If you are not convinced by now that laser phototherapy will help your patients, ask one of the tens of thousands of U.S. pet owners whose pets now live pain free after their laser treatments. If you are not convinced that laser therapy will help your practice, ask one of the thousands of veterinarians whose revenue has grown since incorporating a laser into their practices. The question now should be,“Which laser is best for me?” Differences between commercially available laser units lie solely in the wavelength, power density, pulse modulation and aesthetics. From these parameters, you can derive the penetration depth, dose distribution, treatment time and the estimated biological effect. No single magic wavelength or setting is the cure for a disease, and to claim otherwise (as some distributors or sales reps do) is irresponsible. There are, however, certain operating regimens, such as those from K-Laser USA, that give better results than others and are more effective for particular symptoms. And because the primary mechanism of action is the stimulation of the patient’s immune system, the range of symptoms for which this modality is useful knows no bounds. Educating yourself about the mechanisms and parameters and comparing them will prove invaluable. You can very easily sift through the mountains of marketing propaganda with a few simple questions: • What are the targeted mechanisms? Wavelengths? Frequency ranges? Power settings? • Is the spot size adjustable? • Is there a finger switch? • Are there pre-set protocols? • Is training or marketing material included? • Is upgrading possible? Mechanisms The mammalian immune system can handle an extraordinary range of pathologies. The time scale and degree to which cells can react and combat contaminants are the subjects of much study, but it is clear both that lasers stimulate the immune system and that the restoration of healthy function continues well after the initial irradiation. It’s important to note one very important point: The body does most of the healing work itself and so the aim is to stimulate the appropriate cell compartments that lead to the body’s natural repair mechanisms. Basically, we want to stimulate the cell’s metabolism. Wavelengths Some lasers employ wavelengths more suited to target different absorption peaks, while others do not specifically target anything. Furthermore, each wavelength provides different penetration depth profiles. Some companies offer multiple wavelength beams with or without the ability to select which wavelength to use for a given treatment. This variability could prove very useful when treating different parts of the body or different depths in the same treatment area. Mammalian cells are 80 percent water and so absorption of radiation by water—water’s absorption peak in the NIR is 965 nm—will most efficiently create temperature gradients that will increase local blood throughput and therefore oxygen flow. The second of the principal chromophores is hemoglobin. Once the blood gets to the cells, irradiation that targets oxygenated hemoglobin—with a brad absorption peak between 800-1000 nm—will most efficiently stimulate oxygen passage from the hemoglobin into the cells for use in metabolism. Finally, once the oxygen is in the cell, irradiation that targets the cytochrome c oxidase redox cycle, whose absorption peak is ~805 nm, will most efficiently stimulate the cyclic process of using and replenishing oxygen, thereby maximizing the ATP (energy) throughput of the cell. Remember, the name of the game is oxygen—getting into the cell, getting the cell to use it faster to make more energy and then letting the cell’s natural processes boost the body’s immune system. This will result in curative and analgesic effects upon every administration of treatment as well as continued relief in the future. Versatility Continuous wave exposure refers to the absence of modulation; that is, the beam’s intensity is constant in time. This is the fastest way to deliver the most energy and is useful in keeping treatment times manageable. For the full therapeutic effect, however, this is not the end of the story. Remember, it is not the raising of temperature but rather the creation of temperature differences that is primarily important. Heating through radiation is much quicker and more specific. Radiation absorbed by a water molecule is completely converted to heat by that individual molecule. Individual cells are much smaller than bulk tissue and so can dissipate heat much quicker, on the order of micro- to milliseconds. This means you can achieve even more efficient thermal gradients if you were to modulate the beam, that is, turn it on and off periodically on a time scale that corresponds to the time it takes to dissipate the heat created by an absorption event. Consequently, less dosage can be used to stimulate similar circulation effects. The laser’s ability to frequency modulate is therefore of paramount importance in designing effective treatment protocols. One thing is clear: No single frequency works best on all conditions. The wider the range of available frequency settings, the better equipped you will be when our knowledge base matures. Power Power, given in Joules per second or watts, quantifies the amount of energy emitted from a laser per unit time, which with wavelength information determines the rate of photon emission. With knowledge of the optical properties of the tissue at the wavelength to be irradiated, power is the principal quantity that determines both penetration depth and duration of treatment. Biological tissue is a highly turbid medium; that is, it strongly (exponentially) attenuates radiation through a combination of scattering and absorption, so the dose delivered to the surface can be orders of magnitude higher than what is actually delivered to the depth of the ailment. For this reason, it is important to keep in mind your particular clinical application when choosing among lasers. If only superficial dermatology concerns you, the less intricate and less expensive Class II or III lasers may be suitable. If your focus is subcutaneous, and especially deep muscle or joint ailments, these lower-power lasers cannot deliver sufficient dose at depths to achieve analgesic or biostimulatory effects in reasonable treatment times. Upgradeability The field is still young and we do not yet have a complete understanding of all the mechanisms at work. As we mature as an industry, the scientific literature and clinical success of laser therapy will illuminate new ideas and parameters. It will be advantageous to have an existing platform with all the hardware in place but with update capabilities, so that without downtime, you can install an update that will put you at the state of the art. Dr. Stephens is director of research and development for K-Laser USA of Franklin, Tenn. This Education Series article was underwritten by K-Laser USA of Franklin, Tenn. <Home>12/15/2010 12:25 PM
