Frequently Asked Questions
• What is laser treatment?
• How does it work?
• How deep into the tissue can laser light penetrate?
• Lasers vs LED
• Pulsed vs Continuous wave lasers
• Are laser treatments safe?
• Is low-level laser technology scientifically well documented?
L.A.S.E.R. (Light Amplification by Stimulated Emission of Radiation) is a name for a type of intense radiation of the light spectrum. A laser is a beam of light in which high energies can be concentrated. Laser light has unique physical properties, which other types of light do not have. These are coherence and monochromaticity. These are what makes laser light is so effective compared to other kinds of light in the field of pain reduction and healing. Laser treatment (also known as phototherapy and low level laser therapy) involves the application of low power coherent light to injuries and lesions to stimulate healing and reduce pain. It is used to increase the speed, quality and strength of tissue repair, resolve inflammation and give pain relief. Low level laser technology has been found to offer superior healing and pain relieving effects compared to other electrotherapeutic modalities such as ultrasound, especially in dealing with chronic problems and in the early stages of acute injuries. Low level laser technology is a complete system of treating muscle, tendon, ligament, connective tissue, bone, nerve, and dermal tissues in a non-invasive, drug-free modality.
The effects of low level laser treatments are photochemical. Photons enter the tissue and are absorbed in the cell’s mitochondria and at the cell membrane by chromophores. These chromophores are photosensitizers that generate reactive oxygen species following irradiation thereby influencing cellular redox states and the mitochondrial respiratory chain. Within the mitochondria, the photonic energy is converted to electromagnetic energy in the form of molecular bonds in ATP (Adenosine Triphosphate). In order to interact with the living cell, laser light has to be absorbed by intracellular chromophores. Cell membrane permeability increases, which causes physiological changes to occur. These physiological changes affect macrophages, fibroblasts, endothelial cells, mast cells, bradykinin and nerve conduction rates. The clinical and physiological effects are obtained by the way in which tissues absorb laser radiation. This tissue absorption depends on the wavelength of the beam itself and the power to ensure that the laser energy reaches the target tissue at the necessary clinical levels. The improper wavelength of laser light would not penetrate into the tissue to reach the target area. Furthermore, even if one has a laser with the proper wavelength, if the device does not have enough power to drive the energy into the tissue, the target area may not realize the potential benefits. Each type of laser emits light at a very specific wavelength which interacts with the irradiated tissue. It also acts in particular with the chromophores present in the tissue, but in a different way. A chromophore, intrinsic or extrinsic, is any substance, colored or clear, which is able to absorb radiation. Among the endogenous chromophores are water and hemoglobin, nucleic acid and proteins. Among the exogenic chromophores are porphyrins and hematoporphyrins, which are injected into the organism. These are described as photosensitizers because they fix themselves to the tissue making it photosensitive at specific wavelengths.
How deep into the tissue can laser light penetrate?
The level of tissue penetration by the laser beam depends on the beam’s optical characteristics, as well as on the concentration and depth of the chromophores, which are absorbed at different percentages according to the laser light’s wavelength. For instance, water absorbs almost 100 percent of the laser irradiation at 10,600 nanometers, the wavelength of a CO2 gas laser. That is the reason why this type of laser wavelength is used in surgical applications. Other factors affecting the depth of penetration are the technical design of the laser device and the particular treatment technique used. There is no exact limit with respect to the depth penetrated by the light. The laser light gets weaker the further from the surface it penetrates where eventually the light intensity is so low that no biological effect from it can be measured. In addition to the factors mentioned, the depth of penetration is also contingent on tissue type, pigmentation and foreign substances on the skin surface such as creams or applied oils. Bone, muscles and other soft tissues are transparent to certain laser lights, which means that light can safely penetrate these tissues. The radiation in the visible spectrum, between 400 and 600 nanometers, is absorbed by the melanin, while the whole extension of the visible which goes from 420 to 750 nanometers is absorbed by composite tetrapyrrolics. In the infrared, which covers about 10,000 nanometers of light spectrum, water is the main chromophore. Fortunately, there exists a narrow band in the light spectrum where water is not a highly efficient chromophore, thereby allowing light energy to penetrate tissue that is rich in water content. This narrow band, which extends approximately from 600 to 1,200 nanometers, is the so-called “therapeutic window”. That is the reason why the lasers in the market today have wavelengths within the 600-1,200 nanometer limit. The penetration index is not at the same level throughout the therapeutic window. In fact, lasers in the 600 to 730 nanometer range have less penetration and are more suitable for superficial applications such as in acupuncture methodologies.
Light emitting diodes (LED) are tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they do not have a filament that will burn out. They are illuminated solely by the movement of electrons in a semiconductor material. LED’s produce incoherent light just like an ordinary light bulb. Light from LED’s have very little tissue penetration compared to laser light. By applying the first law of photochemistry (Grotthus-Draper Law) which states that light must be absorbed by a molecule before photochemistry can occur, one can immediately conclude that light from LED’s will work only on skin level conditions. For conditions deeper than skin layers, one must choose laser.
Pulsed vs Continuous wave lasers
In general, laser diodes are either continuous wave or pulsed. The continuous wave (CW) diodes emit laser energy continuously, hence its name. Pulsed diodes emit a radiation impulse with a high amplitude (intensity) and duration which is typically extremely short: 100-200 nanoseconds. Continuous wave lasers produce a fixed level of power during emission. Although lacking the high peak power of a "true" or "super" pulsed laser, most continuous wave lasers can be made to flash a number of times per second to simulate pulse-like rhythms by interrupting the flow of light rapidly as in turning a light switch “off” and “on”. “True” or “super” pulsed lasers, as the name implies, produce a brief high power level light impulse. It is the high power level achieved during each pulse that drives the light energy to the target tissue. Even though the pulse peaks at a high power level there are no deleterious thermal effects in the tissue because the pulses are of such short duration. Therefore, the peak power of a “true” or “super” pulsed laser is quite high compared to its average pulse power. By using “true” or “super” pulsed lasers, one is able to more effectively drive light energy into tissue. The laser and electronic technologies required to use pulsed diodes are more advanced and the diodes themselves are more expensive than the continuous wave diodes. This is why over 90% of the therapeutic lasers in the North American market are low power continuous wave lasers. Some of these lasers provide power literally at the same level as an inexpensive laser pointer costing around $30.
Yes. Laser treatments are drug-free and non-invasive. However, since lasers produce a high intensity light, one should never shine the laser directly into the eye. Furthermore, it is recommended that the laser device not be used directly on any neoplasmic tissue. Pregnant women should refrain from laser treatments applied directly to the abdomen. Also people with pacemakers should not use laser treatments near the heart.
Is low-level laser technology scientifically well documented?
There are more than 120 double-blind positive studies confirming the clinical effects of laser technology. More than 300 research reports have been published. There are over 300 dental studies alone. More than 90% of these studies verify the clinical value of using laser technology. A review of negative results shows that low dosage was the single most significant factor. By dosage is meant the light energy delivered to a given unit area during treatment. The energy is measured in joules and the area in cm2. Assuming that the power of the laser remains constant during the treatment, the energy of the light will be equal to the power in watts multiplied by the time in seconds during which the light is emitted. Therefore, a laser with more power (watts) can deliver the same amount of energy (joules) in less time. A pulsed laser with more average power (watts) can deliver the same amount of energy (joules) in less time and at deeper target tissues than a continuous wave laser
