Influences of Hypothermia on the Cortical Blood Supply by Laser Speckle Imaging

Abstract

Induced hypothermia has been broadly applied in neurological intensive care unit (NICU). Meanwhile, accidental hypothermia is also a threatening condition in daily life. It is meaningful to investigate the influences of temperature change on the cerebral blood flow (CBF). In the present study, temporal laser speckle image contrast analysis (tLASCA) was implemented to study the relative CBF change in cerebral artery, vein and capillary level under mild (35 degrees C) and moderate (32 degrees C) hypothermia. Twelve male Sprague-Dawley rats (300 +/-50 g) were anesthetized with sodium pentobarbital and randomly assigned to mild and moderate hypothermia groups (n=9 each). Laser speckle imaging (LSI) trials were acquired from baseline (37 degrees C), hypothermia (35 degrees C or 32 degrees C), and post-rewarming (37 degrees C) phases. In the mild group, mean CBF in different vessels all increased throughout the hypothermic and post-rewarming phases. On the contrary, mean CBF reduced by 10%-20% at 32 degrees C and returned to approximately 95% of the baseline level during the post-rewarming session in the moderate group. Besides, in the moderate group, a CBF rebound in vein was found in the post-rewarming phase. Our results suggested that the CBF changed differently between mild and moderate hypothermia, which may be worth for further study in clinic. And we demonstrated LSI as a promising method to achieve high spatiotemporal resolution CBF change with minimal invasion.

Expanding Applications, Accuracy, and Interpretation of Laser Speckle Contrast Imaging of Cerebral Blood Flow

“…Initial speckle imaging applications to CBF characterization evaluated the ability to measure the hemodynamic response to functional challenges (i.e., electrical stimulation, hypercapnia, and cortical spreading depressions) and physiologic alterations (i.e., vascular occlusions, hyperoxia, and hypothermia) in the rodent and feline cortices. 17 , 33 , 29 , 34 , 30 , 35 , 36 The focus of many of these pilot studies was an assessment of speckle imaged cortical perfusion dynamics for proof of concept or comparison with a myriad of alternative flowmetry techniques. In particular, Devor et al 37 observed that the rise and increase in speckle predicted functional flows correlated in space and time with arteriolar vasodilation and constriction, confirmed with extensive two-photon microscopy along with multispectral imaging for blood volume and oxygenation metrics.…”

Time-Dependent Effects of Acute Exercise on University Students’ Cognitive Performance in Temperate and Cold Environments

“…Human and animal studies have suggested that significant reduction in body temperature would cause decline in cerebral blood flow and cerebral oxygen consumption (Laptook et al, 2001; Pozos and Danzl, 2001; Li et al, 2009), which would cause cognitive deficits (Raichle et al, 2001). This could be a possible explanation of the mechanism underlying the correlations between cognition, MST and TS in cold and temperate environments.…”

Dedicated hardware processor and corresponding system-on-chip design for real-time laser speckle imaging

“…So a normalizing logic sub-module is placed after the back end of the LSI hardware processor. It is controlled by the back end logic of the LSI hardware processor through signal (2). Each color index value is transferred into FIFO through the writing port controlled by the back-end logic of the normalizer module through control signal (3).…”

“…Laser speckle imaging (LSI) is a technique used to produce a two-dimensional blood flow map in vivo without invasion and scanning. Its high temporal and spatial resolution enables that it is appropriate for the monitoring of the blood flow of cerebral cortices, [1][2][3][4][5][6][7][8] retina, [9][10][11] and skin 12,13 in the research. Real-time visualized LSI is also significant in the application of neurosurgery for monitoring the dynamic blood flow.…”