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Medical Lasers

Lasers (Light Amplification by Stimulation Emission of Radiation) have become a pertinent tool in the medical industry overtime.  The scientific methodology includes the precision use of laser physics to treat tissues, whilst, there are varying types of lasers i.e Gas, Liquid Dye and solid state, to suit differing uses in medicine. In essence, continuous improvement in this field, there has been widespread growth in the applications of cancer treatment, dermatology, ophthalmology to various surgical applications. 


Laser

Scientific Methodology

The primary methodology behind the medical laser is the use of high intensity light beams of varying wavelengths to either treat or remove tissues. Essentially, the narrow beam of pure monochromatic light can focus on tiny areas which allows for the precise surgical application.  The process of laser use includes a medium which has two parallel mirrors which partially reflect and transmit light. Essentially, the medium is excited through the use of an electrical  source in which the number of atoms in this state is greater than the ground state. Through this, the laser medium become activated there is a release of photons in all directions. Alternatively, a small number of the photons move along the middle line of the laser system between the mirrors which then reflect these. This is when the simulated emission is amplified. Hence, the partially transmitting mirror allows for a powerful beam of photons to be passed through as laser light.

In essence, medical lasers produce varying effects on the targeted tissue or area in the human body. This is dependant on factors and properties such as structure, water content, density, heat capacity as well as its ability to absorb, scatter or reflect emitted energy. Each biological target absorbs light in differing ways i.e. visible light and near- infrared – main chromophore are haemoglobin and melanin, in contrast to carbon dioxide laser which use water. Thus, in aim to seek the target zone without causing damage to other tissues, the specific tissue must contain chromophores which absorb a particular wavelength.

Types of Lasers

Type of Laser	General Information	Examples	Application
Gas	-       Absorbed by water and used as a high precision, bloodless, light scalpel. -       Wavelength of 10,600 nm -       Operate in invisible infared waveband	-               Carbon Dioxide - CO2 (Involved in the removal of a thin layer of tissue from the skin) -       Argon ( Laser passed through the outer layers of tissue) -       Krypton	-  Use in surgery
Liquid Dye	-       Uses liquid as a medium   -       Generate laser light through the energy state of organic dyes i.e. methyl or ethyl  dissolved in liquid solvents. -       Wavelength varies from 390 to 1000 nm.	- Dye laser	-Angiomas in children and infants -Treatment of spider naevi -Treatment of rosacea -Psosiaris   -       Photoradiation therapy (PRT)
Solid State	-       Uses a solid as a medium ( glass or crystalline materials) -       Deeply absorbed in tissues -       The light can be carried through to reach internal parts of the body.	-       Alexandrite -       Nd: YAG ( Used to get deeper into the tissue, and laser light can be carried through optical fibres)	-       Vessel coagulation -       Thermal tissue destruction   -       Cancer treatment

Application in Medicine

Ophthalmology

The medical laser is used in the treatment of eye conditions such as myopia and cataract procedures. It enables for patients with vision impairments to regain clear vision, through using bladeless technologies like the laser. An example of this is the LASIK process which involves the precision cutting of the outer layers of the corner to treat either short-sightedness or long sightedness. Other eye procedures include radial keratotomy ( involves changing the curvature of the cornea), photo-refractive keratotomy as well as keratotomy.

Dermatology

Primarily, the medical laser is used to remove defects on the skin i.e., abnormal skin growth and blemishes. Alternatively, it also includes the treatment of pigmented lesions i.e. brown spots, freckles, tattoo or hair removal (removed melanin stored in hair follicles /destroy hair matrix).

Cancer Treatment

Lasers are also used in cancer treatment, specifically, in either shrinking or destroying tumours or pre-cancerous growths. Medical lasers are commonly used to treat cancer on the surface of the body or the inner lining of organs i.e. Basal cell skin cancer.

Lithotripsy

The procedure includes a medical laser also known as FURSL (Flexible ureteroscopy and laser lithotripsy), breaks down stones in the kidney, gallbladder or ureter.

Surgical Application

Medical lasers in surgery are used to make bloodless cuts in tissues or alternatively remove a lesion i.e. skin tumour. The different types of laser emit a particular wavelength which allows for it clot, cut or vaporise biological tissues.

Biomedical Effects of Laser Use

Thermal

Laser-tissue interaction results from the conversion of light to heat, heat transfer and a tissue reaction to the temperature and the duration of the heating àDistortion or destruction of tissue volume.  

-      Factors determining this include degree to which time is heated, heating time and the thermal effects of the laser. The different effects which could occur include hyperthermia (temperature rises by a few degrees), coagulation and ablation.

Mechanical

Due to lasers emitting frequent and short pulses (around a nanosecond to picosecond) on small surfaces, this can in turn induce a destructive shock wave. Photo-ablation

Advantages and Disadvantages of the Medical Laser

Advantages

-      A “No-touch” technique

-      Reduces blood loss in surgical applications, as opposed to the use of medical scalpels.

-      Use of precision handling when operating on tissues

-      Reduced “postoperative pain” involved

-      Since there is no contact involved, sterilization is built in.

-      Ability to use the laser in surgical procedures for internal organs without opening up body.

Disadvantages

-      High costs as large units are required to operate laser

-      Increased complexity

-      Reliability and associated safety problems.

-      Relatively a new procedure, so long term effects are yet to be known.

Safety and Regulation

It is essential that practitioners and medical staff use protective wear such as eye glasses, closed doors, covered mirrors and signages when operating with lasers.

References

https://www.ncbi.nlm.nih.gov/pubmed/6241254

https://healthengine.com.au/info/laser-treatment-of-eye-conditions

https://www.cancer.gov/about-cancer/treatment/types/surgery/lasers-fact-sheet

https://www.physics-and-radio-electronics.com/physics/laser/differenttypesoflasers.html

https://www.medicalnewstoday.com/articles/322355.php

http://www.austin.org.au/Assets/Files/Laser%20information.pdf

http://khartoumspace.uofk.edu/bitstream/handle/123456789/13683/Applications%20of%20Laser%20in%20Medicine.pdf?sequence=1&isAllowed=y

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5220034/pdf/atm-04-23-452.pdf

https://www.physics-and-radio-electronics.com/physics/laser/ndyaglaser.html

https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=85&ContentID=p07250

http://www.optique-ingenieur.org/en/courses/OPI_ang_M01_C02/co/Contenu_04.html

https://file.scirp.org/pdf/JMP_2014032811313401.pdf