Evaluation of blood flow at ocular fundus by using laser speckle

Abstract

We report a method for noninvasively evaluating blood flow at the ocular fundus by using laser speckle phenomena. The intensity fluctuation of speckles scattered from a 1-mm-diameter illuminated area at the fundus is detected and analyzed by the photon-correlation technique, which gives us the relative degree of total blood flows within the probe area. The method is used to evaluate blood flows at the ocular fundus of a rabbit and normal human volunteers. The experimental results show that the present laser speckle method is useful for the relative evaluation of blood flows in the ocular fundus tissue.

High resolution imaged laser speckle strain gauge for vascular applications

“…Located on the smooth surface are two point scatterers, s distance apart and centered about . The light scattered by these two points is observed normally in a plane located at some distance L. From wave optics, we know that the light scattered from each point will interfere in the observation plane and result in an intensity ͑fringe͒ pattern, I(x), given by I͑x ͒ϰ2ϩ2 cos͑kϫoptical path difference͒, (8) where k is the wave number. From Figure 10, the path difference for the two scatterers is ͉͑r 1 ϩr 1 Ј͉͒Ϫ͉͑r 2 ϩr 2 Ј͉͒ϭ͉͑r 2 Ϫr 1 ͉͒Ϫ͉͑r 2 Јϩr 1 Ј͉͒.…”

“…1,2 In biomedical applications, its use has not been as extensive, yet several authors have reported on the use of laser speckle for evaluating strains in biological hard tissues, [3][4][5] for imaging variations in local mechanical properties in soft tissue that is being modulated at acoustic frequencies, 6 and for tissue structure monitoring, 7 among other applications, mostly those that involve blood flow. 8 Most of the speckle-based strain measurements in hard biological tissues such as bone have relied upon classical interferometric techniques, such as electronic speckle pattern interferometry ͑ESPI͒, 3 speckle photography, 4 and speckle interferometry. 5 Speckle interferometric methods have not been entirely successful in the quantitative investigation of strain patterns in soft tissue.…”

Simultaneous imaging of blood flow and hemoglobin concentration change in skin tissue using NIR speckle patterns

“…Dunn et al 6 also studied cerebral blood-flow imaging using speckles. After that, various studies on speckle blood-flow imaging have been reported including blood flow in skin tissue and retina by Fujii et al [7][8][9][10][11] , Fercher et al 12 , Briers et al 13 , and Aizu et al [14][15][16][17][18] . Other studies have been also presented on performance improvement and animal experiments [19][20][21][22][23] .…”

Statistical Mapping of Speckle Autocorrelation for Visualization of Hyperaemic Responses to Cortical Stimulation

“…1,[4][5][6] In situations where the speckle pattern are produced by scatterers with varying velocities, the activation patterns of the moving scatterers can be more appropriately obtained from a study of the temporal statistics of the speckle fluctuations. 8 Briefly, when coherent light such as from a laser is reflected off a diffuse surface a specular pattern is formed.…”