Over the past half century, lasers have found application in ophthalmology, oncology, plastic surgery and many other fields of medicine and biomedical research.
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 the sun and healing.
And only after the invention of a coherent radiation source more than 50 years ago, the potential of the use of light in medicine was really revealed.
Due to its special properties, lasers are much more efficient than radiation from the sun or other sources. Each quantum generator operates in a very narrow wavelength range and emits coherent light. Also, lasers in medicine allow you to create large powers. The energy beam can be concentrated at a very small point, due to which 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.
Skin and eye treatment
The use of lasers in medicine began with ophthalmology and dermatology. The quantum generator was discovered in 1960. And a year after that, Leon Goldman demonstrated how a ruby red laser in medicine can be used to remove capillary dysplasia, a variety of birthmarks, and melanoma.
Such an application is based on the ability of coherent radiation sources to operate at a specific 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 cured lesions and the main absorbing substance inside them. The wavelength also depends on the skin type of the patient.
Today it is impossible to practice dermatology or ophthalmology without lasers, as they have become the main tools for treating patients. The use of quantum generators for vision correction and a wide range of ophthalmic applications has grown since Charles Campbell in 1961 became the first doctor to use a red laser in medicine to heal a patient with retinal detachment.
Later, ophthalmologists began to use argon sources of coherent radiation in the green part of the spectrum for this purpose. Here, the properties of the eye itself, especially its lenses, were used to focus the beam in the area of retinal detachment. Highly concentrated power of the device 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 the blood vessels and slow their pathological growth under the macula.
Similar studies were conducted in 1940 with sunlight, but for their successful completion, doctors needed the unique properties of quantum generators. The next use of an argon laser was to stop internal bleeding. The selective absorption of green light by hemoglobin, the pigment of red blood cells, has been used to block bleeding blood vessels. To treat cancer, the blood vessels that enter the tumor and supply it with nutrients are destroyed.
This cannot be achieved using sunlight. Medicine is very conservative, as it should be, but sources of coherent radiation have gained recognition in its various fields. Lasers in medicine have replaced many traditional instruments.
Ophthalmology and dermatology have also benefited from excimer sources of coherent radiation in the ultraviolet range. They have become widely used for corneal reshaping (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, as they have huge potential for profit. In 2011, the analytical company Medtech Insight estimated the market volume of laser cosmetic equipment worth more than $ 1 billion. Indeed, despite declining overall demand for medical systems during the global recession, quantum-based cosmetic surgery continues 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 became interested in IR spectroscopy using infrared sources of coherent radiation. The reason for this is that cancer and healthy tissue can have different infrared patency. One promising application of this method is the detection of melanoma. With skin cancer, early diagnosis is very important for patient survival. At present, the detection of melanoma is done by eye, so it remains to rely on the skill of the doctor.
In Israel, once a year, everyone can go for free screening for melanoma. Several years ago, studies were conducted in one of the major medical centers, as a result of which it became possible to visually observe the difference in the IR range, the difference between potential, but non-dangerous signs, and real melanoma.
Katsir, the organizer of the first SPIE Biomedical Optics Conference in 1984, and his team in Tel Aviv also developed optical fibers that are transparent to infrared wavelengths, which has extended this method to internal diagnostics. In addition, it can be a quick and painless alternative to cervical smear in gynecology.
The blue semiconductor laser in medicine has found application in fluorescence diagnostics.
Systems based on quantum generators are also beginning to replace x-rays, which have traditionally been used in mammography. X-rays pose a difficult dilemma for doctors: 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 to take pictures of the chest and other parts of the body, such as the brain, is being studied.
OCT for the eyes and not only
Lasers in biology and medicine have found application in optical coherent tomography (OCT), which caused a wave of enthusiasm. This visualization method uses the properties of a quantum generator and can give very clear (about a micron), transverse and three-dimensional images of biological tissue in real time. OCT is already used in ophthalmology, and may, for example, allow an ophthalmologist to see a cross section of the cornea to diagnose retinal diseases and glaucoma. Today, technology is also being used in other areas of medicine.
One of the largest areas formed due to OCT is engaged in obtaining fiber-optic images of arteries. Optical coherence tomography can be used to assess the condition of a tear-prone unstable plaque.
Microscopy of living organisms
Lasers in science, technology, and medicine also play a key role in many types of microscopy. A large number of developments have been made in this area, the purpose of which is to visualize what happens inside the patient's body without using a scalpel.
The most difficult part in removing cancer is the need to constantly resort to the services of a microscope so that the surgeon can make sure that everything is done correctly. The ability to do live and real-time microscopy 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 notches at the ends whose dimensions are less than the wavelength of light. This allowed sub-wave imaging and laid the foundation for imaging biological cells. Using this technology in IR lasers will help to better understand Alzheimer's disease, cancer and other changes in the cells.
PDT and other treatments
Developments in the field of optical fibers help expand the possibilities of using lasers in other fields. In addition to the fact that they allow diagnosis within the body, the energy of coherent radiation can be transferred to where there is a need. It 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 photosensitive 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 at a specific wavelength, indicating the location of the tumor. If these same compounds are then illuminated with a different wavelength, they become toxic and kill damaged cells.
The 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 down inflammatory processes, prevents hyperemia and edema, improves blood circulation.
Personalized treatment
Two other areas where lasers are used are genetics and epigenetics.
In the future, everything will happen at the nanoscale, which will allow medicine to be practiced on a cell scale. Lasers that can generate femtosecond pulses and tune 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, it is impossible not to mention Leon Goldman. He is known as the “father” of laser medicine.
A year after the invention of the coherent radiation source, Goldman was the first researcher to use it to treat skin diseases. The technique used 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 ability of coherent radiation to simultaneously cut through the skin and seal blood vessels, limiting bleeding.
Goldman, who spent 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 foundation for laser safety. 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, fit in the palm of your hand, and even more miniature fiber lasers. These kinds of changes pave the way for new areas of application and development. The medicine of the future will have tiny lasers for brain surgery.
Thanks to technological progress, there is a constant reduction in costs. Just as lasers became commonplace in household appliances, they began to play a key role in hospital equipment.
If earlier lasers in medicine were very large and complex, then their production from optical fiber has significantly reduced the cost, and the transition to the nanoscale will further reduce costs.
Other applications
Using lasers, urologists can treat urethral stricture, benign warts, urinary stones, bladder contracture, and an enlarged prostate.
The use of a laser in medicine allowed neurosurgeons to make accurate incisions and perform endoscopic monitoring of the brain and spinal cord.
Veterinarians use lasers for endoscopic procedures, coagulation of tumors, incisions and photodynamic therapy.
Dentists use coherent radiation to make holes, in gum surgery, for antibacterial procedures, dental desensitization, and orofacial diagnostics.
Laser tweezers
Biomedical researchers around the world use optical tweezers, cell sorters, as well as many other tools. Laser tweezers promise a 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, similar to how metal or plastic tweezers can pick up small and fragile objects. Individual molecules can be manipulated by attaching them to micron-sized glass balls or polystyrene balls. When the beam hits the ball, it bends and has a slight effect, pushing the ball directly into the center of the beam.
This creates an “optical trap” that is capable of holding a small particle in a beam of light.
Laser in medicine: 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, in short, reduces the risk of infection and stimulates healing. The use of quantum generators in surgery increases the accuracy of the dissection, however, they are dangerous for pregnant women and there are contraindications for the use of photosensitizing drugs.
The complex tissue structure does not allow an 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 tissue. This property is an important tool of the microdissection method used for molecular analysis in a 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 in order to facilitate their research in a clearly defined population. In this sense, laser microdissection made a significant contribution to the development of research, to an understanding of the physiological mechanisms that today can be clearly demonstrated at the level of a population and even a single cell.
Functional tissue engineering today has become a major factor in the development of biology. What happens if actin fibers are cut during division? Will the Drosophila embryo be stable if the cell is destroyed during folding? What are the parameters involved in the meristemic zone of the plant? All these issues can be solved with the help of lasers.
Nanomedicine
Recently, many nanostructures have appeared that have properties suitable for a number of biological applications. The most important of them are:
- quantum dots - tiny nanometer-sized light-emitting particles used in highly sensitive cell imaging;
- magnetic nanoparticles that 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, in short, have revolutionized the way drugs are administered. Suspensions of nanoparticles containing drugs can increase the therapeutic index of many compounds (increase solubility and effectiveness, reduce toxicity) by selectively affecting affected tissues and cells.They deliver the active substance and also regulate the release of the active ingredient in response to external stimulation. Nanoteranostics is a further experimental approach, providing the 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 at different levels to understand the physiological mechanisms of the development of the disease. The results will help determine the best methods for diagnosing and treating 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 types of cancer, infectious diseases or diagnostics.