Calculating LLLT Dosage

There has been a lot of discussion about the best method to quantify LLLT dosage.
However, it is my opinion that:

1. There is no agreed method of defining beam area
2. Dosage expressed as J/cm2 is inadequate

No agreed method for measuring LLLT dosage

So beam area is hard to define and there is no agreement in our industry for defining it. [I propose 1/e2 - will explain this soon].

Dosage expressed as J/cm² is inadequate

“Dosage” is usually calculated as Power / Beam Area x Time = J/cm². However, to consider that dosage should equal J/cm² is, in my opinion, inadequate.

Let me explain:

Assume there is a well-defined beam area and thus a quantifiable dosage.

• A 500mW laser with a beam area of 0.25Cm2 used for 20 seconds
  delivers 40 J/cm²
• A 200mW laser with a beam area of 0.1Cm2 used for 20 seconds
  delivers 40 J/cm²
• A 30mW laser with a beam area of 0.015Cm2 used for 20 seconds
  also delivers 40 J/cm²

Each of these probes apparently apply the same "dosage". However, the total energy delivered is clearly different [10 Joules, 4 Joules and 0.6 Joules respectively].While dosage appears consistent using J/cm², I suggest that the clinical results would be quite diverse. So I say that J/cm2 is an inadequate method of expressing dosage.

Calculating the area of an laser beam should be simple: But laser beams are rarely round: Area of a circle = r2 Area of a circle = r1r2     And laser beams are rarely of uniform density: Some diode laser beams appear very distorted   Where is the edge of the beam? What is the beam area?

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