Use and Applications of Diode Laser in Soft Tissue Surgery

Laser Introduction:
‘Laser’ stands for “Light Amplification by Stimulated

Emission of Radiation”. A laser is produced by using energy to excite the atoms of a “lasing medium”; which, in the case of the diode laser, is a p-n junction of a semiconductor diode similar to that found in a light-emitting diode. When the atoms return to their normal state they release the energy in the form of photons – “stimulated emission”. This light wave is of high intensity and monochromatic or coherent and can be used to can cut, seal and vaporize tissue. Most diode lasers operate between the wavelengths of 635nm to 980nm in the near infrared spectrum, and are better absorbed by pigments such as haemoglobin or melanin and, therefore, can coagulate larger blood vessels than a CO2 laser, but do generally result in more collateral thermal damage.

Laser light incises by causing cellular ablation due to vaporisation of intracellular water. The laser-tissue interaction mechanisms are affected by two parameters, the laser exposure time on the tissue and the effective power density taking into account the tissue-specific absorption. The physiological response to photothermal laser incision is similar to a fine burn. The wound edges may develop char, and are surrounded by zones of irreversible coagulative necrosis and reversible inflammation. When incising, the aim is to choose power settings, waveform, and focal distance that minimise this collateral thermal damage. A continuous mode should be used for short (< 3 second) exposures or with irrigation to cool the fibre tip. A pulsed mode allows cooling of the fibre and tissue during exposures. Carbonisation of the fibre tip increases the cutting effectiveness.  [...]