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Human cortical perfusion and the arterial pulse: a near-infrared spectroscopy study.

Kwan HC, Cheng A, Liu R, Borrett DS - BMC Physiol. (2004)

Bottom Line: The arterial pulse pattern was extracted from the left middle finger by means of plethesmographic techniques.Cross-correlation analysis was performed to provide evidence for a causal relation between the arterial pulse and relative changes in cortical total hemoglobin.In addition, the determination of the statistical significance of this relation was established by the use of phase-randomized surrogates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology Medical Sciences Building, Room 3232, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8 Canada. h.kwan@utoronto.ca

ABSTRACT

Background: The pulsatile nature of the arterial pulse induces a pulsatile perfusion pattern which can be observed in human cerebral cortex with non-invasive near-infrared spectroscopy. The present study attempts to establish a quantitative relation between these two events, even in situations of very weak signal-to-noise ratio in the cortical perfusion signal. The arterial pulse pattern was extracted from the left middle finger by means of plethesmographic techniques. Changes in cortical perfusion were detected with a continuous-wave reflectance spectrophotometer on the scalp overlying the left prefrontal cortex. Cross-correlation analysis was performed to provide evidence for a causal relation between the arterial pulse and relative changes in cortical total hemoglobin. In addition, the determination of the statistical significance of this relation was established by the use of phase-randomized surrogates.

Results: The results showed statistically significant cross correlation between the arterial and perfusion signals.

Conclusions: The approach designed in the present study can be utilized for a quantitative and continuous assessment of the perfusion states of the cerebral cortex in experimental and clinical settings even in situations of extremely low signal-to-noise ratio.

Show MeSH
Cross correlation function of the perfusion signal with reference to the arterial pulse (green trace) superimposed on a background (yellow) of 16 surrogate cross correlation functions computed from phase-randomization. The upper and lower red dash lines demarcate the boundaries of ± 3 standard deviations of the surrogates.
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Figure 4: Cross correlation function of the perfusion signal with reference to the arterial pulse (green trace) superimposed on a background (yellow) of 16 surrogate cross correlation functions computed from phase-randomization. The upper and lower red dash lines demarcate the boundaries of ± 3 standard deviations of the surrogates.

Mentions: Cross-correlation analysis, however, demonstrated a clear linear dependence of the total hemoglobin perfusion signal on the arterial pulse (Figure 4). The cross-correlation function (green trace) is superimposed on a background (yellow) of cross-correlation functions computed from phase-randomized surrogates. Highly significant correlation peaks exceeding the boundaries of ± 3 standard deviations can be seen around zero delay, suggesting a causal relationship between the two signals. Significant cross-correlations were observed in 6 of the 7 subjects. The lack of significant correlation in the one subject might have been due to excessive artifacts in the prefrontal optical signal. This abnormally low signal-to-noise ratio might have contributed to the failure of detection of significant correlation.


Human cortical perfusion and the arterial pulse: a near-infrared spectroscopy study.

Kwan HC, Cheng A, Liu R, Borrett DS - BMC Physiol. (2004)

Cross correlation function of the perfusion signal with reference to the arterial pulse (green trace) superimposed on a background (yellow) of 16 surrogate cross correlation functions computed from phase-randomization. The upper and lower red dash lines demarcate the boundaries of ± 3 standard deviations of the surrogates.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC411046&req=5

Figure 4: Cross correlation function of the perfusion signal with reference to the arterial pulse (green trace) superimposed on a background (yellow) of 16 surrogate cross correlation functions computed from phase-randomization. The upper and lower red dash lines demarcate the boundaries of ± 3 standard deviations of the surrogates.
Mentions: Cross-correlation analysis, however, demonstrated a clear linear dependence of the total hemoglobin perfusion signal on the arterial pulse (Figure 4). The cross-correlation function (green trace) is superimposed on a background (yellow) of cross-correlation functions computed from phase-randomized surrogates. Highly significant correlation peaks exceeding the boundaries of ± 3 standard deviations can be seen around zero delay, suggesting a causal relationship between the two signals. Significant cross-correlations were observed in 6 of the 7 subjects. The lack of significant correlation in the one subject might have been due to excessive artifacts in the prefrontal optical signal. This abnormally low signal-to-noise ratio might have contributed to the failure of detection of significant correlation.

Bottom Line: The arterial pulse pattern was extracted from the left middle finger by means of plethesmographic techniques.Cross-correlation analysis was performed to provide evidence for a causal relation between the arterial pulse and relative changes in cortical total hemoglobin.In addition, the determination of the statistical significance of this relation was established by the use of phase-randomized surrogates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology Medical Sciences Building, Room 3232, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8 Canada. h.kwan@utoronto.ca

ABSTRACT

Background: The pulsatile nature of the arterial pulse induces a pulsatile perfusion pattern which can be observed in human cerebral cortex with non-invasive near-infrared spectroscopy. The present study attempts to establish a quantitative relation between these two events, even in situations of very weak signal-to-noise ratio in the cortical perfusion signal. The arterial pulse pattern was extracted from the left middle finger by means of plethesmographic techniques. Changes in cortical perfusion were detected with a continuous-wave reflectance spectrophotometer on the scalp overlying the left prefrontal cortex. Cross-correlation analysis was performed to provide evidence for a causal relation between the arterial pulse and relative changes in cortical total hemoglobin. In addition, the determination of the statistical significance of this relation was established by the use of phase-randomized surrogates.

Results: The results showed statistically significant cross correlation between the arterial and perfusion signals.

Conclusions: The approach designed in the present study can be utilized for a quantitative and continuous assessment of the perfusion states of the cerebral cortex in experimental and clinical settings even in situations of extremely low signal-to-noise ratio.

Show MeSH