Laser Basics - Principles of Low Intensity Laser

#1. Laser Basics – Principles of Low Intensity Laser Therapy (LILT) INTRODUCTION: Low Intensity Laser Therapy (LILT) involves the application of photic energy to the tissues with the object of augmentation of healing and/or the relief of pain. PRINCIPLES OF USE: 1) The usual wavelengths are these which penetrate most deeply due to low absorption in the principal constituent in soft tissue namely water. Typical of these are: a) Gallium Aluminum Arsenide at around 820nm (0.82 microns) which is maximally penetrative. This modality is the most important one for treatment of pain but is also effective in healing, reaching well into connective tissue corium. Absorbed by cell wall chromophores. b) Visible Red at 633nm (0.633 microns) Helium Neon or 660nm (0.66 microns) Diode. These wavelengths have a propensity for healing particularly epithelial tissue and for laser acupuncture. Absorbed by mitochondrial cytochromes. 2) Dosimetry is all important in determining effect and in reporting a treatment episode. It is necessary to specify: a) Wavelength e.g.820nm b) Incident Power of Probe e.g.200mw (a good all around value) c) Energy Per Point e.g. 10-20 joules for myofascial pain or 2-4 joules for healing of an intractable ulcer. A 60 milliwatt probe generates 4 joules in one minute for example. d) Energy Density ("radiant exposure" or "fluence rate") this can be calculated easily by knowing the area of the beam spot and multiplying this as a fraction of a square centimeter by the energy per point e.g. energy per point of 4 joules with the spot which is an eight of a square centimeter will result in an energy density of 4X8=32 joules per square centimeter. It should be emphasized that this is a convention which does not exactly represent the way in which photic energy is scattered in tissue as revealed by CCD camera. A formula for more formal calculation of energy density is: Energy density (J/CM2)= Power (w)X time (s) area(cm2)of spot Where the power of the probe is in milliwatts divide by 1000 to convert to watts in the formula. e) Power Density (or "irradiance" or "fluence") A formula for calculation of power density (w/cm2) =Power(w) area (cm2) of spot This can be converted to milliwatts per square centimeter by multiplying by 1000. f) Pulsing Characteristics and Duty Cycle Declare whether constant wave or pulsed. g) Time of Treatment This is helpful to determine rate of energy application. 3) Mechanisms of Action may be summarized as: a) Energization of Depleted Enzymes. Enzymes may be denatured or depleted in areas of inflammation by hypoxia and acidosis. Important examples are: 1) Sodium Potassium ATPASE: Vital for nerve polarization in transmission of an action potential. Low energies (less than around 4 joules per sq.cm. at the site) tend to increase concentrations and are logical for use in nerve regeneration e.g. in facial paralysis. High energies (more than around 4 joules per sq.cm. at site) tend to decrease concentrations being indicated for pain where the object is stabilization of sensitized pain fibres-nonmyelinated C fibres for slow dull pain and lightly myelinated A delta fibres for rapid sharp pain. This is the so-called Arndt Schultz response where low energies stimulate and high energies suppress. 2) Superoxide Dysmutase (SOD). This enzyme breaks down free radicals which are a cause of pain in trigger areas in muscle in myofascial pain. 3) Transforming Growth Factor Beta Fractions. Energization will help repair and heal. There are several fractions. b) Vascular Effects There is no doubt that laser energy is capable of initiating new vessel formation (angiogenesis) which is an important factor in healing e.g. with soft tissue flaps. It is often suggested that LILT causes an immediate augmentation of blood flow but there is no objective evidence of this unless energies are above normal therapeutic values sufficient to cause local healing (more than 150 joules per sq.cm). c) Immune Augmentation It seems likely that LILT can augment local and systemic immune mechanisms particularly if these are below par. Experience with irradiation of the blood has revealed a balancing effect where low rheology values are raised and high ones brought to normal values suggesting an important role for light in homeostasis. d) Cellular Energization Most cells after LILT demonstrate accumulation of energy molecules in the form of ATP. e) Overall Effect Overall, the laser energy shortens the inflammatory phase after tissue injury hastening repair and remodeling. 4) Models of Usage a) Local application to Nociceptive Foci. e.g. trigger points in muscle. Usually constant wave, adequate power rating for penetration and positive pressure to milk out excessive tissue fluid aiding penetration. b) Entrainment of Bioresonances LILT in pulsed mode may be geared to correspond with central bioresonances. Various frequencies are suggested (Sisken & Walker) e.g. 2Hz Nerve regeneration, neurite outgrowth 7Hz Bone growth 10Hz Ligamentous healing 15, 20, 72, Hz Decreased skin necrosis, stimulation of capillary formation and fibroblast proliferation. c) Ligamentous Healing Low energy d) Nerve Regeneration e) Laser Acupuncture Over acupuncture points or known nerve outflows. These points are highly reactive responding to low energies. f) Component of Multi-Modality Treatment Regimens When treating pain the use of several methods each working through a different substantiated mechanism are more likely to be successful then single methods (Melzak & Wall). e.g. 1) May be combined with medication such as anticonvulsant and antidepressants in chronic pain thereby reducing dosage. Cortisone steroid however may negate LILT's immune enhancement. 2) May be used with other forms of energy medicine e.g Ultrasound Short Wave Diathermy Interferential Treatment Acupuncture Action Molecules (homeopathy) g) Energization of Photodynamic Agents e.g. Toluidene Blue for bacterial reduction. This is an innovative which is in the experimental stage at the moment but which is likely to be increasingly important in the future in view of increasing resistance of bacteria to antibiotics.