Médiathèque Valais

Lawinen über Leukerbad : Historiographie und Quellenkritik

Weber, Bruno

In: Blätter aus der Walliser Geschichte, 2010, no. 42, p. 23-64

Université de Fribourg

Laser speckle analysis synchronised with cardiac cycle

Zakharov, Pavel ; Scheffold, Frank ; Weber, Bruno

In: Proceedings SPIE, 2015, vol. 9540, p. 954008–954008–9

We present an improved Laser speckle imaging approach to investigate the cerebral blood flow response following function stimulation of a single vibrissa. By synchronising speckle analysis with the cardiac cycle we are able to obtain robust averaging of the correlation signals while at the same time removing the contributions due to the pulsation of blood flow and associated tissue adaptation....

Université de Fribourg

Laser Speckle Imaging of Cerebral Blood Flow

Zakharov, Pavel ; Scheffold, Frank ; Weber, Bruno

In: Optical Imaging of Neocortical Dynamics, 2014, vol. 85, p. 255–271

Optical imaging of cerebral hemodynamics has been used extensively to investigate the complex interplay between neurons and the blood-borne supply of oxygen and energy substrates. Among several techniques, the so-called laser speckle imaging (LSI) has found widespread applications for studying (patho-)physiological aspects of neurovascular coupling. LSI is a rather simple and cost-effective...

Université de Fribourg

Noise in laser speckle correlation and imaging techniques

Skipetrov, S. E. ; Peuser, Joern ; Cerbino, Roberto ; Zakharov, Pavel ; Weber, Bruno ; Scheffold, Frank

In: Optics Express, 2010, vol. 18, no. 14, p. 14519-14534

We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent...

Université de Fribourg

Dynamic laser speckle imaging of cerebral blood flow

Zakharov, Pavel ; Völker, A. C. ; Wyss, M. T. ; Haiss, F. ; Calcinaghi, N. ; Zunzunegui, C. ; Buck, Alfred ; Scheffold, Frank ; Weber, Bruno

In: Optics Express, 2009, vol. 17, no. 16, p. 13904-13917

Laser speckle imaging (LSI) based on the speckle contrast analysis is a simple and robust technique for imaging of heterogeneous dynamics. LSI finds frequent application for dynamical mapping of cerebral blood flow, as it features high spatial and temporal resolution. However, the quantitative interpretation of the acquired data is not straightforward for the common case of a speckle field formed...

Université de Fribourg

Quantitative modeling of laser speckle imaging

Zakharov, Pavel ; Völker, Andreas ; Buck, Alfred ; Weber, Bruno ; Scheffold, Frank

In: Optics Letters, 2006, vol. 31, no. 23, p. 3465-3467

We have analyzed the image formation and dynamic properties in laser speckle imaging (LSI) both experimentally and with Monte Carlo simulation. We show for the case of a liquid inclusion that the spatial resolution and the signal itself are both significantly affected by scattering from the turbid environment. Multiple scattering leads to blurring of the dynamic inhomogeneity as detected by...