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Understanding Science of Laser Therapy

By Dennis Arp

Posted: July 7, 2009

Veterinary Practice NewsRonald Riegel, DVM, has long worked to educate colleagues and dispel myths about laser technology, taking on culprits that include an icon of popular culture.

The name is Bond. James Bond.

Laser therapy
Michael Hernandez, director of technical services at The Downing Center for Animal Pain Management in Windsor, Colo.,  administers laser therapy to Freckles.
Fears have lingered since the days when 007 was trying to avoid being sliced in half by an industrial laser in the 1964 film “Goldfinger,” Dr. Riegel says.

“Even these days, practitioners feel that warmth and worry that too much use of a therapeutic laser will damage cells,” says Riegel, who practiced for 22 years. His seven books include manuals on laser use. 

“Then they learn that what they’re feeling is a photochemical reaction, not a photothermal one, and the light goes on, no pun intended.”

Most veterinary practitioners now have at least a cursory knowledge of Class IV laser therapy and its effectiveness in relieving pain, reducing inflammation and accelerating healing, Riegel says.

“The goal … is to obtain a device that provides the deepest penetration and the greatest amount of photobiostimulation in a reasonable amount of time,” he writes in his paper “Scientific Facts Concerning Class IV Laser Therapy in Veterinary Medicine.”

“The most common reason for treatment failure is low power and dosage, short wavelengths and nonscientific treatment protocols,” adds Riegel, who consults for LiteCure, a maker of Class IV therapy lasers for veterinary use.

“Unfortunately, some manufacturers have ‘created’ therapy protocols to fit pre-existing equipment, rather than using scientific facts and clinical results to guide in the design of their laser product.”

Recipe for Success
The key to a successful therapeutic dose of laser energy is achieving the right combination of power, wavelength and time, say Riegel and others with extensive experience accessing the medical benefits of the technology.

A therapeutic dose of energy is measured in Joules delivered per centimeter squared. The World Assn. of Laser Therapy has established that target tissues need a dose of 5 to 10 Joules per centimeter squared to get a biological response in cells, Riegel says.

treating the proximal quadriceps
Hernandez treats the proximal quadriceps.
Wavelength is important because it dictates the depth of penetration, says John Godbold, DVM, one of the first veterinarians to use Class IV laser therapy. He owns Stonehaven Park Veterinary Hospital in Jackson, Tenn.

Basically, the longer the waves, the deeper the penetration and the greater the opportunity for photobiostimulation of cells.

“Power is every bit as important as wavelength because it determines the amount of energy being delivered,” Dr. Godbold notes.

A therapeutic laser needs 6 to 10 watts of power to be practical for clinical use, Drs. Godbold and Riegel say.

Godbold uses the example of a 60-pound arthritic dog with multiple joint involvement. Treating the patient with a 6-watt laser at maximum power and continuous wave, the treatment would need to last eight to 10 minutes to reach an effective dose of eight to 10 Joules per centimeter squared.

To achieve the same target dose with a 1-watt laser would take 48 minutes to an hour, Godbold notes.

“Because the effects of the laser are cumulative, I’m convinced you could get the same results (with a less-powerful therapeutic laser),” he adds. “But is it practical to spend an hour in a clinical situation? It’s really not.”

Pulsing Lasers
Opting for the continuous-wave mode also increases the efficiency of the therapeutic laser, says Robin Downing, DVM, Dipl. AAPM, CVA, CCRP.

When the laser is set to the pulse mode, photons are emitted in short bursts, with slack periods in between. There’s a 50 percent decrease in energy delivered, says Dr. Riegel.

Even superpulsing lasers with a peak power of 20 to 30 watts are “actually delivering energy a very small percentage of the time,” Dr. Riegel writes.

“An analogy is putting a kink in a water hose. Let go of the kink and the flow rate increases temporarily. However the overall amount of water is not increased.”

“We find that continuous wave is the fastest way to achieve the total dose desired,” says Dr. Downing, who owns The Downing Center for Animal Pain Management in Windsor, Colo.

Godbold agrees but acknowledges, “Not everyone who has been intentionally involved with the technology is as convinced as I am that we get as good a response in patients with high-wattage continuous wave vs. multiple-frequency protocols.

“A number of us are pressing for treatment software based on target dose rather than frequency. To me, that’s the logical evolution.”

Not Difficult to Use
For now, simple math can determine the optimal dose of laser therapy, based on the area to be treated, the depth and density of the tissue and the number of Joules per second being emitted, experts say. Even coat and skin can be considerations, since dark hair and skin tone can absorb light energy, Downing notes.

But practitioners shouldn’t be paralyzed by the inexact nature of applying laser therapy, experts say.

“There are no side effects, so there is really no risk of overtreating,” Riegel says. “In many cases we’ve found that we were not treating aggressively enough.

“We need to use enough energy to increase the respiratory rate of cells and put them into hyperdrive. We’re dealing with cells that are already injured, and we’re looking to initiate this whole biochemical cascade of events.”

When knowledge about the science behind the therapeutic laser combines with the clinical experience of seeing it relieve pain and restore mobility, trepidation often morphs into belief, practitioners say.

“I was the skeptic, and I took a lot of persuading,” Riegel notes. “Basically, through research and experience, I figured out what worked and what didn’t.”

A great agent of change is seeing post-op patients heal faster or chronic arthritic patients move with ease for the first time in years, Godbold says.

He adds that with protocols in place, he enjoys having technicians administer the therapy.

“They are the ones in whose hands the healing takes place,” he notes. “And that generates incredible excitement.” <HOME>

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Reader Comments
Where are the double-blind studies that proove these claims?
Daniel, Phoenix, AZ
Posted: 7/25/2013 11:30:40 AM
New technology provides the deepest penetration at the highest wave length using a power source that does not cut or burn the animal and allows the probe to treat direct on the injury
steve, houston, TX
Posted: 6/13/2013 9:43:32 AM
We too have been using the Petlase Therapy Laser for over a year now and are continually blown away by the results. It has benefited our arthritic patients, our wound healing and even our patients with dermatological conditions. We are thrilled to have the laser as an option for our clients! We would highly recommend incorporating the laser into your pain management protocols.
Jennifer, Cleveland, OH
Posted: 10/18/2011 12:59:36 PM
As an internationally recognized lecturer on laser physics for the past 15 years and most recently the NAVC in Orlando Florida, I was disappointed by the incorrect information provided in the article, "Understanding Science of laser Therapy" in the current issue of Veterinary Practice News. There are three primary effects from Therapeutic diode laser wavelengths; photochemical, photothermal, and photomechanical. Heat is a phtothermal not photochemical effect. 980nm diode laser wavelengths have a vary shallow penetration depth of 1-2 cm as opposed to 800-810nm and 900-920nm which can reach depths of 4-6 cm. 980nm diode wavelengths also produce a very large portion of their energy absorption in the form of heat. This wavelength is best suited for surgical coagulation and cauterization. At 5-10 W in continuous wave this wavelength has the potential to cause thermal disruption of the cells and can inhibit cellular recovery. Research now recognizes a bi-phasic effect from diode therapy wavelengths. Too little energy absorption produces no effect, energy transfer from 0.03mJ/s to .3mJ/s produces generally the best photochemical intracellular effect, and energy in excess of .5mJ/s has a potentially a negative effect on cellular respiration. Pulsed energy release has also been show in many scientific papers to have a superior enhancing effect on cellular respiration and cell regeneration compared to continuous wave release of diode energy. Lastly Wavelength, Emission Modality, Time and Irradiance are the key factors in predicting positive therapeutic effect on cellular respiration. Power (W) is a poor guideline for predicting positive cellular effect. The interaction of diode wavelengths and cellular respiration is a complex and variable event that is still not completely understood or quantified. Potential therapy laser users should have a much better understanding of laser wavelength physics than this article promotes before applying this very effective therapeutic modality on their patients. I have a complete physics powerpoint available on my website, for interested colleagues. (Dr. Eeg is a Past President of the Veterinary Surgical Laser Society and internationally recognized expert on Laser Medicine and Physics)
Peter, Poolesville, MD
Posted: 1/26/2011 7:12:04 AM
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