The evidence that low-power light modulates pain dates back to the early 1970s, when Friedrich Plog of Canada first reported pain relief in patients treated with low-power light.¹ Recent reports include studies that indicate that 77% to 91% of patients respond positively to light therapy when treated three times per week over a period of 4 to 5 weeks.¹

Physical Therapy Products spoke to three experts to find out more about the actual laser therapy products that are gaining attention in the area of pain management. Roger White, PEng, is president and CEO, Theralase Inc, Toronto, Ontario, Canada. Fred Kahn, MD, FRCS(c), is president, Meditech International Inc, Toronto, Ontario, Canada. Larry K. Beardall is executive vice president of sales and marketing for Dynatronics Corp in Salt Lake City.

What is an acceptable amount of milliwatts (mW) that a laser therapy product should have, and how does that affect treatment time?

White: A laser therapy product should be a class 3B laser system, which according to IEC-825 guidelines has an average power rating from 5 mW to 500 mW, which is wavelength dependent. From 400 nm to 700 nm, the maximum permissible exposure (MPE) is 200 mW, increasing to 500 mW at wavelengths greater than 900 nm. Exceeding these MPE values will result in a thermal response to tissue. Acceptable average power levels for most patient conditions should be in the 50 mW to 150 mW range, since tissue characteristics vary from patient to patient. Since MPE limits track average power, an exciting way to increase the depth of penetration is to "super pulse" the laser diode; thereby providing 50,000 mW of peak power to the tissue surface for a fraction of a second. Increasing average power will decrease treatment time, but excessive average power (exceeding MPE) will result in negative thermal effects to tissue.

Kahn: This is a complex question that cannot be answered in simple fashion. Our laser probe can deliver 200 mW and the large surface arrays can deliver up to 2,000 mW of power. It must be recognized that there are many other important considerations in applying low-intensity laser therapy (LILT). If power settings are too high, denaturation of intracellular protein and thermal burns can occur, and these are undesirable complications. Waveform, wavelength, frequency, duty cycle, and duration are of equal importance. A properly engineered laser device should have the capacity to adjust the various parameters over an infinite range in order to achieve effective healing in the treatment of pathologies that differ widely in scope. Power settings and duration of treatment are not necessarily related.

Beardall: There is an inverse relationship between power and treatment time—the greater the power, the shorter the treatment time. Since most treatments require an average dose of 6 to 8 joules/cm², it would take a 1,000 mW probe (5 cm² in size or 200 mW/cm² in power density) 30 to 40 seconds per area to deliver this dose. As the power of the probe drops, the treatment time would increase proportionately.

What materials, such as safety goggles and a carrying case, are included with purchase?

White: Theralase supplies a turnkey solution to all our customers, providing: a hard carrying case, two pairs of laser safety glasses, initial marketing materials, an operating manual, a protocol manual, an external power supply, and hands-on training.

Kahn: With every unit shipped, Meditech includes two pairs of safety goggles: one for the patient and one for the practitioner. A specially designed carrying case for each of the four products is considered to be standard equipment to make all systems portable for treatment in any location. Each purchaser of a BioFlex product must attend a training course at our Research and Education Centre to provide the laser therapist with an understanding of the science and proper application of laser therapy. This is essential to ensure the most effective treatment for an extensive variety of medical conditions.

Beardall: Due to the inherent danger of lasers, safety goggles would be required and are usually included with any purchase. However, outdated laser diodes have been replaced with the safer superluminous diodes that do not present any safety risks and, therefore, do not require safety goggles. An applications manual is a standard accessory.

For PTs who want portability, describe what type of chargeable battery is included.

White: The Theralase TLC-1000 therapeutic laser system is a fully portable, ergonomically designed system with a medical grade nickel metal hydride (NiMH) battery source that provides up to 4 hours of continuous use using a multiple laser probe that produces 600 mW of power over five near-infrared and four visible red laser diodes.

Kahn: All BioFlex Systems are fully portable and designed for therapists requiring mobility options. Moreover, our systems do not run in the battery-operated mode. We feel that all therapy devices require a constant source of power that is maintained throughout the course of the treatment session.

Beardall: Currently, Dynatronics does not offer a battery option.

What are the safety features that should be built into a laser therapy product?

White: According to CSA-601 guidelines (international laser safety guidelines), a Class 3B laser must have a key switch (nonremovable in the "on" position), an emergency stop switch, a remote interlock connector (disconnects main power), a real-time power meter, and real-time monitoring of the laser diodes. The Theralase TLC-1000 therapeutic laser system possesses all of these features and is fully CSA-601 certified.

Kahn: All BioFlex Systems incorporate internal diagnostics that continuously moderate the output of the laser beam, ensuring that constant, accurate dosages are delivered to the treatment site. All arrays must be placed over the tissue area in complete contact before they can be activated. This will avoid potential ocular damage. Moreover, all treatment arrays manufactured by Meditech are designed to dissipate heat into the atmosphere to avoid thermal damage to tissues. By this approach, ambient temperature of the skin is maintained as LILT should be an athermal process.

Beardall: Specific built-in features might include remote interlock; constant monitoring of power output; limiting the J/cm² that can be delivered in a specific amount of time, and current detection to identify a failed device. In addition, equipment can be manufactured to fall within the 1M safety classification whenever possible to eliminate the need for auxiliary safety equipment. The greatest advancement in laser safety is the advent of the super-luminous diodes.

What type of maintenance do physical therapists need to perform on the products?

White: The TLC-1000 therapeutic laser system is solid-state technology that requires little maintenance. Recommended maintenance includes cleaning the laser diodes daily with isopropyl alcohol and cotton swabs to prevent contaminants from degrading the optical path and to minimize patient cross contamination. A real-time power meter check of the laser diodes' optical output is recommended once a month. If laser diode output varies by more than +/- 20%, a factory calibration may be required.

Kahn: The BioFlex series of LILT devices require minimal maintenance. All of our systems include a 1-year parts and labor warranty, and extended warranties are available. However, due to human error, malfunctions can occur. These are rare, and therapists are instructed to courier the system via FedEx to Meditech and notify us for an immediate replacement, which should arrive within 24 hours. This enables your clinic to remain operational while repairs are carried out. As an added feature, we do encourage users to have the system examined and calibrated every 2 years.

Beardall: There are no customer serviceable parts on Dynatronics probes, pads, or light therapy base units. It is recommended however, that Dynatronics light therapy devices be returned to the manufacturer annually for verification of calibration.

Daryl Lubinsky is the editor of a sister publication, Chiropractic Products. For more information, contact .

Reference

1. Enwemeka CS. Therapeutic light. Rehab Management. 2004;17(1):20–25,56–57.