The depth of penetration of laser light depends on many parameters such as the laser’s wavelength, the power, the type of device driver (superpulsed, pulsed or continuous wave mode) and lastly the technique used. The higher the wavelength typically, the deeper the penetration; however, with wavelengths greater than 950 nm the water in the tissue absorbs light and the depth of penetration is drastically reduced, in addition to causing heat. Secondly, devices of greater power can provide better penetration, up to the Maximum Permissible Exposure (“MPE”) limit of tissue; whereby, they just induce thermal heat. Thirdly, the peak power of the waveform in the laser system is the most critical factor in providing depth of penetration. Thus, devices which are superpulsed have better penetration versus pulsed or continuous wave devices, because they have greater peak power densities for superior photon concentrations at depth, albeit at shorter time intervals.
Note: The Theralase® CLT can provide a direct penetration of tissue of up to 5 inches into tissue.