Laser speckle imaging for monitoring blood flow dynamics in the in vivo rodent dorsal skin fold model.

The rodent dorsal skin fold model is used routinely as a means to study changes in microvasculature flow and architecture (Barton et al., 2001; Friesenecker et al., 1994; Gourgouliatos et al., 1990; Mordon et al., 1997; Tsuzuki et al., 2000; Vargas et al., 2001; Wettstein et al., 2003). A method for high spatial and temporal resolution imaging of blood flow dynamics is required to provide objective evaluation of external stimuli, such as pharmacological intervention, electrical stimulation, or laser irradiation. Existing methods for blood flow imaging are inadequate. Laser Doppler imaging requires mechanical scanning, limiting spatial and temporal resolution (Forrester et al., 2002). Magnetic resonance imaging (Schauble and Cascino, 2003) is impractical for routine use and has very limited temporal resolution. Doppler optical coherence tomography (Li et al., 2001; Rollins et al., 2002; Yang et al., 2003; Zhao et al., 2000) can provide longitudinal cross sections of the microvasculature, but simultaneous high temporal resolution and lateral imaging of blood flow cannot be achieved. Laser speckle imaging (LSI) (Briers, 2001; Dunn et al., 2001; Forrester et al., 2002) is a technique in which timeintegrated speckle patterns generated by low-power laser irradiation are imaged with a CCD camera. A simple, lowpass-filtering algorithm is used to convert raw speckle images to flow images. LSI has several advantages over existing methods, including simultaneous high spatial and temporal resolution, ease of implementation, and relatively low cost. We now report the use of a LSI system that is