Laser therapy, regardless of the actual laser utilized, relies upon a few key units of measurement. These measurements help select treatment protocols and monitor the dose delivered to each patient.
Average Power
Refers to the average power that a laser emits during the treatment, measured in watts (W).
Duty Cycle
Ratio of “on” duration compared to “off” during one period. A period is the time it takes to complete an on-and-off cycle.
Effective Dose
Is the does or amount that produces a therapeutic response or desired effect.
Energy
Commonly used to characterize laser output, measured in joules (J).
Energy Density/Fluence
The energy density expresses the total amount of energy delivered per unit area, in Joules per square centimeter (J/cm2).
Hertz (Hz)
Unit of frequency, i. e. “pulses per second”, listed in Hz.
Joule (J)
A unit of energy describing the work required to produce one watt of power for one second (one watt-second).
Joule cm2 (J cm2)
A unit of radiant exposure used in measuring the amount of energy per unit area of absorbing surface or per unit area of a laser beam. Also called the dose.
Peak Power
The maximum pulse power output of a laser and it is fixed by the laser manufacturer.
Power
The time rate at which energy is transferred. Usually expressed in watts (joules per second); also termed radiant flux.
Power Density
The intensity of the laser beam; average power divided by size of beam (“spot size”); relates to the dose.
Pulse Mode
The pulse energy is simply the total optical energy content of a pulse. Pulse mode is operation of a laser when the beam is intermittently on in fractions of a second.
Watt (W) The unit of power; equivalent to one joule per second.
Watt cm2 (W cm2)
A unit of irradiance used in measuring the amount of power per area of absorbing surface, or per cross-sectional area of a laser beam. Also called power density.
The Takeaway
Knowing the key units of laser measurement allows us to talk in a common lanagurage about the parameters to treat patients. Please contact us to receive our ebook explaining the science of lasers.
