A note on fractal dimensions of biomedical waveforms.

Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560 012, India.
Computers in biology and medicine (Impact Factor: 1.27). 09/2009; 39(11):1006-12. DOI: 10.1016/j.compbiomed.2009.08.001
Source: PubMed

ABSTRACT In this paper, we study performance of Katz method of computing fractal dimension of waveforms, and its estimation accuracy is compared with Higuchi's method. The study is performed on four synthetic parametric fractal waveforms for which true fractal dimensions can be calculated, and real sleep electroencephalogram. The dependence of Katz's fractal dimension on amplitude, frequency and sampling frequency of waveforms is noted. Even though the Higuchi's method has given more accurate estimation of fractal dimensions, the study suggests that the results of Katz's based fractal dimension analysis of biomedical waveforms have to be carefully interpreted.

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the in vitro antimicrobial and antiviral activities of the lysozyme from marine strain S-12-86 (LS) were investigated. The antimicrobial activity of LS was tested by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) method. The inhibiting effects of LS on pseudo rabies virus (PRV) in swine kidney cells (PK-15 cells) were judged by cytopathogenic effect test (CPE). The results showed LS had a broad antimicrobial spectrum against several standard strains including gram-positive bacteria, gram-negative bacteria, fungi, etc. The MIC of LS was 0.25–4.00 mg mL−1 and its MBC was 0.25–8.00 mg mL−1, respectively. Observation under the transmission electron microscope revealed that the cell wall of Candida albicans was distorted seriously, and the cytoplasm with many cavities was asymmetrical after being hydrolyzed by LS. The median cytotoxicity concentration (TC50) of LS was 100.0 μg mL−1, the median effective concentration (EC50) was 0.46 μg mL−1, and the selectivity index (TI = TC50/EC50) was 217. LS could inhibit PRV in PK-15 cells when it was added to cell culture medium at 0, 2, 4, 6, and 8 h after PK-15 cells had been infected by PRV. From the results, we concluded that LS had broad antimicrobial spectrum and good inhibiting effects on PRV.
    Agricultural Sciences in China. 01/2008;
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, an adaptive electroencephalogram (EEG) analysis system is proposed for a two-session, single-trial classification of motor imagery (MI) data. Applying event-related brain potential (ERP) data acquired from the sensorimotor cortices, the adaptive linear discriminant analysis (LDA) is used for classification of left- and right-hand MI data and for simultaneous and continuous update of its parameters. In addition to the original use of continuous wavelet transform (CWT) and Student's two-sample t-statistics, the 2D anisotropic Gaussian filter is proposed to further refine the selection of active segments. The multiresolution fractal features are then extracted from wavelet data by means of modified fractal dimension. The classification in session 2 is performed by adaptive LDA, which is trial-by-trial updated using the Kalman filter after the trial is classified. Compared with original active segment selection and non-adaptive LDA on six subjects from two data sets, the results indicate that the proposed method is helpful to realize adaptive BCI systems.
    Computers in biology and medicine 06/2011; 41(8):633-9. · 1.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Deep Brain Stimulation (DBS) is a treatment routinely used to alleviate the symptoms of Parkinson's disease (PD). In this type of treatment, electrical pulses are applied through electrodes implanted into the basal ganglia of the patient. As the symptoms are not permanent in most patients, it is desirable to develop an on-demand stimulator, applying pulses only when onset of the symptoms is detected. This study evaluates a feature set created for the detection of tremor - a cardinal symptom of PD. The designed feature set was based on standard signal features and researched properties of the electrical signals recorded from subthalamic nucleus (STN) within the basal ganglia, which together included temporal, spectral, statistical, autocorrelation and fractal properties. The most characterized tremor related features were selected using statistical testing and backward algorithms then used for classification on unseen patient signals. The spectral features were among the most efficient at detecting tremor, notably spectral bands 3.5-5.5 Hz and 0-1 Hz proved to be highly significant. The classification results for determination of tremor achieved 94% sensitivity with specificity equaling one.