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Jena, Germany

Albanna W.,RWTH Aachen | Conzen C.,RWTH Aachen | Weiss M.,RWTH Aachen | Clusmann H.,RWTH Aachen | And 10 more authors.
PLoS ONE | Year: 2016

Background: Timely detection of impending delayed cerebral ischemia after subarachnoid hemorrhage (SAH) is essential to improve outcome, but poses a diagnostic challenge. Retinal vessels as an embryological part of the intracranial vasculature are easily accessible for analysis and may hold the key to a new and non-invasive monitoring technique. This investigation aims to determine the feasibility of standardized retinal vessel analysis (RVA) in the context of SAH. Methods: In a prospective pilot study, we performed RVA in six patients awake and cooperative with SAH in the acute phase (day 2-14) and eight patients at the time of follow-up (mean 4.6±1.7months after SAH), and included 33 age-matched healthy controls. Data was acquired using a manoeuvrable Dynamic Vessel Analyzer (Imedos Systems UG, Jena) for examination of retinal vessel dimension and neurovascular coupling. Results: Image quality was satisfactory in the majority of cases (93.3%). In the acute phase after SAH, retinal arteries were significantly dilated when compared to the control group (124.2±4.3MU vs 110.9±11.4MU, p<0.01), a difference that persisted to a lesser extent in the later stage of the disease (122.7±17.2MU, p<0.05). Testing for neurovascular coupling showed a trend towards impaired primary vasodilation and secondary vasoconstriction (p = 0.08, p = 0.09 resp.) initially and partial recovery at the time of follow-up, indicating a relative improvement in a time-dependent fashion. Conclusion: RVA is technically feasible in patients with SAH and can detect fluctuations in vessel diameter and autoregulation even in less severely affected patients. Preliminary data suggests potential for RVA as a new and non-invasive tool for advanced SAH monitoring, but clinical relevance and prognostic value will have to be determined in a larger cohort. © 2016 Albanna et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Doblhoff-Dier V.,Medical University of Vienna | Doblhoff-Dier V.,Vienna University of Technology | Schmetterer L.,Medical University of Vienna | Vilser W.,IMEDOS Systems UG | And 4 more authors.
Biomedical Optics Express | Year: 2014

We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray's law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood's velocity scaled linearly with the vessel diameter at higher diameters (> 60 μm), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations. © 2014 Optical Society of America.

Reimann M.,TU Dresden | Weiss N.,TU Dresden | Vilser W.,IMEDOS Systems UG | Ziemssen T.,TU Dresden
Vasa - European Journal of Vascular Medicine | Year: 2015

Background: The purpose of this study was to evaluate two alternative non-invasive techniques for assessment of endothelial function in adults with special focus on their ability to monitor acute changes. Patients and methods: Twenty-five clinically healthy men (mean age 24 ± 2 years) underwent endothelial function measurements twice in fasting state and twice after experimental induction of transient endothelial dysfunction by oral application of 0.1g/kg L-methionine and by ingestion of 500 ml whipped cream (30 % fat), respectively. Microvascular vasodilator responses to flickering-light by retinal vessel analysis and vascular responses to inhaled salbutamol by pulse wave analysis were assessed at each occasion. Ultrasound based flow-mediated dilation (FMD) was used as reference method. Results: Transient endothelial dysfunction in response to acute hyperlipidaemia and hyperhomocysteinaemia was verified by blunted brachial responses to hyperaemia. Retinal vessel analysis demonstrated significantly impaired flicker- responses of retinal vessels to both challenges depending on the vessel type. Pulse wave analysis did not show any significant changes in salbutamol responses. Reproducibility of retinal vessel analysis was comparable to FMD and slightly better than pulse wave analysis. Conclusions: Acute changes in endothelial function can be monitored by retinal vessel analysis with comparable repro-ducibility as FMD. Salbutamol based pulse wave analysis is currently unsuited to detect endothelial dysfunction in serial measurements. © 2015 Hans Huber Publishers, Hogrefe AG, Bern.

Werkmeister R.M.,Medical University of Vienna | Vietauer M.,Medical University of Vienna | Knopf C.,Medical University of Vienna | Furnsinn C.,Medical University of Vienna | And 6 more authors.
Journal of Biomedical Optics | Year: 2014

A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats. © 2014 The Authors.

Kotliar K.,TU Munich | Hanssen H.,TU Munich | Hanssen H.,University of Basel | Eberhardt K.,TU Munich | And 5 more authors.
Microcirculation | Year: 2013

Objective: Hypertension is characterized by microvascular remodeling resulting in increased wall/lumen ratio and elevated microvascular stiffness. Aiming to transform the measurement of macrovascular stiffness into a microvascular environment we introduce a noninvasive method to assess rPWV. rPWV alterations in early hypertension are investigated in detail. The developed methodology is compared with its possible computational alternatives. Methods: Time dependent alterations of retinal arterial diameter were assessed noninvasively by the DVA in 65 male normoalbuminuric normotensive to mildly hypertensive subjects (age: 28.7 ± 6.0 years). rPWV was computed using three different methods. "Method 1" used filtration at HR, "Method 2" filtered at higher HR multiples, and "Method 3" used in addition, linear fit for data averaging. Results: "Method 2" and "Method 3" applying filtration at high HR multiples showed strong associations with systolic BP throughout the cohort (r = 0.49, r = 0.63, p < 0.001). Based on the highest association, "Method 3" was proposed to characterize rPWV. Hypertensive patients showed higher rPWV (1243 ± 694 RU/sec) than subjects with high-normal BP (786 ± 486 RU/sec, p < 0.01) or normotensive subjects (442 ± 148 RU/sec, p < 0.001). Conclusions: rPWV demonstrated a strong association with BP and can discriminate between optimal, high-normal, and mildly hypertensive BP values. rPWV may add detailed insights into early microvascular pathophysiology, potentially beyond microalbuminuria. © 2013 John Wiley & Sons Ltd.

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