Lasers in Laboratory Studies: the Need for Special Systems

Laboratory studies of low level laser therapy (LLLT) need special laser systems to deliver consistent laser irradiation parameters. A typical uncorrected diode laser beam is neither round nor homogenous in distribution; even if light is delivered by fiber optics, the beam will be round but not homogeneous. With these non-homogeneous types of beams, cells irradiated in vitro and in vivo are exposed to different amounts of energy.

Some cells may not be exposed to the required intensity or energy threshold for stimulation, while others may be irradiated to the point of inhibition. If we believe that all cells in vitro should be exposed to the same radiant intensity, then a homogenous “flattop” distribution is necessary. Other variations in irradiation parameters can occur when using laser diodes. Laser diodes warm up during use which causes the wavelength to shift 0.4nm for every 1º C rise in temperature. Furthermore, during operation power output drops significantly in many laser systems. These changes in wavelength and power output mean that during the course of an experiment where multiple samples are irradiated, samples would be subjected to different wavelengths and radiant intensities. The strengths of this new device include: a wide range of wavelengths, tunable output power, round homogeneous beam distribution, and extremely stable wavelength and power output. Wavelength and power output stability are achieved by constant real time photodiode feedback and heat stability is managed by thermoelectric Peltier cooling. Round homogeneous beam distribution is achieved with a beam diffuser and circularising lenses adjusted to match required culture plate well size or area of animal model to be irradiated. Both in vivo and in vitro dose ranging studies will benefit from this attention to accuracy.

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