KR100289249B1 - Optically-Pumped High Power Medical Devices - Google Patents

Abstract

The present invention is directed to a system for producing a narrowly focused radiation beam using a conventional light source 10 having a intensity similar to that produced by a laser. The system is broadly comprised of an omnidirectional light source 10 and an elliptical reflector 12 and has physical parameters of the light source and the reflector suitable for generating a beam of narrowly focused strong radiation. Light generated by the system may be combined with the fiber optic system 20 to be delivered to a target point. In one embodiment of the present invention, the size of the light source and the focal length of the reflector are selected so that the focused beam can be easily received by the optical fiber 20, the optical fiber 20 being twice the “F number” of the reflector. It has almost the same angle of acceptance in the station.

Description

Optically-Pumped High Power Medical Devices

1 is a front view of the optical device of the present invention showing a light source positioned during an optical hole comprising a first curved reflector and a second reflector.

FIG. 1 (a) is a front view of the optical device of the present invention showing a second curved reflector for redirecting light into an optical cavity.

FIG. 2 is a diagram showing the geometry of the focused beam reaching the second focal point of the reflector.

3 is a front view of the optical device of the present invention showing the electrode gap in the light source.

4 is a graph of conventional continuous wave power levels and pulsed power levels used in the apparatus of the present invention.

5 is a front view of a cross section of the optical delivery device of the present invention.

6 shows a focused beam of radiation transmitted by the apparatus of the present invention.

7 is a graph of the wavelength of light produced by an arc lamp.

Referring to FIG. 1, a preferred embodiment of the optical device of the present invention is shown. The apparatus comprises a light source 10 mounted in an optical cavity, the cavity comprising a first curved reflector 12 and a second reflector 14 which is curved or planar. The light produced by the cavity is transferred to the delivery device 24 by the optical fiber 20, which is described in more detail below. The embodiment of the invention illustrated in FIG. 1 includes a second reflecting mirror 14 which is planar. An alternative embodiment for the optical cavity shown in FIG. 1 (a) includes a second curved reflector 14 '.

The light source 10 used in the present invention is a conventional light source in the form of an arc lamp.

The arc lamp comprises a cathode 16 and an anode 18 connected to a suitable power source and mounted in the quartz housing 19. The interior of the housing 19 is filled with gas and vapor that produce light when excited by the current between the cathode 16 and the anode 18. Within the arc lamp used in the preferred embodiment of the present invention is xenon-mercury vapor.

When the lamp is activated, cathode 10 emits electrons, and electrons are accelerated toward anode 18. Collision of electrons with xenon or mercury atoms causes the orbiting electrons to move to a higher energy level or “excitation state”. When excited electrons return to their normal energy levels, the electrons emit photons, which have a wavelength determined by the energy difference between the excited and steady states.

1 illustrates a number of light rays produced by the light source 10. The light beams 22a-22b and 22a'-22b ', which originate from the theoretical center of the first focus of the reflector 12, are all reflected toward the second focus of the reflector and reflect the aperture at the second reflector 14 After passing through, it may be combined into the optical fiber 20. The other rays originate from a point between cathode 10 and anode 18 as illustrated by rays 22c and 22c ', respectively. The light rays are also reflected by the reflector 12 but do not pass through the aperture 13 in the second reflector 14, and thus again toward the cavity interior by the reflecting surface 14 of the reflector as will be described in detail below. Reflected. Some rays as illustrated by reference 22d are not reflected by the first reflector 12 and thus exit the reflector cavity.

The light beam focused at the second focal point can be received by the optical fiber 20 if certain constraints are met. Generally, the limiting factors are the size and reception angle of the optical fiber, the gap size of the light source 10 at the first focus of the reflector 12 and the magnification of the reflector 12.

In general, the gap size of the light source is directly correlated with the amount of electromagnetic radiation produced with a large gap size that produces a large power. However, the size of the gap also affects the ability to converge the rays to enter the optical fiber effectively. As described above, FIG. 1 shows light rays generated from various portions of the gap between the cathode 16 and the anode 18 of the arc lamp used in the preferred embodiment of the present invention. Since the light rays originate from the band of points rather than the theoretical focus of the reflector, the group of rays focused at the second focus will reach the band defined by the reflector geometry. The geometry of the reaching beam is shown in FIG. 2 and shows the band of reaching beam passing through the aperture with the width “D”. When the bandwidth of the light beam reflected by the curved reflector 12 and passing through the aperture corresponds to the acceptance angle of the optical fiber, an effective coupling to the optical fiber is made. However, if the bandwidth of the focused light beam exceeds the receiving angle of the mineral oil, light will be inefficiently coupled to the optical fiber. The bands of incident light, denoted 23 and 23 'in FIG. 2, will not be etched with the numerical aperture of the optical fiber, resulting in inefficient coupling. In the present invention, these rays are reflected by the reflective inner surface of the second reflector 14, and the optical cavity geometric parameters prevent these rays from escaping until they meet the criteria for effective coupling.

If all surfaces in the cavity are completely reflected or geometrically complete, the return beam will be captured in a “reflective loop”. However, many factors prevent this phenomenon. The light beam returned by the reflector 14 is reflected back by the first curved reflector facing the interior of the crystal housing of the arclamp. As soon as they pass through the crystal, these rays will be slightly refracted. This will change the direction of the light beam as shown in FIG. 1 (a), thus preventing the light beam from being captured in the reflection loop. And the additional light returned from the reflecting surface will be added to the new light beam to be generated in the arc gap, and will generate the optical amplification generated by the arc lamp between the arc gaps. The amount of amplification is determined by the reflectivity of the reflector and the absorption characteristics of various media in the cavity.

The reflection loop phenomenon can also be eliminated by controlling the position of the second reflecting surface relative to the focus of the first reflecting mirror. In addition, the curved second reflector can be used to minimize the reflection loop, as shown in FIG. 1 (a), and thus can improve the output light generation efficiency.

FIG. 1 (a) shows an alternative embodiment of the present invention using a curved reflector 14 'having a reflective inner surface. The curved reflector 14 'includes an aperture 13' for passing a light beam meeting the acceptance criteria of the reception angle of the optical fiber. In the device of this embodiment, it is possible for these light beams of the cavity to meet the emission criteria, for example the light beam 36, to pass through the aperture 13 ′. However, for example, light rays, such as light rays 38, will be reflected back into the interior of the cavity, where the light rays will be reflected back by the reflecting surface of the elliptical reflector 12 again.

In the present invention, the arc lamp 10 is pulsed at a power level several times higher than that normally used for continuous wave (CW) operation of the lamp. This pulse operation has the effect of generating a fairly strong light. In FIG. 3, a small spherical plasma 15 is shown produced at the end of the cathode 16 of the arc lamp. This plasma is caused by a fairly strong impact of electrons emitted from the end of the cathode 16. This plasma region is generally at the tip of the cathode when the lamp is operating in CW mode. In the present invention, however, the pulsed operation of the lamp will temporarily expand the plasma region in order to bridge the entire gap between the electrodes, as shown by the plasma region 15 'shown in FIG.

4 shows a graph of the power level used in the present invention to generate the pulsed plasma effect described above. The power levels described here are for Mercury-Xenon lamps; However, the principle of pulse operation can be used for other types of lamps to achieve similar results. The normal CW power level shown in Figure 4 has a power consumption of about 28 amps, 1000 watts. However, using the pulse method, the current will be increased above 50 amps for a short period such as, for example, about 1-10 milliseconds, so that more than 2,500 watts will be delivered. In fact, it is possible to increase power to higher levels for shorter periods of time. For example, a lamp can maintain 100 amps for a time period of about 100-500 microseconds.

The pulsed operation of the arclamps used in the present invention, as described above, creates a strong plasma region between the two electrodes, and therefore can achieve beam intensities very similar to those produced by conventional lasers at very small spot sizes. It is possible.

In many embodiments of the invention, curved reflector 12 is geometrically elliptical. However, other forms known to those skilled in the art can be used. For example, a parabolic reflector with a suitable lens system can be used to achieve focusing characteristics similar to those obtained by the elliptical reflector used in the preferred embodiment. The magnification of the elliptical reflector 12 is determined by the distance between the focus of the ellipse and the size of the ellipse. The light source 10 is placed at one of the first foci of the reflector and the optical fiber 20 is placed at the second focal point of the reflector.

The delivery system of the invention shown in FIG. 5 consists of two lenses made in a 4-f arrangement. The delivery system includes a housing 40 with an optical terminator 42 seated at one end. The terminator transfers light from the optical fiber 20 to the first diverging lens 44 to produce a collimated light beam. The aimed light beam passes through a suitable filter 40 which will be described in detail below and is received by the converging lens 48 for focusing light radiation on the tissue to be treated. The filter is placed in the light path to control the wavelength to be delivered to the ablation or solidification part. In order to reduce the tolerances in the filter, the position of the filter is chosen in the delivery system between the two lenses. The filtering action will be selected by pushing the filter into a slot in the delivery system. Two general purpose grating index GRIN fiber lenses can be replaced in place of the current normal lens while providing good propagation in UV and visible wavelengths. The conical tip 50 assists in accurately transmitting light to a desired location on the tissue, as will be described in more detail.

The advantage of the 4-f structure is that the optical fiber output light is focused into smaller spots at a given wavelength. In the present invention, the advantage of using such a lens arrangement is that the UV wavelength is focused into small spots closer to the 2Nd lens than the visible wavelength (due to chromatic aberration).

Conical end 50 is used as a guide to indicate the best focus for optimal cutting operation. 6 shows radiation of a concentric cone generated from light focused by a 4-f lens. UV light forms an ablation sight, shown to contact the tissue surface of FIG. The visible wavelength is focused just under the ablation plane of the delivery system, allowing the underlying vessel to coagulate before the ablation front reaches these layers.

Typical spectra for mercury and xenon are shown in FIG. Mercury lamps have several peaks in the UV and visible range as opposed to xenon lamps with many continuous spectra. Mercury-xenon lamps have characteristics that are quite similar to mercury with additional xenon baselines.

The mercury lamp spectral peaks at 404,430,546 and 579 are very close to the peaks of the absorption characteristics of the blood. On the other hand, the tissue has a visually low absorption characteristics and increases by more than 100 cm ⁻¹ at a UV wavelength of 320 nm or less. At present, an excimer laser at 351 and 308 nm shows good cutting operation with minimal damage in the vicinity of the tissue in the ablation portion. Minimal thermal damage is due in particular to the short pulse width and light-cutting of the UV excimer wavelength.

If only excimer lasers were used to cut tissue, blood would bleed into the tissue because the blood vessels could not coagulate to stop blood flow. Blood coagulation can be improved by using a dye laser tuned to a wavelength of high blood absorption, but has low tissue absorption when the coagulation target is blood rather than normal tissue. Thus, the optimal scalpel will be based on the use of multiple wavelengths such as UV for cleavage and wavelengths near 420,540 and 577 where relative blood absorption is higher than other wavelengths. Mercury lamps (or mercury xenon lamps) have features suitable for the multi-spectral properties required as described above.

The device of the present invention can be operated in a pulsed mode as described above to ablate the site using pulses for several milliseconds. Short pulse widths cause only minimal thermal damage to the tissue.

The present invention can be used to ablate tissue if all available wavelengths are focused at the end of the delivery system. To cauterize or coagulate blood, wavelengths in the visible range, particularly at peaks of 546 and 577 nm, can be delivered at the end to other wavelengths filtered by inserting a suitable filter into the delivery system.

Several different wavelengths of the laser from argon (488 nm and 514 nm) and YAG (1064 nm) and CO 2 (10,600 nm) can be used for tissue bonding. The primary purpose of tissue bonding is to heat the junction of two parts of the tissue (supported against each other) to reach a temperature just below the freezing point that melts the collagen of the tissue. Dissolving the collagen allows for better and faster healing of the tissue junction.

The present invention can generate a beam having a wavelength component that can penetrate tissue to a depth of a few millimeters. Thus, if the system is a structure capable of operating in continuous waveform mode, rather than in pulsed mode, continuous low level light exerts sufficient heat on the tissue so that the present invention can be used in tissue bonding. The temperature monitoring system is combined with the delivery system to provide more accurate tissue heat generation by preventing overexposure of tissue during more even bonding processes.

In general surgery, it is important to use a cutting device to penetrate the tissue or body. The present invention can be used to ablate tissue and cut several layers of skin. The delivery system is placed at the ablation site and the light source is activated to produce a high power pulse of light. The generated light allows for tissue ablation and allows the operator to move the delivery system along a desired cutting pattern on the skin. Complete penetration through the skin generally requires the passage of several tissue removals with a detailed examination of the excision site.

The present invention can also be used to cauterize blood quickly. The cautery filter is placed in the light path and the system is activated while the delivery system is brought to the bleeding site. This technique can be used to coagulate blood vessels under the skin at a depth of 6 millimeters.

Once the operation is complete, the cut size is closed using some conventional sutures. The system is made to operate in junction mode to produce continuous low level light. When activated, the delivery system applies mild heat to the sealed cut as it moves along the cut path. The rate of transfer and the heat of generation can be corrected by the experience of a heat sensitive feedback system or operator. The desired effect occurs at normal junction temperature at 60-85 ° C.

Although the invention has been described in connection with preferred embodiments, the invention is not limited thereto and includes all modifications, alternative details and equivalents as are included in the scope of the invention by the appended claims.

The present invention relates to an apparatus for use in medical applications requiring light with the high power characteristics of a laser. More specifically, the present invention provides a light source, which can produce a radiation beam having a beam intensity and spot size that is essentially the same as the radiation beam produced by the laser.

Lasers have many optical properties that are particularly useful for a wide range of scientific, industrial and medical applications. Two optical properties that are commonly associated with laser beams are the "coherence" and "monochromaticity" of the light beam. Other important properties of laser light are the high level of beam intensity and the ability to focus the light into very small spot sizes. Although the properties of coherence and monochromaticity are essential in some applications, many applications in which lasers are used do not require these properties, but rather only specific beam intensities and wavelengths.

Laser devices are generally expensive to purchase and operate and therefore cannot be used by many potential users. Furthermore, in many applications where lasers are used, the cost to the device arises to obtain different optical beam characteristics than the coherence and monochromaticity unique to lasers only. There is a need for inexpensive optics that provide a strong beam that can be focused into a small area.

Laser simulators based on prior art lamps are described in US Pat. No. 4,860,172 to Schlager et al. In the device proposed by Schlager, light from an omnidirectional conventional light source is collimated and focused into an optical coupling cone by conventional means, which cone typically condenses the focused beam into an optical fiber. Will be sent.

Although the purpose claimed in patent 4,860,172 is to provide a light source having many properties of laser light, the optical parameters of the device described in patent 4,860,172 cannot produce laser simulated light of intensity suitable for most medical applications. . Three parameters must be optimized to produce light with high intensity and small spot size using the optical element shown in patent 4,860,172: 1) gap spacing between electrodes, 2) magnification of reflector, and 3) accommodation of optical fiber Angular or numerical aperture. Larger lamp gap sizes tend to yield higher power output. However, large gap sizes result in large spot sizes due to the magnification characteristics of the reflector. The acceptance angle of the optical fiber represents the maximum spot size on the cone at a given angle of incidence that can be completely incorporated into the optical fiber. The receiving angle is related to the numerical aperture by the following equation:

sin (acceptance angle) = numerical aperture.

Therefore, it is necessary to match the gap size and the magnification of the reflector to make a beam that can be received by the optical fiber to be delivered to the tissue. The device of patent 4,860,172 seeks to optimize the coupling of light into an optical fiber through a cone. More specifically, patent 4,860,172 suggests that light can be coupled into an optical fiber through a cone reducing spot size.

Although the cone shown in patent 4,860,172 makes a small spot size, the power delivered by the beam will in fact be reduced due to the inherent optical properties of the coupling cone and the optical fiber. The inlet of the cone has a receiving angle that determines the first numerical aperture of the cone. Likewise, the outlet of the cone has an output of output numerical aperture that actually increases as the spot size of the output beam is reduced. The increased numerical aperture of the cone exit will cause significant divergence in the exit beam. The divergence of the beam from the cone exit is optically lost because some of the energy emitted from the cone does not meet the criteria for the numerical aperture of the optical fiber. The overall result is a beam that does not have enough power to provide the beam intensity needed for many medical applications.

The present invention provides an apparatus using a conventional light source to produce a narrowly focused radiation beam of similar intensity as the beam produced by a laser. The apparatus includes an omnidirectional light source positioned during an optical hole that includes a first curved reflector and a second reflector that is planar or curved. The optical parameters of the light source and reflector are matched to produce a powerful narrowly focused radiation. The second reflecting surface has an aperture located near the second focal point of the first reflecting mirror. The light source is located at the first focal point of the reflector, and the receiving end of the optical fiber is located at the second focal point of the reflector. The aperture is positioned such that only rays that meet a predetermined geometric emission criterion pass through the aperture and are received by the optical fiber at the second focal point. The rays which fail to meet the emission criteria are reflected by the reflective surface towards the interior of the cavity. Some of the reflected light further amplifies the light produced by the light source, and the path of the light beam is changed to pass through the aperture as the light beam can substantially meet the emission criteria.

Light produced by the device may be coupled into the optical fiber device to transmit to the target area. The size of the light source and the focal length of the reflector in the optical cavity are selected such that the focused beam is easily received by the optical fiber, which has a numerical aperture approximately equal to twice the reciprocal of the “F / number” of the reflector.

A better understanding of the invention may be obtained when the following detailed description of the preferred embodiment is described in conjunction with the drawings.

Claims (10)

An apparatus for producing a strong beam of light having a small spot size for delivery to a tissue site, the apparatus comprising: a radiation source; The radiation source has a first focal point and a second focal point; First reflector means operable to irradiate the beam from the radiation source toward the second focal point, and optical means for limiting radiation received at the second focal point to a specific numerical aperture; An optical receptacle positioned at the second focal point and having a numerical aperture for receiving the beam of radiation passed by the means for limiting the radiation received at the second focal point; And means for delivering the radiation from the receptacle to the tissue site. The apparatus of claim 1 wherein said means for generating radiation comprises a conventional light source. 3. An apparatus according to claim 2, wherein said light source is an arc lamp having first and second electrodes with a gap therebetween. 4. The apparatus of claim 3, wherein the light source is supplied with pulsed power such that a strong pulse of light is generated between the electrodes. 5. The apparatus of claim 4, wherein the power is pulsed for a period between 1 and 10 milliseconds. 6. The apparatus of claim 5, wherein the means for limiting radiation received at the second focal point includes a reflective surface having an aperture therein, the aperture allowing a beam of light that meets a predetermined numerical aperture to pass through. Light that does not meet the numerical criteria is irradiated toward the first reflector. 7. The apparatus of claim 6, wherein said means for delivering radiation comprises an optical fiber. 8. The apparatus of claim 7, wherein the means for delivering radiation further comprises means coupled to act on the optical fiber to receive the radiation passing through the optical fiber and focus the radiation on the tissue site. . 9. The apparatus of claim 8, wherein said means for delivering radiation further comprises filtering means for controlling the wavelength of said radiation focused on said tissue. 10. The apparatus of claim 9, wherein the arc lamp comprises mercury-xenon vapor and the radiation generated by the lamp comprises light of wavelengths corresponding to ultraviolet light, visible light and infrared light.