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Near-infrared Therapeutic Laser and Pain Relief

Pain relief strategies using a continuous output gallium-aluminum arsenide (GaAlAs) laser.
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In previous articles, I have concentrated my discussions on the clinical applications of therapeutic laser for the relief of pain using those protocols involving the GaAs superpulsed laser. In this article, I will discuss treatment protocols and strategies for use with a continuous wave output GaAlAs laser.

Therapeutic lasers have been shown to have pain relieving and anti-inflammatory effects from a variety of mechanisms. Some of these mechanisms are listed below:

  • The GaAlAs laser has been shown to affect substance P and substance P-like immuno reactivity(SP-LI) levels.1
  • Inhibition of nerve action potentials in dorsal roots.2
  • Acceleration of recovery from acute join and soft tissue injuries by 35-50% in 85% of the cases studied.3
  • Pain reduction in neuropathic foot pain.4
  • Pain relief and control of inflammation in degenerative osteoarthritis patients.5
  • Naloxone-reversible analgesia has been observed in rats using a GaAlAs laser.6
  • Significant analgesia in patients with TMJ pain and for the reduction of post impacted 3rd molar extraction pain.7,8
  • Reduction of pain and increased circulation in Reynaud’s phenomenon.9

Near-Infrared Therapeutic Laser

The Gallium-Aluminum Arsenide (GaAlAs) is a semiconductor laser. This is a near infrared laser, which means that the light emission is invisible to the naked eye. This laser has historically operated in the 780-890nm range. This type of laser also has a continuous output of power and is often pulsed with a duty cycle switch. This laser penetrates to 2–3 cm depth. These lasers are often utilized for medium to deep tissue structures such as muscles, tendons, and joints.10

Recommended Anti-inflammatory Dosage for Low Level Laser Therapy
Laser classes 3 or 3 B, 780 - 860nm GaAlAs Lasers
Continuous or pulse output less than 0.5 Watt
Diagnoses Energy dose delivered to the skin over the target tendon or synovia
Tendinopathies Points or cm2 Joules 780 - 820nm Notes
Carpal-tunnel 2-3 12 Minimum 6 Joules per point
Lateral epicondylitis 1-2 4 Maximum 100mW/cm2
Biceps humeri c.l

1-2 8  
Supraspinatus 2-3 10 Minimum 5 Joules per point
Infraspinatus 2-3 10 Minimum 5 Joules per point
Trochanter major 2-4 10  
Patellartendon 2-3 6  
Tract. Iliotibialis 2-3 3 Maximum 100mW/cm2
Achilles tendon 2-3 8 Maximum 100mW/cm2
Plantar fasciitis 2-3 12 Minimum 6 Joules per point
Arthritis Points or cm2 Joules  
Finger PIP or MCP 1-2 6  
Wrist 2-4 10  
Humeroradial joint 1-2 4  
Elbow 2-4 10  
Glenohumeral joint 2-4 15 Minimum 6 Joules per point
Acromioclavicular 1-2 4  
Temporomandibular 1-2 6  
Cervical spine 2-4 15 Minimum 6 Joules per point
Lumbar spine 2-4 40 Minimum 8 Joules per point
Hip 2-4 40 Minimum 8 Joules per point
Knee medial 3-6 20 Minimum 5 Joules per point
Ankle 2-4 1  
Daily treatment for 2 weeks or treatment every other day for 3-4 weeks is recommended
Table 1. GaAlAs Dosage Chart (Courtesy of the World Association of Laser Therapy; WALT).

The GaAlAs laser is perhaps the most widely used infrared therapeutic laser today. This is, in large part, due to it’s availability in a wide range of wavelengths. We will recall that, in large measure, the wavelength determines the depth of tissue penetration. The wide variety of wavelengths available with this diode today—from the high 700 nm to the high 900 nm range—makes this laser diode applicable to many different body tissues. No other therapeutic laser has such a wide range of wavelengths.11

Tissue dosage of light energy is described in joules/cm2 where a joule of energy is the same as a watt-second. The therapeutic dose can be calculated as follows:

Dose (Joules/cm2)= Power (watts) x Time (secs)/Area (cm2)

In other words, dosage equals the laser’s output power (in watts) times the treatment duration (in seconds) and divided by the area treated (in cm2). If the laser is pulsed, one would substitute the mean power output.12

A GaAlAs laser with a 10mW output will require 100 seconds to achieve a 1 joule output. A 100mW GaAlAs laser will require 10 seconds to achieve 1 joule. A 500mW output GaAlAs laser will require 2 seconds to achieve 1 joule output. These exposure times are for each cm2 of area to be treated.13

Accurately determining and following tissue dose recommendations is important when using GaAlAs lasers or any other continuous wave output lasers. This is especially true when using a higher output laser, such as a 500mW GaAlAs laser, in order to minimize the possibility of overdosing the treatment area.

Last updated on: December 13, 2011
First published on: October 1, 2007