Monitoring Changes In Cerebral Blood Flow Under The Effect Of Hypothemia By Optical Imaging

Monitoring the spatio-temporal characteristics of the cerebral blood flow can know the mechanism of the brain protect under the effect of the hypothermia. And this means can act a powerful guidance for clinical therapy. It is necessary for extending the hypothermia application. Optical imaging method can examine the dynamic process at real time in vivo, and can act a powerful measure for clinical diagnosis.The dynamic course of the blood flow is monitored under the effect of mild hypothermia(33℃) and ultraprofpound hypothermia(0℃) by applying the laser speckle imaging technology. The changes of the cerebral blood flow are studied between the normal and trauma structures. The spontaneous cortical spreading depression waves are examined under the effect of mild hypothermia by the optical imaging based on intrinsic signal. The character of optical signals are used to reflect the spreading time course and the spreading dimensional model. The conclusion of the thesis are listed as following:(1) Cerebral blood flow(CBF) of the parietal cortex was measured at the level of mild hypothermia and ultraprofpound hypothermia(0℃) for 1 min and 10 min respectively by laser speckle imaging technique. Experimental results showed that CBF reduced rapidly at the end of the mild hypothermia then increased slowly to exceed the baseline, and finally CBF reduced slowly to the baseline. Another experimental results showed that the spatio-temporal changes of CBF had the difference under the effect of the ultraprofpound hypothermia. CBF reduced obviously at ultraprofpound hypothermia(0℃) for 1 min, then CBF increased rapidly and exceeded baseline to last this state a few time(10±2 min) by keeping the cortex at 37℃, and finally CBF reduced slowly to the baseline. The trend of CBF change in the regions of artery, vein and parenchyma was similar. And the extent of CBF change was different. Another experimental results showed that CBF also reduced obviously at ultraprofpound hypothermia(0℃) for 10 min, but CBF did not increase rapidly and remained this state a few time(12±2 min),then CBF increased gradually(artery) or increased rapidly and reduced little later(vein and parenchyma), and finally CBF increased to the ~75% of the baseline by keeping the cortex at 37℃. The trend and extent of CBF in three regions were all different. The conclusion is that cortex will possibly be formed trauma at 0℃for 10 min. Laser speckle imaging technology provides a new measure for studying CBF monitoring under the effect of the ultraprofpound hypothermia.(2) The optical intrinsic signal imaging at 550 nm was used to examine the dynamic course of the spontaneous cortical spreading depression under the effect of the mild hypothermia. The dimensional models of CSD were same at the mild hypothermia and normal brain temperature. But the spreading time course at the former was more longer than the latter. The conclusion is that the spreading velocity was 2.4±0.4 mm/min. Optical imaging based on the intrinsic signals is an effective method to examine the CSD under the effect of the hypothermia.