Technology and Health Care - Volume 7, issue 2-3

Authors: Alexopoulos, Vassilios | Kollias, Stefanos | Leger, Philippe | Boccalon, Henry | Csiki, Zoltan

Article Type: Research Article

Abstract: This paper presents an application of higher order statistics and spectra to the problem of laser-Doppler Flowmetry (LDF) for microcirculation monitoring. The proposed signal processing technique computes the bispectra of LDF signals after appropriate pre-processing and extracts features which can be used for classification of the signals to a normal or patient category. Bispectra are defined in terms of the third-order moments or cumulants of signals and are shown to contain valuable information for the above classification of LDF signals. Experimental studies, including (a) a set of 17 normal subjects and 69 patients with Raynaud’s phenomenon and (b) 50 LDF-signals …separated to four groups from patients that have different pathologic characteristics, are described and results are presented which illustrate the performance of the proposed approach when applied to the LDF signals. Show more

Keywords: Laser-Doppler flowmetry, higher-order statistics and spectra, bispectral analysis, Raynaud’s phenomenon, classification

DOI: 10.3233/THC-1999-72-301

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 85-101, 1999

Authors: Arnold, M. | Witte, H. | Leger, P. | Boccalon, H. | Bertuglia, S. | Colantuoni, A.

Article Type: Research Article

Abstract: Time-variant AR-modelling was used to analyse the non-stationary properties of LDF signals during provocation tests. The procedure for the estimation of time-varying AR parameters based on Kalman filtering is presented. The estimates can be used to calculate instantaneous measures, such as peak frequency, spectral band power and coherence. The resulting course of instantaneous peak frequency of a sinusoidal signal with frequency jump was compared to similar parameters derived from short-time FFT and Hilbert transformation. Univariate time-variant spectral analysis was used to investigate LDF measurements in patients with Raynaud’s phenomena. The experimental protocol was splitted into phases of different room …temperature. The results demonstrate time-dependent variations of spectral components (amplitude and frequency). By means of time-variant coherence analysis of LDF and diameter measurements of vessels in a hamster skin fold the existence of a main rhythm around 0.1 Hz in the LDF signals which is related to vasomotion is shown. Show more

Keywords: Laser-Doppler flowmetrie, Raynaud’s phenomenon, multivariate time-varying autoregression, Kalman filter, spectral analysis, coherence

DOI: 10.3233/THC-1999-72-302

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 103-112, 1999

Authors: Bertuglia, S. | Leger, P. | Colantuoni, A. | Coppini, G. | Bendayan, P. | Boccalon, H.

Article Type: Research Article

Abstract: Flowmotion was characterized in healthy controls and 61 Raynaud’s phenomenon (RP) patients by spectral analysis of laser-Doppler perfusion monitoring (LDPM) tracings. Healthy subjects flowmotion patterns revealed a main frequency of 3 cycles per min (cpm) with another low frequency and heart rate synchronous components. A first group of RP patients presented a low frequency and heart rate frequency component but no significant difference in blood flow. The second group presented the predominating heart rate related frequency with low microvascular perfusion. The third group presented a flowmotion pattern with overlapping of heart rate and low frequency components. Patients with primary …and secondary RP show specific changes in flowmotion, probably related to increased sympathetic nervous activity or vessel wall alterations causing disappearance of arteriolar tone and impairment of microvascular perfusion. The group of patients with overlapping frequency components presents an intermediate flowmotion pattern indicating a different grade of alterations in microvasculature. Show more

Keywords: Flowmotion patterns, Raynaud’s phenomenon, laser-Doppler technique, spectral analysis, vasodilation

DOI: 10.3233/THC-1999-72-303

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 113-123, 1999

Authors: Greitans, M. | Mikelsons, A. | Möller, K.O.

Article Type: Research Article

Abstract: Non-invasive measuring of blood perfusion of tissue is important for establishing the influence of vascular diseases on microcirculation. A signal processing method for laser-Doppler flowmetry is presented in this article. The method is based on the digital filtering. A couple of filters are suggested. One of them is a digital passband filter, second – a digital filter transforming spectrum P(f) of the input signal to fP(f) spectrum. Performance of the suggested method is investigated in comparison with behaviour of the PERIMED instrument as well as with applications based on DFT.

Keywords: Blood perfusion, microcirculation, laser-Doppler flowmetry, spectral estimation, digital signal filtering

DOI: 10.3233/THC-1999-72-304

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 125-135, 1999

Authors: Krajča, Vladímir | Principe, Jose C. | Petránek, Svojmil

Article Type: Research Article

Abstract: This contribution gives the information on a useful application of principal component analysis (PCA) in the field of electroencephalogram (EEG) and laser-Doppler signal processing. The principal components are estimated by a neural network (NN) approach.

Keywords: Biosignal, principal components, neural nets

DOI: 10.3233/THC-1999-72-305

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 137-141, 1999

Authors: Leahy, M.J. | de Mul, F.F.M. | Nilsson, G.E. | Maniewski, R.

Article Type: Research Article

Abstract: This paper reviews the development and use of laser-Doppler perfusion monitors and imagers over the past two decades. The enormous interest in microvascular blood perfusion coupled with the ‘ease of use’ of the technique has led to 1500+ publications citing its use. However, useful results can only be achieved with an understanding of the basic principles of the instrumentation and its application in the various clinical disciplines. The basic theoretical background is explored and definitions of blood perfusion and laser-Doppler perfusion are established. The calibration method is then described together with potential routes to standardisation. A guide to the limitations …in application of the technique gives the user a clear indication of what can be achieved in new studies as well as possible inadequacy in some published investigations. Show more

Keywords: Blood supply, laser-Doppler flowmetry, microcirculation, Doppler shift, biomedical instrumentation

DOI: 10.3233/THC-1999-72-306

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 143-162, 1999

Authors: Maniewski, R. | Leger, P. | Lewandowski, P. | Liebert, A. | Bendayan, P. | Boccalon, H. | Bajorski, L. | Möller, K.O.

Article Type: Research Article

Abstract: The method of spectral analysis of laser-Doppler perfusion signal measured during thermal test is proposed. During three 20 min phases with 40, 5, and 40°C of thermal test laser-Doppler perfusion signal was recorded. For each signal phase frequency spectra were calculated using the FFT method. Quantitative parameter Spectral Factor for results evaluation was proposed. In total 94 patients were measured: 69 with Raynaud’s phenomenon and 25 normal subjects. Additionaly in 18 Raynaud’s patients the influence of Nifedipine was studied. Results suggest that proposed parameter is able to differentiate between Raynaud’s patients and normal subjects and that is useful for evaluation …of Nifedipine effectivenes. However, further studies are needed to improve the method to differentiate between primary and secondary Raynaud’s patients. Show more

Keywords: Microperfusion, Raynaud’s phenomenon, laser-Doppler, spectral analysis

DOI: 10.3233/THC-1999-72-307

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 163-169, 1999

Authors: de Mul, F.F.M. | Steenbergen, W. | Greve, J.

Article Type: Research Article

Abstract: Doppler Monte Carlo (DMC) simulations of the transport of light through turbid media, e.g., tissue, can be used to predict or to interpret measurements of the blood perfusion of tissue by laser-Doppler perfusion flowmetry. We describe the physical and mathematical background of Doppler Monte Carlo calculations, and present some comparisons with measurements, performed with experimental flow models, built to mimic skin tissue characteristics and for the calibration of perfusion instruments, which are important goals of the Biomed-I concerted action. The measurements deal with coherence effects.

Keywords: Microcirculation, laser-Doppler, flowmetry, blood, perfusion, Monte Carlo, simulations, tissue

DOI: 10.3233/THC-1999-72-308

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 171-183, 1999

Authors: Öberg, P.Å.

Article Type: Research Article

Abstract: The tissue matrix in the human body is continuously in motion driven by forces generated by the circulatory and respiratory systems. The linear velocities recorded can be as high as 300 μm/s. The question raised: is the motion of tissue matrix generating an error signal in laser-Doppler (LD) recordings that is misinterpreted as solely a blood flow signal. The problem is studied by using a physical model demonstrating the contribution from a flow channel and, in addition, from a linear motion of the flow tube. Measurements of skin motion in the forearm have been performed. The corresponding spectra have been …compared with blood flow spectra recorded with the LD method at the same sites. The two types of spectra overlap each other indicating that motion induced signals can be interpreted as a flow signal. The “blood flow” contribution from tissue motion varies strongly with the site studied. Show more

Keywords: Laser-Doppler, tissue motion, disturbance, blood flow signal, velocity spectrum, Doppler spectrum

DOI: 10.3233/THC-1999-72-309

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 185-192, 1999

Authors: Popivanov, D. | Mineva, A. | Bendayan, P. | Leger, P. | Boccalon, H. | Moller, K.O.

Article Type: Research Article

Abstract: The study was aimed at choosing an appropriate characteristic of laser-Doppler flux (LDF) data for (1) distinguishing patients with Raynaud’s disease from normal controls and (2) evaluating the effect of nifedipine under different thermal conditions. We checked the reliability of three characteristics of nonlinear dynamics as statistical dimension D s , correlation dimension D 2 and power-law index PLI. Their values depended heavily on the thermal condition. The most reliable characteristics that enabled us to distinguish the patients from normal controls and the effect of nifedipine under definite thermal …condition proved to be D s and PLI. The latter is simple for computation and is thus recommendable for clinical practice. D s and PLI were higher in patients with Raynaud’s compared to normal controls and diminished during the transitions from low to high temperature. However, the characteristics used were unable to distinguish significantly Raynaud’s I from Raynaud’s II patients. Show more

Keywords: Laser-Doppler, microcirculation, Raynaud’s disease, nifedipine

DOI: 10.3233/THC-1999-72-310

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 193-203, 1999

Authors: Popivanov, D. | Mineva, A. | Dushanova, J.

Article Type: Research Article

Abstract: Methods for tracking the dynamics of the blood flow microcirculation obtained by laser-Doppler flowmetry (LDF) technique are described. It was shown that LDF signals have complex dynamics. It was mainly characterized by fractal structures and chaos, though multiperiodic, trend-like and stochastic components were also established. Procedures for (i) describing the dynamic structure and (ii) tracking the dynamic changes in time of LDF data are proposed. Examples illustrating the efficiency of these procedures are given using both simulated and LDF data collected in experiments with reactive hyperemia. Irrespective of the universality of the methods, the procedures should be specified according to …the problem-oriented clinical and experimental studies. Show more

Keywords: Blood flow, laser-Doppler flux, nonlinear dynamics, chaos, fractal, hyperemia

DOI: 10.3233/THC-1999-72-311

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 205-218, 1999

Authors: Söderström, Torbjörn | Svensson, Henry | Koop, Thoralf | Möller, Karl O.

Article Type: Research Article

Abstract: As conventional graphical laser-Doppler flowmetric (LDF) registrations from free flaps are difficult to interpret we explored the use of refined computerized signal processing to enhance the reliability of the blood flow supervision postoperatively. From eleven free flaps LDF data were collected using a software programme and a personal computer for analysis. Findings were compared with the clinical outcome. Nine flaps healed whereas one had wound problems and one suffered a partial necrosis. From the nine uneventful flaps, a peak within the range of frequencies from 0.04 to 0.23 Hz was seen. In the remaining two, such a low frequency peak …could hardly be observed. Frequency analysis using computerized processing of LDF signals thus has the capacity to demonstrate the status of the flap perfusion. The slow wave vasomotion component seems to be of particular importance. Other frequency components warrant further investigation. A custom made monitoring device would be of great clinical value. Show more

Keywords: Free flap, microsurgery, monitoring, blood flow, vasomotion, frequency analysis

DOI: 10.3233/THC-1999-72-312

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 219-223, 1999

Authors: Stefanovska, Aneta | Leger, Philippe | Bračič, Maja | Bračič, Toni | Bendayan, Pierre | Boccalon, Henri

Article Type: Research Article

Abstract: The paper presents analyses of the dynamics contained in the blood flow signals measured on healthy subjects and on subjects with primary Raynaud’s phenomenon. Different signal processing methods are presented and discussed. The dynamics was evaluated in the time and frequency domains and in phase space. Additionally, changes in the basal value during temperature provocation were studied using multiresolution analysis. The analyses demonstrate differences between the blood flow dynamics in healthy subjects and subjects with Raynaud’s phenomenon. Moreover, the observed decrease in the amplitude of oscillation in regions ≈ 0.04 Hz and ≈ 0.1 …Hz suggests an impairment in the neurogenic and the myogenic regulation of the blood flow. The administration of nifedipine in subjects with Raynaud’s phenomenon results in an increase in the basal value and in the amplitude of the blood flow component oscillating with the heart rate. However, it does not restore the dynamics to that found in healthy subjects. Show more

Keywords: Mathematics – algorithms (H1.548.35), nonlinear dynamics (H1.548.675), blood circulation (G9.330.163), hemodynamics (G9.330.612.+), Raynaud’s disease (C14.907.744.+), nifedipine (D3.383.725.203.540)

DOI: 10.3233/THC-1999-72-313

Citation: Technology and Health Care, vol. 7, no. 2-3, pp. 225-241, 1999