Light comes in many guises

Laser and light based therapies have become commonplace in today’s society. However, it seems to be this mysterious Golden Fleece that everyone knows about, but very few knows what it really is.

Let’s start with the notion that all light is not equal. Simply because two light beams may seem the same to the human eye, doesn’t make it the same. In light therapy we use the light as a carrier of energy, and it is this energy that does the work. You may use a laser beam of 810 nm that has enough energy to destroy the dermal papilla and prevent future hair growth. Or you may use a laser beam of 810 nm that has the right amount of energy to stimulate the dermal papilla to grow a thicker darker hair.

There are a couple of basic principles that you need to understand and adhere to for a successful treatment. I’ll start with the principle that not all wavelengths of light deliver their energy to all biological matter. You can think of the wavelength as a language. If you send a messenger that speaks 810 nm, he can only convey his message (energy) to those cells that understand 810 nm. Our messenger of 810 nm cannot convey his message to a cell that only understands 600 nm. The target tissue determines which wavelength(s) to use. It is possible that some tissue ‘speak’ a range of wavelengths, just as some people can speak a range of languages. However, there is always one native language you will understand better than any other language. Similar to this, there will always be a wavelength that tissue will respond better to than other wavelengths.

Now that we know how to get the energy to the target tissue, let’s look at another of the fundamental principles, fluence. Fluence is the energy in Joules divided over the area in square centimetres, J/cm2. As I mentioned earlier, it is the energy that does the work. But how much energy do you need to get the task done. You can compare fluence with the dose of medicine. Should you have a head ache you may need 500 mg of aspirin to get relief from the pain. However, if you use aspirin to prevent blood clots, 50 mg maybe enough. When you and your partner both have a head ache, you cannot just split an aspirin of 500 mg into two (250 mg each) and expect the same results. You have to double the amount of aspirin from one pill of 500 mg to 2 pills of 500 mg.
Therefore, if you treat a larger area you also need to increase the energy to make sure that the fluence remains the same, the energy per square centimetre. If you compare two machines, one with a spot size of 1 cm2 and 50 J maximum energy (maximum fluence of 50 J/cm2) and another with a spot size of 3 cm2, the maximum energy needs to be 150 J to get the same maximum fluence of 50 J/cm2.

The penultimate principle we will discuss in this article is pulse duration. The pulse duration, also called pulse length, is the time the light beam has to transfers its energy to the target tissue. This principle is more difficult to explain with an analogy since it is very task specific. For laser hair removal the aim is to have the energy absorbed by the melanin in the hair. This energy will be transformed to heat that must spread to the surrounding tissue where the dermal papilla is. The papilla then has to be heated over a minimum temperature for a period of time. Thus, you need a long pulse duration.
When you want to do laser tattoo removal, the energy must be absorbed by the ink molecule, but must not be transmitted to the surrounding tissue or even throughout the ink molecule. Here you need a super short pulse duration so that you heat up one side of the ink molecule, while the other side remains cold. This will cause the ink molecule to breakup into smaller pieces and when small enough the ink will be cleared by the lymph system.

The last principle we discuss here is frequency. This is the amount of times a machine pulses during a second. The frequency has a larger influence on the treatment results than most therapists realize. With photothermal treatments it determines the heat compound effect. This is when there is not enough time between pulses to have enough heat dissipation. The result is that the treatment becomes more painful to the client. Most therapists will respond to this by lowering the energy, which leads to reduced results. By reducing your frequency, you will certainly increase the overall treatment time. But with it, you will increase client comfort and results.

The principles we’ve discussed in this article are commonly known as the treatment parameters. These are the settings that you can adjust on your machine. Knowing how to adjust these settings on a machine will not make you a successful laser therapist. The key to success lays in the knowledge and understanding what it is you’re doing when adjusting the settings. Treatment parameters do not function isolated. Adjusting one parameter will have a cascade of implications on every other parameter and ultimately the end result.

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