Mechanisms of action and requirements for successful laser therapy, laser irradiation
The following points have an influence on the success of the therapy:
1. power (and power density, W/cm2)
2. correct amount of energy (Joules/cm2)
3. duration of therapy
4. frequency modulation, frequency information (Hz)
5. treatment location (local, reflective)
Laser medicine and laser therapy are also governed by the Arndt Schulz Law (so-called biological law), established by the psychologist R. Arndt (1835-1900) and the pharmacologist H. Schulz (1853-1932).
Strong stimuli paralyse, destroy
Medium stimuli inhibit
Weak stimuli promote
Adequate energy releases, applied at the right destination, can harmonize disturbed organ functions again: Not the strongest, just endured stimulus is the best, but the weakest, which still produces a sufficiently good reaction at the "destination".
The right amount of energy (J/cm2) at the destination
The decisive question concerns the sufficient amount of energy (generally 4-6 J/cm2) and, of course, the destination, is it superficial or deep, punctual or extensive? Do the photons or the required amount of energy reach the target location and in what time? Is the required therapy time acceptable for the patient or does the therapist have to choose another laser class to compensate for the losses due to higher power?
The laser beam is reflected, scattered, absorbed and transmitted depending on wavelength and tissue. Strong absorption and reflection takes place below 600 nm and above 950 nm, the tissue is overheated depending on the power.
Which laser power is the best?
The power must always be selected individually and depends on various factors, such as type and depth of tissue, size of the area, energy density of the laser beam, duty cycle of the modulated laser beam and as well treatment duration. The type of disease, the patient's reaction capacity and the therapy method (e.g. trigger points tolerate a strong stimulus) can also play a role.
Radiation behaviour in tissue
As mentioned above, strong absorption and reflection takes place below 600 nm and above 950 nm, the tissue gets heated depending on the power. In case you are using the LightStream you will experience that the "good" wavelenghts are producing already very much heat (depending on the setting as power and duty cycle).
The optical window
Wavelengths in the "optical window" = optimum penetration depth
ABSTRACT Attenuation and penetration of visible 632.8nm and invisible infrared 904nm laser light in soft tissues
Department of Physical Therapy & Rehabilitation Sciences, University of Kansas Medical Center, Kansas City, KS, and Department of Veterans Affairs Medical Center, Kansas City, MO, U.S.A.
We studied the depth of penetration and the magnitude of attenuation of 632.8nm and 904nm light in skin, muscle, tendon, and cartilagenous tissues of live anaesthetized rabbits. Tissue specimens were dissected, prepared, and their thicknesses measured. Then, each wavelength of light was applied. Simultaneously, a power meter was used to detect and measure the amount of light transmitted through each tissue. All measurements were made in the dark to minimize interference from extraneous light sources. To determine the influence of pulse rate on beam attenuation, the 632.8nm light was used at two predetermined settings of the machine; continuous mode and 100 pulses per second (pps), at an on:off ratio of 1:1. Similarly, the 904nm infra-red light was applied using two predetermined machine settings: 292 pps and 2,336 pps. Multiple regression analysis of the data obtained showed significant positive correlations between tissue thickness and light attenuation (p < .001). Student's t-tests revealed that beam attenuation was significantly affected by wavelength. Collectively, our findings warrant the conclusions that (1) The calf muscles of the New Zealand white rabbit attenuates light in direct proportion to its thickness. In this tissue, light attenuation is not significantly affected by the overlying skin, a finding which may be applicable to other muscles. (2) The depth of penetration of a 632.8nm and 904nm light is not related to the average power of the light source. The depth of penetration is the same notwithstanding the average power of the light source. (3) Compared to the 904nm wavelength, 632.8nm light is attenuated more by muscle tissue, suggesting that is is absorbed more readily than the 904nm wavelength or conversely that the 904nm wavelength penetrates more. Thus, wavelength plays a critical role in the depth of penetration of light.
key words: Laser Therapy, Light Attenuation, Light Asorption.
Therapeutically effective wavelengths and best penetration
Biophysical reactions also take place, e.g. depending on the power and duration of therapy, gentle warming can take place.
The correct selection of the wavelength enables, among other things, shorter therapy times, since more energy is made available in the same time. The table on the left shows the better penetration depth (musculature) of 808 nm versus 980 nm.
Application forms of laser therapy, bipolar therapy
1. local irradiation of organs, body parts (macrosystem)
2. reflectorically via acupuncture, ear points, dermatomes (microsystem)
2. systemic, affecting the entire body (laser blood irradiation)
The decision for one or the other type of treatment depends on the orientation of the practice. A combination of the three application forms mentioned above is ideal. With the "Bipolar Therapy" recommended by RJ, the therapist acts in the central area of function control via e.g. ear acupuncture and treats locally, the wound or inflammation etc. in parallel. The RJ laser devices are designed for simultaneous treatment.
Wound healing with the Physiolaser
The laser frequency modulation (Hz) makes a difference
nm, Al-Ga-As) Augments Dermal Wound Healing in Immunosuppressed Rats
Gaurav K. Keshri, Asheesh Gupta*, Anju Yadav, Sanjeev K. Sharma, Shashi Bala Singh
Chronic non-healing cutaneous wounds are often vulnerable in one or more repair phases that prevent normal healing and pose challenges to the use of conventional wound care modalities. In immunosuppressed subject, the sequential stages of healing get hampered, which may be the consequences of dysregulated or stagnant wound inflammation.
Results clearly delineated that 810 nm PBM at 10 Hz was more effective over continuous and 100 Hz frequency in accelerating wound healing by attenuating the pro-inflammatory markers (NF-kB, TNF-α), augmenting wound contraction (α-SM actin), enhancing cellular proliferation, ECM deposition, neovascularization (HIF-1α, VEGF), re-epithelialization along with up-regulated protein expression of FGFR-1, Fibronectin, HSP-90 and TGF-β2 as compared to the non-irradiated controls. Additionally, 810 nm laser irradiation significantly increased CCO activity and cellular ATP contents. Overall, the findings from this study might broaden the current biological mechanism that could be responsible for photobiomodulatory effect mediated through pulsed NIR 810 nm laser (10 Hz) for promoting dermal wound healing in immunosuppressed subjects.
Research information on laser therapy, extracts
"Photobiological Basics", H. Walter
It was in the 1980s when T. Karu began to search for the photobiological "receiver" at the cellular level. In a series of excellent publications (most of which have been compiled into a book) she was able to prove that the main photo-acceptors are the enzymes of the respiratory chain in the mitochondria.
The stimulation of the respiratory chain
In order to understand exactly where the laser radiation intervenes, the processes in the respiratory chain are briefly explained:
The respiratory chain, also known as electron transport chain and oxidative phosphorylation, represents the last step in the human metabolism: The complex metabolites of our daily food, such as carbohydrates, lipids and proteins, are first broken down into their monomeric units, mainly glucose, fatty acids, glycerol and amino acids, and then into their common intermediate product, acetyl-coenzyme A (acetyl-CoA). In the citric acid cycle, acetyl-CoA is oxidized by O2 to CO2, while simultaneously reducing the coenzymes NAD+ and FAD to their high-energy intermediates NADH and FADH2. In the last part of this metabolism, called electron transport and oxidative phosphorylation, these energy-rich intermediates are reoxidized by O2, i.e. electrons are transferred from NADH or FADH2 to oxygen O2, which is reduced to H2O by this and by the uptake of 2 protons H+. The energy released in this process drives the synthesis of the energy-rich ATP from ADP by phosphorylation with Pi.
All these processes take place normally even in the dark and in every healthy cell. If such a cell is additionally irradiated with light, the enzyme complexes are supported in their redox process by the so-called photooxidation. Photooxidation is a process in which a donor molecule excited by light transfers an electron to an acceptor and is thereby oxidized, while the acceptor molecule involved is reduced. This process works because electrons are less strongly bound to the molecule in the excited state than in the ground state. The energy of absorbed photons is thus chemically transferred to the redox centres of the enzyme complexes of the respiratory chain, which makes the latter more easily oxidised or ionised, and increases the synthesis of ATP. At this point, this key point of the light-metabolism interaction should be clearly pointed out again. The term oxidation in chemistry, namely the release of electrons, is the same as ionization in physics, where an electron is also taken away from an atom or molecule. It is generally known that ionisation from an energy level excited (by light) is easier or more probable.
The dependence of light-stimulated ATP synthesis on the wavelength of the irradiated light is determined by the absorption properties (which change slightly in the oxidized or reduced state) of the individual components, the enzyme complexes, mainly cytochromes.
These data show that there are two groups of spectrally sensitive regions. One covers the near ultraviolet and visible blue wavelength range of about 350 - 450 nm, and the second covers the visible red and near infrared range of about 600 - 830 nm. With many such experiments with prokaryotic and eukaryotic cells T. Karu was able to show that in the blue wavelength range the flavoproteins (Fig. 5) of the reductases (dehydrogenases) and in the red wavelength range the semichinone form of the flavoproteins of the reductases (dehydrogenases) and the cytochrome a/a3 (Fig. 6) of the cytochrome c-oxidase are the light receptors. Such investigations are facilitated by the fact that it is a principle of photochemistry that an action spectrum always reflects the course of the absorption spectrum of the light-absorbing molecule.
In accordance with clinical experience, such investigations have shown that for maximum stimulation, not only the energy density must lie within a certain range, but also the power density and thus the irradiation time. It is particularly interesting that the optimum irradiation parameters given in the table correspond well with clinical experience.
"CELLULAR MECHANISMS of LOW-POWER LASER THERAPY (PHOTOBIOMODULATION)", Tina.I. KARU
- What is photobiomodulation (low-power laser therapy?)
More than 30 year ago the first publications about low-power laser therapy or photobiomodulation (at that time called laser biostimulation) appeared. Since then approximately 2000 studies have been published on this topic (analysis of these publications can be found in ). Medical treatment with coherent light sources (lasers) or noncoherent light (Light Emitting Diodes, LED's) has passed through its childhood and early maturity. Photobiomodulation is being used by physiotherapists (to treat a wide variety of acute and chronic muscosceletal aches and pains), dentists (to treat inflamed oral tissues, and to heal diverse ulcerations), dermatologists (to treat oedema, indolent ulcers, burns, dermatitis), rheumatologists (relief of pain, treatment of chronic inflammations and autoimmune diseases), and by other specialists (e.g., for treatment of middle and inner ear diseases, nerve regeneration). Photobiomodulation is also used in veterinary medicine (especially in racehorse training centers) and in sports medicine and rehabilitation clinics (to reduce swelling and hematoma, relief of pain and improvement of mobility and for treatment of acute soft tissue injuries). Lasers and LED's are applied directly to respective areas (e.g., wounds, sites of injuries) or to various points on the body (acupuncture points, muscle trigger points). For details of clinical applications and techniques used, the books [ 1-3] are recommended.
- What light sources (lasers, LED's) can be used?
The field of photobiomodulation is characterized by variety of methodologies and use of various light sources (lasers, LED's) with different parameters (wavelength, output power, continuous wave or pulsed operation modes, pulse parameters). These parameters are usually given in manufacturers manuals.
The GaAlAs diodes are used both in diode lasers and LED's, the difference is whether the device contains the resonator (as the laser does) or not (LED). In latter years, longer wavelengths (-800-900 nm) and higher output powers (to 100 mW) are preferred in therapeutic devices.
Should a medical doctor use a laser or a diode? The answer is - it depends on what one irradiates, in other words, how deep tissue layers must be irradiated. By light interaction with a biotissue, coherent properties of laser light are not manifested at the molecular level. The absorption of low-intensity laser light by biological systems is of a purely noncoherent (i.e., photobiological) nature. On the cellular level, the biological responses are determined by absorption of light with photoacceptor molecules (see the section 3 below). Coherent properties of laser light are not important when cellular monolayers, thin layers of cell suspension as well as thin layers of tissue surface are irradiated (Fig. 1). In these cases, the coherent and noncoherent light (i.e., both lasers and LED's) with the same wavelength, intensity and dose provides the same biological response. Some additional (therapeutical) effects from the coherent and polarized radiation (lasers) can occur in deeper layers of bulk tissue only and they are connected with random interference of light waves. An interested reader is guided to the ref.  for more details. Here we illustrate this situation by Fig. 1. Large volumes of tissue can be irradiated by laser sources only because the length of longitudinal coherence Lcoh is too small for noncoherent radiation sources .
- Enhancement of cellular metabolism via activation of respiratory chain: a universal photobiological action mechanism
A photobiological reaction involves the absorption of a specific wavelength of light by the functioning photoacceptor molecule. The photobiological nature of photobiomodulation means that some molecule (photoacceptor) must first absorb the light used for the irradiation. After promotion of electronically excited states, primary molecular processes from these states can lead to a measurable biological effect (via secondary biochemical reaction, or photosignal transduction cascade, or cellular signaling) at the cellular level. The question is, which molecule is the photoacceptor.
Photobiology on-line, American Society for Photobiology
Photomedicine, scientific overview
Tiina Karu, Action Spectra and their importance for LLLT