Simultaneous infrared thermal imaging and laser speckle imaging of brain temperature and cerebral blood flow in rats.

Takashi Suzuki,Naoya Oishi,Hidenao Fukuyama

doi:10.1117/1.jbo.24.3.031014

Abstract

.Infrared thermal imaging of brain temperature changes is useful for evaluating cortical activity and disease states, such as stroke. However, the changes depend on a balance between changes in heat generation from metabolism and in heat convection related to blood flow. To discriminate between these effects and gain a clearer understanding of neurovascular metabolic coupling, brain temperature imaging must be improved to measure temperature and blood flow simultaneously. We develop an imaging technique that shows a two-dimensional (2-D) distribution of absolute brain temperature and relative cerebral blood flow changes in anesthetized rats by combining infrared thermal imaging with laser speckle imaging. The changes in brain metabolism and cerebral blood flow are achieved using two different anesthetics (isoflurane and -chloralose) to evaluate our system. Isoflurane increased cerebral blood flow but decreased metabolism, whereas -chloralose decreased both parameters. This technique enables simultaneous visualization of brain surface changes in temperature and cerebral blood flow in the same regions. This imaging system will permit further study of neurovascular metabolic coupling in normal and diseased brains.

Highlights

Regional surges in neuronal activity are accompanied by changes in local brain metabolism, cerebral blood flow, and cerebral oxidation
Regional metabolic activity in the brain, which is the primary mechanism that satisfies the energetic demands of the brain,[7,8] generates heat and increases local brain temperature concurrent with cerebral blood flow changes.[9]
After removing the isoflurane (10 to 15 min, 15 to 20 min), there were remarkable positive correlations between cerebral blood flow and brain temperature changes, but we found that the correlation coefficients near the vessels became smaller from 15 to 20 min

Summary

Introduction

Regional surges in neuronal activity are accompanied by changes in local brain metabolism, cerebral blood flow, and cerebral oxidation. The nature of the relationship between neural activity changes, metabolic changes, and cerebral blood flow changes is commonly known as neurovascular metabolic coupling,[1,2,3,4] the mechanism of which remains unclear. Clearer understanding of this coupling will enable greater insight into brain function and be useful in the diagnosis and treatment of neurovascular diseases, such as acute stroke accompanied by neurovascular metabolic uncoupling.[5] In rat brains in which stimulus-induced vasodilation was suppressed using a calcium channel blocker, it has been reported that neurovascular metabolic uncoupling, such as brain temperature increases without cerebral blood flow, changed during stimulation.[6] simultaneous monitoring of spatiotemporal changes in cerebral blood flow and cerebral metabolism is important. The measurement of absolute change in the local brain temperature may allow quantification of neural activity

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