados em eletrocirurgia, visando a otimização do desenvolvimento e performance de um bisturi eletronico [thesis]. Curitiba: Programa de Pós-graduação em Engenharia Elétrica e Informática Industrial, Centro Federal de Educação Tecnológica do Paraná; 2004.
Smith KCA, Alley R. Electrical circuits: an introduction. Cambridge: Cambridge University Press. 1992.
Smith SW. The scientist and engineer’s guide to digital signal processing. 2nd ed. San Diego: California Technical Publishing; 1999. v. 1.
Spangenberg SM, Scott I, Mclaughlin S, Povey GJR, Cruickshank DGM, Grant PM. An FFT-based approach for fast acquisition in spread spectrum communication systems. Wireless Personal Communications. 2000; 13(1-2):27-56. http://dx.doi.org/10.1023/A:1008848916834.
Tang X, Zeng X, Tu C. A sliding DFT algorithm for electric power measurement. In: Fang J, Wang Z, editors. Proceedings of SPIE 6357, 6th International Symposium on Instrumentation and Control Technology: Signal Analysis, Measurement Theory, Photo-Electronic Technology, and Artificial Intelligence; 2006 Oct 24; Beijing, China. Beijing: SPIE; 2006. p. 1-5. http://dx.doi.org/10.1117/12.717112.
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