Q: What is laser therapy?
A: Laser therapy or Laser Phototherapy is a method where light from a laser is applied to tissue (or cells in culture) in order to influence cell or tissue functions with such low light intensity that heating is negligable. The effects achieved are hence not due to heating but to photochemical or photobiologic reactions like the effect of light in plants. The lasers used are normally called therapeutic lasers or medical lasers.
This is in contrast to the use of lasers in surgery and for esthetic purpose where strong lasers are used and where the biologic effects (cutting, evaporating, coagulating) are based on heat development from the absorption of strong light, i.e. burning glass effect.
Q: What is the correct name: LLLT, LPLT, therapeutic laser, soft laser, MID laser or biostimulation?
A: Regarding the therapy, we have chosen to use the term LLLT (Low Level Laser Therapy). This is the dominant term in use today, but there is still a lack of consensus. In the literature LPLT (Low Power Laser Therapy) is also frequently used.
Regarding the laser instrument, we have chosen to use the term "therapeutic laser" rather than "low level laser" or "low power laser", since high-level lasers are also used for laser therapy.
The term "soft laser" was originally used to differentiate therapeutic lasers from "hard lasers", i.e. surgical lasers. Several different designations then emerged, such as "MID laser" and "medical laser".
"Biostimulating laser" is another term, with the disadvantage that one can also give inhibiting doses. The term "bioregulating laser" has thus been proposed. An unsuitable name is "low-energy laser". 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. Other suggested names are "low-reactive-level laser", "low-intensity-level laser", "photobiostimulation laser" and "photobiomodulation laser". "LPT - Laser Photo Therapy" is a recently suggested term, and winning acceptance.
Thus, it is obvious that the question of nomenclature is far from solved.
This is because there is a lack of full agreement internationally, and the names proposed thus far have been rather unwieldy. Feel free to forget them, but remember LLLT until agreement is reached on something else.
Q: Is laser therapy scientifically well documented? A: Basicly yes. There are more than 130 double-blind positive studies confirming the clinical effect of LLLT. More than 3000 research reports are published. Looking at the limited LLLT dental literature alone (370 studies already in 1999), more than 90% of these studies do verify the clinical value of laser therapy. About 250 papers are annually published in peer reviewed scientific papers.
Q: Where do I find such documentation? A: The book "Laser Therapy Handbook" is the best reference guide for literature documentation. Abstracts from scientific papers can be found on PubMed, http://www.pubmed.com
Q: But I have heard that there are dozens of studies failing to find any effect of LLLT?A: That is true. But you cannot just take a any laser and irradiate for any length of time and using any technique. A closer look at the majority of the negative studies will reveal serious flaws. Look for link under Laser literature and read some examples. But LLLT will naturally not work on anything. Competent research certainly has failed to demonstrate effect in several indications. However, as with any treatment, it is a matter of dosage, diagnosis, treatment technique and individual reaction. Se link critic on critic.
Q: Which lasers can be used in medicine?A: Examples of lasers which can be used in medicine, both for surgery and therapy:
Therapeutic lasers (where the mechanism is not based oh heat):
GaAs904 nm (super pulsed) Treatment of deep problems (back, shoulders, knees, head ache etc)
GaAlAs780-808-890 nm (cont. or chopped)Also deep problem, often a complement ot the GaAs-laser
InGaAlP630-700 nmTreatment of skin and mucose problems
HeNe633 nmAlternative to InGaAlP (see above)
Thermal lasers (for surgery or esthetic use):
Ruby694 nmHair removal (for Q-switch type: tattoo bleaching)
Nd:YAG1064 nmCoagulation of tumors, eye surgery (cataracts)
Ho:YAG2130 nmCrushing of kidney stones, surgery
Er:YAG2940 nmDental drill, laser peeling of wrinkles and scars
KTP/532532 nmCoagulation of blood vessels, hemangioma.
Alexandrite755 nmHair removal (for Q-switch type: tattoo bleaching)
CO2 laser10600 nmSurgery and laser peeling of wrinkles and scars
Argon514 nmEye surgery (treatment of retinopathy)There are many other types, but those mentioned above are the most common.
Q: How do I know which laser I should buy? A: The laser market is very complicated and full of pitfalls. How do you know which instruments are good? What is expensive? Will it be expensive in the long run to buy something cheap? It is easy to make hasty decisions when faced with a skilful salesman - who is likely to know much more about the field than the customer. Before you know it, you've signed on the dotted line. All lasers are given a laser class. This classification is only to indicate the possible eye risk and has nothing to do with the possible efficktiveness in treatment. There are four laser classes where class 4 is the strongest and class 1, 2 and 3A and 3B are less hazardous to eyes. Lasers in CD players and for reading bar codes are usually class 1 lasers while surgicla and industial lasers usually are class 4 lasers.
Here are a number of questions which you should ask both the salesman and yourself. You would be well advised to read these carefully in case you regret not doing so later on!
1 "Laser instruments" have been sold which do not even contain a laser, but LEDs or even ordinary light bulbs. These instruments have been sold for between US $3,000 - $10,000. How can you acquire proof that the instrument really does contain a laser?
2 In a number of products, laser diodes have been combined with LEDs. This is often kept secret and the salesman has only talked about a laser. Are all light sources in the apparatus (except guide lights and warning lights) really lasers?
3 Is a strong laser better than a week? No, not necessarily. There is an optimal dose for what ever treatment - let's say that you want to administer 10 joules to a certain area. If the laser output is 1 watt, it takes 10 seconds to give 10 joules. With a 100 mW laser it takes 100 seconds to produce 10 joules. Further, it has become clear that also treatment time should not be too short or too long. As high power has become a more and more common sales argument, it can be difficult to achieve both optimal dose and optimal treatment time. Naturally, also a too weak laser can make the treatment less successful.
4 For oral work and wound healing, InGaAlP and GaAlAs are the most common types, with GaAlAs as the most versatile one. For injuries to joints, vertebrae, the back, and muscles, that is, for the treatment of more deep-lying problems, the GaAs laser is the best documented. For veterinary work, a laser is needed which is designed so that the laser light can pass through the coat, and penetrate to the desired depth. For superficial tendon and muscle attachments, the required depth can be reached with the GaAlAs laser. Many companies have only one type of laser, such as a GaAlAs, and the salesman will naturally tell you that it is the best model for everything, and that it is irrelevant which type of laser is used. However, research tells quite a different story. GaAs further requires lower dosage than GaAlAs, so nominal power is not everything.
Q: How come some LLLT equipment has power in watts and some only in milliWatts? A: A typical example is GaAs lasers. As a GaAs laser always works in a pulsed fashion, the laser light power varies between the peak pulse output power and zero. Then usually the laser's average power output is of importance, especially in terms of dose calculation. The peak pulse power value is of some relevance for the maximum penetration depth of the light. Some manufacturers specify only the peak pulse output in their technical specifications. "70 W peak pulse output" or even "70 000 mW power output" naturally sounds more impressive than 35 milliwatts average output!
Q: Which frequency (pulsing) should be used for the various therapies?
A: First we must differentiate between “chopping” and “superpulsing”. Some lasers, like the GaAs laser, are always pulsed. The pulses are very short but the peak power of the pulse is very high, several watts, but the pulse duration is typically only 100 to 200 nano seconds. Other lasers like the HeNe and the GaAlAs are normally continuous, but can be pulsed by mechanical or electrical devices. This means that the beam is turned off and on but the peak output power of each pulse is the same as if the light is continuous.
If a continuous laser is pulsed, the average output power will be lower. With most GaAs lasers the power decreases with lowered frequencies (unless there is a pulse train arrangement) and with “chopped” lasers we typically loose 50% (50% duty cycle).
There is some evidence from cell studies that the pulsing can makes a difference. But the evidence from clinical studies is almost absent. Since GaAs is always pulsed, we have to choose a frequency and then to use the anecdotal evidence there is about what frequency is good for what.
200-300 mW laser diodes are now relatively cheap and the GaAlAs laser gives "a lot of milliwatts for the money". Recently, GaAlAs lasers have appeared on the market with an impressive output of over 500 mW. In Europe, GaAlAs laser with powers above 500 mW can only be used by doctors and dentists, being Class 4 lasers.
Q: Can carbon dioxide lasers be used for LLLT?A: Yes. Therapeutic laser treatment with carbon dioxide lasers has become more and more popular. This does not require instruments expressly designed for that purpose. Practically any carbon dioxide laser can be used as long as the beam can be spread out over an appropriate area, and as long as the power can be regulated to avoid burning. This can always be achieved with an additional lens of germanium or zinc selenide, if it cannot be done with the standard accessories accompanying the apparatus.
It is interesting to note that the CO2 wavelength cannot penetrate tissue but for a fraction of a mm (unless focused to burn). Still, it does have biostimulative properties. So the effect most likely depends on transmittor substances from superficial blood vessels. Conventional LLLT wavelengths combine this effect with "direct hits" in the deeper lying affected tissue.
Q: Can LLLT cause cancer? A: The answer is no. No mutational effects have been observed resulting from light with wavelengths in the red or infra-red range and of doses used within LLLT.
But what happens if I treat someone who has cancer and is unaware of it? Can the cancer's growth be stimulated? The effects of LLLT on cancer cells in vitro have been studied, and it was observed that they can be stimulated by laser light. However, with respect to a cancer in vivo, the situation is rather different. Experiments on rats have shown that small tumours treated with LLLT can recede and completely disappear, although laser treatment had no effect on tumours over a certain size. It is probably the local immune system which is stimulated more than the tumour.
The situation is the same for bacteria and virus in culture. These are stimulated by laser light in certain doses, while a bacterial or viral infection is cured much quicker after the treatment with LLLT
Q: What happens if I use a too high dose? A: You may have a biosuppressive effect or just a non optimal effect. That means that, for instance, the healing of a wound will take longer time than normally. Very high doses on healthy tissues will not damage them.
Q: Are there any contraindications? A: No, no medical contraindications. In most countries there are legal contraindications, i.e. you should not treat cancer or some other seious deseases. Pregnancy is not a contra indication if treatment is done with common sense. Pacemakers are electronical and are not influenced by light. The most valid contraindication is possible lack of adequate medical treatment.
Q: Does LLLT cause a heating of the tissue? A: Principally yes - all light will cause some heating if absorbed by tissue. However stronger laser types. like GaAlAs lasers in the 300-500 mW range may cause a noticeable heat sensation, particularly in hairy areas, dark tattoo and on sensitive tissues such as lips. The amount of melanin in the skin is an important factor; dark skin will be more heated than fair skin. The biological effects have nothing to do with heat. Due to increased circulation there is usually an increase of 0.5-1 degrees Celcius locally.
Q: Does it have to be a laser? Why not use monochromatic non coherent light?A: Monochromatic non coherent light, such as light from LED's can give good effect on superficial tissues such as wounds. In comparative studies, however, lasers have shown to be more effective than monochromatic non coherent light sources, especially in deep tissue.
Q: Does the coherence of the laser light disappear when the light is scattered in the tissue?A: No. The length of coherence, though, is shortened. Through interference between laser rays in the tissue, very small "islands" of more intense light, called speckles occur. These speckles will be created as deep as the light reaches in the tissue and within a speckle volume, the light is partially polarized. It is easy to show that speckles are formed rather deep down in tissue and the existence of laser speckles prove that the light is coherent.
Q: Do therapeutic lasers produce so-called soliton waves?A: No. Such claims are just sales tricks.