Mettler Electronics Laser Sys Stim 540, Инструкция по эксплуатации

Страница: 21 / 32

Laser Sys*Stim 540, Therapeutic Laser— Rev.F_07/03/12
21
5 Laser Therapy
5.1 Introduction
Laser Therapy is a relatively new therapeutic modality. For some time, high power lasers have been
used in medical treatments such as surgery and coagulation. Some beneficial effects were noticed
near the treated areas which led to research into the benefits of lower powered lasers. Laser Therapy
at low powers has been investigated for many years and recently authorities such as the FDA have
recognized the efficacy of therapeutic lasers in some applications after many years of rigorous
research.
5.2 What is a Laser?
The word LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation. Light
emitted from a Laser has three important optical characteristics, Monochromaticity, Coherence and
Collimation.
Most common sources of light such as incandescent light globes or heat lamps are composed of
many colors of light, whereas a laser generates one pure color of light. Colors can be defined and
measured in terms of their wavelength. For visible light the wavelength is around several hundred
nanometers (nm). For example, light from a light bulb is composed of many wavelengths of light (500
nm to 3000 nm), a red LED used on many appliances as an indicator may span less wavelengths
(590 nm to 670 nm), but a laser’s span of wavelength (780 nm to 790 nm) is very narrow. This narrow
range of wavelengths or pure color is called Monochromaticity.
The second parameter is Coherence. Coherence is the characteristic of light waves being in
synchronicity with each other.
The final parameter is Collimation. Collimation is a product of the Monochromaticity and Coherence,
which enables the beam of light from a laser to be emitted in a parallel beam.
5.3 Laser interaction with the Human Tissue
Laser radiation directed at tissue can either be reflected off the surface of the tissue or penetrate into
the tissue. Whether the light is reflected or penetrates depends on several factors such as
wavelength, tissue surface condition, and the beam angle of incidence.
Once the laser light has penetrated the tissue, the light is internally scattered by three optical effects:
divergence, reflection and refraction. These effects, plus the absorption of light by photochemical
effects, reduce the depth of penetration in the tissue.
This process of photochemical stimulation is considered to be the prime interaction that provides the
therapeutic benefit, although some photo-thermal interactions are considered beneficial as well.
These photochemical interactions are elaborated in greater depth by the references listed in section 6.
5.4 Wavelengths
Wavelengths of light from 600 nm to 1300 nm have been found to penetrate distances of
approximately 4 mm into human tissue. Although this depth is shallow, the photochemical interactions
are thought to mediate processes deeper in the tissue.
Light at wavelengths shorter than 600 nm is attenuated by the tissue, and wavelengths above 1300
nm are primarily thermal interactions, and can be achieved more effectively with thermal modalities.
For these reasons therapeutic lasers have emission wavelengths in the 600 nm to 1300 nm range.
5.5 Pulsed Modes
The output of the laser can be modulated by rapidly switching the laser on and off. In the Laser
Sys*Stim 540 the Pulse Mode selection turns the laser on and off at rates from 10 Hz to 5000 Hz. As