Frequently Asked Questions - Laser Therapy, Photobiomodulation

Answer: The term LLLT (Low Level Laser Therapy) is generally choosen for cl. 3B. The laser instrument is the term "therapeutic laser" rather than "low level laser" or "low power laser", because cl. 4 at high-level are used for laser therapy as well. The term "soft laser" is an old term.
The energy transferred to tissue is the product of laser output power and treatment time, which is why a "low-energy laser", over a long period of time, can actually emit a large amount of energy. In USA many use the term "cold laser" but in reality there is not cold laser even a single photon generates "heat".

Answer: Yes, there are some 100 double-blind positive studies confirming the clinical effect of LLLT. Thousands of research reports are published, cell studies, animal studies and on humans. 

Answer: Subscribe the journal "Laser Therapy and Photomedicine", get books on laser therapy such as "Low Level Laser Therapy - clinical practice and scientific background". More contact data can be found on our webpage.

Type your questions at https://pubmed.ncbi.nlm.nih.gov

Answer: Yes, some studies fail. In some cases the power is too low, others use simply not the correct wave length, not the correct tratment duration and technique etc.. Laser is not laser. Therapy success is a matter of correct dosage, diagnosis, treatment technique and individual reaction. 
And finally laser therapy cannot work on everything, this would be more than a miracle.

Answer: For photobiomodulation generally diode lasers in the range between 600 nm to 915 nm (optical window). Both continuous and pulsed lasers, cl. 3B and cl. 4.

Below 600 nm and above 950 nm there is too much absorption, no stimulation of photoacceptors. Wavelengths around and above 1000 nm are hardly unexplored for photobiomodulation and they unnecessarily heat the tissue.

Answer: Yes, but depending on various facts. The power, wavelength and divergence of the laser beam are the decisive factors. If the beam runs parallel or is focused with a small diameter, it is dangerous, especially if it comes from the non-visible range (infrared, UV), as no blinking reflex is generated here. If it enters the pupil completely and is focused by the lens on a point with a diameter of a hundredth of a millimeter, retinal damage is possible. Even a 10 mW beam can have a power density of up to 12,000 W/cm2, the power of surgical lasers.
The visible wavelengths cause a fast blinking reflex, which reduces the exposure time and thus the light energy entering the eye.

Class 3B and 4 lasers must not be operated without protective goggles.

Translated with www.DeepL.com/Translator (free version)

Answer: You can limit the selection according to the following criteria:

1. application-related for small or large areas
2. therapy related, conventional or complementary (e.g. ear acupuncture)
3. the power, time, energy and frequency should be adjustable
4. the wavelengths should be therapeutically documented
5. stationary or mobile (e.g. sports and veterinary medicine)
6. expandability, updateability
7. handling, shape/size
8. budget

For a 3B class laser, a power of 200 to 500 mW or even 90 W pulsed is desirable. For an area probe a multiple of this.

For a therapy laser of class 4, 10 to 15 W continuous beam is more than sufficient. Higher power levels tend to have disadvantages, because the tissue is heated up too much.

Good service and easy accessibility of the manufacturer/supplier is extremely important, as laser therapy quickly becomes indispensable in daily practice.

The manufacturer/laser must be medically certified and approved and the manufacturer should also have the possibility to check according to ISO 13485:2016.

Answer: GaAs laser diodes emit pulsed laser radiation with a pulse duration of 100-200 nsec. depending on the frequency. The single pulse has a peak power of 90 W, for example. The average power is then, depending on the pulse frequency, still in the range of Kl. 3B (up to 500 mW). Rule of thumb: "Watt peak pulse", divided by two gives approximately the average power in mW (as continuous beam).

The situation is different with class 4 lasers, which are usually always specified in watts as continuous beam.

Answer: For punctual therapy a point probe is required and for larger area therapy a kind of "laser shower" or scanner. A cl. 4 laser meets both requirements, because for larger areas only the distance probe/skin needs to be increased.

Observe sufficient power: In laser therapy one is always confronted with losses (the beam is reflected, scattered, absorbed). The laser beam should always emit a defined amount of energy at the target location. If it is deep, the laser beam has to penetrate tissue and is weakened, which results in a longer therapy duration for the corresponding amount of energy. Depending on the power, this can lead to several hours of therapy (with higher power, the patient can be treated within reasonable limits). Large areas are also easier to treat with higher power.

The exact "biofrequency" (laser resonance therapy) can make a significant contribution to the success of the therapy, even at low power, because the information is crucial. The laser should have options to select frequencies, if possible already pre-programmed.

Please refer as well to the point "How do I know which laser I should buy"?

Answer: In some respects it is possible, but it is primarily a heat therapy, because the wavelength in the upper layers of the skin is absorbed by the water. The danger of overheating/burning is quite high.
However, there are better possibilities today, as technological development has led to compact laser diodes with high power from the wave range of the "optical window". Furthermore the diode laser can be modulated perfectly and are ideal for frequency therapy.

Answer: The penetration depth of the laser light depends primarily on the wavelength of the laser and also on the tissue, skin color. For example, the penetration depth of the laser through the bone is less than that of the fat. Dense hair, dark hair, dark skin also prevents or reduces the penetration depth.
There is no defined limit to the penetration depth. It is certain that the light becomes weaker and weaker the further it penetrates from the surface. At a certain point, however, the light intensity is so low that no biological or therapeutic effect occurs. This limit, at which the effect stops, is called the greatest active depth.

The treatment technique is also important. The depth of penetration is improved, for example, by applying pressure to the tissue with the tip of the probe and thus getting closer to the target site and additionally displacing tissue fluid.

Example of the penetration depth (muscles) for 808nm versus 980 nm


Many therapists (among others Dr. Uwe Petermann) recommend the pulsed laser diode 90W/904 nm for optimal depth effect and indeed it seems to be well suited for this purpose, on the one hand from the colour (infrared) and on the other hand from the pulse behaviour and power.

Answer: The usual therapeutic wavelengths are not in the range of short wave carcinogenic radiation (UV). So far, no mutation effects have been observed that could result from light with wavelengths in the red or infrared range or from the dosages used in laser therapy.
Cancer cells that were irradiated in vitro could be stimulated. However, the situation is different for cancer in vivo. Laboratory experiments on rats have shown that small tumours can regress and disappear completely, although laser treatment has had no effect on large tumours. Presumably, the local immune system is stimulated more strongly than the tumour.
Laser therapy is recognized and is now a standard therapy for the treatment of chemotherapy-induced mucositis.

Answer: Here too, it depends on the indication, the individual case. Trigger points, acupuncture points etc. can hardly be over-stimulated. However, cells in the test tube can be over-stimulated, but they will tend to stagnate (open wounds as well). In any case, sufficient energy must be provided, which is generally 4-6J/cm2. Based on this the dose is increased or reduced depending on the reaction.

Normal skin, muscles etc. are stimulated by high doses (up to warming at cl. 4) and are not damaged.
dose must also be considered in relation to power density (200 mW as a tiny point leads to combustion).  
The dose must also be set in relation to time. If a high dose is delivered within 1 second, it will probably not cause a reaction in the tissue. Biological processes need time to "mature".

The study by Asheesh Gupta (see laser therapy) clearly shows how little energy can be used to initiate wound healing processes, for example.

Answer: You should not treat cancer, for legal reasons. Pregnant women is not a counter indication, as long as you e.g. do not stimulate acupuncture points related to uterus contractions. Pace makers and other implanted electronic devices, do not respond to light. The most valid counter indication seems to be lack of medical training.

Exact data can be found in your device manual.

Answer: Due to the increased circulation, an increase of 0.5-1 degrees Celsius can be observed locally (depending on duration). The biological effect has nothing to do with heat. GaAlAs lasers in the range of 200-500 mW can cause a noticeable sensation of warmth, depending on the size of the exit and skin colour.
Blue and violet lasers will produce heat by as little as 50 mW after a few minutes of exposure.

There are no cold lasers, each photon is energy (heat), but in this case very little.
The increase in heat depends on several factors, such as body part, skin type, wavelength, power, energy density.

Heating and burns can occur

• If the energy of the laser cannot be dissipated, e.g. by blood circulation or if it cannot penetrate deeply.
• On pigmented skin (e.g. patients of African/Indian origin), moles, birthmarks, tattoos, high risk when used with short wavelengths (green, blue, violet), below 600 nm.
•  If the laser output is a small spot (high energy density)
• If the laser probe stays on the skin too long

Answer: LEDs are not monochromatic and their light is not coherent. The coherence is important because it is highly organized and the beam can be manipulated with lenses, it can penetrate deeper. Monochromatic laser light is crystal clear and such a single wavelength can reach absorption peaks up to 100%. Monochromatic, highly organized light is important for information transmission (bio frequencies, resonance frequencies).
If the LED has a narrow bandwidth, this can be useful for superficial tissues such as wounds. In comparative studies, lasers have proven to be more effective than monochromatic, non-coherent light.

Answer: Coherence is the degree of order of the light (or other system). The higher the degree of order, the clearer and more distinct the communication and behaviour of the parts among each other. In the case of laser light, the waves and phases have an exactly defined distance.

In the case of laser light, the length of coherence is divided into tiny, small coherent "spots" called specles. Such specles remain coherent and penetrate deep into the tissue.

Answer: For the same application areas, a laser of class 4 provides more photons and guarantees a sufficient threshold stimulus. Class 4 includes class 3B, i.e. the power can be reduced accordingly if necessary. Why high power? The treatment effect often occurs faster. The patient feels a pleasant warmth as a reaction to the higher laser energy. This deep warmth has a positive effect especially in pain therapy and orthopaedic indications. Therapy times are shortened and treatment intervals are often extended.

Answer: The treatment effect often occurs more quickly. The patient feels a pleasant warmth as a reaction to the higher laser energy. This deep warmth has a positive effect especially in pain therapy and orthopaedic indications. The therapy times are shortened and the treatment intervals are often extended.

Answer: The penetration depth depends primarily on the wavelength (colour). At the same wavelength, a class 4 laser reaches the therapeutically effective dose faster than a class 3B laser. 500 mW (808 nm) cw are reduced to about 2 mW power after about 2 cm of tissue. To obtain 2 J at the target site takes about 15 minutes! With a surface area of 5 cm2 this would be over 1 hour of therapy. 15 W, on the other hand, achieve 2 J within 33 seconds, which would be about 2 minutes of therapy time for an area of 5 cm2. Wavelengths within the "optical window" penetrate into deep tissue layers, wavelengths below 550 nm and above 950 nm have no depth effect because, among other things, water, melanin, hemoglobin are absorbed and they heat the tissue unnecessarily. A stimulating ATP effect (cytochrome-c-oxidase) has also not been proven.

Answer: Both punctual (point attachment) and on large areas can be worked. The distance between the probe and the skin must simply be increased or the diameter of the laser beam is increased.

Answer: Yes, both cl. 3B and cl. 4 lasers can over-stimulate the tissue. This primarily affects
exposed tissue structures, e.g. wounds.

Answer: Yes, combustion can occur with both cl. 3B and cl. 4 depending on energy density,
application time and absorption. The therapy with the class 4 laser probe is usually carried out with light movement (brushing, dabbing). If the treatment is carried out correctly, no burns will occur.

Answer: YYes, depending on the model, the known bio-frequencies are used. All RJ laser devices offer bio-frequencies.

Answer: No, almost the same safety regulations apply, the only addition is a flashing light at laser triangle (warning sign) on the door to the treatment room.

Answer: Yes, because the acceptance of the patient is very high and a noticeable effect
occurs quickly and thus the willingness to pay in cash increases.

Answer: Both punctual (point attachment) and surface work can be carried out. For area therapy, the distance between the probe and the skin is simply increased or the diameter of the laser beam is increased.