Review of laser speckle-based analysis in medical imaging

Abstract

Speckle pattern forms when a rough object is illuminated with coherent light (laser) and the backscattered radiation is imaged on a screen. The pattern changes over time due to movement in the object. Such time-integrate speckle pattern can be statistically analyzed to reveal the flow profile. For higher velocity the speckle contrast gets reduced. This theory can be utilized for tissue perfusion in capillaries of human skin tissue and cerebral blood flow mapping in rodents. Early, the technique was suffered from low resolution and computational intricacies for real-time monitoring purpose. However, modern engineering has made it feasible for real-time monitoring in microcirculation imaging with improved resolution. This review illustrates several modifications over classical technique done by many researchers. Recent advances in speckle contrast methods gain major interest, leading towards practical implementation of this technique. The review also brings out the scopes of laser speckle-based analysis in various medical applications.

Laser speckle contrast imaging: theoretical and practical limitations

“…[37][38][39][40] Nonmedical applications have included measuring the velocity of vehicles 41,42 and monitoring the drying of paint. In addition to the above (and much other) work, there have been several reviews of speckle contrast imaging, [44][45][46][47][48] including some comparative studies with laser Doppler techniques. [49][50][51] This recent work on LSCI has, of course, been accompanied by improvements in the images produced.…”

Accessing to arteriovenous blood flow dynamics response using combined laser speckle contrast imaging and skin optical clearing

“…It was also demonstrated that LSCI would has an optimal contrast-to-noise ratio (CNR) and a low noise when the exposure time of the CCD camera T is set to 5 ms [57]. Under the widely-used assumption of a random Lorentzian velocity distribution, the speckle contrast C spec can be simplified as follows [54,58,59]:…”

Review of near-infrared methods for wound assessment

“…[69][70][71][72][73] Noninvasive alternatives to visualize perfusion seem better suited to that role. One such class of methods exploits the variance of laser speckle imparted by flooding blood.…”

“…Various combinations of spatial and temporal pixel statistics have been proposed to quantify speckle variance from a spatiotemporal series of speckle patterns. [71][72][73] These methods offer a compromise between LASCA and LSI.…”