by Patrick J. Clark, A.A.S., C.M.L.S.O.*
Medical Laser Dynamics, Highland Village, Texas
Background and Objectives: The skin comprises the epidermis and the dermis and often contains unwanted items such as hair and vascular lesions.
Targeting those items is a function of:
- The wavelength to determine depth and nature of the target.
- The power and spot size to generate a specific amount of heat to alter the target.
- The time period in which the energy is delivered.
Most unwanted hair and vascular targets have very similar size and shape (60-100 micron cylinders) and therefore have very similar ideal pulse times.
Pigmented lesions are not as thick as the diameter of the unwanted hair or vessel but exist in a sheet, which has about twice the thermal relaxation time (TRT) resulting in the need for a similar 3-5 millisecond pulse time.
Conclusions:
It is generally agreed by practitioners, when the choice of pulse times between 3 and 5 milliseconds exists, it is better to select 5 milliseconds for the sake of patient safety and reduced discomfort. Longer pulse times (10 milliseconds or beyond) do not have the same ability to match the natural physical responses of these targets and therefore much more energy is required of those devices using longer pulse times and with a higher risk of complications.
To download the full abstract, please click on the link below:
"The Efficiency of Capturing True Reaction Times in Tissue" (3MB PDF) |
