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Calculating Dosage


Laser Therapy dosage

In "real life" laser therapy is applied by physio's much like the apply an ice pack or suntan lotion. In trials you can bet Ambre Solair report using so many mg of lotion but in "real life" people just rub a blob on. In my experience thats how patients are treated with electrotherapies and laser.

does that work ?

My customers think so and judging by the wide variety dosages reported in clinical trials it makes me wonder how critical these things are.

I suspect that in-vivo it is not so critical. In-vitro is another matter.


Many authors have studied the amount of energy which should be delivered to tissue per unit of time (the energy density). This aspect of the matter has been considered by most a major issue. However, looking at the results reported in the literature, the results are anything but clear. Since Mester, the energy delivered on tissue has been expressed as joules per square centimetre, but the results been that every author reports different and personal data, causing considerable confusion.


If you are a student, the following is what they want you to know about dosage:

It is calculated by multiplying the Irradiance x Time

The following triangular format may be familiar to you.

If you know any two bits of data you can work out the third bit of the triangle

You may find some research expressed in Joules :


Joules is the energy applied but with without considering the size of the beam.

Quoting Joules alone is considered to be an inadequate way of expressing dosage as it does not take into account the size of the beam.

However both methods are on there own are insufficient.


a) Bolton, Young and Dyson (1) showed that an identical "dosage" from two different power lasers do not give the the same results in vitro.

(1) Bolton, P., Young S., Dyson M., (1991) Macrophage responsiveness to Light Therapy with Varying Power and Energy Densities. Laser Therapy Journal 105-111

b) It is difficult to accurately measure the spot size of an invisible infrared beam that is only a couple of mm2. The beam is usually not circular, and the density of the light across the beam is not uniform (see example of typical LLLT beam below). I suggest that there is little consistency between manufacturers / researchers regarding measurement of beam density (irradiance).


c) I suggest that different treatment dosage should be given for patients of different build and presenting with different conditions.

In clinical practice the science gets forgotten and the "art" is practiced


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