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Variability and repeatability of quantitative, Fourier-domain optical coherence tomography Doppler blood flow in young and elderly healthy subjects

Tayyari F, Yusof F, Vymyslicky M, Tan O, Huang D, Flanagan JG, et al.

Invest Ophthalmol Vis Sci, 2014 Dec;55(12):7716-25.
PMID: 25335983 DOI: 10.1167/iovs.14-14430

The purpose of this study was to determine the within-session variability and between-session repeatability of spectral Fourier-domain optical coherence tomography (Doppler FD-OCT) Doppler retinal blood flow measurements in young and elderly subjects.

Matched MeSH terms: Laser-Doppler Flowmetry/methods*
Reproducibility of laser Doppler fluximetry and the process of iontophoresis in assessing microvascular endothelial function using low current strength

Al-Tahami BA, Yvonne-Tee GB, Halim AS, Ismail AA, Rasool AH

Methods Find Exp Clin Pharmacol, 2010 Apr;32(3):181-5.
PMID: 20448860 DOI: 10.1358/mf.2010.32.3.1423887

Iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) combined with laser Doppler fluximetry (LDF) is a tool used to determine microvascular endothelial function. Our aim was to study the reproducibility of different parameters of this technique using iontophoresis with low current strength on the forearm skin of healthy subjects. Baseline skin perfusion was done before application of five current pulses with 1 min of current-free interval. Current strength of 0.007 mA, current density of 0.01 mA/cm(2) and charge density of 6 mC/cm(2) were used, along with 1% ACh and 1% SNP. The absolute maximum change in perfusion (max), percent change in perfusion (% change), peak change in perfusion (peak) and area under the curve during iontophoresis (AUC) at the anodal and cathodal leads were recorded. Measurements were performed in three sessions for 2 days. The coefficient of variation (CV) was calculated for each parameter. Among the parameters studied, maximum change in perfusion and peak flux were the most reproducible parameters.

Matched MeSH terms: Laser-Doppler Flowmetry/methods*
Objective assessment of psoriasis erythema for PASI scoring

Ahmad Fadzil MH, Ihtatho D, Mohd Affandi A, Hussein SH

J Med Eng Technol, 2009;33(7):516-24.
PMID: 19639508 DOI: 10.1080/07434610902744074

Skin colour is vital information in dermatological diagnosis as it reflects the pathological condition beneath the skin. It is commonly used to indicate the extent of diseases such as psoriasis, which is indicated by the appearance of red plaques. Although there is no cure for psoriasis, there are many treatment modalities to help control the disease. To evaluate treatment efficacy, the current gold standard method, PASI (Psoriasis Area and Severity Index), is used to determine severity of psoriasis lesion. Erythema (redness) is one parameter in PASI and this condition is assessed visually, thus leading to subjective and inconsistent results. Current methods or instruments that assess erythema have limitations, such as being able to measure erythema well for low pigmented skin (fair skin) but not for highly pigmented skin (dark skin) or vice versa. In this work, we proposed an objective assessment of psoriasis erythema for PASI scoring for different (low to highly pigmented) skin types. The colour of psoriasis lesions are initially obtained by using a chromameter giving the values L*, a*, and b* of CIELAB colour space. The L* value is used to classify skin into three categories: low, medium and highly pigmented skin. The lightness difference (DeltaL*), hue difference (Deltah(ab)), chroma (DeltaC*(ab)) between lesions and the surrounding normal skin are calculated and analysed. It is found that the erythema score of a lesion can be distinguished by their Deltah(ab) value within a particular skin type group. References of lesion with different scores are obtained from the selected lesions by two dermatologists. Results based on 38 lesions from 22 patients with various level of skin pigmentation show that PASI erythema score for different skin types i.e. low (fair skin) to highly pigmented (dark skin) skin types can be determined objectively and consistent with dermatology scoring.

Matched MeSH terms: Laser-Doppler Flowmetry/methods
Fulltext Effects of water drinking test on ocular blood flow waveform parameters: A laser speckle flowgraphy study

Bhatti MS, Tang TB, Laude A

PLoS One, 2017;12(7):e0181512.
PMID: 28742142 DOI: 10.1371/journal.pone.0181512

The water-drinking test (WDT) is a provocative test used in glaucoma research to assess the effects of elevated intraocular pressure (IOP). Defective autoregulation due to changes in perfusion pressure may play a role in the pathophysiology of several ocular diseases. This study aims to examine the effects of WDT on ocular blood flow (in the form of pulse waveform parameters obtained using laser speckle flowgraphy) to gain insight into the physiology of ocular blood flow and its autoregulation in healthy individuals. Changes in pulse waveform parameters of mean blur rate (MBR) in the entire optic nerve head (ONH), the vasculature of the ONH, the tissue area of the ONH, and the avascular tissue area located outside of the ONH were monitored over time. Significant increases in the falling rate of MBR over the entire ONH and its tissue area and decreases in blowout time (BOT) of the tissue area were observed only at 10 minutes after water intake. Significant increases in the skew of the waveform and the falling rate were observed in the vasculature of the ONH at 40 and 50 minutes after water intake, respectively. In the avascular region of the choroid, the average MBR increased significantly up to 30 minutes after water intake. Furthermore, the rising rate in this region increased significantly at 20 and 40 minutes, and the falling rate and acceleration-time index were both significantly increased at 40 minutes after water intake. Our results indicate the presence of effective autoregulation of blood flow at the ONH after WDT. However, in the choroidal region, outside of the ONH, effective autoregulation was not observed until 30 minutes after water intake in healthy study participants. These pulse waveform parameters could potentially be used in the diagnosis and/or monitoring of patients with glaucoma.

Matched MeSH terms: Laser-Doppler Flowmetry/methods*
Reproducibility of different laser Doppler fluximetry parameters of postocclusive reactive hyperemia in human forearm skin

Yvonne-Tee GB, Rasool AH, Halim AS, Rahman AR

J Pharmacol Toxicol Methods, 2005 Sep-Oct;52(2):286-92.
PMID: 16125628

Postocclusive reactive hyperemia in forearm skin is a commonly used model for studying microvascular reactivity function, particularly in the assessment of vascular effect of topically applied pharmacological substances. In this study, we investigated the reproducibility of several different laser-Doppler-derived parameters in the measurement of postocclusive reactive hyperemia at forearm skin in healthy subjects.

Matched MeSH terms: Laser-Doppler Flowmetry/methods*
Pulse waveform analysis on temporal changes in ocular blood flow due to caffeine intake: a comparative study between habitual and non-habitual groups

Ismail A, Bhatti MS, Faye I, Lu CK, Laude A, Tang TB

Graefes Arch Clin Exp Ophthalmol, 2018 Sep;256(9):1711-1721.
PMID: 29876732 DOI: 10.1007/s00417-018-4030-9

PURPOSE: To evaluate and compare the temporal changes in pulse waveform parameters of ocular blood flow (OBF) between non-habitual and habitual groups due to caffeine intake.
METHOD: This study was conducted on 19 healthy subjects (non-habitual 8; habitual 11), non-smoking and between 21 and 30 years of age. Using laser speckle flowgraphy (LSFG), three areas of optical nerve head were analyzed which are vessel, tissue, and overall, each with ten pulse waveform parameters, namely mean blur rate (MBR), fluctuation, skew, blowout score (BOS), blowout time (BOT), rising rate, falling rate, flow acceleration index (FAI), acceleration time index (ATI), and resistive index (RI). Two-way mixed ANOVA was used to determine the difference between every two groups where p

Matched MeSH terms: Laser-Doppler Flowmetry/methods
Assessment of macrovascular endothelial function using pulse wave analysis and its association with microvascular reactivity in healthy subjects

Ibrahim NNIN, Rasool AHG

Skin Res Technol, 2017 Aug;23(3):321-325.
PMID: 27868242 DOI: 10.1111/srt.12338

BACKGROUND: Pulse wave analysis (PWA) and laser Doppler fluximetry (LDF) are non-invasive methods of assessing macrovascular endothelial function and microvascular reactivity respectively. The aim of this study was to assess the correlation between macrovascular endothelial function assessed by PWA and microvascular reactivity assessed by LDF.
METHOD: 297 healthy and non-smoking subjects (159 females, mean age (±SD) 23.56 ± 4.54 years) underwent microvascular reactivity assessment using LDF followed by macrovascular endothelial function assessments using PWA.
RESULTS: Pearson's correlation showed no correlation between macrovascular endothelial function and microvascular reactivity (r = -0.10, P = 0.12).
CONCLUSION: There was no significant correlation between macrovascular endothelial function assessed by PWA and microvascular reactivity assessed by LDF in healthy subjects.

Matched MeSH terms: Laser-Doppler Flowmetry/methods