The Use of High Powered 867nm Laser Diodes in the Luminex® Therapy
A Laser Diode for LLLT
Laser Penetration Through Fabric: Why we Recommend the Contact Method
Laser as a Therapeutic Tool
Understanding Low Level Laser Therapy (LLLT)
Laser Diode Selections in the Luminex® Laser System
This paper provides background information on the reasons for using
laser diodes with wavelengths of 830, 867nm, and 670 nm in the Luminex®
How are Laser Diodes Used?
Laser diodes are used in industry and medicine to generate laser light from 360nm
to 25,000nm. This is an extremely broad range of products, but the applications
for laser diodes fall into five or six major categories. The list shown below
indicates where laser diodes find application.
635-690nm In the visual light range, diodes are used in medicine to generate
light for Photo Dynamic Therapy (PDT), bar code readers and for pumping metal
vapor gas lasers. The term pumping means to use laser diodes to generate laser
light at a specific wavelength that, in turn, starts up a more powerful gas, dye,
or tunable solid state laser. In effect, laser diodes at a variety of wavelengths
start-up or pump more powerful lasers.
785nm Pumping exotic metal YAG laser systems.
808nm Pumping Nd:YAG laser systems
830nm In general use for laser printers, laser readers.
904nm Short pulse laser diodes are commonly used in ranging (measuring
distances). Continuous wave 904nm diodes are used in the military for target
940-980nm Pumping exotic metal, dye or tunable laser systems.
1300-1550nm Fiber optic communications is the main use.
> 1550nm Pumping highly exotic laser systems
A laser diode has never been produced specifically to generate
laser light for use in Low Level Laser Therapy (LLLT). Laser therapy manufacturers
have been using whatever laser diodes were available from industrial, military
or medical applications. For these applications, the laser diode's wavelength,
and various other important parameters, were carefully matched to the design needs
of printers, fiber optic transmission systems, ranging systems, target illuminators
or PDT. Nothing has ever been done to manufacture laser diodes with the wavelength,
half power points, slope efficiency and power output required to optimize LLLT
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A Laser Diode for LLLT
The Luminex® System has been designed with
output powers up to 500mW (average power). A 500mW laser diode generates
a great number of photons and the treatment time is far shorter
than using a diode with less power. Jan Tuner and Lars Hode indicate
the advantage of irradiating with higher power lasers is that their
photobiological effect is greater and, consequently, the therapeutic
effects are felt more quickly and at greater depth.
They make the following observation: "The (research)
literature supports the hypothesis that higher power density yields
better clinical results."
Second, the Luminex® System has been engineered
to deliver high output power per unit of current, resulting in less
heat dissipation, a direct cause of laser diode failures. High efficiency
laser diodes result in longer mean time to failure rates.
Third, the laser diode in the Luminex® System has a narrow spread
of wavelength at the half power points, providing a sharp peak output power (intensity)
with little side lobs (wavelength). The result is maximum output power at one
wavelength with the half power points, perhaps at ±5nm from the center.
Fourth, the Luminex® System has chosen a wavelength
with ideal penetration characteristics, using higher energy photons
to accomplish this work faster. As demonstrated by our laboratory
tests, the amount of forward light scatter in tissue is high at
904nm. In shorter wavelengths, the energy of the photons and their
absorption nearer the surface of the skin is increased while the
amount of deep scatter of laser light is reduced.
Ohshiro summarized the comparative transmission of laser wavelengths
in tissue, in vivo, and found that the absorption and penetration characteristics
of laser light in the 830nm and 904nm window was preferred as a clinical LLLT
tool. The summary compared the absorption and penetration characteristics of laser
light from argon-pumped dye lasers at 488-514.5nm to carbon dioxide at 10,600nm.
Another notable reference is the Ohshiro & Calderhead report
on the relationship between penetration of laser light and wavelength. The report
eliminates the absorption component and gives us a clear picture of the penetration,
or deep scatter, of laser light. The peak penetration occurs at about 904nm, which
supports our laboratory depth of penetration work.
Over the years, researchers have studied laser light absorption
at various wavelengths in different media, i.e., water, skin, liver, and blood.
From Charschan's report (see table below), typical values of absorption coefficients
can be obtained for some basic components of the human body at selective wavelengths:
Absorption Coefficients vs. Λ (cm-1)
Note the large spread in absorption coefficient values in the
table above. The absorption factor for water increases rapidly with longer wavelengths
from a valley at about 660nm. At 660nm the absorption factor is approximately
0.0073 cm-1. In the region near 860 to 870nm, the absorption value has jumped
40 fold to about 0.30 cm-1. Similar jumps in absorption factors can be observed
for all of the components as wavelength increases.
In summary, due to good forward scatter (depth of penetration)
and good absorption (a higher proportion of photons are absorbed) wavelengths
between 860 and 870nm are highly desirable. Shorter wavelengths (860-870nm) have
the advantage of creating photons with more energy per photon, bringing more energy
to the cells being photoactivated.
Selecting a Laser Diode for LLLT
The shape of the intensity of the laser light output vs. the wavelength further
supports the choice of the 867nm laser diode. In general, a sharp intensity peak
at one wavelength with little spread is the most effective. The laser diodes at
867nm only spread ±1.8nm at the half power points, a low value. This means
no jagged or odd shaped, multi-wavelength power spikes in the power output, rather
a pure beam of laser light at one wavelength. These desirable characteristics
can be traced to the purity of the elements and compounds used in the fabrication
of the laser diodes, as well as the lack of contamination in the clean room assembly
Many LLLT professionals express an interest in the spot
size of the laser beam; some prefer tight, narrow beams (focused), whereas others
prefer a spread beam. The Luminex® System utilizes a 500mW diode. The laser light
output is 500mW (average power) measured at the lens of the diode. The laser light
generated within the diode itself is from a pinpoint source measuring 1µm
by 50µm; with laser light generated from a narrow slot called the emitter
aperture. The light generated from this pinpoint source is dispersed in a wide
elliptical pattern from the front lens. This spread of laser light, or beam divergence,
is characterized by two divergent angles. One is parallel to the "slot"
and the other perpendicular to the "slot", corresponding to the full
angle at the point that is ½ of the peak power. The beam divergence of
the Luminex® System's 867nm diode is 8° by 35°, a narrow beam in one axis
and a wide beam in the other axis. The distribution of light intensity follows
a Gaussian curve wherin the laser light is highly concentrated at the center and
grows progressively weaker as one moves to the edges of the ellipse. The power
density represents an average for the entire spot size area. Because of the Gaussian
distribution of light over the area being irradiated, a 500 mW laser is effective
for LLLT professionals desiring high laser light intensity, with the greatest
amount of laser light concentrated at the center of the spot.
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Laser Penetration Through Fabric: Why we
Recommend the Contact Method.
Medical Laser Systems' engineers did a study to observe what
happens to laser output when laser light is shined through clothing. Using both
an infrared 867nm laser diode and a red beam 670nm laser diode, the engineers
used a cotton t-shirt to demonstrate the dramatic power loss when laser light
is shined through fabric.
||mW without t-shirt
||mW through t-shirt
This CLEARLY indicates that although some laser light penetrates
through clothing, the power output is severely decreased. If you were to attempt
to treat through heavier fabric, such as dungarees or sweatshirts, the laser energy
reaching the skin would be even lower. If you are using a low powered laser with
a 5 or 10mW diode and lose 79% of that power by treating through clothes, you
are left with only about 1mW of power reaching the skin.
This is why we recommend that practitioners doing laser treatment
always use the "contact method", with the laser probe in direct contact
with bare skin.
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Laser as a Therapeutic Tool
Lasers have been used safely as a therapeutic tool for over
30 years. Laser Therapy (LT) differs from the use of lasers in surgery due to
a lower output power and reduced energy density. Instead of ablating tissue, LT
stimulates cellular activity that improves the speed and quality of healing. In
over 1,800 publications worldwide, LT has demonstrated its non-invasive, non-toxic
quality, and its ability to augment and in some cases, replace, pharmaceuticals
and surgical intervention. LT is most often used as a primary medical treatment,
but is also effective as a complement to other modalities, such as needle acupuncture
and chiropractic adjustment. Acupuncturists, Chiropractors, Physical Therapists,
Dentists, Osteopaths and M.D.'s currently use LT for a variety of problems; including
the treatment of acute pain and chronic degenerative conditions, improving the
speed and quality of wound healing, and for muscle, tendon and ligament injuries.
Laser Therapy as a Healing Stimulus
Lasers commonly in use for LT operate at a wavelength between 600 and 1060 nanometers
(nm). Laser devices in this range are known to be safe because they do not include
wavelengths in the lower end of the spectrum, which includes X-RAYs and Gamma
Rays that cause destructive ionization in the cell. The first lasers used for
LT were gas-tube, helium neon lasers at 632nm. Developed in the 1960's, these
lasers were very expensive to purchase and too difficult to operate, limiting
their availability to just a few well-financed researchers. In the 1980s however,
technological advances allowed for the emergence of relatively inexpensive laser
diodes with a wide range of wavelengths. Many Therapeutic Lasers were developed
and sold during this period, but were all very low power, around 1 miliwatt(mW).
The development of devices for LT has proceeded in such small steps because rather
than being driven by the demand for LT devices, the production and availability
of laser diodes is driven by the massive demand for laser diodes in technology
such as compact disc players, laser scanners, and for a wide range of defense
applications. As these technologies matured in the 1990's, they were able to handle
much higher power outputs, as high as 500mW, resulting in shorter treatment times
for LT applications. The availability of more powerful lasers for LT allowed for
the treatment of a number of new conditions, and may explain some early clinical
studies that showed non-significant results using LT with very low power, sometimes
less than 1 miliwatt(mW). Typical power outputs of diode lasers currently available
range from 50mW to 500mW.
Wavelengths and Impact of Penetration and Absorption
Portions of these diode laser wavelengths are visible, from 600 up to approximately
780 or 820 nm. Humans have a declining ability to see light above approximately
820nm. Photon energy increases as the wavelength decreases; conversely, penetration
through the skin increases as wavelength increases. Thus, certain conditions may
benefit from lower wavelengths where most of the energy is absorbed at the surface,
and other conditions may benefit more from higher wavelengths that permit deeper
penetration. It follows that an ideal wavelength for treating most conditions
would be in the midrange.
LT in the Literature
Below we summarize the wide range of effect of LT. A lengthy bibliography
can be accessed by downloading or viewing our Laser
Bibliography PDF file. More reference can be located by viewing our Links
page that connects you to a wide range of sites with even more literature citations.
Cellular: Cellular homeostatis of the mitochondria is modified
by laser irradiation, promoting a cascade of events in the respiratory chain of
cytochromes, cytochrome oxidase and flavine dehydrogenase that permit absorption
of light. The redox status of both mitochondria and cytoplasm are impacted, resulting
in improved production of ATP. When cellular membranes are irradiated, the flow
of the membrane ion carriers sodium and potassium are altered, affecting the movement
of calcium between cytoplasm and mitochondria. (Karu)1
. Recent study by (Naviaux)2 et. al. Demonstrate
the affinity of varying mitochondria to varying wavelengths, promoting an enticing
model which matches mitochondria of one tissue type with its most effective laser
wavelength. (Naviaux) Cell proliferation, motility and secretion are altered when
irradiated with laser with specific wavelength, intensity and dose.(Basford)3
Improved micro-circulation after laser irradiation promotes accelerated
recovery after injury, resulting from reduced arteriolar and venular vessles and
improved blood-flow in nutritional capillaries and activation of angiogenisis.
(Zhao4 , Skobelkin5
, Kozlov6 ,and Telfer7
Collagen synthesis, proliferation of fibroblasts, faster edema
reduction and enhanced lymph flow from LT can accelerate recovery after trauma,
through improved edema resolution, regenerated blood and lymph vessels and tendon
strength (Lievens8 ).
The improvements induced by laser on collagen production lead
to significant increases in collagen content and tensile strength of wounds at
one and two weeks following laser treatment (Lyon9
, Abergel10 ). Similarly, (Braverman11
) and (Enwemeka11) found improved tensile
strength in laser treated wound and tendon groups. Also, Enwemeka found that Laser
Therapy not only improved the rate of healing; but led to a better quality of
healing. Shoulder tendinitis showed statistical improvement after LT (England12
Beneficial Effect on Nerve Cells and the Production of B-Endorphins
Laser light has a highly beneficial effect on nerve cells which
blocks pain transmitted by these cells to the brain. Studies have shown that laser
light increases the activity of the ATP-dependent NaK pump. In this case, laser
light increases the potential difference across the cell membrane moving the resting
potential further from the firing threshold, thus, decreasing nerve ending sensitivity.
A less understood pain blocking mechanism involves the product of high levels
of painkilling chemicals such as endorphins and enkephalins from the brain, adrenal
gland and other areas, as a result of stimulation by laser light. Lombard concluded
that the neuropharmacological analgesic effects of lasers are likely due to the
release of serotonin acetylcholine at the site and in higher centers. This pharmacological
effect leads Baxter to conclude that laser is the premier pain reliever compared
to other electro-therapeutic modalities.
How is Laser Therapy Administered?
LT is usually conducted in an outpatient clinic setting, and requires
no unusual equipment or precautions except that safety glasses are normally recommended
for the patient and therapist. In the United States, the Food and Drug Administration
(FDA) requires that laser devices be measured at a distance of 20cm, through a
7mm aperture stop; this measurement is applied to the laser's label. This standard
measurement permits the therapist to assess the potential for eye hazard.
The laser is held against the skin in a contact mode (Oshiro
), applying the maximum amount of laser light to the area of consideration. Many
therapists recommend applying light to firm pressure to the area to distress the
underlying blood vessels and tissue to improve the penetration of the energy.
The laser is applied at a given power output for a specified period of time, to
deliver the proper amount of laser energy, measured in joules. Dosages can range
from 1 joule up to 30 or more, depending upon the condition being treated and
the schedule of treatments. A wavelength is chosen which meets the absorption
requirements of the condition, with wounds and aesthetic conditions benefiting
from higher absorption (lower wavelengths), and deep tissue benefiting from deeper
penetration (higher wavelengths). Normally, multiple treatments are needed to
resolve chronic conditions and injuries. Laser can be directed to acupuncture
points, trigger points, nerve endings and directly to the specific injury. Recent
findings conclude that, with few exceptions, patients do better when treatment
begins as quickly as possible.
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1Karu, T. Molecular
mechanism of the therapeutic effect of low-intensity laser irradiation. Lasers
in the Life Sciences, 1988:;2:53-74.
2Naviaux, Robert K. Mitochondrial Metabolism and the Injured Cell Response
to Near Infrared Light, at the N.A.A.L.T, April 5, 2003, Bethesda, MD..
3Basford, J. Laser Therapy: Scientific Basis and clinical role, Orthopaedics,
4Zhao, Y, Yasudam S, Yamamoto M, et al. He-Ne lasr irradiation against
rat adjuvant arthritis. Jap J Assoc.
Phys. Med. Balneol Climatol, 1990;53 No. 2:95-100.
5Skobelkin O, Kozlov V, Litwin G, et al. Blood microcirculation under
laser physiotherapy and reflexotherapy in patients with lesions in vessels of
low extremeties. Laser Therapy, 1190; 2 No.2; 69-77.
6Kozlov V, Terman O Builin V,et. al. Structural and functional basis
at laser microvessels interaction. Proc of SPIE, 1993:48-55
7Telfer J, Filonenki N, Salansky N. Leg ulcers: Plastic surgery descent
y laser therapy. Proc of SPIE, 1993;2086:258-261.
8Lievens, P. The influence of laser irradiation on the motricity of
lymphatical system and on the wound healing process. InLT. Congress on Laser in
Medicine and Surgery, Bologna, June 26-28, 1985.
9Lyons R, Abergel R, White R, et al. Biostimulation of wound healing
in-vivo by a helium neon laser. Annals of Plastic Surgery, 1987;18:47-50.
10Abergel R, Lyons R, Castel J. Biostimulation of wound healing by
lasers: experimental approaches in animal models and fibroblast cultures. J Dermatological
Surgery Oncology, 1987;13:127-133.
11Enwemeka, C. Rodriquez O., Gall N., et. al, Correlative Ultrastructural
and biomechanical changes induced in regenerating tendons exposed to laser photostimulation.
Lasers in Surgery and Medicine, 1990: (Suppl.2)" 12-19.
12England S, Farrell J, Coppock G, et al. Low power laser therapy of
shoulder tendonitis. Scand J Rheumatologoy, 1989;18:427-431.
13Baxter D, Bell A, Allen J. et al. Low Level Laser Therapy. Current
clinical practice in Northern Ireland. Physiotherapy, 1991;77:171-178.
14Oshiro, T. Low Level Laser Therapy, Wiley and Sons, Bath Press, Avon, U.K., 1988,