Instrumentation is the foundation

The acronym “LASER” stands for Light (photons) Amplification by Stimulated Emission of Radiation. Low level laser therapy (LLLT) is the best and most widely accepted descriptor of the type of lasers used in rehabilitation. The instrument itself is considered a “therapeutic laser”. LLLT has historically been classified as a non-thermal modality. Non-thermal modalities are those physical agents that do not raise the subcutaneous tissue temperature greater than 36.5oC. Therefore the therapeutic effects of LLLT are not associated with a heating response, but rather a photochemical response. When light (photons) enters the cell, certain molecules called chromophores react to it, and trigger a photochemical reaction that leads to desirable physiologic effects. LLLT is simply another form of energy (physical agent) that can be used to create physiological changes in tissue. 

Classification of Lasers.

 Some of the confusion regarding LLLT is associated with the wide spread use of lasers in medicine and industry. There are a wide range of applications for laser technology in industry and medicine. Laser devices are classified based on their power output, measured in millliwatts (mW), and their relative risk for causing biological damage (most notably retinal damage when the eye is directly exposed to the beam). The 5 classes of laser are 1, 2, 3A, 3B, and 4. They are listed in order of increasing power and risk for biological damage

LLLT devices are generally classified as class 2, 3a and 3b laser devices.

Brief History of the Development of Laser.

 Albert Einstein is credited with providing the basic science and theory necessary for the development of laser. It was not until 1960 that the first laser was developed in the United States by a physicist named Theodore Maiman.2 As will be discussed later, all laser devices require an active medium; Maiman used a ruby crystal as the amplifying medium within the lasing chamber to produce the “ruby laser”. The ruby laser emits visible red light. In the 60’s and 70’s a Hungarian physician named Endre Mester experimented with using the ruby laser (red light) to destroy implanted tumors in laboratory rats. At the time, Mester believed that the ruby laser was a ”high powered, tissue destroying laser” . He was not able to destroy tumors in his experiments; however, the research did lead to an important discovery. Mester observed that the surgical incisions in the group of rats that received laser consistently healed faster than the control group that was not treated with laser.3 This lead Mester to refocus his research agenda on the application of LLLT for the acceleration of tissue healing. His research went on to show faster healing of experimental skin defects, diabetic skin ulcers, venous insufficiency ulcers, and bedsores. Endre Mester is credited with the discovery that LLLT can accelerate soft tissue healing. He is often referred to as the “father of low level laser therapy.

Production of Therapeutic Light.

How is the light energy produced and emitted from the laser applicator? This first step in understanding this process is to identify the 4 components of a laser and the role of each in the production of laser energy. There are 4 main components to a laser 

1) Laser Chamber 

The laser chamber is also known as an optical resonance cavity. The chamber is a tube that has mirrors on both ends. The end that the laser beam emits from is semipermeable compared to the other end which is totally reflective. The laser chamber houses the lasing medium.

2) Lasing Medium 

Laser devices utilize what is known as a lasing medium within the lasing chamber. It is the excitation of the atoms within this lasing medium that allows for amplification of light. There are a variety of lasing media that can be used for LLLT applications. The earlier generations of laser devices used media such as the ruby crystal, Helium–Neon (HeNe), and Gallium –Arsenide (GaAs). The type of lasing medium is significant in that its properties determine the laser’s wavelength. Wavelength is an important factor for the appropriate application of LLLT. The definition and clinical relevance of wavelength will be discussed later.

3) Pumping system (energy input to the laser) 

Contemporary lasers use semiconductor technology and commonly use Gallium AlumInum-Arsenide (GaAlAs) as the lasing media. There are several advantages to this newer technology; for instance, manufacturers are able to customize laser applicators to a specific wavelength by modifying the ratio of gallium and aluminum in the medium. In addition, GaAlAs lasers typically have higher power outputs which translate into shorter treatment times. 

The purpose of the pumping system is to supply energy input into the lasing medium within the chamber. When the power source (electricity or battery) applies energy into the lasing medium, the atoms within the medium are stimulated within the enclosed lasing chamber. It is this pumping up of the medium inside the enclosed chamber that stimulates its atoms to an excited state. In an excited-state atom, one of the electrons is temporarily promoted to a higher energy level. Movement of the majority of atoms to their excited state is known as population inversion. As the electrons return to lower energy levels, light energy (expressed in photons) is released. Exactly one photon is emitted for each electron that returns to the lower energy level. The collision of photons with excited atoms causes a domino effect in which more and more photons are released. This process is referred to as stimulated emission. Light amplification is facilitated by the use of mirrors on each end of the lasing chamber. The photons are reflected back and forth within the chamber (“ping-pong” effect), resulting in more collisions with excited-state atoms, more stimulated emission events and a greatly increased number of photons. When the concentration of photons is sufficiently high, light is emitted through the semipermeable miirror at one end of the chamber. This emitted light is the laser beam. 

4) Applicator (laser probe)

The laser applicator, also sometimes referred to as a probe, is used to direct the photons (light energy) into the patient. Contemporary laser applicators look similar to therapeutic ultrasound applicators and many have an activation switch to initiate the dose of laser energy that the practitioner set within the device. In the early years of LLLT single diode applicators where the standard. Eventually cluster applicators where developed to treat larger areas more efficiently and also to facilitate adding other non-laser light therapy products such as superluminous diodes (SLDs) and light emitting diodes (LEDs) into the laser applicator. 

PHYSICS OF LOW LEVEL LASER THERAPY 

A laser beam is essentially a beam of light. While regular white light from a light bulb scatters light of multiple wavelengths in multiple directions, laser light is a very concentrated beam of light of a single wavelength (monochromatic), with all light waves aimed in a single direction (collimated) and all in phase with each other (coherence).

Electromagnetic Spectrum 

LLLT is simply another form of energy that is applied to human tissue to stimulate a physiologic response. Similar to many other therapeutic modalities it resides on the electromagnetic spectrum. Therapeutic modalities are arranged on the electromagnetic spectrum based on their wavelength and frequency. The wavelength and frequency are inversely proportional. Simply put, this means that the longer wavelengths have a lower frequency and the shorter wavelengths have a higher frequency.

More on Wavelengths 

Wavelengths between approximately 600 -1000 nanometers (nm) are commonly used for the application of LLLT in rehabilitation. It is clear that the shorter wavelengths in the 400-700 nm fall into the Visible Light Range. The colors of light within this range have historically been recalled using the Pneumonic ROY-G-BIV (Red, Orange, Yellow, Green, Blue, Indigo, and Violet). Wavelengths in the 700-1000 nm range fall into the Infrared Range. The infrared range is not visible to the human eye. The eye does not have a protective blink response to wavelengths in the infrared range, which could put the unprotected eye at risk for retinal damage should the laser beam be inadvertently directed toward the eye. It is the characteristics of the lasing medium that dictate the wavelength and by definition the color of a laser beam. For example the laser device that Endre Mester used in his early wound healing research was a ruby laser. The wavelength of this early laser device was 694.3 nm.3 This wavelength produces red light and was found to be effective for superficial soft tissue healing such as skin wounds for example.

Low level laser Therapy (LLLT) devices

These devices have at least one true laser diode and, therefore have the capacity to emit a monochromatic, collimated, and coherent light beam. Clinically, it is believed to be the light source of choice to treat deeper lying tissue. The laser property of collimation allows the laser beam to maintain a small spot size (less divergence) over greater distance.

For example RED cluster applicator includes a total of 25 diodes (9 SLDs, 4 LEDs, and 5 laser diodes). It uses 940-1000 (nm) wavelengths. Wavelength is the distance between two peaks of a wave. The shorter wavelengths used in LLLT are considered to be those in the approximate range of 620-695 range (visible light). Two classic examples of lasers with short wavelengths include the Helium-Neon (HeNe) laser which has a wavelength of 632.8 nm and the ruby laser with a wavelength of 694.3 nm. Both of these lasers emit red light and are typically lower powered lasers compared to contemporary LLLT devices. Although these lasers are less commonly used in contemporary practice, much of the early research was done using these types of LLLT devices. The depth of penetration of these shorter wavelength devices is up to 1 centimeter. The longer wavelengths used in LLLT are considered to be those in the approximate range of 760 – 1000 nm. The power of the LLLT device is measured in milliwatts (mW). It is typically preset in the device. The power output is labeled on the device, it can commonly be found on the co- axial cable leading to the applicator or on the applicator itself. As discussed in the first module, the LLLT devices typically utilize power of less than 500 mW. The higher power levels in new generation LLLT devices decrease necessary treatment time, and enhance the depth of penetration. 

As with other therapeutic modalities such as therapeutic ultrasound and shortwave diathermy the power can be delivered in continuous or pulsed mode. The power can be decreased by pulsing the laser beam. Selecting a duty cycle that pulses the laser beam will decrease the net power (mW) delivered. 

Power Density

Power density describes the average power per unit area of the beam (spot size). It is measured in W/cm2 or mW/cm2 . This unit of measurement is familiar since it is used in ultrasound therapy. The power density is determined by dividing the power level of the laser by the area of the beam (spot size). Keep in mind that the area of the beam is fixed. Smaller beam areas will result in a higher power density because the light is concentrated over a smaller area. 

Energy (Joules) 

Energy is the power multiplied by the treatment time. It is measured in Joules (J). It is important to remember that the amount of energy delivered in Joules does not account for the area of the laser beam or the area of the surfaces being treated. This is why it is not the preferred method of measuring the dose of LLLT delivered in patient care.

Energy Density (Dosage) Joules/ cm2 

Energy density is a unit of measurement that describes the amount of energy delivered per unit area. It is measured in Joules/cm2 . This is the preferred method of dosing LLLT. It represents the actual amount of energy delivered to each cm2 of the treatment area.

Pulsed output Mode 

The power on most LLLT devices can be periodically interrupted for a very brief period on time. This is called “pulsing”. When pulsed mode is used the average power delivered will decrease proportional to the pulse frequency that is selected. Setting the pulse frequency determine the number of laser pulses delivered per second during a pulsed LLLT treatment. Pulse frequency is measured in Hertz (Hz). When a low pulse frequency is selected the pause between laser pulses is greater so less power is delivered. When high pulse frequencies are selected there is less of a pause between laser pulses e.g. it is closer to continuous output. The term average (or mean) power is used to describe the net power delivered after factoring for both the on and off time of the beam. 

“Pulsing” is a familiar concept in therapeutic modalities. Both therapeutic ultrasound and short wave diathermy have pulsed mode options. In those modalities it is intended to minimize the heating effect and while capturing the non-thermal tissue healing properties. Since LLLT is defined as a nonthermal modality the rational of minimizing thermal effects can not be used. Optimal pulsed LLLT frequencies for clinical application in the treatment of specific conditions and tissues have yet to be established in the research. There is a limited understanding of the physiologic relationship of using one pulse frequency over another during clinical applications. From a molecular biology standpoint, there is some evidence that specific pulsing frequencies may have a positive effect on macrophage responsiveness. 14 Additional research is necessary in this area. It has been theorized that acute injuries should be treated with low pulse frequencies (<100 Hz)1, subacute injuries with higher pulse frequencies, and chronic conditions should be treated with continuous mode. There is some evidence in the molecular biology LLLT research that specific pulsing frequencies may have a positive effect on   macrophage responsiveness. 14 There is also some support in the LLLT animal research. Dyson and young found better wound healing of surgical skin lesions in mice with a 700 Hz infrared pulse (HeNe 632.8 nm) when compared to a 1200 Hz pulse frequency.

Physiologic Effects of LLT Related to Tissue Healing Acceleration of tissue healing.

• Acceleration of inflammatory phase of healing allowing for earlier initiation of the proliferative phase of tissue healing

• Stimulates increased fibroblastic activity leading to increased collagen synthesis

• Increases protein synthesis2

• Promotes revascularization of wounds

• Enhances the production of type I and type III procollagen mRNA30 

• Increased tensile strength of collagen 

• Increased ATP production as a result of absorption of photons by chromophores. Enhanced ATP production fuels the metabolic pathways necessary to synthesize DNA, RNA, and proteins for tissue repair. 

• Stimulation of macrophages, fibroblasts, and lymphocyte activity are biological processes that are activated through the application of LLLT.

These biological processes are essential to the tissue healing process.

There is support for the commonly held assertion that LLLT increases microcirculation. The extent of these increases of microcirculation has not been completely established. However, it is likely that small, but clinically significant increases in the perfusion blood to healing tissue occur during LLLT treatments. Tuner and Hode refer to this as increased microscopic circulation to differentiate this subtle increase in blood flow from the more substantial increase in blood flow produced by heating modalities. Physiologic Effects of LLLT Related to Pain Modulation Pain reduction (analgesia). The exact mechanisms involved in pain reduction through the application of LLLT continue to be investigated. The photochemical stimulation of endogenous opiates33, nitric oxide34, and serotonin35 has been reported in the literature as plausible mechanisms. Low level laser therapy has also been shown to modulate prostaglandin levels which may lead to a decrease in the chemical inflammatory mediators that irritate free nerve endings.36 Lastly, as with many therapeutic modalities LLLT has been shown, in some instances, to alter nerve conduction velocities, leading some researchers to conclude that there is a possible gating mechanism involved (gate control theory).2 It is likely that a combination of two or more of the above physiologic mechanisms are involved in the reduction of pain associated with the application of LLLT.

Physiologic Effects of LLLT Related to Anti-inflammatory properties Decreased Inflammation36 It has been theorized for some time that LLLT has anti-inflammatory properties. A 2006 study in the British Journal of Sports Medicine confirmed this commonly held assertion with in vivo data to support the claim that LLLT suppresses inflammation. In this study Bjordal et al reported a decrease in prostaglandin levels and pain in the Achilles tendon of subjects with Achilles tendonitis.

Summary 

Low level Laser Therapy has a photobiomodulation effect in tissue. Simply put, this means that a photochemical reaction is responsible for the physiologic effects of LLLT. This reaction can cause either photobiostimulation or photobioinhibition depending on the dosage of LLLT applied to tissue. Lower dosages are associated with photobiostimulation and higher doses are associated with photobioinhibition.

The food and drug administration (FDA) has evaluated and cleared several LLLT devices for the following conditions  

Carpal tunnel syndrome  

Neck and shoulder pain of musculoskeletal origin In addition, the FDA has cleared the use of Infrared light for: Increase in local circulation  

Relief of minor muscle and joint aches  

Pain and stiffness  

Relaxation of Muscles  

Muscle Spasms  

Minor pain and stiffness associated with arthritis

Low level laser therapy research studies have indicated that it is likely to be beneficial in the following:  

Wound healing (diabetic ulcers, venous ulcers, bedsores)  

Musculoskeletal conditions (tendon, ligament, and muscle injuries)  

Trigger points Inflammatory conditions (tendonitis, bursitis, arthritis)  

Acute pain  

Chronic Pain  

Chronic joint disorders  

Neuralgia (nerve pain)  

Diabetic Neuropathy 

Contraindications : 

• Cancer (tumors or cancerous areas)

• Direct irradiation of the eyes 

• Photophobia or abnormally high sensitivity to light

• When using photosensitizing medication

• Direct irradiation over the fetus or the uterus during pregnancy

• Direct irradiation over the thyroid gland

• Over hemorrhaging lesions

Application Technique 

The skin should be cleaned with alcohol prior to treatment. It is important to note that no coupling media is used during the delivery of LLLT (e.g. no lotions, gels, or ointments should be between the applicator and the patient’s skin). A stationary technique should be used. This allows for the best transfer of energy. Maintaining firm direct contact with the intact skin to increase depth of penetration.

How to Use RED DEVICE:  

▶ Step One: Before beginning treatment, ensure that the device is fully charged. To ensure the device is fully charged, charge the device overnight or for 6 hours uninterrupted.  

▶Step Two: Face should be clean and dry before beginning treatment; do not apply lotion or other products to the skin prior to treatment.  

▶Step Three: Turn the device on, and the treatment head of the device will begin to heat up. The device uses a smart sensor which only activates the treatment head when in contact with the skin. Apply light pressure to the skin using small circular motions. (you can also glide it upwards, always pulling skin up)  

▶Step Four: Continue treatment in this manner for three to five minutes on each area: below the eyes from cheek to chin, forehead, and neck. Making sure to avoid the eyelids. 

▶Step Five: After each session, it’s recommended that you apply a small amount of moisturizing cream to the treated areas. Clean the device after each use with a rubbing alcohol cloth or paper towel. Do not wash the device or allow too much moisture to penetrate the interior of the unit. For best results, repeat these steps three times a week during the first month, and then once a month after that, as needed for pain as well.  

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