Q-Switched UV Laser Interactions with the Human Blood in Vitro

A Q-switched UV laser beam emitting wavelength at 355 nm with different energy densities (fluence, J/cm2) was used for shining sixty human blood samples in vitro. Absorption spectra of hemoglobin were measured for the first time for the samples that exposed to 500 laser pulses in comparison to control samples. It was found that the peak absorbance decreases as the laser fluence increases. This decrease in the peak absorption has been found to be due to the red blood cells deformation and aggregation resulting from the effect of the laser pulses. This phenomenon has been confirmed by examination of the blood cells slides after exposing to the laser radiation. Furthermore, the red blood cells (RBCs) counts were found to be decreased with increasing the laser fluence. The decrease in the RBCs after the irradiation explains the decrease in the hemoglobin absorbance and that represents additional evidence to the structural change according to the optical microscope images. The changes in hemoglobin absorbance are used in a clinically available optical oxymeters. The immediate hematology measurements of the blood samples after the exposure to the laser pulses indicate an increase in the white blood cells (WBCs) of the type basophiles. The measurements were obtained with a significant difference with the level of probability (p≤ 0.05) between the laser exposed samples and the control samples. This laser effect is also due to structural changes in the WBCs. The changes in mitochondria resulting in cells division are in a good agreement with many results in the literature for other types of laser irradiation and other types of the WBCs. The proliferation of the basophiles upon laser photolysis plays a vital role in the activation of the immune system and a consequent destruction of pathogens by these cells

CO2 Laser Photothermal Effects on Rats Skin Tissues

Spectroscopic and histological study of CO2 laser interaction with rats tissues were carried out. We detected for the first time the changes in optical absorption spectra of rat's tissues with selective CO2 laser optical densities ranging from 20.64 to 34.40W/cm2. The laser exposed tissues show higher absorbance in hemoglobin than that for the unexposed tissue. Using the same laser and same optical densities, the absorption spectra of fresh blood were measured. Much intense peaks of hemoglobin than that for the corresponding peaks for the tissue were detected. A scheme based on recent experimental findings is proposed for explanation of this novel phenomenon. The histological study shows thermal damage of blood vessels localized at the dermis layer. At high laser optical densities a vessel rupture with hemorrhage were occurred. The results indicate a pronounced modification of skin absorption properties by laser irradiation. Such an effect is due to thermally induced biophysical and biochemical processes inside the highly heterogeneous tissue structure. Keywords: CO2 laser, Photothermal effects, Hemoglobin absorption, Histolog