Laser Therapy,
by Mary Dyson PHD FCSP continued page 2 For
sale outside of the United States only!
LASERS
This is an acronym for Light Amplification by the Stimulated Emission
of Radiation. The stimulated emission of radiation occurs when a photon
interacts with an energized atom. When an atom is energized, for example
by electricity, one of its electrons is excited, i.e. raised to a
higher energy orbit than its orbit when in the resting state. If the
energy of the incident photon is equal to the energy difference between
the electron’s excited and resting states, then stimulated emission
of a photon occurs and the excited electron returns to its resting
state. This photon has the same properties as the incident photon,
which it also emitted. This process is repeated in the adjacent energized
atoms, producing a laser beam. Unlike light from non-laser sources,
this light is:
Monochromatic, i.e. of a single wavelength
Collimated, i.e. its light rays are non-divergent
Coherent, i.e. in phase, the troughs and peaks of the waves coinciding
in time and space.
With regard
to the biomedical effects of LLLT, monochromaticity is its most important
characteristic. To produce an effect, the light must be absorbed,
and absorption is wavelength-specific. Different substances absorb
light of different wavelengths. Mitochondria, present in all mammalian
cells except erythrocytes, contain cytochromes that absorb red light.
LLLT EQUIPMENT
This has three essential components:
Lasing medium, which is capable of being energized sufficiently for
lasing to occur
Resonating cavity containing the lasing medium.
Power source that transmits energy into the lasing medium.
The type of lasing medium used determines the wavelength, and therefore
the colour, of the laser beam. For example, a HeNe laser, in which
the lasing medium is a mixture of helium and neon gases, produces
red light with a wavelength of 632.8 nm. Gallium, aluminium and arsenide,
the lasing medium of GaAlAs semiconductor diodes, also produces monochromatic
radiation, but the wavelength of this depends on the ratio of these
three materials and is in the red-infrared range of the electromagnetic
spectrum, typically 630-950 nm.
The resonating cavity containing the lasing medium has two parallel
surfaces, one being totally reflecting, the other being partially
reflecting. Photons emitted from the lasing medium are reflected between
these surfaces, some of them leaving through the partially reflecting
surface as the laser beam. The cavity of a HeNe laser is many cms
long, whereas that of a GaAlAs semiconductor diode is tiny, the diode
being the lasing medium and its polished ends the reflecting surfaces.
Modern low intensity laser therapy devices are generally of the GaAlAs
type. Their treatment heads may contain either one or several diodes.
Those with one diode resemble laser pointers and are designed to treat
acupuncture and trigger points; they can also be used to treat points
in and around skin injuries. Those with many diodes are generally
called cluster probes and allow large areas to be treated rapidly.
The diodes may be housed in a rigid head or in a flexible material.
The latter can be applied around curved surfaces such as the shoulder.
Each diode emits either red or IR radiation. Red light is absorbed
by all cells, whereas different wavelengths in the infrared range
appear to target specific cell types.
The power source for a LILT device may be either a battery or mains
electricity. Many LILT devices are portable. The main function of
the power source is to energize the lasing medium.
How
LLLT Works Continued>> page 3
Back to Laser therapy >>
