What is laser therapy?

For a long time now L.A.S.E.R. (Light Amplification by Stimulated Emission of Radiation) was an acronym and today a word of common use. The word LASER is the name of a device that projects intense radiation of the light spectrum. It produces a beam of light in which high energies can be concentrated. Laser light has unique physical properties, which no ordinary light has. The unique properties of coherence and monochromaticity are the key to why laser light is so effective compared to other kinds of light in pain reduction and healing. Laser therapy, 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. Laser therapy has been found to offer superior healing and pain relieving effects compared to other electrotherapeutic modalities such as ultrasound, especially in chronic problems and in the early stages of acute injuries. Laser therapy is a complete system of treating muscle, tendon, ligament, connective tissue, bone, nerve, and dermal tissues in a non-invasive, drug-free modality.

How does it work?

The effects of laser therapy are photochemical in general and with super-pulsed lasers such as the InSight Series also photomechanical. 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. It is obvious that, in order to interact with the living cell, laser light has to be absorbed by intracellular chromophores. Cell membrane permeability increases, which promotes 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 the 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 use of an improper wavelength laser 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, water and hemoglobin, nucleic acid and proteins can be listed. Among the exogenic chromophores we can instead find 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 its optical characteristics, as well as on the concentration and depth of the chromophores, which according to the wavelength are absorbed at different percentages. For instance, water absorbs almost 100 percent of the laser irradiation at the 10,600 nanometer wavelength, the wavelength of the 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 treatment technique used. There is no exact limit with respect to the penetration of the light. The laser light gets weaker the further from the surface it penetrates with a limit at which the light intensity is so low that no biological effect of the light can be measured. In addition to the factors mentioned above, the depth of penetration is also contingent on tissue type, pigmentation and foreign substances on the skin surface. Bone, muscles and other soft tissues are transparent to certain laser lights, which means that laser light can safely penetrate these tissues. The radiation in the visible spectrum, that 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 the 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 therapeutic lasers in the market today have wavelengths within this therapeutic window. The penetration index is not the same level throughout the therapeutic window. In fact, lasers in the 600 to 730 nanometers have less penetration and are suitable for superficial applications such as in acupuncture.

Lasers vs. LED.

Light emitting diodes (LED) are just 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 does. 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 would work only on skin level conditions, if at all. For conditions deeper than skin layers one must choose light from a laser source.

Pulsed vs. continuous wave lasers.

In general, lasers diodes are either continuous wave or pulsed. The continuous wave (CW) diodes emit laser energy for the entire time it is electrically driven, hence its name. Pulsed diodes emit a radiation impulse with a high amplitude or intensity and duration of which is typically extremely short such as 100 to 200 nanoseconds. Continuous wave lasers produce a fixed level of power during the 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 “off” and “on” a light switch. Pulsed lasers, as the name implies, produce a high power level impulse of light for a very brief duration for each pulse. It is the high power level 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 thermal effects in the tissue because the pulses are of extremely short duration. Therefore, the peak power of a pulsed laser is high compared to its average pulse power. By using pulsed lasers, one is able to more effectively drive light energy into the tissue. The laser and electronic technologies required to use pulsed diodes are more advanced and the diodes themselves are more expensive than the CW diodes. These are probably the main reasons why over 90% of the therapeutic lasers in the North American market are low power CW lasers. Some of these CW lasers provide power on the order of inexpensive laser pointers costing around $30 USD.

Is laser therapy safe?

Yes. Laser therapy is a drug-free, non invasive therapy with superior healing ability. However, since lasers produce a high intensity light, one should never shine the laser directly into the eye. Further it is recommended that the laser device not be used directly on any neoplasmic tissue. Pregnant patients should refrain from laser therapy applied directly on the abdomen.

Is laser therapy scientifically well documented?

There are more than 120 double-blind positive studies confirming the clinical effects of laser therapy. More than 300 research reports have been published. Looking at the laser therapy dental literature alone there are over 300 studies. More than 90% of these studies do verify the clinical value of laser therapy. A review of the research literature of studies that produce negative results one finds that low dose was the single most significant factor. By dose is meant the energy of the light delivered to a given unit area during a treatment session. 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. If we use a pulsed laser we can extend the above statement by saying that 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 continuous wave lasers.

What is pulsed electromagnetic therapy?

Magnetic fields play a key role in biological life. A magnetic field is created when a conductor is crossed by an electrical current. Magnetic fields arranged around single conductors are summed in a coil producing a density of magnetic force lines. If current produced in this way flows in pulses, then a pulsed magnetic field is created. In the bioenergetic and chemical terms of the organism, the essential concept of magnetism is not the magnetic load, but the energy-rich dipole which is surrounded by a magnetic field and whose transformation and exploitation for the production of energy in the organism is highly significant. The most important effect from pulsed electromagnetic fields (EMF) therapy is found on the cellular transmembrane potential (TMP). It is known that damaged or diseased cells present an abnormally low TMP, up to 80% lower than healthy cells. This signifies a reduced metabolism, impairment of the electrogenic sodium-potassium (Na-K) pump activity, and therefore, reduced ATP production. In a nutshell, the TMP is proportional to the activity of the Na-K pump and thus to the rate of healing. Healthy cells have TMP voltages of 70 to 100 millivolts. Due to constant stresses of modern life and a toxic environment, cell voltages tend to drop as we age or due to illness. As the voltage drops, the cell is unable to maintain a healthy environment for itself. If the electrical charge of a cell drops to 50, the patient may experience chronic fatigue. Electromagnetic therapy with the Maxi provides one effective way to affect healing rates by increasing cellular TMP.

Does laser therapy cause heat damage or cancer in the tissue?

No. The average powers and the type of light source (non-ionizing) do not permit heat-damage or carcinogenic (cancer-causing) effects. Due to increased blood circulation there is sometimes a minimal sensation of warmth locally.

Trends in laser therapy.

Therapeutic lasers are getting better every year. New lasers have entered the North American markets that provide deeper tissue penetration, higher power densities and reliable electronics to achieve better clinical outcomes. The trend has been to increase power density and dose, since these have been shown to produce better clinical outcomes. In the case of superficial target tissues, clinicians have several laser options to consider. For tissue just beyond a few millimeters from the skin surface, underpowered lasers currently available in North America do not deliver the needed light energy to the treated tissues that present in patients in a typical healthcare office.