Laser light sources for photobiomodulation: The role of power and beam characterization in treatment accuracy and reliability.

PURPOSE: Daily clinical use of therapeutic light sources can lead to changes in light emission stability with potentially significant consequences for usage in photomedicine treatment. The aim of this study was to evaluate the average and maximum power and to describe the beam diameter of different low-power laser photobiomodulation devices in clinical use in Brazil. METHODS: The power and light-emitting beam diameter of twenty-four therapeutic devices with an average age of 11±5 years, with an average weekly use of fewer than thirty minutes, were measured. RESULTS: The analyzed power varied between 2% to 134% of the values declared by the manufacturers. Differences in beam diameter of between 38% and 543% of the nominal values were also observed. It is also noteworthy that even between the same brand and model, differences in diameter were obtained. Finally, differences were observed in the power output after one and three minutes of sequential emission for 830 nm and 904 nm (p < 0.05), but not when comparing the difference between wavelengths in factor time. CONCLUSION: There is a need for a shared effort on the part of laser manufacturers to improve standardization and consistency of laser output power and beam diameters. At the same time, medical laser operators should also consider development of standardized protocols for maintenance and monitoring equipment performance over time to correct for fluctuations that could ultimately impact on treatment outcomes.

Nondestructive inspection of metal specimen using tone-burst vibro-acoustography.

Even though the pulse-echo ultrasonic technique is commonly used for the assessment of metal structures, it has some inherent limitations. Vibro-acoustography (VA) is a relatively new ultrasonic technique which has demonstrated a great potential in revealing defects in objects, however it is traditionally used to analyze the integrity of specimens made of low-stiffness materials. This work presents the evaluation of the performance of VA technique for the inspection of a steel structure, which was manufactured with defects of known geometry on its inner surface. All the inspection process was done automatically, from the data acquisition to the image processing for characterizing the defects. Experimental results show that VA was able to identify and characterize even the smallest defects in the structure, with a diameter of 2 mm. In addition, the results show that VA was able to characterize the artificial defects in the steel structure with almost the same errors as the traditional pulse-echo method, which indicates a potential use of VA in the inspection of materials with high mechanical stiffness.