May 27, 2020
We know that the terms used when talking about laser surgery and laser science can be confusing. So we have taken the time to define some of the important terms that are used when talking about soft-tissue lasers, laser surgery, and laser dentistry. LightScalpel was founded by a laser physicist, laser education is what makes us different from most other manufacturers. If you are finding it hard to understand laser science or laser-tissue interaction, feel free to ask us.
Laser Surgery Terms Defined
Ablation of soft tissue by laser energy: Removal of the irradiated volume of the soft tissue through the conversion of laser energy to heat leading to intra- and extra-cellular water vaporization.
Ablation of soft tissue on contact with hot tip: Removal of soft tissue by heat transfer from hot charred glass tip leading to tissue decomposition (ex. Diode).
Absorption: The transfer of radiant energy into internal energy of absorbing tissue resulting in a change in that tissue.
Active Medium: Any material within the optical cavity of a laser that, when energized, emits photons (radiant energy).
Attenuation: The decline in energy or power as a beam passes through an absorbing or scattering medium.
Average Power: An expression of the average power emission over time expressed in Watts; the total amount of laser energy delivered divided by the duration of the laser exposure. For a pulsed laser, the product of the energy per pulse (Joule) and the pulse frequency (Hertz).
Beam: Radiant electromagnetic rays that may be divergent, convergent, or collimated (parallel).
Chromophore: A substance or molecule exhibiting selective light-absorbing qualities, often to specific wavelengths.
Class IV Laser: A surgical laser that requires safety personnel to monitor the nominal hazard zone, eye protection, and training. This class of laser poses a significant risk of damage to eyes, any non-target tissue, and can produce plume hazards.
Coagulation: An observed denaturation of soft tissue proteins that occurs at 60°C.
Contact Mode: The direct contact of charred hot glass tip (of diode or Nd:YAG laser) to the target tissue.
Continuous Mode: A manner of applying laser energy in an uninterrupted (non-pulsed) fashion, in which beam power density remains constant over time; also termed continuous wave, and abbreviated as ‘CW.’ Contrast with ‘Pulsed Mode.’
Energy: The ability to perform work, expressed in Joules. The product of power (Watts) and duration (seconds). 1 Joule = 1 Watt x 1 second.
Energy Density: The measurement of energy per area of spot size, usually expressed as Joules per square centimeter; also known as fluence.
Fluence: See Energy Density.
Free-Running Pulse Mode: A solid-state laser operating mode where the emission is truly pulsed and not gated. A flashlamp is used as the external energy source so that very short pulse durations and peak powers of thousands of Watts are possible. A laser operating in this mode cannot be operated in a continuous wave.
Gated Pulse Mode: A laser operating mode where the emission is a repetitive on-and-off cycle. The laser beam is actually emitted continuously, but a mechanical shutter or electronic control ‘chops’ the laser beam into pulses. This term is synonymous with chopped pulse mode.
Intensity: See Power Density.
Irradiance: See Power Density.
Joule: See Energy. A unit of energy or work equal to an exposure of 1 Watt of power for 1 second.
Noncontact Mode: A laser technique in which the delivery system is used without touching the target tissue; light radiation may be defocused or focused, depending on the operator’s technique and procedure.
Peak Power: The highest power in each pulse.
Plume: Essentially the smoke produced from aerosolization of by-products due to laser-tissue interaction. It is composed of water vapors (dominant component) and particulate matter, cellular debris, carbonaceous and inorganic materials, and potentially biohazardous products.
Power: The amount of work performed per unit time, expressed in Watts (Joules per second). 1 Watt = 1 Joule / 1 Second.
Power Density: The measurement of power per area of spot size, usually expressed as Watts per square centimeter; also known as intensity, irradiance, and radiance.
Pulse Duration: A measurement of the total amount of time that a pulse is emitted; also known as pulse width.
Pulsed Mode: Laser radiation that is emitted intermittently as short bursts or pulses of energy rather than in a continuous fashion. Contrast with ‘Continuous Mode.
Repetition Rate: Number of pulses per second, also known as pulse rate; usually expressed in Hertz (Hz).
Scattering: beam disperses throughout the tissue in all directions
Soft-Tissue: includes skin, tendons, ligaments, fascia, fibrous tissues, fat, muscles, and synovial membranes.
SuperPulse: A variation of high peal power pulsed mode producing char-free tissue ablation, in which the pulse durations are shorter than Thermal Relaxation Time, and pulse spacing is greater than Thermal Relaxation Time.
Thermal Relaxation Time: The rate of how fast the irradiated tissue diffuses the heat away from the irradiated volume of the tissue defines the Thermal Relaxation Time. Is the value is controlled by the wavelength-dependent absorption coefficient.
Vaporization: conversion of liquid water into vapor.