Laser: The Future Looks Bright

Laser therapy is a remarkable modality that more sports chiropractors and athletes are inquiring about. I have written this article to help you understand the difference in lasers and explain the basic science behind this amazing modality. When you are finished reading, my goal is that you understand that all lasers are beneficial, but each laser may work better on certain conditions than others. Not based on the brand, but on the technology and the physics inside each laser.

Let me first explain light, color and the wavelength spectrum. Visible light occurs in the 380nm to 760nm wavelength range. Each color has a specific wavelength. 760nm to 600nm is in the red to orange range. 600nm to 550nm is in the yellow range. 550nm to 500nm is the green range. 500nm to 450nm is in the blue range. 450nm to 400nm is in the violet range. Under 400nm you begin to reach the ultraviolet range. Continuing lower takes you into the ionizing radiation range (x-rays). Continuing higher, between 760nm and 1000nm, is the infrared spectrum of light which is invisible light but still in the therapeutic spectrum. Above 1500nm and 2000nm and higher is outside of the therapeutic window and enters surgical, microwave, and radiowaves. Some surgical lasers are actually very low wavelengths such as 193nm-650nm.

What is Laser? Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a called a light amplifier if it is in the visible range or a radiation amplifier if it is in the infrared range. Each laser by design has an energy source or power supply consisting of electrical current, optical radiation from a flash lamp, radio waves, microwaves or chemical reaction. It has an amplifying medium which is a solid, liquid, or gas or a semiconductor, which dictates the wavelength. It also may have a resonating cavity often with mirrors which stimulates new light production and makes the light more coherent. A laser is monochromatic (one color) and coherent. A regular light bulb is multicolor and non-coherent and scattered.

Lasers are of two major types: Continuous and Super Pulsed. Continuous laser emits a specific wavelength of light out of a diode at a constant intensity and power. The wave can be modulated, chopped, turned on and off, or sent at different frequencies (pulses per second) which many call pulsed. Do not be confused, this is not the same as superpulsed and the pulse frequency has nothing to do with the frequency of the wavelength of the laser which always stays constant. Superpulsed is like a flash bulb having a very intense light pulse blast of very high power for deep penetration but for an extremely short interval so damaging heat is not produced. There are only a few superpulsed lasers available because they are more expensive to build.

Every laser unit will have a benefit and a downfall based on the target tissue you want to be using it on. Items such as low power, too large of an aperture, low penetration ability, too much heat at the surface, battery operated, and so on, depending on how and where you want to use it. Each laser has a fixed wavelength per diode. There are a few laser devices that have two or more laser wavelengths in the console of the machine but there multiple separate laser devices in the unit. You can not combine two wavelengths in one medium or semiconductor, but you can transmit multiple wavelengths out of an aperture via fiber optics or separate diodes. It is usually agreed upon that the longer the wavelength (bigger nm) the deeper the penetration of tissue up to the 980nm range where the skin begins to absorb the wavelength again and heat is generated.

Each laser device has a certain output power measured in milliwatts (mW). The pulse peak power and the average power output are two values that are very important. This value is significant in order for you to calculate the correct dose to give the patient. A higher powered device gives an advantage of less time required to reach a given dose. A higher output power gives a higher power density which is often beneficial. Power is important in respect to deeper light penetration according to Tuner and Hode, the experts in laser. Please remember though, power is not required in achieving results if you are using laser acupuncture, meridian therapy, muscle energy techniques, and for superficial burns, abrasions and scars. It is however required if you want the actual laser energy to reach deep down into the cervical and lumbar facet joints and nerve roots. A potential problem with higher power direct emission continuous wave lasers is that their electronic components, when not sufficiently cooled, will heat up and drastically reduce the life of the laser diode, sometimes to as little as 2-3 years. Laser diodes that are properly "heat sunk" and transmit the laser beam via fiber optics can last 10-15 years. Do not add the mW of each diode to determine the power of your machine if the laser emitters are independent from each other unless the various emitters are being combined into a single beam via optic fibers or an appropriate lens system. The powers of the separate beams should not be added together as some manufactures want you to believe. Do not add any power of LED’s. LED’s are not lasers and should not be construed as such. They have benefit for superficial skin lesions when used for prolonged periods of time. Eventually they may show to be beneficial for some superficial muscle conditions but they are presently proven not to work as well as lasers even for skin. Unless you have a burn clinic or if you treat a large amount of road rash from cyclists, there is no need for a chiropractor to spend extra money on LED’s. Many laser devices in the infrared spectrum (invisible light over 760nm) may have a visible LED indicator to tell you where you are treating, but this has no extensive therapeutic value.

According to Jan Tuner and Lars Hode, in their textbook “Laser Therapy-Clinical Practice and Scientific Background”, they reveal that a HeNe laser of 7mW has a greatest active depth of penetration (where the laser is still strong enough to make a therapeutic effect) of 8 to 10 mm. A GaAs laser has a greatest active depth of 20mm to 30mm and sometimes up to 40mm. Although these authors express these listed depths, superpulsed GaAs lasers have been shown to go up to 50mm. A GaAlAs laser penetrates deeper than a HeNe but less than a GaAs laser. If you need to make physiological change of a ligament for a finger sprain or foot sprain a HeNe should do the job. A Gallium Aluminum Arsenide laser would get the job done faster. The GaAlAs type of laser could be the best choice for tendonitis. If you wanted to treat a lumbar nerve root, piriformis muscle, or cervical facet joint with a HeNe Laser, it would most likely never reach the target tissue regardless of the power. A Gallium Aluminum Arsenide laser could reach the target tissue with a very high power diode only. If you compared a 4cm depth target site using a Gallium Aluminum Arsenide laser and a Gallium Arsenide laser with equal power of a 100mW diode, it would only require 2 minutes for the GaAs to reach the target versus 20 minutes for the Gallium Aluminum Arsenide. The two authors feel it would be unrealistic to expect a 25mW or less diode laser to penetrate 3 cm.

The optimal dose for biostimulation has ranges according to the research; it has been quoted as .05 to 1 J/cm² in an open wound. When treating tissue beneath the skin the optimal dose has been quoted as 2 to 4 J/cm², for each location. 4 to 6 J/cm² has also been quoted as the optimal dose at a target tissue for biostimulation. Some studies reveal you need more, some older studies feel it is too much. More recent discussions have revealed that for pain reduction, much higher doses even in the 100’s J/cm² at the target may be a better dose, and then less of a dosage for inflammation and biostimulation. This seems to now be in agreement with clinicians and researchers on live subjects. Additional research claims that there are peaks and valleys of biostimulation and inhibition at certain dosages and that even though a certain dose may inhibit, a little more may again biostimulate. This still remains to be fully understood. Here is a simple clinical example, let us take 4 to 6 J/cm² and try to deliver it to a diseased target tissue 4cm beneath the skin (i.e. lumbar nerve root). The skin dose needed could be more like 90 J/cm² because of the scattering and absorption losses on the way down into the 4 cm of target tissue. There are calculations but for simplicity, the amount of energy is reduced by approximately 50% each centimeter you penetrate due to absorption. If you do the math, 90 J/cm² at the skin, 45 J/cm² at 1cm, 22.5 J/cm² at 2cm, 11.25 J/cm² at 3cm, 5.625 J/cm² at your target tissue (i.e. lumbar nerve root). This is being conservative, because some other articles of literature reveal a 63% energy loss just from the skin and up to a 92% energy loss from the skin to 3 cm, and 5-10% loss for each additional mm of penetration but the calculation averages remains similar depending on the type of laser used. How long does it take for your machine to generate 90 J? A 10 mW diode takes 2.5 hours to produce 90 Joules. A 30 mW diode takes 49.5 minutes to produce 90 Joules. A 200mw diode takes 7.5 minutes to produce 90 joules. Contrary to what some may have told you, power may be extremely important after all, except if you are treating conditions of the skin or working with the meridians.

Laser therapy has shown to be effective in increasing collagen production, nerve regeneration, tissue and bone repair, reducing edema and inflammation, increasing lymphatic drainage, increasing production of capillary beds, and reducing pain. It works by increasing ATP synthesis in the mitochondria, activating the electron transport system, and a host of many other chemical and physical reactions in the tissue that allow the healing time to be reduced dramatically.

When it comes to choosing a laser, choose one that is best for the type of work you will be doing every day. Consider the time it will take to administer the effective dose so it is cost effective. Consider getting the highest power you can afford if you are treating the deep structures of the lumbar spine. Ask the manufacturer for an extended warranty on all continuous wave diodes over 90mW because they may burn out after two years. Keep asking questions until you fully understand.

Written & Contributed by: Mike Mathesie, DC, CCSP

Coral Springs, FL

954.755.1434

____________________________________________________
About Dr. Michael W. Mathesie: Dr. Mathesie was first exposed to the therapeutic use of lasers in the early 1990’s and currently uses a high power super-pulsed system, in his own private practice in Coral Springs, Florida. He has served as President of the Florida Chiropractic Association’s Council on Sports Injuries, Physical Fitness, and Rehabilitation. He holds certificates from the American Chiropractic Board of Sports Physicians and the American Chiropractic Rehabilitation Board. He has served as an expert for several agencies and departments of the state. Governor Bush appointed him to the Florida Board of Athletic Training. Governor Crist appointed him to the Florida Board of Chiropractic Medicine, where he presently serves until 2012. He was awarded Sports Chiropractor of the Year and Broward County Chiropractor of the year from his peers. You may reach him at (954) 755-1434.

______________________________________________________________________________________

A chiropractor who advertises that he or she has attained recognition as a specialist in any specific chiropractic or adjunctive procedure by virtue of a certification received from an entity not recognized under this rule may use a reference to such specialty recognition only if the board, agency, or other body which issued the additional certification is identified, and only if the letterhead or advertising also contains in the same print size or volume the statement that “The specialty recognition identified herein has been received from a private organization not affiliated with or recognized by the Florida Board of Chiropractic Medicine”.

*The CCSP (Certified Chiropractic Sports Physician) designation is recognized by the American Chiropractic Association (ACA), The United States Olympic Committee, the ACA Sports Council, the American Chiropractic Board of Sports Physicians, ProSport Chiropractic and F.I.C.S.