In vitro comparison of different signal processing algorithms used in laser Doppler flowmetry
Tóm tắt
The paper reports the results of investigations comparing the relative in vitro responses of different signal processing algorithms commonly employed in laser Doppler flowmetry (LDF). A versatile laser Doppler system is described which enabled complex signal processing to be implemented relatively simply using digital analysis. The flexibility of the system allowed a variety of processing algorithms to be studied by simply characterising the algorithm of interest under software control using a personal computer. An in vitro physical model is also presented which was used to maintain reproducible fluid flows. Flows of particles were studied in a physical model using both a near-infra-red (NIR) diode and an He/Ne laser source. The results show that frequency-weighted algorithms are responsive to both particle velocity and concentration, whereas non-weighted algorithms respond to concentration only. The linearity of the velocity response is critically dependent on both the dimensions of the in vitro model and the frequency bandwidth of the signalprocessing algorithm.
Tài liệu tham khảo
Berne, B. J. andPecora, R. (1976)Dynamic light scattering. John Wiley & Sons Inc., New York.
Boggett, D., Obeid, A. N., Blond, J. andRolfe, P. (1986) Calibration of a laser Doppler skin blood flow meter using a simple fluid model and digital signal processing. InElectronics in medicine and biology—selected papers.Copeland, K. (Ed.), IERE, London, 241–247.
Bonner, R. F., Bowen, P., Bowman, R. L. andNossal, R. (1978) Proc. Electro-Optics/Laser '78 Conf., Industrial & Scientific Conference Management Inc., Chicago,III, 539.
Bonner, R. andNossal, R. (1981) Model for laser Doppler measurements of blood flow in tissue.Appl. Optics.,20, 2097–2107.
Holloway, G. A. andWatkins, D. W. (1977) Laser Doppler measurement of cutaneous blood flow.J. Invest. Dermatol.,69, 306–309.
Holloway, G. A. (1980) Cutaneous blood flow responses to injection trauma measured by laser Doppler velocimetry. ——Ibid.,74, 1–4.
Nilsson, G. E., Tenland, T. andÖberg, P. Å. (1980a) Evaluation of a laser Doppler flowmeter for measurement of tissue blood flow.IEEE Trans.,BME-27, 597–604.
Nilsson, G. E., Tenland, T. andÖberg, P. Å. (1980b) A new instrument for continuous measurement of tissue blood flow by light beating spectroscopy. ——Ibid.,BME-27, 12–19.
Nilsson, G. E. (1984) Signal processor for laser Doppler tissue flowmeters.Med. & Biol. Eng. & Comput.,22, 343–348.
Obeid, A. N., Boggett, D., Barnett, N. J., Dougherty, G. andRolfe, P. (1988) Depth discrimination in laser Doppler skin blood flow measurement using different lasers. ——Ibid.,26, 415–419.
Obeid, A. N. (1989) The measurement of blood flow in the microcirculation using laser Doppler flowmetry. Ph.D. Thesis, CNAA, Oxford Polytechnic.
Obeid, A. N., Barnett, N. J., Dougherty, G. andWard, G. (1990a) A critical review of laser Doppler flowmetry.J. Med. Eng. & Technol.,14, 178–181.
Obeid, A. N., Dougherty, G. andPettinger, S. (1990b)In vivo comparison of a twin wavelength laser Doppler flowmeter using He−Ne and laser diode sources. ——Ibid.,,14, 102–110.
Öberg, P. Å., Tenland, T. andNilsson, G. E. (1983) Laser Doppler flowmetry—a noninvasive and continuous method for blood flow evaluation in microvascular studies.Acta Med. Scand., Suppl. 687, 17–24.
Stern, M. D., Lappe, D. L., Bowen, P. D., Chimosky, J. E., Holloway, G. A., Keiser, H. R. andBowman, R. L. (1977) Continuous measurement of tissue blood flow by laser Doppler spectroscopy.Am. J. Physiol.,232, H441-H448.
Watkins, D. andHolloway, G. A. (1978) An instrument to measure cutaneous blood flow using the Doppler shift of laser light.IEEE Trans.,BME-25, 28–33.