Wavelet entropy of Doppler ultrasound blood velocity flow waveforms distinguishes nitric oxide-modulated states.
Wavelet entropy assesses the degree of order or disorder in signals and presents this complex information in a simple metric. Relative wavelet entropy assesses the similarity between the spectral distributions of two signals, again in a simple metric. Wavelet entropy is therefore potentially a very attractive tool for waveform analysis. The ability of this method to track the effects of pharmacologic modulation of vascular function on Doppler blood velocity waveforms was assessed. Waveforms were captured from ophthalmic arteries of 10 healthy subjects at baseline, after the administration of glyceryl trinitrate (GTN) and after two doses of N(G)-nitro-L-arginine-methyl ester (L-NAME) to produce vasodilation and vasoconstriction, respectively. Wavelet entropy had a tendency to decrease from baseline in response to GTN, but significantly increased after the administration of L-NAME (mean: 1.60 ± 0.07 after 0.25 mg/kg and 1.72 ± 0.13 after 0.5 mg/kg vs. 1.50 ± 0.10 at baseline, p < 0.05). Relative wavelet entropy had a spectral distribution from increasing doses of L-NAME comparable to baseline, 0.07 ± 0.04 and 0.08 ± 0.03, respectively, whereas GTN had the most dissimilar spectral distribution compared with baseline (0.17 ± 0.08, p = 0.002). Wavelet entropy can detect subtle changes in Doppler blood velocity waveform structure in response to nitric-oxide-mediated changes in arteriolar smooth muscle tone.
Northern Ireland Regional Medical Physics Agency, Royal Group of Hospitals, Belfast, Northern Ireland.
Christina E
CE
Agnew
Centre for Experimental Medicine, Queens University Belfast, School of Medicine, Dentistry and Biomedical Sciences Institute of Clinical Science-Block A, Royal Group of Hospitals, Belfast, Northern Ireland. Electronic address: pk_hamilton@yahoo.co.uk.
Paul K
PK
Hamilton
Northern Ireland Regional Medical Physics Agency, Royal Group of Hospitals, Belfast, Northern Ireland.
Aaron J
AJ
McCann
Northern Ireland Regional Medical Physics Agency, Royal Group of Hospitals, Belfast, Northern Ireland.
R Canice
RC
McGivern
Centre for Experimental Medicine, Queens University Belfast, School of Medicine, Dentistry and Biomedical Sciences Institute of Clinical Science-Block A, Royal Group of Hospitals, Belfast, Northern Ireland.
Gary E
GE
McVeigh
D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D005996:Nitroglycerin / Q000494:pharmacology; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018608:Ultrasonography, Doppler / Q000379:methods*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology; D058067:Wavelet Analysis; D055815:Young Adult
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide; D005996:Nitroglycerin; D019331:NG-Nitroarginine Methyl Ester
Doppler; Entropy; Nitric oxide; Resistive index; Vasoconstriction; Vasodilation; Wavelet transform