Deep Penetration Therapeutic Laser
Painful conditions that can therapeutically benefit from laser irradiation are associated with pain generators found at varying tissue depth, ranging from relatively shallow target tissues (skin, subcutaneous structures, etc.) to much deeper tissues. GaAs therapeutic lasers are useful for anti-edema and lympathic effects, treating painful conditions of the skin and subcutaneous tissues, wound healing, anti-inflammatory effects, and tissue regeneration. GaAs lasers can also provide the same therapeutic results for deep tissue structures—such as facet joints, acetabular joints, herniated discs, etc.
Gallium Arsenide (GaAs) therapeutic lasers present an interesting challenge when applying them to tissues of varying depths and when attempting to achieve different therapeutic effects. GaAs laser diodes penetrate more deeply than any other commonly used therapeutic laser.1 This phenomenon is largely a result of the fact that the GaAs diode operates at a wavelength of 904 nm or 905 nm and is also due to its superpulsing mode of energy delivery. I explained in a previous article that the higher the wavelength of a therapeutic laser, the deeper the penetration.2 Superpulsing is a mechanism whereby there are continuous bursts of very high power pulses of light energy (10-100 Watts peak power) that are of extremely short duration (100 – 200 nanoseconds/Hertz). This works something like a camera flashbulb. Superpulsing allows the mean or average power output to be relatively low—when compared to continuous wave output therapeutic lasers—and still achieve deep tissue penetration, as well as comparatively short treatment times.3 The GaAs laser penetrates to tissue depths of 3–5 cm and deeper.4 There are even some versions of GaAs therapeutic lasers that actually penetrate to tissue depths of 10–14 cm.5
In this article, I will discuss ways to obtain maximum treatment effects utilizing this type of laser.
Review of Laser Effects
I discussed in a previous article that there were three different types of effects that therapeutic lasers have in the body. They are:
Primary effects — created by direct photoreception of photons with cytochromes resulting in increases in ATP production and changes in cell membrane permeability; this response is specific to phototherapy. Photoreception is generally followed by transduction of light into cellular energy, amplification of the signal and a photo-response—the last of which can be classified as either secondary or tertiary.
Secondary effects — occur in the same cell in which photons produced the primary effects; they are induced by these primary effects. Secondary effects include cell proliferation, protein synthesis, degranulation, growth factor secretion, myofibroblast contraction, and neurotransmitter modification—depending on the cell type and its sensitivity. They are less predictable than primary effects; the sensitivity of the cells are dependent on internal and external environment factors.
Tertiary effects — indirect responses of distant cells to changes in other cells that have interacted directly with photons. They are the least predictable because they are dependent on both variable environmental factors and intercellular interactions. They are, however, the most clinically significant. Tertiary effects include all the systemic effects of phototherapy.7
Therapeutic lasers can be applied in such a way as to stimulate any or all of these three effects.8 These effects are achieved when using a GaAs laser by using various frequencies.9,10 In fact, the standard method for achieving successful treatment of various tissues, at varying depths, is by utilizing different frequencies.6,7
Frequency Selection for Specific Therapeutic Effects
I will now discuss the specifics of each frequency commonly used when treating with GaAs laser so that the best therapeutic effects can be achieved. These frequencies and resulting therapeutic effects are summarized in Table 1.
|Frequency Range||Therapeutic Effect|
|1000-3000 Hz||anti-edema effects; lymphatic system circulation; skin treatment|
|1000 Hz||analgesia for chronic pain; painful conditions of the skin; wound healing|
|50 Hz||anti-inflammatory; analgesia effect on subcutaneous tissues, fascia, tendons, and small joints|
|5 Hz||deepest penetration; effective treatment of deeper tissue structures, including facet joints, acetabular joints, herniated discs; tissue regeneration.|
Frequencies that several other researchers have observed to be therapeutic for specific diagnoses are presented in Table 2.
|Pain, neuralgia||1-100 Hz|
|General stimulation||700 Hz|
|Edema, swelling||1000 Hz|
|General stimulation||2500 Hz|
|After Tuner and Hode (courtesy of Doug Johnson, ATC, CLS)|
1000–3000 Hz. Frequency Range
This frequency range has been shown to have anti-edema effects and a profound effect on the lymphatic system11 and is characterized as a systemic or tertiary effect. When attempting to treat an edematous area it has been found to be important to treat the lymph nodes proximal to the edematous site with the laser. This opens up the lymph vessel and allows more rapid reduction of the local edema. This technique is know as Oshiro’s Principle (see Figure 1).
The 1000 – 3000 Hz. frequency range has been also been found to be effective in treating the skin. This frequency range has been shown to stimulate collagen production and help resolve scar tissue. These are examples of local tissue effects.
1000 Hz Frequency
This frequency is commonly used to produce analgesia, especially in pain of more chronic duration12 and is characterized as a systemic effect. Trigger Point reduction and muscle relaxation, which are local effects, are also enhanced at this frequency. Dr. Pontinen’s technique (see Figure 2) is intended to maximize treatment response in the same visit by palpating the treatment area for pain sensitivity between successive laser applications.
1000 Hz. has been widely used for painful conditions of the skin and subcutaneous tissues. Accelerating wound healing would be a prime example. This would be another example of a local effect.