Lasers in medicine. Application of lasers in medicine and science

Over the past half century, lasers have found application in ophthalmology, oncology, plastic surgery and many other areas of medicine and biomedical research.

About the possibility of using light to treat diseases was known thousands of years ago. The ancient Greeks and Egyptians used solar radiation in therapy, and these two ideas were even related to each other in mythology - the Greek god Apollo was the god of sun and healing.

And only after the invention of a source of coherent radiation more than 50 years ago was indeed revealed the potential of the use of light in medicine.

Due to the special properties, lasers are much more effective than the radiation of the sun or other sources. Each quantum oscillator operates in a very narrow wavelength range and emits coherent light. Also, lasers in medicine allow the creation of large capacities. A beam of energy can be concentrated at a very small point, so that its high density is achieved. These properties have led to the fact that today lasers are used in many areas of medical diagnostics, therapy and surgery.

Treatment of skin and eyes

The use of lasers in medicine began with ophthalmology and dermatology. A quantum generator was discovered in 1960. And a year later, Leon Goldman demonstrated how a ruby red laser in medicine can be used to remove capillary dysplasia, a variety of birthmarks, and melanoma.

This application is based on the ability of sources of coherent radiation to operate at a certain wavelength. Sources of coherent radiation are now widely used to remove tumors, tattoos, hair and moles.

In dermatology, lasers of various types and wavelengths are used, which is due to different types of healing lesions and the main absorbing substance inside them. The wavelength also depends on the skin type of the patient.

Today, one can not practice dermatology or ophthalmology without having lasers, since they have become the main tools for treating patients. The use of quantum generators for vision correction and a wide range of ophthalmic applications grew after Charles Campbell became the first physician in 1961 to use a red laser in medicine to heal a patient with retinal detachment.

Later for this purpose, ophthalmologists began to use argon sources of coherent radiation in the green part of the spectrum. Here, the properties of the eye, especially its lenses, were involved, to focus the ray in the region of the retinal detachment. The highly concentrated power of the apparatus literally welds it.

Laser surgery, laser coagulation and photodynamic therapy, can help patients with some forms of macular degeneration. In the first procedure, a beam of coherent radiation is used to seal blood vessels and slow their pathological growth under the macula.

Similar studies were conducted in the 1940s with sunlight, but for their successful completion, physicians needed the unique properties of quantum generators. The next application of argon laser was the stop of internal bleeding. Selective absorption of green light by hemoglobin - a pigment of red blood cells - was used to block bleeding blood vessels. For the treatment of cancer, the blood vessels that enter the tumor and supply it with nutrients are destroyed.

This can not be achieved by using sunlight. Medicine is very conservative, as it should be, but sources of coherent radiation have been recognized in various areas. Lasers in medicine have replaced many traditional instruments.

Ophthalmology and dermatology also benefited from excimer sources of coherent radiation in the ultraviolet range. They have become widely used to change the shape of the cornea (LASIK) for vision correction. Lasers in aesthetic medicine are used to remove stains and wrinkles.

Profitable cosmetic surgery

Such technological developments are inevitably popular among commercial investors, since they have a huge potential for profit. The analytical company Medtech Insight in 2011 estimated the volume of the market of laser cosmetic equipment worth more than 1 billion US dollars. Indeed, despite the decline in overall demand for medical systems during the global recession, cosmetic operations based on the use of quantum generators continue to be in constant demand in the United States, the dominant market for laser systems.

Visualization and Diagnostics

Lasers in medicine play an important role in the early detection of cancer, as well as many other diseases. For example, in Tel Aviv a group of scientists was interested in infrared spectroscopy using infrared sources of coherent radiation. The reason for this is that cancer and healthy tissue can have different patency in the infrared range. One promising application of this method is the detection of melanoma. With skin cancer, early diagnosis is very important for the survival of patients. Currently, the detection of melanoma is done by eye, so it remains to rely on the skill of the doctor.

In Israel, once a year, every person can go for a free screening of melanoma. Several years ago, in one of the major medical centers, studies were conducted, as a result of which it became possible to visually observe the difference in the infrared range between the potential, but non-dangerous signs, and real melanoma.

Katsir, the organizer of the first SPIE conference on biomedical optics in 1984, and his team in Tel Aviv also developed optical fibers that are transparent to infrared wavelengths, which allowed this method to be extended to internal diagnostics. In addition, it can become a quick and painless alternative to cervical smear in gynecology.

A blue semiconductor laser in medicine has found application in fluorescent diagnostics.

Systems based on quantum generators also begin to replace X-rays, which have traditionally been used in mammography. X-rays give doctors a difficult dilemma: reliable detection of cancers requires their high intensity, but the increase in radiation itself increases the risk of cancer. As an alternative, the possibility of using very fast laser pulses for imaging the breast and other parts of the body, for example, the brain, is being studied.

OCT for the eyes and not only

Lasers in biology and medicine have found application in optical coherence tomography (OCT), which caused a wave of enthusiasm. This visualization method uses the properties of a quantum generator and can give very precise (micron order), transverse and three-dimensional images of biological tissue in real time. OCT is already used in ophthalmology, and can, for example, allow an ophthalmologist to see the cross section of the cornea for the diagnosis of retinal and glaucoma diseases. Today, technology is also being used in other areas of medicine.

One of the largest areas, formed by OCT, is engaged in obtaining fiber-optic images of arteries. Optical coherence tomography can be used to assess the condition of an unstable plaque prone to rupture.

Microscopy of living organisms

Lasers in science, technology, medicine also play a key role in many types of microscopy. In this area, a large number of developments have been made, the purpose of which is to visualize what is happening inside the patient's body without using a scalpel.

The most difficult thing in removing cancer is the need to constantly use the services of a microscope, so that the surgeon can make sure that everything is done correctly. The ability to make microscopy "live" and in real time is a significant achievement.

A new application of lasers in engineering and medicine is scanning in the near field of optical microscopy, which can produce images with a resolution much larger than that of standard microscopes. This method is based on optical fibers with incisions at the ends, the dimensions of which are smaller than the wavelength of light. This allowed subwave visualization and laid the groundwork for obtaining images of biological cells. The use of this technology in IR lasers will make it possible to better understand Alzheimer's disease, cancer and other changes in cells.

PDT and other treatments

Developments in the field of optical fibers help to expand the possibilities of using lasers in other spheres. In addition, that they allow for diagnostics within the body, the energy of coherent radiation can be transferred to where it is necessary. This can be used in treatment. Fiber lasers are becoming much more advanced. They will radically change the medicine of the future.

The field of photomedicine, using light-sensitive chemicals that interact with the body in a special way, can resort to the help of quantum generators for both diagnosis and treatment of patients. In photodynamic therapy (PDT), for example, a laser and a photosensitive drug can restore vision in patients with a "wet" form of age-related macular degeneration, the main cause of blindness in people over the age of 50 years.

In oncology, some porphyrins accumulate in cancer cells and fluoresce when illuminated with a certain wavelength, indicating the location of the tumor. If these same compounds are then illuminated by another wavelength, they become toxic and kill the damaged cells.

Red gas helium-neon laser in medicine is used in the treatment of osteoporosis, psoriasis, trophic ulcers, etc., since this frequency is well absorbed by hemoglobin and enzymes. Radiation slows inflammation, prevents flushing and swelling, improves blood flow.

Personalized treatment

Two more areas in which there is an application for lasers - genetics and epigenetics.

In the future, everything will happen at the nanoscale, which will allow us to practice medicine on a cell scale. Lasers that can generate femtosecond pulses and be tuned to a specific wavelength are ideal partners for physicians.

This will open the door for personalized treatment based on the individual genome of the patient.

Leon Goldman - the founder of laser medicine

Speaking about the use of quantum generators in the treatment of people, we can not fail to mention Leon Goldman. He is known as the "father" of laser medicine.

A year after the invention of the source of coherent radiation, Goldman became the first researcher who applied it for the treatment of skin disease. The technique applied by the scientist paved the way for the subsequent development of laser dermatology.

His research in the mid-1960s led to the use of a ruby quantum generator in retinal surgery and to discoveries such as the possibility of coherent radiation to simultaneously cut the skin and seal blood vessels, limiting bleeding.

Goldman, who worked for most of his career as a dermatologist at the University of Cincinnati, founded the American Society of Lasers in Medicine and Surgery and helped lay the foundations for the safety of lasers. He died in 1997.

Miniaturization

The first 2-micron quantum generators were the size of a double bed and cooled with liquid nitrogen. Today there are diode, fits in the palm of your hand, and even more miniature fiber lasers. This kind of change paves the way for new applications and developments. Future medicine will have tiny lasers for brain surgery.

Thanks to technological progress, there is a constant reduction in costs. Just as lasers have become familiar in household appliances, they have begun to play a key role in hospital equipment.

If before, lasers in medicine were very large and complex, today their production from optical fiber significantly reduced the cost, and the transition to the nanoscale will further reduce costs.

Other applications

With the help of lasers, urologists can treat urethral stricture, benign warts, urinary stones, bladder contracture and prostate enlargement.

The use of a laser in medicine allowed neurosurgeons to make precise incisions and to perform endoscopic control of the brain and spinal cord.

Veterinarians use lasers for endoscopic procedures, coagulation of tumors, cuts and photodynamic therapy.

Dentists use coherent radiation to make holes, in gum surgery, for carrying out antibacterial procedures, tooth desensitization and roto-facial diagnostics.

Laser Tweezers

Biomedical researchers around the world use optical tweezers, cell sorters, and many other tools. Laser tweezers promise better and faster diagnosis of cancer and have been used to capture viruses, bacteria, small metal particles and DNA strands.

In optical tweezers, a beam of coherent radiation is used to hold and rotate microscopic objects, just as a metal or plastic tweezers can pick up small and fragile objects. Individual molecules can be manipulated by attaching them to micron-sized glass or polystyrene beads. When the beam hits the ball, it bends and has little effect, pushing the ball straight into the center of the beam.

This creates an "optical trap" that can hold a small particle in a beam of light.

Laser in medicine: the pros and cons

The energy of coherent radiation, the intensity of which can be modulated, is used to dissect, destroy or alter the cellular or extracellular structure of biological tissues. In addition, the use of lasers in medicine, briefly, reduces the risk of infection and stimulates healing. The use of quantum generators in surgery increases the accuracy of dissection, however, they pose a danger to pregnant women and there are contraindications to the use of photosensitizing drugs.

Complex structure of tissues does not allow to make unambiguous interpretation of the results of classical biological analyzes. Lasers in medicine (photo) are an effective tool for the destruction of cancer cells. However, powerful sources of coherent radiation act indiscriminately and destroy not only the affected, but also the surrounding tissues. This property is an important tool of the microdissection method, used for conducting molecular analysis in the place of interest with the possibility of selective destruction of excess cells. The purpose of this technology is to overcome the heterogeneity present in all biological tissues, to facilitate their research on a clearly defined population. In this sense, laser microdissection has made a significant contribution to the development of research, to an understanding of physiological mechanisms that can now be clearly demonstrated at the level of the population and even one cell.

Functional tissue engineering today has become a major factor in the development of biology. What happens if you cut the actin fibers during division? Will the Drosophila embryo be stable if the cell is destroyed in folding? What are the parameters involved in the meristem zone of the plant? All these questions can be solved with the help of lasers.

Nanomedicine

Recently, many nanostructures have appeared that have properties suitable for a variety of biological applications. The most important of them are:

• Quantum dots are tiny light-emitting nanoscale particles used in highly sensitive cellular imaging;
• Magnetic nanoparticles, which have found application in medical practice;
• Polymer particles for encapsulated therapeutic molecules;
• Metal nanoparticles.

The development of nanotechnology and the use of lasers in medicine, briefly, revolutionized the way drugs were introduced. Nanoparticle suspensions containing medicaments can increase the therapeutic index of many compounds (increase solubility and efficacy, reduce toxicity) by selectively affecting affected tissues and cells. They deliver the active substance, as well as regulate the release of the active ingredient in response to external stimulation. Nanoteraphy is a further experimental approach that provides dual use of nanoparticles, drug compounds, therapy and diagnostic imaging tools, which opens the way to personalized treatment.

The use of lasers in medicine and biology for microdissection and photoablation made it possible to understand at different levels the physiological mechanisms of the development of the disease. The results will help determine the best methods of diagnosis and treatment for each patient. The development of nanotechnology in close connection with the achievements in the field of visualization will also be indispensable. Nanomedicine is a promising new form of treatment for certain cancers, infectious diseases or diagnostics.