JPH0411213B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a fiber-guided laser external therapy device, and particularly relates to two types of lasers including a CO laser oscillator whose cutting ability and coagulation ability can be arbitrarily controlled. The present invention relates to a fiber-guided laser external treatment device that includes an oscillator and a flexible optical fiber as a light-guiding path.

(2) Background of the Technology In recent years, medical technology has made remarkable progress, and for example, endoscopy using glass fibers for diagnosis of the gastrointestinal tract, etc., has been developed. Apart from this, various applications of lasers in medical fields have also been proposed. For example, especially as a treatment device using laser,
There is great interest in research and clinical treatment of laser coagulators using Nd-YAG lasers and laser scalpels using CO ₂ lasers.
Among treatments using lasers, treatments that became possible for the first time with the advent of laser therapy devices are particularly important. This is because, even for subjects for which treatment with a laser treatment device is effective, if other treatment methods are available, it is often not necessary to use an expensive laser treatment device from a cost-effective standpoint.

In recent years, there has been a desire to develop a laser treatment device in which an optical fiber is capable of guiding light and whose interaction with a living body, ie, incision ability and coagulation ability, can be freely adjusted.

As a method for adjusting the incision power and coagulation power, it is possible to use a wavelength tunable laser or a means of providing two laser devices with different wavelengths and adjusting the mutual power ratio.

The former of these methods requires a high-output continuous laser that is tunable over a range of at least 1 μm to 2 μm or more in the near-infrared region, but a tunable continuous high-output laser is easy to use from a laser engineering perspective This is not something that can be realized, and it is extremely difficult to realize it if practical aspects such as efficiency are taken into consideration. Therefore, the latter seems more likely to be realized.

This is because the following three points are listed as requirements that an optical fiber should have for use in a laser therapy device.

(1) Energy transmission (2) Quality of transmitted light (spatial coherence) (3) Practicality as a medical light guide First of all, laser therapy equipment is one of the applications of laser energy, and to a certain extent Must be able to transmit energy. This point is a completely different condition from the light guide path for communication. That is, the light guide path is required to have high transmittance at the wavelength used, and to be durable against transmission power. Endurance to transmitted power is determined by various factors. Fiber damage is most often caused by heat generated within the fiber, which requires the fiber material to have low light absorption. Furthermore, if a defect with large absorption occurs locally during fiber formation, thermal damage will occur in that area, so it is necessary to select a material and to produce a fiber with fewer defects. Furthermore, it is necessary to have mechanical and physical properties that are strong against a certain degree of temperature rise. In other words, in the case of a glass having a small coefficient of thermal expansion, various conditions such as a high crystallization temperature and a lack of cleavability in the case of a crystal are required for the fiber. Furthermore, if necessary, a core clad structure should be used instead of a loose clad structure, and a fiber cooling mechanism should also be considered. The effect of laser light differs depending on the irradiation power density even if the wavelength is the same, so the absolute value of the laser power you want to transmit is determined by the high irradiation power density (1-
In the case of a laser scalpel that requires a power output of 10Kw/cm ² ), it varies greatly depending on the light collection performance after transmission. However, in general, considering the size of the laser device, its interaction with the living body, etc., laser treatment devices such as
It is considered that light guiding with a laser power of up to about 100W should be considered.

Second, regarding the convergence (spatial coherency) of the laser beam after guiding, for example, in current optical fibers whose diameter is considerably thicker (>50 times) than the wavelength, the incident laser beam essentially The laser beam propagates in multiple modes, and the spatial coherence of the laser beam is lost at the output end due to multimode dispersion. Therefore, at the output end, it is regarded as an incoherent light source having approximately the core diameter of a fiber, and even if a convex lens were to condense the light, the focal diameter could only be reduced to about the diameter of the fiber. For this reason, it is necessary to make the diameter of the optical fiber as small as possible to reduce the focal spot diameter when condensing light. Since a smaller diameter of an optical fiber means an increase in the power density of transmitted light, the fiber is more likely to be damaged due to an increase in the amount of heat generated per unit volume due to medium absorption. Furthermore, transmission loss is expected to increase due to the rise of scattering phenomena due to nonlinear optical effects, for example.

Third, because the light guide is used for medical applications, it also poses unique limitations. That is, in medical applications, since the fiber is used in a bent state and while changing the degree of bending, the fiber material is required to have mechanical strength that can withstand repeated bending. Also,
The problem of optical transmission loss in such a state also needs to be studied more precisely as the fiber becomes more flexible. Furthermore, it is desired that the fiber material be as chemically stable as possible and safe for living organisms. Furthermore, due to the special nature of the range of use, sufficient consideration should be given to safety measures in the event of an accident such as breakage of the light guide.

On the other hand, it has an advantage over communication use, in that for medical light guides, a length of at most 2 m is sufficient, so fiber transmission loss, manufacturing speed, manufacturing cost per unit length, etc. conditions are considerably relaxed.

From these conditions, regarding the laser oscillator,
For example, an Nd-YAG laser is most suitable as a practical high-output continuous laser type in the 0.8 to 1.8 μm band for coagulation. In other words, the Nd-YAG laser is an ideal
Since it is a level laser and has high thermal conductivity, it is capable of continuous high output oscillation with water cooling even though it is a solid state laser. In addition, as an incision laser that can be combined with this, Nd
- It is required to be able to simultaneously transmit YAG lasers through one optical fiber transmission line.

Next, we will discuss the CO laser below.

The history of the development of CO lasers is relatively old, and oscillation was reported in 1964 by Patel, who also developed the CO ₂ laser, several months after the appearance of the CO ₂ laser. Basically, it is a molecular laser that uses vibrational-rotational transition between levels, and like a CO ₂ laser, it can be excited by glow discharge. However, the excitation process to form population inversion and the oscillation mechanism are completely different from CO ₂ lasers.

The mechanism of population inversion formation in CO lasers is generally different from the formation of population inversion only by electron collision excitation due to ordinary glow discharge. Since CO is a diatomic molecule with low harmonicity, the rate of energy exchange between CO molecules is extremely fast. Energy exchange occurs between CO molecules excited to a relatively low vibrational level and CO molecules excited to a higher vibrational level,
Energy is injected into the higher vibrational level and population inversion occurs. This process, ie the V-V excitation (Vibrational-Vibrational) process, requires a low gas temperature, so high efficiency CO lasers require cooling of the gas temperature. In addition,
CO laser oscillation is a cassgate oscillation peculiar to diatomic molecules, and there is no particular upper or lower level of laser transition, and when oscillation occurs between arbitrary levels, the 2 The oscillation spreads to other levels due to the next population inversion. Therefore, unless selective oscillation is performed, the oscillation wavelength oscillates at several tens to more than ten oscillation lines.

(3) Prior art and problems Conventionally, among optical fiber transmission lines, the development of infrared optical fibers has mainly focused on the 4 to 5 μm band.
Research is underway to create ultra-low loss fibers for communications. Generally, infrared optical fibers with shorter wavelengths are easier to obtain. Light transmitting materials in the wavelength range of 7 to 8 μm or more are limited to crystals such as alkali halide, and there are few substances that can be used as materials. On the other hand, in the short wavelength range below this, various infrared glass materials can be found in addition to crystalline materials, and there is a large degree of freedom in material selection. When converting crystals into fibers, there are two methods: obtaining single crystal fibers by growing the crystals at a slow rate, and extrusion methods that take advantage of the plastic deformability of some crystalline materials. body) There is a way to obtain fiber. Both require the development of completely new techniques to obtain fibers with no internal defects, optical fibers with smooth surfaces, and fibers with a core-clad structure. On the other hand, glass fiber is an extension of the conventional silica-based glass fiber manufacturing technology, and the surface tension of molten glass allows fibers with smooth surfaces to be produced, making it easy to manufacture fibers with a core-clad structure. . Additionally, fibers with a narrow transmission wavelength range are generally easier to obtain. This is because there are few substances that have a wide transmission wavelength range for fiber materials, and in the case of fibers with large scattering loss,
For example, since Rayleigh scattering loss has a dependence on the wavelength to the fourth power, it is difficult to obtain a wide transmission wavelength range when fabricated into a fiber.

As described above, various conditions are required of the optical fiber used as the light guide path of a medical laser therapy device.

Further, a laser device conventionally used as a medical treatment device is used as a scalpel, for example, to remove a tumor on the skin. However, for example, parts of the oral cavity, trachea, gastrointestinal tract, cavity, bladder, etc. that can be considered external from a topological perspective can be observed using an endoscope, but laser light cannot be used directly. Previously, no treatment method using a scalpel had been developed, and the range of treatment was narrowly limited.

(4) Object of the Invention In view of the above-mentioned drawbacks of the conventional technology, an object of the present invention is to use a flexible infrared glass fiber as a light guide, and furthermore, to combine an Nd-YAG laser beam with excellent coagulation ability and the infrared Coagulation can be applied to areas that can be topologically regarded as external surfaces by combining a CO laser beam that is suitable for light guidance with a glass fiber and has sufficient cutting power to form a laser scalpel device. and make the incision adjustable
An object of the present invention is to provide a CO laser scalpel device.

(5) Structure of the Invention According to the present invention, the present invention provides an output adjustment mechanism for adjusting the mutual output ratio of the two types of laser devices in two types of laser devices having different wavelengths and having cutting ability and coagulation ability. , and an optical transmission line that guides two types of laser beams of different wavelengths from the laser device into a single beam, and is characterized in that the optical transmission line is irradiated through the endoscope. This is achieved by providing a fiber guided laser surgical treatment device.

(6) Embodiment of the Invention An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a CO laser scalpel device using the present invention.

In FIG. 1, for example, in order to operate a CO laser 4 with an oscillation wavelength of 5.2 μm and an Nd-YAG laser 5 with an oscillation wavelength of 50 W and a wavelength of 1.06 μm, they are connected to power supplies 3 and 2, respectively.
Output adjustment mechanism 1 to adjust the output of both lasers
are connected to power supplies 3 and 2. Then, the laser beams of the CO laser 4 and the Nd-YAG laser 5 are combined into a single beam via a beam blender 6,
Furthermore, a condensing lens 7 made of a convex lens is provided coaxially in front of the beam blender 6. The laser beam focused by the condensing lens 7 is configured to be guided by providing a flexible infrared glass optical fiber 8, and this light guide path is then passed to the endoscope 9. It is connected. Such an endoscope 9 is configured to condense the laser beam, which spreads from the distal end 10 to about the diameter of the fiber 8, by a convex lens 11 (not shown) and irradiate it to the affected area.

When diagnosing the affected area by illuminating it with an endoscope 9 (using a predetermined light beam as a guide) and incising the affected area while forming a surgical field, for example, a CO laser 4 is used, which has a large incision power effect due to the output adjustment mechanism 1. Increases the output and irradiates the affected area.

In addition, when there is a lot of bleeding when cutting the affected area, the output adjustment mechanism 1 increases the current supplied to the Nd-YAG laser 5 to greatly improve the blood coagulation ability.
The output of the Nd-YAG laser 5 is increased to stop the bleeding at the incision.

Next, Figure ₂ shows the energy absorbed per unit volume of a living body (hereinafter referred to as
This graph shows the deposit energy density (deposit energy density) as a function of distance from the biological surface.

Note that FIG. 2 shows experimental data for examining the coagulated layer thickness, and it is assumed that only the absorption process is considered as the interaction between the living body and light, and that the Beer-Lambert law is apparently established. Also, the absorption coefficient is Bayly
(“The absorption spectra of liquid phase
H ₂ O, HDO and D ₂ O from 0.7μm to 10μm”,
A report on the infrared absorption coefficient of water by Infra, Physics pp 211-(1963)) is used. The incident power density of each laser beam was the same. The vertical axis is a logarithmic axis with an arbitrary scale, and graphs a, b, and c are graphs for YAG, CO, and CO ₂ lasers, respectively.

The graph shown as a result is an extremely rough estimate considering the various complex phenomena that actually occur in living organisms, but it is a very rough estimate of the CO, CO ₂ laser light within the irradiation time, which is not dominated by thermal conduction. That is, it is effective as data on the order of the solidified layer thickness within a time of less than 4 seconds, for example.

From Figure 2, regarding the Nd-YAG laser,
Although the deposit energy density is about half the power of CO and CO ₂ lasers,
It can be seen that it is suitable for coagulation because it penetrates about 1.5 times and twice as deeply. Also, CO and
CO ₂ laser has a deposit energy density of Nd−
It can be seen that it is suitable for incisions because it has approximately twice and three times the penetration depth compared to YAG laser, respectively, and the penetration depth is shallow.

Next, the wavelength dependence of the absorption coefficient and optical extinction length of water in the infrared region will be explained using FIG. 3.

Figure 3 shows the Lambert-Beer absorption coefficient α [cm ^-1 ] and the optical extinction length in the infrared region of liquid water at the same time. Living tissue is composed of 60 to 70 percent by weight water. In the visible light range, the light absorption of oxidized hemoglobin contained in red blood cells has a large influence, but in the infrared range, the light absorption of living organisms is thought to be dominated by the light absorption characteristics of water. C.O.
The laser oscillation wavelength (5μm) is the same as the Nd-YAG laser (1.06μm) currently used as a coregulator and the laser scalpel used as a laser scalpel.
It is approximately in the middle of CO ₂ laser (10.6μm). However, as is clear from FIG. 3, the absorption coefficient (ie, optical extinction length) of the CO laser wavelength is close to that of the CO ₂ laser wavelength. CO laser light has a wavelength about half that of CO ₂ laser light, and it is expected that the influence of scattering by biopolymers (Mie scattering) will increase. However, even if the scattering process increases, the range of its influence is extremely narrow because the optical extinction length is short. From these facts, it is thought that the effect of CO laser light on living organisms is similar to that of a CO ₂ laser, which has superior incision ability rather than coagulation ability.

FIG. 4 is a graph showing the incision properties of dog liver by CO and CO ₂ laser irradiation used in the present invention.

Note that the incision depth is shown on a log-log graph as a function of the incision speed (beam movement speed). In this experiment, the average power density (the value obtained by dividing the laser beam power by the beam cross-sectional area at the spot diameter, which is 1/2 of the power density at the beam center) was
It is 2.6Kw/ ^cm2 . The incision vibration value was measured by dividing the sample immediately after incision into two along the incision surface. In Figure 4, the incision depth at the same incision speed is d in the case of incision by CO laser irradiation and e in the case of CO ₂ laser irradiation.
There is almost no difference.

Next, the case where the laser power is changed in the incision of the dog's liver using the CO laser used in the present invention will be explained using FIG. 5.

In FIG. 5, the average power density of the CO laser is 2.6 Kw/cm ² and 1.3 Kw/cm ² . The rate at which the cutting density decreases when the power density is decreased is approximately consistent with the empirical rule for CO ₂ lasers. The slope of the graph is exactly the same in the two cases.

Furthermore, even when isolated bovine liver was used as a sample, no significant difference was observed between the results obtained with dog liver. Therefore, the cutting power of the CO laser is almost the same as that of the CO ₂ laser, and considering the thickness of each layer of living tissue, the CO laser is suitable for use as a laser for living body cutting.

(7) Effects of the Invention As described above, the present invention uses an infrared optical fiber, which is a highly flexible and compact optical transmission path, so it cannot be directly attached to a conventional endoscope. It has the effect of making it possible to treat areas that are topologically considered external, such as the oral cavity, trachea, gastrointestinal tract, cavity, and bladder, while directly viewing the endoscope.

Furthermore, when the present invention is used, CO of approximately 5 μm
Since a laser is used, there is a great degree of freedom in selecting infrared glass fibers, such as chalcogenide, oxide glass, and fluoride glass, as the material used for the light guide, and manufacturing can be performed at low cost.

In addition, when the present invention is used, an Nd-YAG laser and an incision laser with an output adjustment mechanism can be used.
The CO laser is integrated into a single light guide path and controlled according to the state of the living tissue during surgery, making it possible to use a laser scalpel that can simultaneously exhibit a hemostasis effect.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the configuration of a CO laser scalpel device using the present invention, and Fig. 2 shows the energy absorbed per unit volume of the living body for the CO ₂ laser and the CO laser and YAG laser used in the present invention. Graph as a function of distance from the surface,
Figure 3 is a graph of the wavelength dependence of water absorption coefficient and optical extinction length in the infrared region, and Figure 4 shows the incision properties of dog liver by CO laser and CO ₂ laser irradiation used in the present invention. FIG. 5 is a graph showing the case where the laser power is changed in the incision of a dog's liver using the CO laser used in the present invention. 1...Output adjustment mechanism, 4...CO laser, 5...Nd-
YAG laser, 8...Infrared glass optical fiber, 9
…Endoscope.

Claims (1)

[Claims] 1. A CO laser device, an Nd-YAG laser device having a different wavelength, an output adjustment mechanism that adjusts the mutual output ratio of the two types of laser devices by input power, and a A fiber light guiding laser comprising: an optical transmission path having an infrared glass fiber that guides laser beams of different wavelengths into one beam; the optical transmission path is irradiated through the inside of an endoscope. External treatment device.