In neurosurgical operations, such as cerebral aneurysm clipping, bypass surgery and arteriovenous malformations, monitoring of cerebral blood flow is critically important. Currently, surgeons do not have real-time noninvasive methods for intraoperative visualization of cerebral blood flow. Laser speckle contrast imaging (LSCI), widely used in the diagnosis of blood flow, may be promising for solving this problem. In the present study, the LSCI was demonstrated for the evaluation of acute cerebral blood flow abnormalities in laboratory animals. To visualize cerebral blood flow, the rats underwent cranial trepanation. The disruption of cerebral blood circulation was simulated by clamping both common carotid arteries through the neck approach. A specially designed LSCI system was used to assess blood flow. A distinct reduction in blood flow in the cerebral cortex after carotid artery clipping was shown, which lasted for 10 min continuously. At the same time, a more intensive blood flow decrease was observed in the right hemisphere, which can be related to the blood supply of the left hemisphere through the circle of Willis. After the clips were removed, blood flow in both hemispheres was restored to a level higher than the initial level. The results obtained show the prospects of using LSCI for the control of acute disorders of cerebral blood flow during neurosurgical operations in real-time.
We studied the formation of a composite from an aqueous dispersed medium with albumin and carbon nanotubes under the action of laser radiation in continuous wave (CW) mode and pulsed mode with a repetition rate of 10 Hz and pulse duration of 16 ns. During the experiments, the temperature was monitored at the site of exposure, as well as its distribution in the liquid. Pulsed solid-state Nd:YAG laser and CW diode laser with an irradiation power of ∼500 mW were used as radiation sources. However, a three-dimensional composite was formed only with constant exposure. The effect of pulsed laser radiation with an intensity corresponding to nonlinear interaction with water dispersion led only to its enlightenment. Thus, it is important not only the energy parameters of radiation but also the frequency of energy portions exposure for the fabrication of tissue-engineered structures (composites). As a result, it was found that the curing of the dispersion and the composite formation occurs under the action of continuous or pulsed (with a high pulse repetition rate) laser radiation at a temperature in the range from 45°C to 50°C; in case the pulse repetition rate is insufficient, composite formation is not observed even under the action of high intensity radiation and heating occurs only to a temperature of ∼40 ° C. This formation process can be generated both in the visible 532 nm and in the infrared 810-nm wavelength ranges. In this case, one of the main conditions is the absence of albumin or cells absorption at these wavelengths so that absorption occurs mainly with single-walled carbon nanotubes. Studies of the surface and internal structure of the composite made it possible to demonstrate the binding of nanotubes to each other. This happened under the influence of laser radiation. This led to high hardness values of the composites. The average value of hardness was 0.26 ± 0.02 GPa.
Increase the weld strength is main directions of development of laser welding technology. Laser solders are used to increase tensile strength of welds and reduce of tissue temperature necrosis. Soldering components interaction effect the solder tensile strength characteristics of laser welds. Tensile strengths for welds obtained using of solder various concentration BSA and SWCNT was measured. Dimensions laser solder aggregates were measured. The dependence between the dimensions of the aggregates of laser solder and the tensile strength of the weld has been revealed.
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