LASER TECHNOLOGIES FOR MEDICINE

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Опубликовано в библиотеке: 2021-08-19
Источник: Science in Russia, №1, 2010, C.9-12

The RAS Institute of Problems of Laser and Information Technologies in the town of Shatura (Moscow Region) is one of the leading institutions in the country, engaged in creation of potent technological CO2 lasers and equipment based on them. Recently the development of a new research trend connected with the creation of systems for stereolithogra-phy (technologies for rapid "modeling" of experimental samples), micro and optoelectronics, and biomedicine has started there. Natalia Firsova, an expert of the Russian Nanotechnologies journal, reviews these innovations in a special article for STRF.ru electronic version.

 

Today one of the most promising methods for effective treatment of coronary heart disease is the so-called transmyocardial laser revascularization of the myocardium. This technology consists in the creation of channels in the left-ventricular myocardium, thus restoring the blood supply to this muscle. This new procedure supplements widely used cardiovascular bypass surgery and angioplasty (repair of stenosed or blocked arteries and veins).

 

Perfocor intellectual systems have been developed for operations of this kind and are manufactured at the Institute of Problems of Laser and Information Technologies. These systems, based on a potent waveguide CO2 laser, deliver radiation directly to the operation table by means of a mirror-hinged optical manipulator. The systems have been used in clinical practice since the middle of the 1990s and are in many cases really  indispensable.  The  matter is that  insufficient blood supply to the myocardium leads to its illness and gradual necrosis. Aortocoronary bypass surgery, traditionally used for the repair of the impaired bloodflow. prevents a tissue necrosis. However, the bypass works during 10-15 years, after which it cannot function any longer, and the operation has to be repeated. Moreover, such operations have contraindications for many patients for various reasons. In such cases, laser comes to their rescue. A small hole is made between the ribs— a passage to the myocardium. A potent (about 40 J) laser pulse is "shot" through this passage into the heart, making a hole in it. Bleeding rapidly ceases, and the organism starts reconstruction of new blood vessels around this channel. The entire operation takes no more than 30 minutes. Staff members of Bakulev Scientific Center for Cardiovascular Surgery (Moscow), where one of the two existing devices is working (the other one is installed at Vladimirsky Moscow Regional Research and Clinical Institute), believe that after several months of training with the help of such equipment, any qualified cardiosurgeon will be able to carry out laser revascularization. And the need in such operations is great: according to the most approximate estimates, about 100,000 Russians are in need of them.

 

The specialists from Shatura created Perfocor in close cooperation with cardiologists and biologists. The heart is to be pierced by one flash during a strictly defined moment of the cardiac cycle, otherwise the operation will cause arrhythmia. Consequently, the device is supplied with a system of automatic monitoring, coordi-

 
стр. 9

 

nating  laser pulses  and   realizing  synchronization between the pulses and patient's heart beats.

 

The European medics, who tried Perfocor (one of the samples was made for the Czech Republic) admitted that by technological characteristics it was not inferior to, and by some parameters (power efficiency, radiation quality, weight characteristics) is even superior to the Heart Laser analog manufactured by PLC Medical System (USA). One more touch: the price of this latter device is about I mln dollars, which makes it in fact unavailable for the majority of hospitals. Russian intellectual surgical lasers are much cheaper, and 7-10 such devices can be manufactured at our Institute annually without additional financing.

 

However, at present the scientists of the Institute are engaged in the production of one more medical innovation: a device for the diagnostics of biological tissue evaporation, based on the so-called Doppler* effect, according to which the wave frequency and length are liable to change depending on the movement of their source. This device will help an operating surgeon precisely locate tumor borders and remove it without damaging the adjacent organs and tissues. The physicians highly appreciated an important property of the new equipment—the possibility of adjusting it to surgical interventions of different extents of risk. If a malignant tumor to be removed is located near vital organs, the surgeon "tunes" the system to switch off the laser ray during transition from one type of tissue (to be removed) to the other one (to be saved). And if the tumor is localized in a less hazardous place, the device reacts to acoustic signals during this transition. Within just 10-3 sec the device reports that abnormal cells have been removed and laser is already destroying normal cells. Not a single surgeon, even the most experienced one, can react so rapidly! The authors of the device from Shatura are proud that their system requires no

 

 

* Christian Doppler ( 1803-1853)—a German physicist, specializing in optics and acoustics. In 1842, he theoretically validated the relationship between the frequency of fluctuations, perceived by an observer, and the velocity and direction of movement of the source of waves. Later on this phenomenon was named after him—the Doppler effect.-Ed.

 
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additional diagnostics: one and the same ray works as an instrument and as an information channel.

 

Natalia Firsova adds that scientists of the Institute of Problems of Laser and Information Biotechnologies started the creation of the device with biotissue evaporation diagnostics in 2002 in collaboration with colleagues from the Tula Instrument-Making Bureau. Today the experiments are in progress: differentiation between normal tissues and malignant tumors should be as distinct and rapid as possible. The trials are carried out at the Moscow Research Oncological Institute named after P. Hertzen.

 

An important contribution to modern medical physics is a sparing method for laser-induced modification of cartilage shapes, developed there in the 1990s. It is not a secret that millions of people are in need of a certain correction: some do not like the shape of their ears, others suffer from deformed nasal septum, still others from trauma consequences, etc. However, these cosmetic defects are difficult to repair: a surgical intervention often fails to guarantee a desired result. After the operation, the organs lose elasticity and after some time, as a rule, become in fact the same as before the operation.

 

On the basis of studies of this problem, specialists from the Institute established the following regularity: cartilage tissues can be plastically deformed under conditions of thermal impact on laser radiation of moderate intensity. If it is warmed up to 70°C for a short period, the reorganization of internal mechanical tensions will without fail take place, with fixation of the new shape of the cartilage.

 

Thorough physico-chemical and histological studies had to be carried out for developing the mechanism and choosing the protocols of laser correction. On their basis, the scientists concluded that the effect of modification of cartilage shape is caused by a phase transition of water from bound to free state under conditions of a certain thermal mode. One more circumstance became clear: a thermal laser source impact provided warming of the treated tissue to the temperature needed for plastic deformation without damaging its structure. As a result, Emil Sobol, Dr. Sc. (Phys. & Math.), and his colleagues precisely defined optimal parameters of radiation, transforming a cartilage into "plasticine". It is noteworthy that after "memorizing" the new shape, the cartilage remained as elastic as before, without changing its structure and characteristics. The tissue retained the previous configuration even after a repeated laser correction.

 

The new method of sparing laser exposure opened up new prospects for plastic surgery, ENT surgery, and orthopaedics. Moreover, it is widely used in clinical practice, for example, at Sechenov Moscow Medical Academy* and Vladimirsky Moscow Regional Research and Clinical Institute, where more than 300 operations for the nasal septum correction have been carried out.

 

According to Natalia Firsova, lately an X-ray examination was the only objective and rapid method for obtaining information about the inner structure of human organs, detection of bone fractures and alien objects, evaluation of the state of transplants and endoprostheses. However, the traditional roentgenogram is a

 

 

See: M. Paltsev, "From the 18th to the 21st Century", Science in Russia, No. 4. 2008.-Ed.

 
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two-dimensional image and cannot show all features of the surface relief, distorts true sizes, and therefore does not always provide complete information essential for diagnostics and treatment of the patient. The potentialities of laser stereolithography—the best developed and most accurate of the rapid prototyping technologies-are much wider.

 

Using this method, models of nodes, constructions of any shape and complexity of a size of several tens of nanometers are "grown" by scientists at the Department of Intellectual Optico-Informational Systems of the Shatura Institute (supervisor of studies Academician Vladislav Panchenko). The three-dimensional object, designed by means of computer technologies, is formed under the impact of laser radiation from polymerized (capable of passing from liquid to solid state) composition by a succession of fine (25-300 µm) layers.

 

Due to laser stereolithography, the way from a design idea to a ready prototype has become truly rapid (from several hours to several days). The surface of the prototype is easily polished, it resembles epoxy resins by strength, and can be heated up to 100oC without changes of its shape and size.

 

This method opens up fantastic prospects in medicine. A surgeon needs a model of an organ or a bone, he has to work with. This model is "created" by tomography data, and, besides, the diagnostic complex can be situated thousands of kilometers away from the center, where the prototype is made (all necessary data are sent through the Internet). Specialists of the Institute cooperate in this sphere with 27 clinics. After physicians receive an exact model of the damaged joint, skull, or spine, they can adjust future titanium implants beforehand and plan an operation scenario. This makes the operation time 2-3 times shorter, and hence, even babies, who often cannot stand a long narcosis, can be treated.

 

By the way, the rapid simulation method can be used in industry as well (for example, aircraft construction) or for creation of exact copies of works of art or archaeological objects. Improving the technology, scientists suggested to make small parts from powder using the caking method (instead of polymers). The idea is the same: the laser draws the required contour on powder, and the powder is caked, while the part, which is not caked, crumbles—and thus layer by layer, till reconstruction of the object. The method is needed by bio-and nanotechnologists engaged in creation of porous and gradient materials with properties of variable directions. All processes in such cases require preliminary simulation.

 

N. Firsova, "Commercial Pulses of Laser", an electronic version ", "Science and Technologies of the Russian Federation ". September 1, 2009


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© N. Firsova Marina KHALIZEVA () Источник: Science in Russia, №1, 2010, C.9-12

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