Surgery – Instruments – Light application
Reexamination Certificate
1998-06-24
2001-07-03
Peffley, Michael (Department: 3739)
Surgery
Instruments
Light application
C606S003000, C372S022000
Reexamination Certificate
active
06254596
ABSTRACT:
FIELD OF THE INVENTION:
This invention relates generally to optically-based therapeutic procedures.
BACKGROUND OF THE INVENTION:
Photodynamic Therapy (PDT) uses specifically designed drugs such as Foscan® (Scotia Pharmaceuticals), ALA (DUSA) and Photofrin (QLT Phototherapeutics) to destroy rapidly dividing cells. These drugs are selectively retained or generated at rapidly dividing cells and are subsequently excited by light to produce the desired effects. The primary mode of activity usually involves energy transfer from these photoexcited drugs to O
2
to produce superoxides or O
2
in its singlet state. To date this excitation has been provided by lasers, lamps, and new materials such as LaserPaint™ (laser action in amplifying scattering media). Some of these sources are generally expensive and require complicated delivery systems.
Two of the most important photodynamic therapy drugs are the naturally occurring ALA compound and Photofrin. Both of these are porphyrin compounds that have a peak absorption at 630 nm with a linewidth of approximately 35 nm.
Photofrin has recently received FDA approval for the treatment of esophageal cancer. As such, a low cost optical source at 630 nm has become a very important goal.
FIG. 1
illustrates a conventional optical source
1
that is suitable for use with Photofrin and similar photodynamic therapy drugs. The source
1
includes a pulsed (e.g., 150 nanosecond pulse width, 25 KHz pulse repetition rate) Nd:YAG laser
2
that outputs 1.064 &mgr;m light to a frequency doubler, such as a KTP crystal
3
. A 532 nm output of the KTP crystal
3
is used to drive a dye laser
4
, which provides the desired 630 nm light at the required power.
As those skilled in the art will appreciate, the use of the dye laser
4
has a number of disadvantages, including high initial and operating expense, a required use of fluids, pumps and plumbing, and a frequent need for service.
A number of additional photomedicine applications use laser treatment techniques. For example, U.S. Pat. No.: 5,735,844, issued Apr. 7, 1998, entitled “Hair Removal Using Optical Pulses”, by Anderson et al., discloses the use of light energy to remove hair follicles within a skin region. U.S. Pat. No.: 5,707,403, issued Jun. 13, 1998, entitled “Method for the Laser Treatment of Subsurface Blood Vessels”, by Grove et al., discloses positioning a laser so that light from the laser impinges a selected area of a patient's dermis to selectively destroy blood vessels at a selective depth. Grove et al. further disclose photomedicine applications including the removal of port wine stains, leg veins and hair follicles. Additionally, U.S. Pat. No.: 5,217,455, issued Jun. 8, 1993, entitled “Laser Treatment Method for Removing Pigmentations, Lesions, and Abnormalities from the Skin of a Living Human”, by Tan, discloses a laser treatment technique in which successive irradiations of a treatment site on the skin of a patient is performed to remove, in one embodiment, pigmentations representing a tattoo.
It can be appreciated that in each of the above mentioned photomedicine techniques, and others, a low cost, reliable laser source is beneficial. Similarly, it would be beneficial for a single laser system to deliver light having a range of wavelengths over a range of pulse durations.
OBJECTS AND ADVANTAGES OF THE INVENTION:
It is a first object and advantage of this invention to provide a lower cost, essentially solid state optical source providing optical radiation for a photomedicine and/or phototherapeutic application.
It is another object and advantage of this invention to provide a lower cost, essentially solid state optical source providing optical radiation for treating a region of tissue.
It is a further object and advantage of this invention to provide a single laser system which delivers light having a range of wavelengths over a range of pulse durations to a region of tissue.
It is a still further object and advantage of this invention to provide a lower cost, essentially solid state optical source providing optical radiation for treating a region of tissue to remove a port wine stain, a tattoo and hair follicles.
Further objects and advantages of this invention will become more apparent from a consideration of the drawings and ensuing description.
SUMMARY OF THE INVENTION
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
This invention discloses an optical source for performing photomedicine. The optical source includes, by example, a Nd:YLF laser having an output providing light having a wavelength of 1.053 micrometers; a frequency doubler that is optically coupled to the laser output for converting a portion of the light to frequency doubled light, the frequency doubler having an output providing frequency doubled light having a wavelength of 526.5 nm; coupled to the output of the frequency doubler, a unit for shifting the frequency doubled light to light having a longer wavelength in a range of about 600 nm to 1200 nm; and a device for conveying the light having the longer wavelength to a region of tissue. The shifting unit includes a device for performing stimulated Raman scattering of the frequency doubled light.
This invention also discloses a method for providing an optical source for performing photomedicine. The method includes the steps of: (a) providing a Nd:YLF laser capable of emitting light having a wavelength of 1.053 micrometers; (b) phase matching a frequency doubler to the Nd:YLF emission to provide frequency doubled light having a wavelength of 526.5 nm; (c) shifting the frequency doubled light to light having a longer wavelength; and (d) conveying the light having the longer wavelength to the region of tissue.
In accordance with the present invention, the Nd:YLF laser is frequency doubled and then Raman shifted to produce a pump source of suitable wavelengths for a number of photomedicine applications. In one aspect of the present invention, suitable for treatment of subsurface blood vessels to remove port wine stains, the pump source has a wavelength of between 700 nm and 1,100 nm, a fluence of between 5 J/cm
2
and 100 J/cm
2
, and pulse duration of between 0.2 ms to 100 ms. In a second aspect of the present
5
invention, a region of tissue is treated to remove a tattoo. In the second aspect of the present invention, a suitable pump source has a wavelength of between 600 nm and 1,100 nm, a fluence of between 1 J/cm
2
and 20 J/cm
2
, and pulse duration of between 10 ns to 300 ns. In a third aspect of the present invention, a region of tissue is treated to remove one or more hair follicles. In the third aspect of the present invention, a suitable pump source has a wavelength of between 680 nm and 1,200 nm, a fluence of between 10 J/cm
2
and 200 J/cm
2
, and pulse duration of between 50 As to 300 ms.
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patent: 5112328 (1992-05-01), Taboada et al.
patent: 5163061 (1992-11-01), Moberg
patent: 5217455 (1993-06-01), Tan
patent: 5304170 (1994-04-01), Green
patent: 5448582 (1995-09-01), Lawandy
patent: 5632741 (1997-05-01), Zavislan et al.
patent: 5707403 (1998-01-01), Grove et al.
patent: 5721748 (1998-02-01), Injeyan et al.
patent: 5735844 (1998-04-01), Anderson et al.
patent: 5793781 (1998-08-01), Lawandy
patent: 5796761 (1998-08-01), Injeyan et al.
“Stimulated Raman scattering of picosecond pulses in barium nitrate crystals”, Petr G. Zverev et al., Optics Communications 97 (1993), 59-64.
“Stimulated Raman scattering of the beam from a copper-vapor laser in a barium nitrate crystal”, S.A. Vitsinskii et al., Quantum Electron, 23 (12), Dec. 1993, 1001-1004.
“Generation of radiation in a resonator under conditions of stimulated Raman scattering in Ba(NO3)2, NaNO3, and CaCO3, crystals”, S.N Karpukhin et al., Sov. J. Quantum Electron., 16(8), Aug. 1986, 1027-1030.
“Conversation of tunable radiation from a laser utilizing an LiF crystal containing F2color ce
Ohlandt Greeley Ruggiero & Perle LLP
Peffley Michael
Spectra Science Corporation
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