Surgery – Instruments – Light application
Reexamination Certificate
1999-02-05
2001-06-26
Cohen, Lee (Department: 3739)
Surgery
Instruments
Light application
C372S034000, C372S035000, C607S089000, C606S013000
Reexamination Certificate
active
06251102
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to medical lasers, and more particularly to a surgical laser device and a method of its use in the filed of dermatology.
BACKGROUND OF THE INVENTION
A variety of lasers have been used in modern dermatology for correction of inborn and acquired skin defects and diseases. One of the reasons for wide proliferation of the lasers in this field is that their properties support the medical postulate—“do not harm” a patient.
Drug therapy has been the most commonly used method of treatment in dermatology mainly because it is readily available, simple and less painful. However, drug intolerance, side effects, common allergic reactions as well as low efficiency in treatment of a substantial number of disorders often make this treatment of a substantial number of disorders often make this treatment less desirable.
A need for more efficient cure of dermatological defects and diseases made surgical involvement quite popular in this area of medicine. As to the surgical methods of treatment of skin disorders, doctors are often compelled to resort to such procedures as dissection followed by transplantation, use of ultrasound and cryotherapy, application of magnetic fields of ionizing radiation, electrocoagulation, utilizing of plasma currents, etc. These surgical methods are used in spite of a great number of drawbacks and harmful side effects which include: destructive nature of the treatment, protractive healing process, high risk of hypopigmentation, possibility of atrophy, destruction of a skin texture, formation of scars, damage to an adjacent skin area including healthy regions. These problems are often alleviated when a surgeon uses local methods of treatment having short and fixed duration of action at a specified depth of a skin integument. This is one of the reasons why lasers have become recently the instrument of choice for may dermatologists.
Currently, lasers having different wavelength laser irradiation are used in dermatology. Examples of such lasers are: excimer, ruby, argon laser; alexandrite and garnet laser; tunable semiconductor laser; etc. These devices generate laser beams having the wavelength in the visible range of the spectrum (0.4-0.7 micron) as well as in the invisible, the UV range (0.18-0.40) micron. For instance, infrared lasers include a set of CO
2
lasers (with the wavelength of 10.6 micron), variations of neodymium lasers (with the wavelength of 1.06 micron), etc. These lasers are produced by Candela Laser Corporation and are described by “Lasers in Medicine” Tashkent, 1989.
In spite of the fact that these lasers maintain a short duration of action and provide certain localization in the plane of the action, they do not guarantee control of the treatment, especially as to the depth of penetration in the skin integument. Thus, use of these lasers does not eliminate such negative consequences as formation of hypotrophic scars and penetration of a laser beam into the area of healthy skin.
It is a matter of general knowledge that a layer of water practically does not allow optical irradiation at certain wavelength to pass therethrough. This region of the spectrum is typically known as the “window of non-transparency” and includes the following wavelength ranges: 1.25-1.40; 1.7-2.1; 2.5-3.1 and 5.5-7.5 microns. At these ranges optical irradiation is strongly absorbed by water and by living tissue which also consists of up to 90 percent of water. Such absorption leads to a rapid heating of water and vaporization of the treated living tissue. At these wavelengths a laser beam acquires an important quality, that is that laser irradiation can not penetrate deeply in to living tissue substantially consisting of water. As a result, a scattered laser beam propagates in living tissue only within the range which does not exceed the depth of 15-20 microns and does not destroy adjacent tissue. Such a mode of operation of a laser can be implemented only at specific levels of power density and energy, predetermined rate and duration of the pulse and only when a temporary stability of all these characteristics is achieved during a surgical procedure.
One of such known device is the aluminum-yttrium-erbium garnet laser having the wavelength of 2.94 micron of laser irradiation. Initial reports about stomatological application of this laser appeared in 1989. However, its properties such as energy pulse of 1-2 J; the wavelength of 2.94 micron and the pulse rate of 1 Hz enabled doctors to use this laser as surgical device in the filed of dermatology. The first reports of such use became known in Germany and Slovenia in 1991.
A schematic diagram of
FIG. 1
illustrates that such a device consists of a power unit, a cooling unit, a laser cavity and an articulated mirror light-guide unit. In view of the multiple reflections of the laser beam in the articulated mirror light-guide, the efficiency of the device is quite low and does not exceed 60 percents at the wavelength of 2.94 micron. This makes it necessary to sustain energy input of the laser irradiation at the level 2.5-3.0 J and the operating power of the power unit at 300 W. Naturally, a laser of such high power has to have a very efficient cooling system. Therefore, a special water cooling system was provided in this prior art device. In view of that, the weight of the device was 70 kgs with overall dimensions of 0.5 m3. Thus, large weight and dimensions as well as instability of the laser beam characteristics greatly limited employment of this prior art laser in dermatology.
The water cooling system was necessary in the high powered prior art device to keep the temperature of the active element within 20±10° C. range. When this temperature range was exceeded the thermolens effect developed in the active element which resulted in considerable laser beam scattering and in the loss of energy in the focal plane of a treated tissue.
One way of resolving these problems is through the formation of a more efficient laser system which lacks the articulated mirror light guide and requires substantially less power. This makes it possible the replacement of the water cooling system by its air cooling counterpart. Such changes ultimately led to a substantial reduction of the weight and overall dimensions of the laser assembly.
Thus, there has been a considerable need for an efficient hand held laser surgical device usable in the filed of dermatology which is capable of providing and controlling a predetermined depth of skin penetration and does not damage healthy regions of tissue adjacent the operation site.
SUMMARY OF THE INVENTION
One aspect of the invention provides a laser device for conducting dermatological surgery including a housing having interior and exterior regions. The housing forms a part of a handpiece adapted for positioning in a hand of an operator. A laser cavity extends within the interior region of the housing. An operating laser element generates an operating beam. At least a portion of the operating laser element is positioned within the interior region of the housing. A cooling arrangement generates a stream of a first coolant. A precooling unit is provided containing a second concentrated coolant. The cooling arrangement communicates with the precooling unit in such a manner that the stream of the first coolant entrains particles of the second concentrated coolant so as to form a stream of mixed coolant within the interior region of the housing. The mixed coolant has a thermal calorific capacity higher than the thermal calorific capacity of the first coolant.
According to another aspect of the invention, the second concentrated coolant is a solid carbon dioxide or dry ice. The precooling unit includes a chamber adapted for receiving the carbon dioxide. The chamber communicated with the interior of the housing. The cooling arrangement is a fan generating a stream of gaseous coolant containing particles of carbon dioxide within the interior region of the housing. The solid carbon dioxide situated within the chamber of the precooling unit is formed with at least o
Efremkin Pavel V.
Gruzdev Valentin A.
Cohen Lee
Farah A.
Fridman Lawrence G.
Innotech USA Inc.
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