Document Detail


Fractal dimensions of laser doppler flowmetry time series.
MedLine Citation:
PMID:  11891142     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Laser Doppler flowmetry (LDF) provides a non-invasive method of assessing cutaneous perfusion. As the microvasculature under the probe is not defined the measured flux cannot be given absolute units, but the technique has nevertheless proved valuable for assessing relative changes in perfusion in response to physiological stress. LDF signals normally show pronounced temporal variability, both as a consequence of the pulsatile nature of blood flow and local changes in dynamic vasomotor activity. The aim of the present study was to investigate the use of methods of nonlinear analysis in characterizing temporal fluctuations in LDF signals. Data were collected under standardised conditions from the forearm of 16 normal subjects at rest, during exercise and on recovery. Surrogate data was then generated from the original time series by phase randomization. Dispersional analysis demonstrated that the LDF data was fractal with two distinct scaling regions, thus allowing the calculation of a fractal dimension which decreased significantly from 1.23 +/- 0.09 to 1.04 +/- 0.02 during exercise. By contrast, dispersional analysis of the surrogate data showed no scaling region.
Authors:
G Carolan-Rees; A C Tweddel; K K Naka; T M Griffith
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical engineering & physics     Volume:  24     ISSN:  1350-4533     ISO Abbreviation:  Med Eng Phys     Publication Date:  2002 Jan 
Date Detail:
Created Date:  2002-03-13     Completed Date:  2002-07-09     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9422753     Medline TA:  Med Eng Phys     Country:  England    
Other Details:
Languages:  eng     Pagination:  71-6     Citation Subset:  IM    
Affiliation:
Department of Medical Physics, University Hospital of Wales, Heath Park, Cardiff CF14 4XW, UK. carolan-rees@cf.ac.uk
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MeSH Terms
Descriptor/Qualifier:
Adolescent
Adult
Blood Flow Velocity
Exercise
Fractals*
Humans
Laser-Doppler Flowmetry / methods*
Male
Middle Aged
Time Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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