When speaking with doctors about lasers, we are frequently asked to compare lasers on the basis of Joules. Joules are the units of energy produced by lasers, measuring the amount of work required to produce one watt of power for one second.
Let’s look at some examples of how joules can be produced, using a Continuous Wave laser firing for one minute:
Energy produced by laser/second Time needed to produce 60 Joules
0.001 W or 1 milliwatt 100 minutes = 60 Joules
0.100 W or 100 milliwatts 10 minutes = 60 Joules
1.000 W or 1,000 milliwatts 1 minute = 60 Joules
10.000 W or 10,000 milliwatts 6 seconds = 60 Joules
The table above shows that we can produce 60 joules of therapeutic energy, using either an output of 1 milliwatt per second, or 10 watts per second, to achieve the same dosage for treatment.
But Are The Clinical Results The Same?
Is a joule always a joule, for clinical effectiveness? Research demonstrates that clinical effectiveness is based on laser photons reaching the target tissue.
Depth of penetration of laser photons is based on Peak Power, not total joules. If depth of penetration is not clinically required, i.e., only superficial stimulation of acupuncture points or superficial tissues are targeted, then a source of either 1 milliwatt or 1 watt could be effective.
If deeper tissues are targeted, higher wattage delivery is required.
A joule is a joule, as a measurement of energy. When using joules to compare therapeutic effects of a laser NOT all joules are equal. Higher watt lasers permit deeper penetration to underlying structures.