A 100 Watt Laser – And My Doctor Says It Won’t Hurt?!?!

It is an unfortunate business practice, but the sale of medical lasers is largely being promoted by their hardware profile: “X” number of watts, “Y” number of pulses at “Z” nanometers etc.  What is unfortunate about this is that it does not really paint a good picture on what the clinical qualities of a laser really are, because this type of advertising does not really address what kind of “tissue interaction” it produces.  This however is ultimately the most important quality of any laser.  I’ll explain…

First and foremost, the power of the laser (usually displayed in Watts) is the true output power in terms of light energy emitted.  This is in direct contrast to a light bulb for instance.  A 60-Watt light bulb will draw 60 Watts of power out of the socket, but only deliver a fraction thereof as light energy, because most of the power drawn gets converted to heat energy.  In a laser the power rating is NOT what it draws out of the electric socket, but rather the light energy it produces.

Another concept that needs to be addressed is that this power claim describing a laser, can often be misleading.  More often than not, a “high-powered” healthcare laser in the 20 – 100 Watt range achieves this kind or output power mostly in a “pulsed” mode.  This means that the laser will be “on” and “off” several hundred or even several thousand times a second and every time it is “on” it emits 100 Watts.  Since this is a pulse train of laser light, it is important to note that the AVERAGE power may only be in the milliwatt range, so there is effectively only less than 1 Watt being absorbed by the tissues.

The last and most important concept which needs to be addressed is that of the power density at the output tip (aka “fluence”).  A 50-Watt laser with an output diameter of 1 cm will have an entirely different effect on tissues than a 6-Watt laser with an output diameter of only a few hundred microns.  The former will have a biostimulatory effect, whereas the latter will be able to cut tissue.

So, as we can see, the advertising profiles of lasers do not really always reflect the clinical relevance.  It is my opinion that this needs to change eventually, so that the tissue interaction is placed into the foreground and not the hardware profile.


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