Introduction
The term LASER is an abbreviation for “Light Amplification by Stimulated Emission of Radiation”. These are special devices that produce light that can be directed towards an object, and is monochromatic and coherent. These special characteristics are used in designing a laser device that is widely used for industrial purpose as well as in medicine . In the US, about 500,000 to 700,000 health care workers are involved in the use of medical lasers .
History and Progress of Lasers
The history of lasers dates back to 1916, when Albert Einstein discussed the possibility of stimulating radiant energy based on Niels Bohr’s theory that atoms emitted energy in quanta when transitioning from excited states back to resting states. An experimental proof was also carried out that received little attention . Although the essential ideas for constructing a laser were known around 1930, it was not before the early 1950s that electrical engineers and physicists began to work together with the research on monochromatic radiation of constant amplitude at very small wavelengths studying the microwave and radio frequency spectra of molecules. In this context, in 1953 and 1954, several physicists independently suggested the use of stimulated emission for microwave amplification, creating the acronym MASER to stand for ‘microwave amplification by stimulated emission of radiation’ . Further many researchers like Joseph Weber, Nikola Basov, and Alexander Prokhorov, etc. worked around this invention and invented the ammonia beam maser that was not particularly useful, as its operation was limited to the resonant frequency of the ammonia molecule and could only be used at barely detectable power levels . Many physicists further contributed in the form of a solid-state maser and Kikuchi ruby maser. In 1960, Theodore H. Maiman presented the first functional optical ruby maser excited by a xenon flash lamp to produce a bright pulse of 693.7 nm, deep red light of about an 1- ms duration and a power output of about a billion watt per pulse . His invention rapidly led to the development of multiple other optical masers, now called laser (light amplification by stimulated emission of radiation). The medical specialists who were already treating diseases with sunlight and technical light sources were also the first to carry out biomedical research with lasers . A year after Maiman had presented the first ruby laser, ophthalmologists using xenon lamps for retinal photocoagulation published on ocular lesions experimentally produced in a rabbit by an optical maser . These studies were soon followed by clinical experience on patients treated for retinal tears, angiomas, flat detachments, and tumors .
In dermatology, the treatment of skin diseases with light has a long tradition – using Finsen lamp to treat lupus, artificial UV light sources for wound healing and rickets; and combination of light and tar to treat psoriasis. Hence, it was not surprising that the American Society for Laser Medicine and Surgery honored a dermatologist, Leon Goldman, as the ‘father of lasers in medicine in the US” . Leon Goldman, the Chairman of Dermatology Department at the University of Cincinnati and the founder of first biomedical laser laboratory at the same university did vast research on the application of lasers in dermatological medicine and has published several research papers. In 1973, Goldman published promising effects on angiomas with the Nd:YAG laser . After this prime research, laser research was carried out and lasers tested in almost most of the fields of medicine that will be discussed in this article.
With continuous new developments in the area of laser research, an early continuous- wave laser was invented that emitted an uninterrupted beam of light which effectively destroyed the desired target, but also exposed the surrounding healthy tissue to laser energy for a longer time. The result was a collateral damage in the form of hypertrophic scar and pigmentation . In an attempt to minimize this injury, a mechanical shutter was invented to interrupt the beam of light. After a long time of investigations and new developments in laser technology, the first clinical applications were performed by Choy and Ginsburg in 1983 . In 1996, the erbium (Er):YAG laser with a very short wavelength of 2,940 nm was invented that allowed a more superficial vaporization of tissue and was used together with CO2 lasers for skin resurfacing. Later, the new technical concept of fractional photothermolysis was introduced, which received FDA approval in 2004 for skin resurfacing and in 2005 for the treatment of melasma . This is how lasers have progressed so far and are widely used in medicine.
Types of lasers
Lasers are named for the solid, liquid, gas, or electronic substance that is used to create the light. Today, many types of lasers are used to treat medical problems, and new ones are being tested all the time. The most common ones in use are the carbon dioxide (CO2), argon, and neodymium: yttrium aluminum garnet (Nd:YAG) lasers. Some newer types of lasers – the erbium: yttrium aluminum garnet (Er:YAG); holium: yttrium aluminum garnet (Ho:YAG), copper vapor, and diode lasers – are also being used in medical and dental treatments .
Where and how lasers are used?
The acceptance of lasers in medicine by doctors and by patients has always been very high. Laser, regarded as a powerful source of harmless looking light, has become a magic bullet for treatment of many diseases in medicine and has also replaced the surgeon’s knife. Medical uses of lasers include surgery, dermatology, gynecology, cardiology, otology, ophthalmology, etc. Recent uses include angioplasty, photodynamic therapy (PDT), and diagnostic image processing .
Lasers are used in dermatology since the very beginning particularly to treat skin cancers, for permanent removal of pigmented hair, and even as a treatment modality for tattoos .
Since the 1970's lasers have been increasingly used in oral and maxillofacial/head and neck surgery for evaporation, excision and coagulation of tissue. The commonly used lasers include carbon dioxide (CO2), neodymium:yttriumaluminium- garnet (Nd:YAG) and Argon lasers. The CO2 laser was one of the earliest gas lasers invented in 1964, and it still remains the most useful lasers in oral and maxillofacial/head and neck surgery practice. In this field, lasers have been employed to treat premalignant and early oral carcinomas .
Lasers are most commonly used in urology too most commonly in the surgical management of benign prostatic hyperplasia (BPH) and as intracorporeal lithotripters. Other uses include ablation of various urologic tumors and incising strictures of the upper- and lower urinary tract .
A growing use of medical lasers is in the area of photodynamic therapy (PDT) where lasers provide a convenient source of intense, narrow bandwidth light .
Like every medical device/ application, lasers too have some advantages and disadvantages compared to standard surgical tools.
The advantage in using lasers is that they are more precise than scalpels, the heat produced by lasers at the time of its usage helps clean the edges of the body tissue that it is cutting thus reducing the risk of infection, and since laser heat seals blood vessels, there is less bleeding, swelling, pain, or scarring. Sometimes, the operating and healing time is shorter; and in use in surgeries, it just means less cutting and damage to healthy tissues .
On the other hand, the disadvantages are that, even today fewer doctors and nurses are trained to use lasers; and the equipment costs a lot and is bulky. Importantly, strict safety precautions must be followed in the operating room where lasers are used. A major drawback of using laser for surgical use is the effect of some laser treatments may not last long, so they might need to be repeated; and sometimes the laser cannot remove the entire tumor mass in one go, so repeated sittings/ hospitalizations are essential .
Lasers used in medical applications are incorporated into an apparatus that includes a delivery system to direct the output of the laser, a power supply with control and calibration functions, mechanical housing with interlocks, and associated fluids and gases required for the operation of the laser .
How do lasers and biomedical technicians relate?
Biomedical technician (BT) is a laser technical support staff. They do not personally care for the patient, but play a vital role in patient care. With a medical technology like laser, a BT will carry out a job of inspecting, maintaining, and repairing the laser and related equipment. A BT should be responsible for performing the following tasks with respect to laser equipment - installing and carrying out acceptance testing of laser and its supporting system; conducting preventative maintenance and repairing broken equipment; conducting safety testing & standards compliance . Only an authorized BT can remove the laser system outside its cover after they complete the appropriate training to prevent electric shock .
In summary, lasers are doing a great job in the field of medicine; and have replaced the common surgical knife for many surgeries; however, just like any medical equipment, they too have pros and cons. A BT is a trained laser technical support staff who is indirectly involved in patient care.
References
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