MODERN RADIATION SOURCES AND APPARATUS FOR LOW-LEVEL LASER (Cold laser) QUANTUM THERAPY

S.V.Moskvin

The firm "Technica", Moscow, Russia

From time immemorial, the Sun has been perceived as a source of light, warmth and life. The use of natural light in therapeutical purposes is, probably, as old as mankind itself. The sun light and water have always been maximum close and available medical means. The first known mentioning of the practical use of sun rays in prevention and therapeutical purposes dates back to the time of Pharaoh Amenhotep's reign in Egypt (presumably from 1375 to 1358 B.C.). Medical characteristics of the Sun are described in the works of Herodotus, Hippocrates, A.C.Celsius, C.Galen, Abu Ali ibn Cena and others. One can say, that the Sun is the first radiation source in phototherapy, which has a wide spectrum range, unstable power density and unstable polarisation degree.

At the end of the last century, artificial light sources appeared, which had a narrower spectrum range and stable radiation power, thus giving rise to an intense development of light therapy at this period, as they showed a considerably more prominent and lasting medical effect, than sun therapy. Moreover, with the appearance of better controllable means of an action, it became possible to carry out investigations of photobioactivation phenomena. First of all, the success of light therapy is connected with the name of the Danish physiotherapist Nilse Ruberg Finsen (1860-1904), who offered to concentrate sun rays, simultaneously excluding visible and infra-red parts of the spectrum, for the treatment of tuberculosis cutis (lupus), and he also offered to treat skin pox by red light. In 1903 he was awarded the Nobel prize in medicine for the elaboration of a new method of treatment [ 10].

The second part of the XX century was marked by the appearance of lasers - light sources with new characteristics, such as: monochromatism, coherence, polarisation, directivity. This fact didn't go unnoticed, and in the middle of the 60-s the study of photobioeffects, caused by low-level intensity radiation began. One of the first questions was the question of comparability of the monochrome radiation of He-Ne laser and red-lamp light. V.M.Inyushin [6, 7] and other scientists convincingly proved the laser radiation advantages, which greatly influenced further development of low-level laser therapy.

Below is shown the classification of lasers, according to different parameters [4,8, 12, 13, 15, 16].

1. Physical (aggregation) state of the laser working substance

- gas (helium-neon, helium-cadmium, carbon-dioxide and others);

- excimer lasers (argon-fluorine, krypton-fluorine and others);

- solid state (ruby, alumo-yttrium garnet and others, alloyed by various ions);

- liquid (organic dyes);

- diode (arsenide-gallium, arsenide-phosphide-gallium, selenide-lead and others).

2. The method of working substance pumping

- optical

- gas-discharge

- electronic excitation

- injection of charge carriers

- heat

- chemical reaction

- others.

3. The wavelength of laser radiation

If the radiation spectrum is concentrated in a very narrow interval of wavelength (less 3 nm), the radiation is considered to be monochromatic, and its technical description includes the concrete wavelength, corresponding to the maximum of the spectral line. The wavelength is determined by the working substance material, but may vary slightly, depending, for example, on the temperature. Equal wavelength can be generated by lasers of different types, for example, the following lasers work with about λ=633 nm: He-Ne, dye, gold vapour, diode (AIGalnP) lasers.

4. According to the character of the emitting energy, continuous and pulse lasers are differentiated. One shouldn't mix the notions "pulse laser" and "modulating continuous radiation" lasers, as in the second case we deal, practically, with pulse radiation of various frequency and form, but with the maximum power not exceeding (or exceeding insignificantly) its value in the continuous mode. Pulse lasers have high power in the impulse, which reaches 10⁷ W and more for some types, but the pulse duration is extremely small, so the period average power is not high.

5. The characteristic of laser average power is very important.

• more than 10³ W-high power laser
• less than 10^-1 W-low power lasers.

Intermediate values aren't interesting from the point of view of this topic. Lasers for medicine should be viewed from the position of their influence on a biological object. In some cases "low power" - 100 W, may turn out to be quite high. The works on laser therapy [1] offer to divide low-level laser radiation into the conventional groups: "soft" -up to 4 mW/cm²; middle - from 4 to 30 mW/cm² and "hard" - more than 30 mW/cm². In the therapeutical process soft radiation is used for reflexotherapy on the points of classical acupuncture, middle-for the action on superficial pathological foci or on projection mnes of certain organs. Hard low-level radiation, of a helium-neon laser in particular, is recommended for the use in stomatologу, in the treatment of some dental and mouth cavity diseases [II].

Yet, still open is the question, concerning the energy classification of therapeutical pulse lasers, which should be viewed in complex, with regard to the biological effect of laser radiation, taking into account not only average outlet power, but the level of impulse power, impulse duration and laser radiation action duration.

6. According to the degree of danger of the generated radiation for the service staff, lasers are divided into 4 classes:

- Class 1. Laser devices are safe in the supposed conditions of maintenance.

- Class 2. Laser devices, generating visual radiation in the wavelength range from 400 to 700 nm. The eye protection is achieved by natural reactions, including wink reflex.

-Class ЗА. Laser devices, safe for the observation with unprotected eyes. For laser devices, generating radiation in the wavelength range from 400 to 700 nm, the protection is achieved by natural reactions, including wink reflex. For other wavelengths the danger for an unprotected eye is no more, than for class 1.

The direct observation of the beam, issued by laser devices of class ЗА with the help of optic tools (binocular, telescope, microscope, for example) may be dangerous.

- Class 3В. The direct observation of such laser devices is always dangerous. Visible radiation scattering is usually safe.

Note - The conditions of safe observation of the diffuse reflection for laser devices of class 3В in the visible area: minimal distance between an eye and a screen - 13 cm, maximum observation time - 10 sec.

- Class 4. Laser devices, producing dangerous scattered radiation. They may cause skin injury, and also fire danger. One should be highly careful in using them.

This gradation is defined by AUSS R 50723-94 Laser Safety. General safety requirement for the elaboration and maintenance of laser devices [3].

7. For the therapeutical process such laser characteristic as beam angular divergence is very important. It is measured in degrees, minutes of arc (1/60 of a degree), seconds of arc (1/60 of a minute) or radian (1° = π/180 ≈ 0.0175 rad.) Gas lasers have the least divergence-about 30 seconds (≈ 0.15 mrad.) The beam divergence of solid-state lasers

- about 30 minutes of arc (≈10 mrad.). Diode lasers have: in the plane parallel to p-n junction - from 10 to 20 degrees (depending on the laser type); in the plane perpendicular to p-n junction - about 40 degrees.

8. Laser efficiency.

Theoretically there is possible (quantum output) and real (full) efficiency. The last is determined by the relation of laser radiation power to the power of a dye source. Gas lasers have full efficiency 1-20% (helium-neon- up to 1%, carbon-dioxide

- 10-20%), solid-state - 1-6%, diode - 10-50%, in some constructions up to 95%). So it becomes clear, why only diode lasers can be used in autonomous and portable medical equipment.

Gas lasers vary much according to the substance type: He-Ne, CO, C0_2, N, Ar and others. It determines a very wide wavelength range, on which generation is obtained. Dyeing is realised through producing a subnormal discharge in the pipe, which is possible only with high power supply. From all laser types, they have the minimal width of the spectral line - up to 10⁷ nm.

Excimer lasers are modifications of gas lasers, they work on the compounds, which can exist only in the excited state - halogens and inert gases. Emit in ultra-violet part of the spectrum.

Solid-state lasers - are, mostly, alumo-yttrium garnet (YAG), alloyed by the ions of rare-earth metals (Nd, Er, Go and others). These ions themselves present the radiation source, while the garmet is only a matrix for their correct position in the space. Solid-state lasers may be both - pulse and continuous, and work on an average power level.

Dye lasers (using a liquid solution of special dyes as their working substance) are characterised by the ability to tune to the wavelength in a wide spectral range.

Diode lasers (DL) occupy a special place due to their constructive peculiarities and physical working principles. Small sizes of the lasers are determined by high efficiency and the necessity to provide a high density current pumping to achieve the inverse population. The diode lasers pumping is realised by a weak current (tens of mA) with the power about 2-3 V, whereas other laser types require thousands of Volt. It should be noted, that we mean exceptionally injection diode lasers, pumped by the direct current, going through the diode structure. The drawback of DL is their high radiation divergence, which limits its application in other, than laser therapy, spheres. DLs work in the wavelength range from 0.63 to 15 μm. The most widespread lasers are lasers in the nearest IR area (λ=0.78-0.93 μm), based on the crystal Ga_1-x AI_xAs. Diode lasers, based on AIGalnP (λ=0.633-0.64 μm) are becoming more popular, replacing traditional He-Ne lasers. Lasers with the wavelength 0.67 μm and average power up to 10W are used for photodynamic therapy (PDT) with the same success. There is information about the beginning production of green (λ=0.53 μm) and blue (λ=0.42 μm) diodes Zn_1-x Cd_x Se, with the power of several milliwatts and work failure time up to 1000 hours [18]. The table shows general types of diodes, applied in LLLT, and their characteristics.

The equipment, used in medicine, besides lasers themselves, also includes: a device for radiation power modulation for continuous lasers, or master oscillator for pulse lasers; a timer, setting the time of work; radiation power indicator or meter (photometer); a device for bringing radiation to the object (light guides), etc.

The most perspective in LLLT are diode lasers. Small overall dimensions, low power supply, a wide range of radiation wavelength and power, possibilities of direct radiation modulation, comparatively low price - all this allows to say, that diode lasers are above competition in this branch of medicine.

Nowadays, a lot of laser therapy devices (LTD) are produced: stationary and portable, multidiscipline and specialised; using different laser types and their combinations, and so on. During the years of laser therapy development the requirements to laser devices (in the general form comparatively recently) have been formulated [14, 19]. With the increase of laser medicine level the requirements to the modern LTD have grown as well, the next stage of laser therapeutical equipment, as a branch of medical engineering, has come, which aim is to formulate a unified purposeful policy in the elaboration and production, based on the maximum close collaboration of scientists of different specialities, general practitioners and producers.

Universality is one of the basic principles of the doctor's or researcher's modern "instrument". The main aim of universality is to fulfil, with minimal expenditures, numerous, contradictory sometimes, doctors' requirements to the equipment. The block principle of an equipment construct ion [14,19] allows to combine incompatible. The equipment, worked out on this principle, is divided into 3 parts: a base block, radiation heads and extensions. The principle of universality is realised in full measure in the LTD "Mustang".

The base block, the basis of each set, is, in fact, a supply and control block. Its main functions -to set a mode of radiation: frequency, time, power. Most models allow to control several parameters of radiation, the basic being the power (average and impulse). Base blocks differ in their functional abilities and they may be divided into two conventional types: with the fixed set of parameters and arbitrarily prescribed. When working in certain conditions (a medical nurse, providing the procedure, and a large number of patients), the LTD with the "fixed frequencies" principle is more preferable. On the front panel of a such base block there is a row of buttons with frequency indications on each, the frequency will be automatically set after a button is pressed. The necessary attribute in this case will be a light indication of the switch, which confirms the correctness of the set mode. In the same way the work time is set (timer). Such principles are realised in the LTD models "Mustang "-016,017, 022.

A small number of fixed parameters, set by these devices, cause the limited possibilities, which, to some extent, are eliminated with the help of the base blocks, allowing a doctor to set necessary parameters himself (LDT "Mustang" -models 024, and 026). The visual representation of the chosen parameters is provided by digital indicators of different types. The devices of all types must have radiation power indicators or meters (photometers).

One, two or even more emitting heads may bejoined up, two-channel devices being more popular. As a rule, a modern doctor's arsenal includes several head types, which provides a full realisation of laser therapy possibilities.

In this case, the use of different types of commutators, distributors, splitters, etc. is very convenient, as there is no need to change a head with each procedure, and there is a possibility to control their power independently. One can quickly connect any of the heads, two and more heads may be used simultaneously and in any combination, for example, red and infra-red lasers. The interchangeability of the emitting heads and extensions allows each doctor, according to a concrete task, to set up his own, optimal complex of equipment, or organize multifunctional, efficient medical rooms.

The control simplicity is necessary in any equipment, including medical. The criterion for the control simplicity estimation is time for thinking over actions, concerning the tuning of parameters, and a number of mistakes made. The simplicity of LTD control is closely connected with its ergonomics. The work of a medical staff should be organised in such a way, that all their attention be concentrated on a patient, on achieving the main task - a qualitative treatment, and not on the equipment maintenance.

The parameter control of laser radiation is extremely important for the validity of the applied methods of treatment and right dosage, which provides the most qualitative and effective treatment, and also for the safety of both - a doctor and a patient. Proceeding from these tasks, it seems necessary to control the following parameters:

1) The radiation wavelength.

This parameter is determined by the laser type and is stated in the documentation by a plant-producer. No additional indication is necessary.

2) The frequency of impulse radiation or of modulation.

It is set by a switch of any of the stated above types on the panel of the base block (control block). The information about the frequency exact value is presented either by a digital indicator in concrete figures, or by fixing of a discrete switch in the necessary position. One should note, that in the second case each discrete mark must provide information about a concrete parameter value and dimension, for example, 80, 150, 300, ...Hz. It is forbidden to use abstract figures type of: 1,2,3... with the recommendation of the producer to look for real parameter values in the passport or maintenance manual. It is inconvenient and, what is more important, the possibility of a mistake in parameter setting still grows.

3) The work time (timer).

In addition to the requirements to the frequency indication, a sound indication of the beginning and ending of the work should be provided.

4) Radiation power.

Due to the fact, that LTD action has a dose-dependable character, and the radiation power can change through various reasons - the temperature of the environment, energy supply and others - the compulsory control of the radiation power is necessary for the precise action dose. If one can notice the power decrease in lasers of the visual range, the problem of infra-red lasers power control and safety is still acute.

The wide power range, recommended for various diseases and methods, determines the presence of a power level regulator, and in this case the control of these changes is quite necessary.

Emitting heads are joined up to the base block directly or through a splitter. They consist of one or several diode lasers (more rarely of light guides) and an electronic control circuit, which sets laser pumping current and provides the head adaptation to the unified block supply. Sometimes, the electronic circuit provides the realisation of other functions as well. One should note, that it was a diode laser, which allowed to create a system of removable emitting heads and to realise in full measure the principle of block construction of modern equipment for low-level laser therapy.

Matrix radiators present a peculiar class of heads and autonomous devices. Only special magnetic extensions (MM-2, MM-3) are used here. The matrix radiator heads and autonomous devices, containing 10 pulse infra-red lasers, are most often used in medical practice [2, 17].

Weight-dimension characteristics of the devices are not always important. The prior characteristics remain to be those, which help to obtain the best therapeutical effect: universality, the possibility to change and control the radiation parameter maintenance simplicity and others. The problem of the device dimension and weight is acute only in cases, when it is systematically moved. Such situations most often occur in the following cases:

1) The working conditions of a doctor: on board a ship, plane, in mobile clinics, in isolated associations (duty points, search departments, expeditions), in camping-field conditions, etc. Country-side and private doctors have this problem too.

2) When, with a periodical doctor control, patients perform the procedure themselves. It is especially urgent in the treatment of heavy chronic patients, whose movement is hampered, and also patients, who locate far from medical institutions which allows not to break the treatment during week-ends and holidays.

In these situations, portable devices have all the advantage, as they have minimal weight and dimensions, and can work from both - mains (through an adapter) and a battery. In the first case, the compensation for minimal dimensions and weight is the loss of universality and, as a result, limited possibilities of laser therapy; in the second case, the simplicity of such devices is even more expedient, as it allows not to worry about their wrong application by a patient. At the same time, the abilities of portable devices can be enough even for a general practitioner.

Autonomous portable devices of laser therapy use both - matrix radiators (LTD "Muravei") and single, which have the advantage of being able to work with different extensions (magnetic and optic) [9]. They are indispensable in the work wilt intracavitary instruments (otolaryngologic, stomatologic, etc.), but especially well they showed themselves in reflexotherapy. For example, special LTD "Motyilek-reflex" (with a special extension A3) was elaborated for laser acupuncture. The specialised direction of their application determines the use of lasers with most effective for acupuncture radiation wavelength - 0.63 and 1.3 μm.

Optic extensions for intracavitory laser therapy. Historically, helium-neon lasers (λ=0.63 μm) were the first in LLLT. The radiation with this wavelength penetrates into not deep tissues, so to act on inner organs was possible only with the help of a corresponding light guide instrument. Nowadays, with the appearance of pulse infra-red diode lasers, and especially matrix radiators on their basis, the extensions are refused in favour of non-invasive radiation on the projection of a sore organ.

Significant increase of the frequency range, without upsetting the harmony of inner rhythms, can be achieved by temporary synchronisation of the influence on a biosystem. Basically, to achieve the synchronised LLLT action on all levels is possible through the co-ordination of the time characteristic of the radiation and the periods of all endogenic biorhythms, but, due to principle difficulties, the realisation of such mode is limited by the apriori calculation of no less than 3 inner rhythm frequencies for each patient, as it is realised in the "Mustang-BIO" (Russia). The use of diode lasers provides small dimensions and user's convenience [5].

The specialisation of some devices requires, first of all, other, than universality, which is not always absolutely necessary, principles. To some extent, it was already shown on the example of autonomous devices. In 1982-1989 it was informed about the effectiveness of intravenous blood irradiation (IVBI) for the treatment of patients with stenocardia and acute myocardial infarction. The method was also applied in other medicine branches. It required a special equipment. For a long time, the device АЛОК had been used, with He-Ne laser with λ=0.63 μm and the power 2.5 mW. Now it is being replaces by devices, which use DL with the similar wavelength. The LTD "Mulat", which has been elaborated by the firm "Technica" and underwent technical and clinic tests, is designated, mostly, for IVBI (maximum radiation power 4.5 mW).

The analysis of literature data allows to make the following conclusions about the perspective development of LLLT technology:

1. The production of universal devices, built according to the block principle (base block - emitting head - extension), and allowing to rediscipline them for the treatment of various diseases with minimal waste.

2. The production of specialised complexes, combining, as a rule, several methods of influence on a human organism. Such complexes, supplied with detailed methodological equipment, allow to realise the possibilities of physical medicine i” the treatment of 1-2 diseases with maximum effectiveness. The devices for intravenous blood radiation, specialised according to the method of action, can serve as an example of this direction of instrument engineering.

3. The production of small-sized, autonomous, exceptionally simple in maintenance and maximally safe devices, meant for independent use by patients, prescribed and controlled by doctors. Such LTD can sometimes be useful for doctors as well.

4. The elaboration and general introduction of LLLT methods, based on the influence of several wavelengths of the monochromic radiation (blue, green, red, infra-red). Diode lasers with corresponding radiation wavelengths make it realisable in a compact and universal device. There appears a possibility to influence by all wavelengths simultaneously, or in any other combination, by various radiators.

5. The replacement of continuous lasers by those, generating nanosecond impulses with the peak power 1-10 W and having an average power 2-3 times less, than continuous lasers, used today. Again, the only possible sources of radiation in this case can be diode injection pulse lasers with different radiation wavelengths.

6. The realisation of the multifrequent modulation mode of laser radiation by all the hierarchy of endogenic rhythms of a concrete patient (or its maximally possible set), ranging from ontogenesis (10^-10 Hz) to the frequencies of the optic range of electro-magnetic waves (10¹⁴ Hz), which realise the influence. In other words, in order to get a maximum effect, one should take into account the age of a patient and vary the radiation wavelengths. Between these extreme points of the frequency hierarchy of life organisation, there is a number of peculiar ranges, which are being studied today, and which should be considered in the multifrequent mode of LLLT influence.

Литература:

1. Байбеков И.М., Касымов А.Х., Козлов В.И. и др. Морфологические основы низкоинтенсивной лазеротерапии. - Ташкент: Изд-во им. Ибн Сины, 1991. - 223с.
2. Буйлин В.А. Низкоинтенсивная лазерная терапия с применением матричных импульсных лазеров. - М., ТОО "Фирма "Техника", 1996. - 118с.
3. ГОСТ Р 50723-94 Лазерная безопасность. Общие требования безопасности при разработке и эксплуатации лазерных изделий. - М.: Издательство стандартов, 1995. - 34с.
4. Грибковский В.П. Полупроводниковые лазеры: - Мн.: Университетское, 1988.- 304с.
5. Гримблатов В.М. Современная аппаратура и проблемы низкоинтенсивной лазерной терапии // Применение лазеров в биологии и медицине (Сборник). - Киев, 1996, С. 123-127.
6. Инюшин В.М. Лазерный свет и живой организм. - Алма-Ата, 1970. - 46с.
7. Инюшин В.М., Чекуров П.Р, Биостимуляция лучом лазера и биоплазма. - Алма-Ата, "Казахстан", 1975. - 120с.
8. Кейси X., Паниш М. Лазеры на гетероструктурах. - М., т.2., 1981. - 3б4с.
9. Москвин С.В., Радаев А.А., Ручкин М.М. и др. Новые возможности портативных лазерных терапевтических аппаратов "Мотылёк" // VII Межд. науч.-практ. конф. "Применение лазеров в медицине и биологии". - Ялта, Украина, 1996.-C.I 11-113.
10. Москвин С.В. Лазерная терапия, как современный этап развития гелиотерапии (исторический аспект) // Лазерная медицина. - 1997. T.I. вып. 1. - С.45-49.
11. Прохончуков А.А., Жижина Н.А. Лазеры в стоматологии / Лазеры в клинической медицине. Руководство для врачей // Под ред. С.Д.Плетнёва. - М.: Медицина, 1996. - С.283-303.
12. Справочник по лазерам / Под ред. А.М.Прохорова, пер. с англ. - т. 1-2, М., 1978.
13. Справочник по лазерной технике: Пер. с нем. - М.: Энергоатомиздат, 1991. - 544с.
14. Титов М.Н., Москвин С.В. Фирма "Техника"- разработчик лазерной медицинской аппаратуры // Лазер-маркет, (3-4) 1993.-С. 18-19.
15. Электроника: Энциклопедический словарь. - М.: Сов. энциклопедия, 1991. - 688с.
16. Федоров Б.Ф. Лазеры. Основы устройства и применение. - М.: ДОСААФ, 1988. - 190с.
17. McKibbin L., Downie R. Treatment of Post Herpetic Neuralgia using a 904nm (infrared) Low Incident Energy
18. Laser: a Clinical Study // LLLT for Postherpetic Neuralgia, 1991. - pp.35-39.

18. OE Reports, №155 / November, 1996.
19. Titov M.N., Moskvin S.V. and Priezzhev A.V. - Opimisation of the parameters of biostimulator "Mustang" in respect to the light scattering properties of the tissues // Paper # 2086-22 presented at SPIE's Symposium "Biomedical Optics Europe'93", Budapest, Hungary, 1993