Laser Speckle Flowmetry for the Study of Cerebrovascular Physiology in Normal and Ischemic Mouse Cortex

Abstract

Summary:Laser speckle flowmetry (LSF) is useful to assess noninvasively two-dimensional cerebral blood flow (CBF) with high temporal and spatial resolution. The authors show that LSF can image the spatiotemporal dynamics of CBF changes in mice through an intact skull. When measured by LSF, peak CBF increases during whisker stimulation closely correlated with simultaneous laser-Doppler flowmetry (LDF) measurements, and were greater within the branches of the middle cerebral artery supplying barrel cortex than within barrel cortex capillary bed itself. When LSF was used to study the response to inhaled CO 2 (5%), the flow increase was similar to the response reported using LDF. For the upper and lower limits of autoregulation, mean arterial pressure values were 110 and 40 mm Hg, respectively. They also show a linear relationship between absolute resting CBF, as determined by [ 14 C]iodoamphetamine technique, and 1/ c values obtained using LSF, and used 1/ c values to compare resting CBF between different animals. Finally, the authors studied CBF changes after distal middle cerebral artery ligation, and developed a model to investigate the spatial distribution and hemodynamics of moderate to severely ischemic cortex. In summary, LSF has distinct advantages over LDF for CBF monitoring because of high spatial resolution.

Thrombotic distal middle cerebral artery occlusion produced by topical FeCl3 application: A novel model suitable for intravital microscopy and thrombolysis studies

“…Laserspeckle recordings showed a rapid decline in rCBF in 8±1 minutes and total occlusion was attained in 17 ± 2 minutes (Figure 3). Two hours after FeCl 3 application, rCBF in the MCA-supplied cortex reached 34%±5% of the baseline at the center and 52% ± 4% at the periphery when measured from a rectangular region of interest (0.05 mm 2 ) away from vessels, in accordance with values reported after distal MCA occlusion with suture in the mouse (Ayata et al, 2004) (Figure 3).…”

Rho-Kinase Inhibition Improves Ischemic Perfusion Deficit in Hyperlipidemic Mice

“…1 Focal cerebral ischemia was induced by distal middle cerebral artery occlusion (dMCAO) as previously described. 11 After general surgical preparation, mice were placed in a stereotaxic frame, and skull surface was prepared for optical imaging. Temporalis muscle was separated from the temporal bone and removed, and a burr hole (2 mm diameter) was drilled under saline cooling in the temporal bone overlying the middle cerebral artery just above the zygomatic arch.…”

Evaluation of Laser Speckle Flowmetry for Imaging Cortical Perfusion in Experimental Stroke Studies: Quantitation of Perfusion and Detection of Peri-Infarct Depolarisations

“…The pixel matrix was 768 (width) Â 512 (height), and the image field was typically 22.2 Â 15 mm, giving a pixel area of approximately 29 Â 29 mm. Software was custom-written (AKD) to allow derivation of an image of the inverse of the calculated laser speckle contrast and speckle correlation times (ICT) as described elsewhere (Dunn et al, 2001;Ayata et al, 2004a), and implemented on a 1.2 GHz Pentium-4 or 2.4 GHz Xeon CPU. Since speckle correlation time is inversely proportional to perfusion (Briers, 2001), this approach enabled grey level images representing perfusion to be stored at intervals of approximately 22 (1.2 GHz CPU) and later of 13 (2.4 GHz) secs.…”