Laser Mechanism and The Benefits

Hi guys,

Welcome back to the second post of my blog, I finally can blog again in between my assignments. So this post will be covering a little bit in depth about the Laser and IPL settings such as the wavelength, pulse duration, fluence, frequency and etc. Not only that, it will discuss about the pros and cons of laser and IPL, Fitzpatrick skin types, types of lasers and how to know which modality is suitable for you. Therefore, please bear with me for some minutes or you can just skip till the end if you already know about the laser terms.

What is Light?

It is an electromagnetic radiation within a certain portion of the electromagnetic spectrum. The amount of energy that is carried by each photon can be determined by the wavelength of the light. Some research shown that the light is exist in two ways which are the particles (light moves as a stream of photon particles; each particle represent a single quantum of light) and waves (a disturbance or oscillation that travels through either matter or space resulting in a transfer of energy).

Laser Terminology:

·         Wavelength (λ) is the length of a complete wave cycle measured from crest to crest or trough to trough. The standard international (SI) unit is in meter (m). The energy of photon can be described by the wavelength: the shorter the wavelength, the higher the energy and the longer the wavelength, the lower the energy of photon.

·         Amplitude (A) is the amount of displacement of a particle from its position of rest. It measure from the distance from the resting position (center line of the wave) to the tip of the crest or trough. The SI is in meter (m). The energy of photon can be described by the amplitude: the higher the amplitude, the greater energy and the lower the amplitude, the lower the energy.

·         Pulse duration is the length of time laser beam is being delivered or the exposure duration per pulse that usually measured in second, millisecond or nanosecond. Sub-pulses are some pulses with the equal total energy in the same length of time.

·         Frequency is the energy delivered to the tissue unit area. It can be measured in second (s) or Hertz (Hz) represent 1 wave per second. Fluence is the pulse energy in the treated area, often measured in J/Cm². The shorter wavelength has a high frequency and the longer wavelength has a lower frequency.

·         Spot Size is the size of the laser pointer and it can alter the depth of the focal point reached within the skin and the level of light scattering when performing the treatment. It usually measured in mm and used depend on size of the treatment area.

How does stimulated emission work in laser?

The laser utilise stimulated emission to create light by stimulating the electrons to its excited state within the laser medium. It is called population inversion which means that the electrons are moving from the ground energy state to the higher energy state forming a photon. This process is achieved by adding electric energy into the laser medium resulting in the spontaneous emission (the unstable state of electrons). Then, there are millions of photons released into the laser cavity via the spontaneous emission and traveling into random directions.

Fortunately, there is only one photon travels in the right direction initiating the stimulated emission (the ground state of electron). Then it released the photons and allows atom to emit light and hence the laser beam is produced. The produced laser beam then going through a process called amplifications. It is to ensure that there is enough photons to be emitted to produce laser beam by amplify the photons. By using mirror, the photons are being amplified in the laser cavity and reflects the newly photons back into the same directions and collide into each other creating stimulated emission. After going through this process, the laser beam is produced to create energy.

Is laser for hair reduction ionising or non-ionising?

It is non-ionising, which mean it safer and not enough to cause chemical changes by breaking the chemical bonds of the tissue.

What is electromagnetic spectrum?

It includes radio waves, microwaves, infrared rays, light rays, ultra violet rays, X‑rays and gamma rays. It is transmitted through empty space at 3.0 X 10⁸ m/s (300 thousand kilometres per second). There are two ways to distinguish the forms of electromagnetic spectrum: from their wavelength and form the amount of energy transfer. The longer the wavelength the non-ionising it is and the higher the energy is the more ionizing.

What is Fitzpatrick Skin Phototype Classification (FSPC)?

It is a tool to assess his patient’s sensitivity response to phototoxic reactions during their phototherapy treatments. It is made up of 4 elements; Fitzpatrick, Hyperpigmention, Glogau and Scarring.

What are the types of laser available and what are the pros and cons?

·         Ruby laser 694nm

(+)   For Fitzpatrick I & II

         Shorter wavelength therefore superficial penetration

        Suitable for dark hair with lighter skin

(-)    Darker Fitzpatrick III – VI

Not usually used as it can cause post hypopigmentation in Fitzpatrick II

·         Alexandrite Laser 755nm

(+)   For Fitzpatrick I – III

          More painless than the other lasers

        Good results and minimal side effects

        Cost effective

(-)    Darker Fitzpatrick IV - VI

·         Diode Laser 800-8100nm

(+)   For Fitzpatrick I - III

(-)    Darker Fitzpatrick IV – VI

·         Nd:YAG (Neodymium: yttrium aluminium garnet) Laser 1064nm

(+)   Darker Fitzpatrick III – VI

         Longer wavelength or penetration

        Suitable for dark and coarse hair

(-)    Lighter Fitzpatrick I & II

·         Intense Pulsed Light (IPL) 400-1200nm

(+)   Lighter Fitzpatrick I – III

         Lower cost

        Larger spot size therefore minimal treatment time

Have many filters, so it can be modify to suit specific skin and hair types

        Can be used to treat vascular lesion

(-)    Darker Fitzpatrick IV - VI

References:

Ahluwalia, G. (2009). Cosmetic Applications of Laser and Light Based Systems. Burlington: Elselvier

AS/NZS4173:2004 Guide to the Safe Use of Lasers in Health Care

Alqubaissy, Y, Mcleod, MP & Nouri, K 2011, ‘Laser hair Removal Pearls in Skin of Color’, Journal of Drugs in Dermatology, vol. 10, no.12, pp. 12-13.

Babilas, Philipp., Schreml, S., Szeimies, R-M., & L, M. (2010). Intense pulsed light (IPL): a review. Lasers in Surgery and Medicine,42, 93-104

Csele, M. (2004). Fundamentals of Light Sources and Lasers. Hoboken: Wiley

Goldberg, DJ 2007, ‘Laser-and light-based hair removal: an update’, Future Drugs Ltd, no. 1743-4440, no. 10, pp. 253-260.

Hruza, G.J., & Avram, M.M. (2012). Lasers and Lights. Philadelphia: Saunders

Hooker, S & Webb, C 2010, Laser Physics, Oxford University Press, New York, United States.

Ibrahimi, O, A., Avram, M, M., Hankes, C, W., Kilmer, S, L., & Anderson, R, R. (2011). Laser hair removal. Dermatologic therapy, Vol 24, 94 - 107

Kitsinelis, SP. (2011). Light Sources Technologies & Applications. Boca Raton: Taylor & Francis

Lipson, SG, Lipson, H, Tannhauser, DS 1995, Optical Physics, 3rd edn, Cambridge University Press,Cambridge, Great Britain

Ravnbak, M, H. (2008). Objective determination of Fitzpatrick skin type. Danish Medical Bulletin, pg 1 -6

Tay, Y.K., & Chan, Y.C. (2011). Textbook of Laser and Light Dermatology in the Asian Skin. New Jersey: World Scientific

Wassserman, DI & Chuang GS 2011, ‘Update on cutaneous laser therapy: recent medical advances of laser light and skin interactions’, Cosmetic dermatology review, vol. 6, no.2, pp. 163-174

Watanabe, S. (2008). Basics of laser application to dermatology. Arch Dermatol Res S21 – S30